Tag Archives: mammals

What are fisher cats, the most misleadingly-named animals out there?

One of the more obscure animals out there, fisher cats (Pekania pennanti) or ‘fishers’, in short, are predators endemic to North America. Despite the name, these animals are not cats, and they do not fish. They are, however, increasingly moving into a lot of urban and suburban areas across the USA.

Image credits of USFWS Pacific Southwest Region / Flickr.

Fisher cats are slim, short-legged mammals that resemble weasels or small wolverines. They can grow to about 145 centimeters in length (4 ft 9 in) including the tail. They’re covered in dark-brown fur, which is glossy and thick in the winter, and more mottled in the summer. They have rounded ears, and overall look quite cute and cuddly. Don’t let that fool you, however: fisher cats have vicious, retractable claws, and are quite fearsome predators for their size.

The species is endemic to various areas of North America. New England, Tennessee, the Great Lakes area, and the northern stretches of the Rocky Mountains all house populations of fisher cats. Smaller populations have also been reported in California, the southern Sierra Nevada, and the west coast of Oregon. The boreal forests of Canada also make great homes for these mammals.

The cat that’s not a cat

Taxonomically speaking, fisher cats are closely related to martens, being part of the Mustelidae family. This is the largest family in the order of Caniformia (‘dog-like’ animals) and the greater order Carnivora (meat-eaters). As such, they’re part of the most successful and rich group of predators on the planet.

Despite this taxonomic allegiance to the group Carnivora, fisher cats are omnivorous. They will happily hunt a wide range of animals of comparable size to them. They are of the very few animals that even attempt to hunt porcupines, and do so quite successfully, but prefer to hunt hares. They’re not above scouring the forest floor for plants to eat, however. They generally forage around fallen trees, looking for fruits, mushrooms, nuts, and insects. A bit surprisingly, given their name, fisher cats only very rarely eat fish.

It’s not exactly clear, then, how the animal got its name. Folklore says that fisher cats would steal the fish the early settlers used to bait traps in the Great Lakes region, but this is wholly unconfirmed. More likely, the ‘fisher’ in ‘fisher cat’ comes from ‘fisse’, the Dutch equivalent of the word ‘fitch’, from early settlers in the region. It’s also possible that it draws its roots in the French term ‘fishe’. These words refer to the European polecat or its pelt, respectively; given that fur trade was an important source of income for early settlers, it is likely that fisher cats were prized and sought-after for their pelts, and the species became associated with the polecat, who was raised for fur in Europe.

It’s easy to see why their pelts were so prized. Image via Wikimedia.

However, due to this association, fisher cats have been hunted to extinction in some parts of their natural habitat. Due to a drop in hunted pelts since the Americas were first colonized by Europeans, the animals are making a comeback and their populations are recovering and moving back into the areas they previously inhabited. Despite this, legal harvesting for fur, through trapping, is still one of the main sources of information regarding their numbers at our disposal right now.

A baby fisher cat is called a ‘kit’. Females tend to give birth to litters of one up to four kits at a time in the spring and nurture them until late summer. The kits are sightless and quite helpless at first, but become well able to take care of themselves by summertime and leave in search of their own mates.

How do they live?

Fishers spend most of their time on the ground, and have a marked preference for forested lands compared to other habitats. They’re most often found in boreal or conifer forests, but individuals have been seen in transition forests as well, such as mixed hardwood-conifer forests. They seem to avoid areas where overhead cover isn’t very thick, preferring at least 50% coverage.

Female fisher cats also make their dens in moderately large and large trees when giving birth and rearing their kits. Because of these factors, they’re most likely to be seen in old-growth forests, since heavily-logged or young forests seem not to provide the habitat that fishers like to live in.

Towards the west of the continent, where fires routinely clear forests of fallen trees (the most-liked foraging environments of the fishers), these animals tend to gravitate towards forests adjacent to bodies of water (riparian forests). They also seem to not be fond of heavily snowed areas regardless of geographical location.

Despite their habitat preferences, fisher cats have been seen encroaching ever more deeply into urban landscapes, most likely drawn by the prospect of easy food. While it is still unclear whether fisher cats hunt for pets such as household cats or small dogs, such activities would be within their abilities. Most likely, however, they search for food items discarded in trash cans.

Fisher cats stay away from humans for the most part and avoid contact. They will defend themselves if they feel cornered, however. They are quite small, so the chances of a deadly encounter with a fisher cat are slim to none, but if you ever meet one, don’t be fooled by their cuddly exterior. Give it space; their claws and fangs can be quite nasty, and there’s always the risk of infection when dealing with wounds from wildlife.

Today, these furry mammals are listed as Least Concern on IUCN Red List of Threatened Species; they are making quite a successful comeback following their historic lows. Still, habitat destruction and human encroachment remain serious issues for the species. Their ever-more-frequent sightings in cities and urban landscapes across North America are a warning sign of an issue wildlife everywhere faces: humans are taking up more space than ever, so they are coming to visit our cities, as well. Depending on what we do in the future, they may be forced to set up shop here for good.

“Hobbit” creature shows life evolved quickly after dinosaur extinction

The epic adventures of Bilbo Baggins act as a prequel to J.R.R. Tolkien’s Lord of The Rings trilogy. Bilbo encounters many creatures and races, including an enormous, shape-shifting warrior named Beorn.

“He is very strong, and he is a skin-changer,” the wizard Gandalf says of him, noting that “Sometimes he is a huge black bear, sometimes he is a great strong black-haired man with huge arms and a great beard.”

Researchers have now immortalized Beorn with the discovery of an extinct mammal that rose to prominence 65 million years ago, shortly after the demise of the dinosaurs. They call this creature Beornus honeyi.

Left to right, Conacodon hettingeri, Miniconus jeanninae, Beornus honeyi. Credit: Banana Art Studio

The creature is part of a group of three newly discovered species: Miniconus jeanninae, Conacodon hettingeri, and Beornus honeyi. They differ in size, with the Beorn-named creature being about as big as a cat — much larger than the mostly mouse-to-rat-sized mammals that inhabited North America after the fall of the dinosaurs.

So although the creature wasn’t necessarily large by today’s standards, it was relatively big for its day. In fact, the difference between the three creatures is so significant that the researchers now believe mammal evolution after the dinosaurs occurred much quicker than previously expected.

All three creatures are part of the group of mammals called archaic ungulates (or condylarths) — ancestors of today’s hoofed mammals (horses, elephants, cows, hippos, etc.). Specifically, they belong to a family called Periptychidae, which is known for its teeth.

This family of animals has swollen premolars and unusual vertical enamel ridges on their teeth, which may be linked to an omnivorous diet (but also don’t rule out a herbivore diet). Due to these teeth, researchers also believe that the creatures had puffy cheeks — hence the Hobbit name: when Beorn transformed into a bear, he had similarly puffed cheeks.

Beornus was probably just one of the many mammals that filled in the environmental niches left open by the dinosaurs.

“When the dinosaurs went extinct, access to different foods and environments enabled mammals to flourish and diversify rapidly in their tooth anatomy and evolve larger body size,” says lead author Madelaine Atteberry from the University of Colorado Geological Sciences Department. “They clearly took advantage of this opportunity, as we can see from the radiation of new mammal species that took place in a relatively short amount of time following the mass extinction.”

Previous studies suggested that condylarths and their relatives were diversifying slowly. However, some recent studies, including this one, suggest more diversity than previously expected. The team used phylogenetic techniques to analyze fossil findings, including the teeth and lower jawbones, from 29 fossil condylarth species in the Great Divide Basin in Wyoming.

Although these analyzed species represent a relatively small part of the entire fauna discovered at the site, it seems unlikely for this to be a coincidence; instead, it’s more likely that the fauna in the area diversified quicker than expected.

“Previous studies suggest that in the first few hundred thousand years after the dinosaur extinction (what is known in North America as the early Puercan) there was relatively low mammal species diversity across the Western Interior of North America, but the discovery of three new species in the Great Divide Basin suggests rapid diversification following the extinction,” says Atteberry. “These new periptychid ‘condylarths’ make up just a small percentage of the more than 420 mammalian fossils uncovered at this site. We haven’t yet fully captured the extent of mammalian diversity in the earliest Paleocene, and predict that several more new species will be described.”

The study “New earliest Paleocene (Puercan) periptychid ‘condylarths’ from the Great Divide Basin, Wyoming, USA” was published in the Journal of Systematic Palaeontology.

Small but sneaky. These are the world’s 10 smallest mammals

Mammals come in all shapes and sizes, from breathtakingly huge to really tiny. We usually think that bigger is better, but while it does have many advantages, being small can also work out. It means you can squeeze into all sorts of places to hide and escape from predators and hibernate. You also end up needing much less food to survive.

The bumblebee bat, Craseonycteris thonglongyai, is considered the world’s smallest bat and the smallest mammal in the world based on skull size. It weighs less than a penny and has a length of about two centimeters. The name comes from the fact that it’s usually confused for a bumblebee buzzing by your ear in the night – all because of its small size.

However, there are plenty more small mammals worth naming. The world is filled with them, and they’re more than just adorable: they’re excellently adapted to diverse ecosystems. Here’s a list with some of our favorite small mammas — get ready to be surprised by amazing facts and figures regarding their way of living, favorite foods, specific locations, and challenges from other predators and human activities.

The Etruscan shrew

The Etruscan shrew. Image credit: Flickr / Mick Sway

The Etruscan shrew (Suncus etruscus), also known as the Etruscan pygmy shrew or the white-toothed pygmy shrew, is usually considered the smallest known existing mammal by mass – weighing only about 1.8 grams on average and with a body length of four centimeters. Despite its size, it has a huge appetite, eating about twice its body weight every day. Talk about calorie consumption!

The shrew feeds on various small invertebrates and vertebrates, mainly insects, and can hunt individuals of the same size as itself. It prefers warm and damp climates, living in the belt between 10° and 30°N latitude stretching from Europe and North Africa up to Malaysia. While widespread, they are generally uncommon and are endangered in some countries.

Pygmy jerboa

Pygmy jerboas are considered the smallest rodents in the world. Their bodies start at four centimeters and they have tails up to seven centimeters long. Despite their size, they can jump very large distances thanks to their kangaroo-like legs. This helps them move fast over the arid deserts where they mainly live.

They are native to Pakistan and Afghanistan and their habitat includes rolling sand dunes, barren flat gravel, and sandy deserts. They are nocturnal herbivores, feeding on seeds and leaves from the desert. They have highly sensitive hearing, which allows them to detect predators, and mainly live in burrows excavated under small bushes.

Bumblebee bat

We mentioned the Kitti’s hog-nosed bat (also called the bumblebee bat) at the start of the article. At just a few grams, this tiny creatue truly is a wonder of nature.

It can only be found in some selected limestone caves in south-west Thailand. Surveys from 1997 to 2008 counted around 10,000 bats in 44 caves. The single species represents an entire family of bats, which split from the rest about 33 million years ago. It’s just one of around 440 bat species found in Asia — a continent that has more than one-third of the world’s 1,200 bat species.

Mouse lemurs

The Madame Berthe’s mouse lemur. Image credit: Flickr / Allan Hopinks

The adorable mouse lemurs (Microcebus) are considered one of the world’s smallest primates, measuring up to 27 centimeters in length including their tails. There are more than 20 species of mouse lemurs, and several have been identified only in recent years. The smallest species is the Madame Berthe’s mouse lemur, which measures only nine centimeters in length (3.5 inches).

They are forest dwellers that live in female-dominated groups of up to 15 animals. They spend most of their time in trees and can move from branch to branch and tree to tree. They sleep during the day and forage at night for insects, fruit, flowers, and other plants. They store fat in their tails and hind legs, burning it when forage is lean.

Least weasel

Least weasels are very small carnivores in the weasel family (Mustelidae). Males reach 17 centimeters, while females grow to 12 centimeters. Despite their size, they are the worst nightmare of small rodents, as they have a much bigger and ferocious personality than their size might suggest. They have long and slender bodies and short legs.

They are commonly found from Alaska and Canada through the upper Midwest, and portions of Appalachia. populations range from secure in Michigan and South Dakota to vulnerable in Minnesota and Iowa. They can be found in a wide variety of habitats, but prefer forests and woodlands with rocky slopes. They occupy and build nests of grass.

Pygmy possum

Pygmy possums are extremely cute but they’re more than just a pretty face. They range in length between five and seven centimeters and are commonly found in Australia, Papua New Guinea, and Indonesia. The family is divided into two groups, the genus Burramys, and the genus Cercartetu. Burramys only has one surviving species, the Mountain Pygmy Possum.

Pygmy possums are excellently adapted to their environment. They are tree-dwelling marsupials with large eyes, large ears, and long whiskers. Their soft, fur coat is fawn to grey on top and white underneath and, like many marsupials, their long tails swell with extra fat in times of plenty. They use their tails like fifth limbs to climb swiftly and can deftly leap between tall trees. Sky resorts and bush fires have affected parts of the habitats.

African pygmy mouse

Mice are generally known as small creatures, but the African pigmy mouse takes that to the extreme. It measures between two and seven centimeters and it’s considered the world’s smallest mouse. It’s so small that it stays hydrated by licking dew off tiny pebbles that it cleverly stacks in front of its burrow. Some people keep them as pets but they are very fragile.

Their geographical range extends from Central Africa all the way across to Eastern Africa and down to South Africa. They are social species and live in burrows or individual family units. These are constructed under piles of debris or fallen logs. They have a pale belly and their oats are typically red or blue.

Pygmy marmoset

The pigmy marmoset. Image credit: Flickr / BBC

Usually described as “pocket monkeys” as they can fit into your breast pocket, pigmy marmosets are considered the world’s smallest monkeys. They rarely have a length larger than 12 centimeters and, going about the Amazon rainforest in South America, using their sharp teeth and nails to gouge holes in trees and eat the sap, gums, and resins found inside.

These monkeys usually make their home in forests or bamboo thickets near or alongside rivers and floodplains. They prefer living in dense rainforests where there are lots of hiding places among the plants. Each marmoset group has a small home range of less than half an acre. They are orange-brown and their coloration gives them good camouflage.

Long-tailed planigale

The long-tailed planigale is the world’s smallest marsupials, with a length averaging five centimeters – including the tail. Their size and flattened head allow them to squeeze into crevices and cracks any other mammal would find impossible. This enables them to find food in unusual places and hide from predators. They hunt insects and even young mammals.

They belong to the family Dasyuridae, with three subspecies that can be found in northern parts of Australia. They inhabit grasslands, black soil plains, and wooded savannas and face many major threats such as habitat destruction (wildfires and overgrazing) and an increased number of predators. They are widely spread and numerous in the wild.

American shrew mole

The American shrew mole. Image credit: Flickr / Wikipedia Commons

Measuring about 10 centimeters including the tail, the American shrew mole is the smallest species of mole in the world. They are adorable underground dwellers that can be found in the U.S. Northwest and Canada’s British Columbia. They have small front paws than most other moles and travel in groups of 11 or more and spend more time above ground than other moles.

It’s the only living member of the genus Neurotrichus and the tribe Neurotrichini. They are active above ground, foraging in leaf litter for earthworms, insects, snails, and slugs, and can climb bushes to forage for food. They are called shrew mole instead of just shrew or mole because of its fur, a feature of most shrews, its large head and heavy dentition, a feature of moles.


So, there you have it — just some of the smallest mammals out there. Are they cute? Absolutely! But “cute” doesn’t cut it in the animal world. You need to be well-adapted to your environment, otherwise you just won’t make it. So the next time you see one such creature, don’t just think of it as adorable — cherish it as the magnificent creature it truly is.

Social behavior in mammals is as old as dinosaurs, fossil shows

Artist impression of a social group of Filikomys primaevus in a burrow. Credit: Misaki Ouchida

Virtually all mammals show some degree of social behavior, however infrequent their contact with other members of their own species. One may say this is a defining feature of our taxa, with humans being a prime example. According to a new study, mammals have mingled with one another since at least 75 million years ago, while the Earth was still dominated by the dinosaur lineage. Previously, scientists used to think mammals first exhibited social behavior after dinosaurs went extinct.

“It was crazy finishing up this paper right as the stay-at-home orders were going into effect—here we all are trying our best to socially distance and isolate, and I’m writing about how mammals were socially interacting way back when dinosaurs were still roaming the Earth!” said lead author Luke Weaver, a graduate student in biology at the University of Washington. “It is really powerful, I think, to see just how deeply rooted social interactions are in mammals. Because humans are such social animals, we tend to think that sociality is somehow unique to us, or at least to our close evolutionary relatives, but now we can see that social behavior goes way further back in the mammalian family tree.”

Weaver and colleagues at the University of Washington and Burke Museum examined the fossil skulls and skeletons of 22 individuals of Filikomys primaevus, a small, rodent-like mammal whose name aptly translates to ‘youthful, friendly mouse.’  F. primaevus belonged to the extinct taxon of rodent-like mammals known as multituberculata, which existed from about 178 million to 50 million years ago.

“Multituberculates are one of the most ancient mammal groups, and they’ve been extinct for 35 million years, yet in the Late Cretaceous they were apparently interacting in groups similar to what you would see in modern-day ground squirrels.”

Credit: Credit: Misaki Ouchida.

The fossils were found clustered together in groups of two to five individuals, with at least 13 individuals found within a 30 square-meter area in the same rock layer at Egg Mountain, a famous dinosaur nesting site in western Montana. The ancient mammals were found in a mixture of multiple mature adults and young adults, suggesting that these groups weren’t simply parents raising their young but rather the social members of a pack.

A block of Filikomys primaevus fossils analyzed from the Egg Mountain Formation in western Montana. Credit: Luke Weaver.

Strong shoulders and elbows suggest that F. primaevus were likely burrowing animals that nested together in the caverns they built.

Up until now, scientists used to think that social behavior in mammals first emerged long after the dinosaurs went extinct, and mostly in animals in the Placentalia group —  a rather diverse group, with nearly 4000 described species alive today including such diverse forms as whales, elephants, shrews, and humans.

However, the new findings show that social behavior was likely present well within the age of dinosaurs, and in an entirely different, more ancient group of mammals to boot.

“These fossils are game changers,” said senior author Gregory Wilson Mantilla, a University of Washington professor of biology and curator of vertebrate paleontology at the Burke Museum. “As paleontologists working to reconstruct the biology of mammals from this time period, we’re usually stuck staring at individual teeth and maybe a jaw that rolled down a river, but here we have multiple, near-complete skulls and skeletons preserved in the exact place where the animals lived. We can now credibly look at how mammals really interacted with dinosaurs and other animals that lived at this time.”

The findings appeared in the journal Nature Ecology & Evolution.

Tiny 200-million-year-old teeth show the first mammals were actually more like reptiles

Cementum (the structure that locks tooth roots to the gum) from the earliest mammals showed they lived much longer than previously thought. Credit: Nuria Melisa Morales Garcia.

We mammals might be high and mighty now, but it wasn’t always like this. Some 200 million years ago, the earliest mammals were tiny shrew-like creatures that lived in the shadows of the dinosaurs. In fact, the dominance of the dinosaur lineage ensured that our distant mammalian ancestors never grew larger than a cat during the next 145 million years of evolution.

There is still much we don’t know about the very first mammals, and how these little creatures morphed into a panorama of mammals with fur, hooves, fangs, as well as streamlined swimmers in the deep ocean. But a new study might cast more light onto the dawn of the age of mammals.

Mammalian evolution was more complicated than previously thought

In this new research, scientists at the University of Bristol in the UK and the University of Helsinki in Finland analyzed ancient teeth belonging to Morganucodon and Kuehneotherium, two of the earliest mammals known so far, using powerful X-rays.

Like counting a tree’s rings in order to determine its age, the researchers analyzed growth rings deposited every year in the cementum of the teeth, the structure that locks tooth roots to the gum. This procedure allowed the scientists to determine how long these animals lived.

Similarly sized modern-day mammals, such as mice and shrews, tend to survive only 1-2 years in the wild. But the researchers were surprised to find the ancient mammals lived much longer.

“The surprisingly long lifespan of these mammals, 14 years for Morganucodon and 9 for Kuehneotherium, are much longer than living small-bodied mammals, and more similar to small reptiles. This suggests a comparably slower pace of life to warm-blooded mammals and that the earliest mammals had yet to develop this important feature,” Dr. Elis Newham, Research Associate at the University of Bristol and lead author of the new study, told ZME Science.

Reconstruction of Morganucodon (left) and Kuehneotherium (right) hunting in Early Jurassic Wales 200 million years ago. Credit: John Sibbick, Pam Gill.

The project is the brainchild of Newham’s supervisor, Dr. Pam Gill, who is a senior research associate at the University of Bristol. Gill was inspired to employ advanced imaging technology on ancient mammalian fossils after one of his colleagues had a tooth removed that they wanted to get X-rayed because ” it can tell all sorts of things about your life history.” Why not do the same to learn more about the lives of the first mammals?

Over a period of six years, during which Newham took this project up for his MSc in Palaeobiology at the University of Bristol, and then as a Ph.D. at the University of Southampton, hundreds of teeth were examined. The fossils were scanned at the European Synchrotron Radiation Facility and the Swiss Light Source, among the world’s brightest X-ray light sources, in France and Switzerland, respectively.

“Perhaps the greatest challenge during the study was the very intense experiments at the synchrotrons. Located in Switzerland and France, the synchrotrons we visited operate 24-hours a day and so often require gruelling shifts through the night where small crews of scientists are continually swapping specimens, firing X-rays and drinking coffee!” Newham told me.

Synchrotron micro-CT scan of a fossil Morganucodon tooth root from 200 million years ago. Each annual growth ring is less than a hundredth of a millimeter thick. Credit: Elis Newham.

The cementum scans allowed the researchers to reconstruct the tooth roots in 3D, showing that Morganucodon lived for up to 14 years, and Kuehneotherium for up to nine years.

What’s more, the researchers also measured the size of major blood vessels in the femur bone of Morganucodon. This showed that Morganucodon could have had higher blood flow than living reptiles, but it was still significantly lower than that of living mammals. “This in-turn indicates that the earliest mammals could not sustain the same level of demanding exercise of living mammals,” Newham said.

These intriguing results suggest that the earliest mammals weren’t really warm-blooded like today’s mammals, although even 200 million years ago they had relatively large brains and whiskers.

“We are continuing using the method developed in this paper to study the physiological evolution of mammals through their early stages, to plot the pace and pattern of the evolution of warm-bloodedness. We are also looking at the possibility of analyzing other important life history information from the cementum growth rings in both living and fossil mammals,” Newham concluded.

The findings appeared in the journal Nature Communications.

More mammal species face extinction by 2100 if further action isn’t taken soon

If conservation efforts don’t step up, the number of mammal species going extinct could reach 558 by 2100, according to a new study, which estimated the number based on fossil evidence of past extinctions.

Unlike previous extinction events, however, humans are largely to blame for this one, researchers argued.

Credit k_t Flickr (CC BY-NC-ND 2.0)

The current diversity of mammals consists of approximately 5700 species, with at least 351 that have gone extinct since the Late Pleistocene 12 thousand years ago. These increasing trends of extinctions are matched by similar trends in other animal groups, which have lead scientists to declare the current events as a planetary biodiversity crisis for which our very own species is to blame.

The human impact in the most recent extinctions is undeniable, previous studies showed, with researchers concerned over the effect that elevated extinction rates will have on future mammalian diversity. Human activity has led to decreases in population sizes and species ranges for a large fraction of mammalian species, while global warming places additional stress on all species

Tobias Andermann from the University of Gothenburg and his colleagues compiled scientific literature the most recent fossil occurrences for all 351 mammal species that are known to have become globally extinct since the beginning of the Late Pleistocene. They estimated the times of extinction using computer-based simulations, finding that the extinction rate has accelerated. Even worse, it seems to continue accelerating.

“According to these models, the extinctions that have occurred in the past centuries only represent the tip of the iceberg, compared to the looming extinction of the next decades. Our human impact has led to several species extinctions in the past but additionally has severely decimated the population sizes and habitats of many more,” the researchers wrote.

Andermann and his team predict that by 2100 all areas of the world will have entered the second wave of extinctions of mammal species. Their simulation results indicate that this additional wave of anthropogenic extinctions may be much greater than the currently increased rates, by several orders of magnitude.

Australia and the Caribbean in particular have already entered the second extinction wave, the researchers argued, based on the extinctions that have occurred during the past decades. This shows that, although our predicted future rates and associated biodiversity losses are shockingly high, they are within a realistic range.

Current extinction rates are around 1700 times higher than those at the beginning of the Late Pleistocene. The 351 global mammal species that have gone extinct since then would have gone extinct within only 810 years under the current extinction rates.

On a global level, the researchers predicted 558 more mammal species to be lost by 2100 based on the current extinction rates. The most affected areas would be Africa, the Americas, and Eurasia, since current extinction rates for these continents are still at a comparatively moderate level, yet many species are severely endangered so there is plenty of bad news looming on the horizon.

“For all these continents, we also expect large biodiversity losses based on expected human population size increases, leading to significantly higher rates compared to the present. Therefore, human population size increases will undoubtedly pose a serious challenge for the future conservation of biodiversity in these areas,” the researchers wrote.

The scenario might seem bleak but there’s is still a window of opportunity to prevent many species extinctions by improving conservation efforts, the study showed. Even by not increasing future threats hundreds of predicted mammal species extinctions could be prevented, the researchers argue, “hoping” their predictions will lead to further conservation action.

Worldwide, populations of vertebrate animals such as mammals, birds, fish, amphibians and reptiles have diminished by 60% between 1970 and 2014, according to the Living Planet report by the World Wildlife Fund (WWF).

The rate of species extinction is currently 1,000 times higher than before humans dominated the planet.

The study was published in the journal Science Advances.

New heart rate measurements suggest that blue whales are about as large as animals can get

Researchers at Stanford University have made the first recording of a wild blue whale’s heart rate to date. The data suggests that the animals’ hearts are operating close to their maximum capacity, which may act as a hard cap on their maximum possible size.

Image credits Thomas Kelley.

The team developed a sensor array which, through the use of four suction cups, can be secured near a whale’s left flipper. This device was used to record the heart rate of a wild blue whale, and offer an explanation as to why they are the largest animal we’ve ever found. The recording points to some unusual features that help whale hearts pump enough blood.

Studying animals that operate “at physiological extremes” can help us better understand biological limits on size, the team explains. Furthermore, such species may also be “particularly susceptible” to environmental changes that disrupt their food supply, since large animals need large meals. All in all, the team hopes that their research will help us design new and better conservation and management schemes for endangered species like blue whales.

Big-hearted

“We had no idea that this would work and we were skeptical even when we saw the initial data. With a very keen eye, Paul Ponganis — our collaborator from the Scripps Institution of Oceanography [Ed. Note also a co-authror of this study] — found the first heart beats,” said Jeremy Goldbogen, assistant professor of biology in the School of Humanities Sciences at Stanford and lead author of the paper.

“There were a lot of high fives and victory laps around the lab.”

The current study draws its roots in some of Goldbogen’s and Ponganis’ previous research, in which they measured the heart rates of diving emperor penguins in McMurdo Sound, Antarctica. The duo wanted to do the same with a blue whale, but there were several issues to overcome: “finding a blue whale, getting the tag in just the right location on the whale, good contact with the whale’s skin and, of course, making sure the tag is working and recording data,” said Goldbogen.

They first tested their sensors on smaller, captive whales, to make sure the technology is sound. However, they didn’t accurately reflect the behavior of wild whales — which aren’t, for example, trained to flip belly-up for a human caretaker. Blue whales also have a wrinkly structure to the skin on their underside that expands during feeding; this could mechanically dislodge the sensor array.

“We had to put these tags out without really knowing whether or not they were going to work,” recalled David Cade, a recent graduate of the Goldbogen Lab who is a co-author of the paper and who placed the tag on the whale.

“The only way to do it was to try it. So we did our best.”

Despite all this, everything went swimmingly with the wild whales, the team reports. Cade managed to fix the tag on his first attempt near the flipper (where it could pick up on signals from the heart).

The recordings showed that when the whale dives, its heart rate slows down to an average of about 4 to 8 beats per minute, although the team did see activity drop down to just 2 beats per minute. At the lowest point of their foraging dives — when the whale needs to swim upwards and catch its prey — heart rate rose to 2.5 times above this minimum value, and then slowly decreased. The highest heart rate was recorded at the surface, between 25 to 37 beats per minute, while the whale was breathing and replenishing its oxygen stocks.

All in all, the team says the findings are very surprising. The upper limit of heart rate was faster than expected, and the lowest ones were about 30-50% slower. The lower-end heart rates seen can be explained by the whale’s elastic aortic arch, which slowly contracts and keeps blood flowing to the body between heartbeats. The highest heart rates seen are likely made possible by small features of the heart’s shape and movement which prevent pressure waves generated during contraction from disrupting blood flow, the team adds.

The blue whale’s heart likely operates near or at the limit of its capacity. The team believes that the energy needs of a larger body would simply outpace the ability of a heart to pump blood, which would explain why no animal has ever outgrown them.

Currently, the team working on improving their sensor array and plan to expand their research to other species such as fin whales, humpbacks and minke whales.

The paper “Extreme bradycardia and tachycardia in the world’s largest animal” has been published in the journal PNAS.

Small Somalian cavefish hints at mammals’ nocturnal ancestor

The blind, pale-pink cavefish has lived in constant darkness for millions of years, which caused it to lose an ancient system of DNA repair.

This image shows a Somalian blind cavefish that, after evolving for millions of years in darkness, has lost the capacity to harness light for repairing DNA. Image credits: Luca Scapoli / University of Ferrara.

If you spend an hour in a dark room, you’ll start to notice significant changes. Your eyes start to get used to the darkness, your other senses sharpen, and you might feel a bit weird. Imagine living the rest of your life in darkness — and then your offspring and your offspring’s offspring do the same thing, for countless generations. Much more would start to change than your eyesight.

This is particularly noticeable in the case of cave creatures. The cave is a very specific environment, with little to no light and generally constant temperatures. There are more than 200 scientifically described species of cavefish, all of which show specific adaptations to this environment — and one of them can teach us something very important about mammals, including ourselves.

Organisms such as bacteria, fungi, plants, and even most animals have the ability to harnesses energy from visible light to repair DNA damage induced by ultraviolet (UV) light. But placental mammals don’t. So all these mammals, humans included, probably originate from a creature that somehow lost this ability — just like this cavefish in Somalia.

This supports the theory that the mammals’ ancestor had a subterranean or exclusively nocturnal lifestyle, perhaps as a strategy to avoid being eaten by predators such as dinosaurs.

“We have revealed in a species of blind cavefish the loss of an ancient DNA repair system that is highly conserved,” says Nicholas Foulkes of Karlsruhe Institute of Technology, Germany. “Curiously, the only other animals previously known to lack photoreactivation DNA repair are placental mammals. So, what we see in this species of cavefish may be the first stages in a process that happened before in our ancestors in the Mesozoic era.”

The fish in case, Phreatichthys andruzzii has lived in complete darkness for some three million years, much more than other cavefish which haven’t yet lost this ability. So this gives us an approximate idea of how long it takes for this to happen — an important clue to identifying the mammals’ ancestors.

“Many features of modern mammals, such as the anatomy and function of the eye, show tell-tale features of a nocturnal life style,” Foulkes says. “It means we can now more confidently predict that mammalian ancestors experienced a prolonged period of evolution in complete darkness.”

Now, researchers want to study the fish more and see whether the fish has lost or altered any other abilities that rely on sunlight to function properly.

Journal Reference: Current Biology, Zhao et al.: “Modulation of DNA Repair Systems in Blind Cavefish during Evolution in Constant Darkness” https://www.cell.com/current-biology/fulltext/S0960-9822(18)31123-0

Mammaliaform Morgauncodon

Mammals’ evolutionary success relied on our ancestors growing very tiny

Mammals cashed in big on growing smaller, new research reveals.

Mammaliaform Morgauncodon

Morganucodon, a mamaliaformes and one of the best-preserved species from which all mammals originate, grew up to only 4-6 cm length.
Image credits Bob Nicholls.

The bubbly evolution of mammal species over the last 200 million years is owed in no small part to their propensity for growing smaller, a new paper reports. This trend is most evident when compared to that of the dinosaurs — the former de-facto winners of the evolutionary lottery — which spawned some of the largest beasts to ever walk the Earth.

Smaller, better, harder, stronger

When mammals first started popping up around 200 million years ago, our planet was still dominated by dinosaurs. So for the following 150-ish million years, mammals literally and figuratively kept a low profile. While dinosaurs were growing bigger, mammals shrank in size.

An international team of researchers set out to understand why and how this shift took place. Using modern computer modeling and analysis, they analyzed the skeletons of our tiny ancestors to better document their evolutionary path.

Mammals stand out among all other vertebrates on the planet in that they have a single bone bearing teeth for their lower jaw. Everyone else has more complex lower jaws, formed from no fewer than five bones linked together, the team explains.

As mammals evolved, most of these bones shrank in size and became more simplified. The new jaw retained a single bone, and the others moved higher in the skull, into the inner ear. They now help us hear.

The team focused their research efforts on understanding how this lower jaw restructuring process took place — as they were occurring, these changes had to allow the animal to keep feeding itself and hear, else they wouldn’t be viable organisms. Starting from X-ray computed tomography (CT) scans of several fossil skulls and lower jaws, the team created digital models of the bones. Later, they ran these models through extensive computer simulations to see how they would function.

For smaller animals, the team reports, jaw bones experience reduced stress when feeding. The jaws themselves could thus become simpler and tinier while still retaining enough structural strength to bite through prey.

“Our results provide a new explanation of how the mammalian jaw evolved over 200 million years ago,” says Dr Stephan Lautenschlager, lead author of the paper and lecturer at the University of Birmingham.

“Getting very small appears to have been crucial for our mammalian ancestors. This allowed them to reduce the stresses in the jaw during feeding and made the restructuring of the jaw bones possible.”

University of Bristol Professor Emily Rayfield, who co-authored the study, says that the research addresses a 50-year-old open debate in paleontology.

“Using computational methods we can offer explanations to how our mammalian ancestors were able to maintain a working jaw while co-opting bones into a complex sound detection system,” she explains. “Our research is about testing ideas of what makes mammals unique among the animal kingdom, and how this may have come about.”

The paper “The role of miniaturisation in the evolution of the mammalian jaw and middle ear” has been published in the journal Nature.

Grooming claws.

Fossils reveal that primates initially had nails and claws, we just lost the latter ones

If you like having nails instead of claws, give a shout-out to society.

Nails.

Image credits Daniel Nebreda.

Unlike other mammals, us humans and our primate cousins sport nails instead of claws. However, this wasn’t always the case — new fossil evidence shows that ancient primates had specialized grooming claws as well as nails. The findings showcase how primate social structure helped shift claw and nail evolution, the team writes, and overturns our assumption that the earliest primates had nails on all their fingers.

Nailed it

“We had just assumed nails all evolved once from a common ancestor, and in fact, it’s much more complicated than that,” said Jonathan Bloch, study co-author and curator of vertebrate paleontology at the Florida Museum of Natural History.

Grooming goes beyond just looking good. The thick body hair of primates is an ideal habitat for ticks, lice, and a whole host of other creepy crawlies which are both annoying and potential health hazards. As such, the ability to remove these pests formed an evolutionary advantage — and they evolved specialized grooming claws for the purpose. Many primates today retain such claws. Lemurs (subfamily Lemuroidea), lorises (subfamily Lorinae), and galagoes (family Galagidae) have grooming claws on their second toe, while tarsiers (family Tarsiidae) boast them on their second and third toe.

Up to now, we’ve believed that grooming claws developed independently across several primate lineages up to those alive today. However, new fossil evidence suggests that such claws are, rather, a key feature — they date back at least 56 million years, to the oldest-known primates.

Back in 2013, the study’s lead author Doug Boyer found several curious primate fossils at the University of California Museum of Paleontology. These fossils — distal phalanges, the bones that make the tips of fingers or toes — were hidden in sediment samples collected in Wyoming several decades earlier; as often happens, however, they were left waiting in a drawer in the archives. Based on the shape of these fossils, Boyer suspected that their owners sported grooming claws — in general, distal phalanges topped with a claw will be more narrow and tapered, while those supporting a nail will be flat and wide.

Grooming claws.

Lemurs, lorises, and galagoes have nails on most digits and grooming claws on their second toes, as seen on the feet of two greater slow lorises, Nycticebus coucang, in the Florida Museum mammals collection.
Image credits Kristen Grace / Florida Museum.

Bloch’s work involved material recovered from Bighorn Basin, Wyoming. He discovered what initially looked like a “strange, narrow nail” bone, but on later comparison with modern specimens “it looked just like a tarsier grooming claw,” he recounts. Although smaller than a grain of rice, the bone matched the proportions of grooming claws of Teilhardina brandti, a mouse-sized, tree-dwelling primate.

Claw me, claw thee

These were the first hints that the fingers of early primates had grooming claws. To get to the bottom of things, the duo went out to Omomys Quarry, Wyoming, a site once inhabited by an early primate family, Omomys. Here, they found omomyoid grooming claws at three sites spanning 10 million years in the fossil record. The fossils proved beyond a doubt that early primates sported grooming claws.

Why, then, don’t we have some as well?

“The loss of grooming claws is probably a reflection of more complex social networks and increased social grooming,” said Boyer, an associate professor in the department of evolutionary anthropology at Duke University.

“You’re less reliant on yourself.”

This hypothesis could also explain why some species of (more) solitary primates, such as the titi (subfamily Callicebinae) or owl monkeys (family Aotidae) have re-evolved a grooming claw.

But why develop nails in the first place? The team believes it came down to shifts in how primates got around. As climbing, leaping, and grasping took center stage, claws simply became impractical — whereas nails wouldn’t snag or get in the way of anything.

Furthermore, the claws provide new insight into the lives of ancient primates, the team notes, many of which are only known from fossil teeth. Even these tiny claws can offer insight into how our ancestors moved about, their daily behavior, and their social structures.

“We see a bit of ourselves in the hands and feet of living primates,” Bloch said. “How they got this way is a profoundly important part of our evolutionary story.”

The paper “Oldest evidence for grooming claws in euprimates” has been published in the Journal of Human Evolution.

Mammals were free to occupy day-time niches after dinosaurs disappeared. Credit: Carl Buel.

After the dinosaurs went extinct, mammals crawled out of the dark to take over

New evidence backs up a 75-year-old evolutionary theory that said early mammals had to creep in the darkness to escape dinosaur predators which lurked at day.

Mammals were free to occupy day-time niches after dinosaurs disappeared. Credit: Carl Buel.

Mammals were freed to occupy day-time niches after the dinosaurs disappeared. Credit: Carl Buel.

Behavioral data on 2,415 mammal species, representing 91 percent of all mammal families, was plugged into a computer model that constructed multiple family trees (phylogenies). About 60 percent were nocturnal, like the vampire bat or the four-toed hedgehog, and 26 percent were diurnal, like squirrels or humans. The rest, like the star-nosed mole or muskrat, are characterized as cathemeral, meaning they exhibit irregular activity at day or night, and a few crepuscular (active only at twilight) and ultradian (active in cycles of only a couple of hours at a time) mammals were included in the analysis as well.

The so-called “nocturnal bottleneck” hypothesis was first coined in 1942 by paleontologist Gorden Lynn Wall, who reckoned mammals had to be nocturnal to survive in a dinosaur-dominated world. Ever since the theory was first proposed, scientists have been looking for proof.

There are quite a few clues that point towards a darker mammalian past. Most mammals, humans not included, lack a fovea — a small, central pit composed of closely packed cone cells in the eye, located at the center of the retina — which biologists say can perceive for the sharpest images. The shape of mammalian eyes also seems to favor low-light conditions.

Now, with such an extensive behavioral dataset in their palm, the authors say mammals were likely nocturnal throughout the Mesozoic, an era which lasted between 252 million to 66 million ago. Quite the long night.

Remarkably, the first mammals that were active during both day and night appeared only 200,000 years after the extinction event that wiped out the dinosaurs, as reported in the journal Nature Ecology & Evolution. The researchers at Tel Aviv University in Israel and University College London say these mammalian day-time pioneers were most likely the ancestors of today’s even-toed ungulates (cattle, llamas etc.) but also those of cetaceans like dolphins. In evolutionary time, that’s really fast, signaling that the numerous empty niches favored rapid adaptation of diurnal activity.

The first truly diurnal mammals seem to have appeared 52.4 million years ago, or 13 million years since the last dinosaur was alive. These were the ancestors of simian primates — such as gorillas, gibbons, and tamarins. The analysis bodes well with what our current understanding of the biology of various animal families. The visual acuity and color perception of simians, for instance, is comparable to those of diurnal reptiles and birds, which never left the daytime niche.

“We were very surprised to find such close correlation between the disappearance of dinosaurs and the beginning of daytime activity in mammals, but we found the same result unanimously using several alternative analyses,” explained lead author Roi Maor, Phd. student at Tel Aviv University and UCL.

The research is quite brilliant in the sense that it found a workaround for the scarcity of the fossil record and for the challenge of inferring behavioral traits from fossils. Working with data on the behavior and ancestry of living animals can tell us surprisingly many things about their ancestors’ past. At the same time, no one can say for sure that dinosaurs going extinct is what eventually let mammals out of the dark. For instance, maybe there were actually day-time mammals living alongside dinosaurs. There’s pretty strong evidence, however, that at least most mammals alive until 66 million years ago likely lurked under the cover of darkness.

To come up with more accurate results, the authors plan on populating the mammalian family tree with more species.
Iguana sun basking.

Warm-bloodedness shown to be millions of years older than we thought — maybe as old as the dinosaurs

The first warm-blooded animals may have evolved millions of years earlier than believed, researchers at the University of Bonn report.

Iguana sun basking.

Those of you who have a pet lizard or snake probably know how much they like to bask in the sun or a heat lamp. They’re especially fond of doing this in the morning after a cold night. It’s all because of the way they regulate their internal temperature — reptiles rely on external heat to limber them up, as they can’t don’t use their energy to generate heat. You, me, a mouse, or other mammals and birds instead generate heat internally, by burning calories.

Because of this, reptiles are often referred to as cold-blooded, and as warm-blooded. Cold-bloodedness made a lot of sense in the Earth’s past, as mean temperatures were a lot higher back when reptiles were still news. Today, being cold-blooded is ‘cheaper’ in a nutritional sense — these animals need to eat a lot less because their bodies don’t burn anything to keep warm. Having warm blood means you’re more resilient in the face of environmental factors and allows animals a higher metabolic rate (what you perceive as being ‘lively’,) since the extra thermal energy makes biochemical reactions underpinning their activity take place faster.

Until now we’ve believed that the transition from cold to warm blood took place in a four-legged land animal somewhere around 270 million years ago.

“However, our results indicate that warm-bloodedness could have been created 20 to 30 million years earlier,” says Prof. Martin Sander from the Steinmann Institute for Geology, Mineralogy and Paleontology at the University of Bonn.

Since you can’t exactly slap a thermometer onto a fossil and see how warm the original animal was, the team had to use other methods of discerning between cold and warm-bloodedness. Thankfully, the trait leaves behind certain characteristics in the fossils that the team was able to draw on.

Bone-afide data

Warm-blooded animals tend to grow faster than their cold-blooded counterparts, which is reflected in the structure of their skeleton. Bones are a mix of protein fibers (such as collagen) and a material known as bone mineral, a form of hydroxyapatite. Collagen fibers in particular need to be well ordered during bone development since collagen makes them flexible and binds everything together. The more well ordered these fibers are, the stronger the bone becomes — but it also takes more time to grow.

Ophiacodon bones.

The fossils used for the study.
Image credits Shelton, C.D., Sander, P.M., Long, C. R. Palevol (2017).

Since mammals grow faster than reptiles, their bones are also based on a special structure (fibrolamellar) which allows for faster growth without sacrificing strength. And that’s what the researchers looked for.

Teaming up with his PhD student Christen D. Shelton, Prof. Sander analyzed the humerus and femur bones of the long extinct, lizard-like mammal predecessor Ophiacodon. They found that its bones relied on a fibrolamellar structure, suggesting that the “animal could already have been warm-blooded.”

The finding is especially exciting since Ophiacodon is closely related to both reptiles and mammals — it’s just beyond the spot in the tree of life where these two branches diverge. Up to now, we’ve simply assumed cold-bloodedness was the first type of metabolism to develop since today’s reptiles have the longest evolutionary heritage and are all cold-blooded. Warm blood, the theory goes, developed later as mammals evolved further.

But the findings, coupled with other known or suspected cases of warm-blooded ancient animals, could throw this theory into question.

“This raises the question of whether its warm-bloodedness was actually a completely new development or whether even the very first land animals before the separation of both branches were warm-blooded,” says Sander.

It’s currently just speculation, and the team will need to look at a lot more fossils before they have a clear picture. But if their theory is correct, we would have an interesting couple of questions on our hands: when, and why, did reptiles forgo warm blood?

The paper “Long bone histology of Ophiacodon reveals the geologically earliest occurrence of fibrolamellar bone in the mammalian stem lineage” (original title “L’histologie d’os longs d’Ophiacodon révèle l’occurrence la plus précoce d’os fibro-lamellaire dans la lignée souche mammalienne) has been published in the journal Comptes Rendus Palevol.

New paper explains why predatory dinosaurs walked on two feet while mammals stayed on all fours

A new paper from the University of Alberta details a novel theory as to why predatory dinosaurs took up bipedal movement, while their mammal counterparts didn’t.

Image credits Chase Elliott Clark / Flickr.

Even dinosaurs have ancestors. One feature some of them (carnivores) inherited from these so-called proto-dinosaurs is bipedalism — walking on their two hind legs as opposed to all fours, like for example the sauropods. This trait comes down to the way their tail evolved, explains lead author and postdoctoral fellow Scott Persons

“The tails of proto-dinosaurs had big, leg-powering muscles,” he says. “Having this muscle mass provided the strength and power required for early dinosaurs to stand on and move with their two back feet. We see a similar effect in many modern lizards that rise up and run bipedally.”

The paper contradicts theories which state that early proto-dinosaurs rose on two legs to free their ‘hands’ for hunting. Persons and his team mate Phil Currie, paleontologist and Canada Research Chair, say that such theories don’t explain why some herbivore groups of dinosaurs retained bipedalism. Instead, they believe proto-dinosaurs evolved over time to run faster and over longer distances.

This specialization was reflected in anatomical changes such as longer hind limbs to allow faster walking speeds and smaller fore limbs to reduce overall weight and help improve balance. These changes became significant enough in some proto-dinosaur families that they gave up quadrupedal walking altogether.

Because mammals were initially adapted to burrowing and hiding from the much bigger and more powerful dinosaurs, they didn’t have any need to move fast. They also needed powerful (and heavy) fore limbs to dig. Having a big tail or a muscular back actually became a disadvantage for the burrowers, so they lost their big tail-based leg muscles and for the most part remained quadrupedal.

“Looking across the fossil record, we can trace when our proto-mammal ancestors actually lost those muscles. It seems to have happened back in the Permian period, over 252 million years ago,” Persons says.

“[Having a long tail] also makes the distance a predator has to reach in to grab you that much shorter. That’s why modern burrowers tend to have particularly short tails. Think rabbits, badgers, and moles.”

In the end, burrowing saved mammals from going extinct with the dinosaurs at the end of the Permian. But when mammals did crawl out and some evolved into apex predators, they lacked the tail muscles that would have inclined them towards bipedalism.

The full paper “The functional origin of dinosaur bipedalism: Cumulative evidence from bipedally inclined reptiles and disinclined mammals” has been published in the Journal of Theoretical Biology.

Climate change has already harmed more than half of all mammals

The time where we could think about the effects of climate change in the future tense is long gone. A survey of studies found that the effect of global warming on mammal species, especially endangered species, have been wildly underestimated.

Snow leopards are among the most threatened animals. Climate change has caused massive decline in their population. Credits: Tambako the Jaguar

The study published in the journal Nature Climate Change found that 700 species on the International Union for the Conservation of Nature (IUCN) “red list” were harmed by climate change. This red list is the world’s most comprehensive inventory of the global conservation status of biological species, featuring some of the most iconic and threatened species on the planet. Researchers stress that these effects are being felt now and not at some vague point in the future, expressing their disappointment that most climate studies on biodiversity focus on the effects of climate change 50 to 100 years from now. We need to shift away from that mentality and focus on imminent threats. James Watson, a researcher at the University of Queensland in Australia who participated in the study explains:

“It’s a scientific problem in that we are not thinking about climate change as a present-day problem, we’re always forecasting into the future,” he said, adding, “When you look at the evidence, there is a massive amount of impact right now.”

He and the rest of his team examined some 130 previous studies, putting all their conclusions together. They found that animals from all continents were affected. Animals with highly specialized diets and animals living in high altitudes were especially at risk, but even those with a wide range of diets were suffering. Iconic creatures such as snow leopards, gorillas, and elephants have all suffered from massive declines.

They also showed that animals that breed fast better adapted to the conditions, as were animals who are natural burrowers. At the crossroad of these two traits, rodents came out as natural survivors in the face of climate change. But slow breeders, including primates, elephants, and marsupials, were less able to adapt to the changing conditions. Because they’ve lived for so long in a stable environment, they can’t really adapt to rising temperatures and extreme weather events.

The study also found that previous works have drastically underestimated the effects of global warming. However, they do note that their study was mostly focused on animals from Europe and the Americas, so their findings might be less generalizable to other parts of the world.

“We have seriously underestimated the effects of climate change on the most well-known groups, which means those other groups, reptiles, amphibians, fish, plants, the story is going to be much, much worse in terms of what we think the threat is from climate change already,” he said.

Michela Pacifici of the Global Mammal Assessment program at Sapienza University of Rome, a lead author of the study, says that things are about to get worse in the future — the near future.

“It is likely that many of these species have a high probability of being very negatively impacted by expected future changes in the climate,” she said.

Artist impression of Kimbetopsalis. Credit: Sarah Shelley

Newly discovered beaver-like mammal took over after the dinosaurs disappeared

An asteroid impact wiped out the dominant life forms on the planet, both on land and in the oceans, some 65 million years ago. Like in all matters of life, there are winners and losers, and incidentally those who had most to profit from the demise of the dinosaurs were also the weakest: mammals. Small, battered and restricted to only a couple of ecological niches, not only were the mammals more adapted to a post-apocalyptic Earth devoid of sunshine and with little food to spare, but once everything cleared they simply took over. Now, paleontologists have come across a totally new genus of ancient mammals that used to share the planet with the dinosaurs, but managed to survive the fallout and continued its lineage for millions of years after.

Artist impression of Kimbetopsalis. Credit: Sarah Shelley

Artist impression of Kimbetopsalis. Credit: Sarah Shelley

It’s hard to imagine how the world’s terrestrial dominance rapidly shifted from fierce dinosaurs like T-Rex to mellow, furry creatures like Kimbetopsalis simmonsae. Like other mammals, Kimbetopsalis used to be no bigger than a modern mouse when dinosaurs were still around. Only 500,000 years after the fall of the dinosaurs, however, the critter jumped in size growing to the size of a beaver. That’s the blink of an eye on a evolutionary timescale.

Remarkably, the discovery was made by Carissa Raymond, a sophomore student at the University of Nebraska, who had never gone fossil hunting. Carissa found some odd set of dentures while digging around in the New Mexico desert last summer. She didn’t think too much of them, but when the fossils were shown to her supervisor it was soon clear the student had in fact made a big find. Not only was this a new species of mammal, but a totally new genus – one that was still alive when dinosaurs roamed the Earth (it appeared about 100 million years before extinction event) and represented a lineage that survived for 160 million years. In fact, despite Kimbetopsalis was evolutionary superseded by rodents, its 160-million-year run is longer than that of any mammal species alive today, according to Thomas Williamson, a curator at the New Mexico Museum of Natural History and Science and the project’s leader. “It’s rare for anybody to find one of these,” Williamson said. “I wish I had found it.”

The complex teeth of Kimbetopsalis were adapted to munch on semitropical vegetation. Image: Steve Brusatte/University of Edinburgh

The complex teeth of Kimbetopsalis were adapted to munch on semitropical vegetation. Image: Steve Brusatte/University of Edinburgh

Kimbetopsalis measured a meager three feet in length, and looked sort of like a beaver sans the paddle tail, paleontologists reported in Zoological Journal of the Linnean Society. Judging from the fossilized teeth which include rows of cusps at the back and incisors at the front for gnawing, the animal was a highly specialized plant-eater. In fact, the psalis in Kimbetopsalis is latin for cutting shears, in reference to its blade-like teeth.

There’s a lot scientists can learn simply by looking at teeth, as these tell what kind of food was available at the time and what the environment or climate used to look like. For instance, despite today’s New Mexico is largely covered in desert, 66 million years ago it was filled with a lush tropical forest. More than anything, though, Kimbeopsalis is an exciting find in science since it helps us understand how one of the most dramatic transitional periods in the history of life occurred.

“[During the Jurassic] these animals were all pretty small,” said Dr Stephen Brusatte from the University of Edinburgh, one of the researchers involved in the study.

“Then the asteroid hit, wiped out the dinosaurs and suddenly – in geological terms – this [group of animals] started to proliferate and get bigger.

“That’s how the rise of mammals started and really the end result of that is us being here today.”

How humans turned “safari” to “safe” – what large mammals diversity worldwide would look without us

The fact that the greatest biodiversity of large mammals we know of today is recorded in Africa is a legacy of past human activity, not climate or environmental phenomena, new study reveals. The paper theorizes at how the world today would look if Homo sapiens had never existed.

In a previous analysis, the researchers from Aarhus Univeristy, Denmark, they showed how the mass extinction of large mammals during the last Ice Age and the subsequent millennia, most notably the late-Quaternary megafauna extinction, is largely explainable by the expansion of modern humans across the world.

Building on the findings of their previous research, they imagine what the natural worldwide diversity patterns of mammals would be like in the absence of past and present human impacts. They base this human-free world on estimates of the natural distribution of each species according to its ecology and biogeography by overlapping it with the current natural environment template. The results suggest that in a world without us, most of northern Europe would probably now be home to more common animals such as wolves, Eurasian elk (moose) and bears, but also much larger mammals such as elephants and rhinoceroses. North and South America would also boast much more diverse populations of big mammals.

The natural diversity of large mammals is shown as it would appear without the impact of modern man (Homo sapiens). The figure shows the variation in the number of large mammals (45 kg or larger) that would have occurred per 100 x 100 kilometer grid cell. The numbers on the scale indicate the number of species.
Image via sciencedaily

“Northern Europe is far from the only place in which humans have reduced the diversity of mammals — it’s a worldwide phenomenon. And, in most places, there’s a very large deficit in mammal diversity relative to what it would naturally have been,” says Professor Jens-Christian Svenning, Department of Bioscience, Aarhus University, who is one of the researchers behind the study.

Africa, the final frontier

Current mammal diversity maps show that Africa is virtually the only continent where large mammals still boast good numbers and diversity. The world the researchers envisioned on the other hand shows far greater distribution of high large-mammal diversity across most of the world, particularly in North and South America, areas that are currently relatively poor in large mammals.

Image via wikipedia

“Most safaris today take place in Africa, but under natural circumstances, as many or even more large animals would no doubt have existed in other places, e.g., notably parts of the New World such as Texas and neighboring areas and the region around northern Argentina-Southern Brazil,” says Postdoctoral Fellow Soren Faurby, Department of Bioscience, Aarhus University, lead author on the study. “The reason that many safaris target Africa is not because the continent is naturally abnormally rich in species of mammals. Instead it reflects that it’s one of the only places where human activities have not yet wiped out most of the large animals.”

Africa then alarmingly becomes not the most-diverse continent due to climate or environment, but the one least un-diversified by humans. The underlying reasons cited by the team includes evolutionary adaptation of large mammals to humans as well as greater pest pressure on human populations in long-inhabited Africa in the past.

Platform to improve nature preservation

The study’s openly accessible data set of natural range maps for all late-Quatenary mammals gives scientists a powerful tool to analyse the natural patterns in the species diversity and composition of mammals worldwide. The data it shows can be used to provide a better understanding of the natural factors that determine the biodiversity in a specific area.

Today, there is a particularly large number of mammal species in mountainous areas. This is often interpreted as a consequence of environmental variation, where different species have evolved in deep valleys and high mountains. According to the new study, however, this trend is much weaker when the natural patterns are considered.

“The current high level of biodiversity in mountainous areas is partly due to the fact that the mountains have acted as a refuge for species in relation to hunting and habitat destruction, rather than being a purely natural pattern. An example in Europe is the brown bear, which now virtually only live in mountainous regions because it has been exterminated from the more accessible and most often more densely populated lowland areas,” explains Soren Faurby.

The study has been published in the scientific journal Diversity and Distributions.

The Quaternary period saw the extinctions of numerous predominantly larger, especially megafaunal, species, many of which occurred during the transition from the Pleistocene to the Holocene epoch. Among the main causes hypothesized by paleontologists are natural climate change and overkill by humans. Image: Wikimedia Commons

The Sixth Grand Extinction Will Be ‘Invisible’

Life on Earth has so far passed through five distinct crises that threatened to wipe it out, typically referred to as mass extinctions. The direst one was some 252 million years ago when 96 percent of marine species and 70 percent of life on land became extinct following a yet unconfirmed series of cataclysmic events known as the end-Permian extinction. Mass extinction is an alarming, scary term, but while it’s natural to shiver at the idea, it’s worth considering that we’re actually living through a mass extinction, the sixth so far. This one is different though. While past mass extinctions were triggered by cataclysmic events, the sixth great extinction will be the only one caused single-handedly by a singular species: us. If this wasn’t sad enough, the sixth extinction might be remembered (if there’s anyone left to recollect) as the ‘invisible’ extinction.

The sixth grand extinction

The Quaternary period saw the extinctions of numerous predominantly larger, especially megafaunal, species, many of which occurred during the transition from the Pleistocene to the Holocene epoch. Among the main causes hypothesized by paleontologists are natural climate change and overkill by humans. Image: Wikimedia Commons

The Quaternary period saw the extinctions of numerous predominantly larger, especially megafaunal, species, many of which occurred during the transition from the Pleistocene to the Holocene epoch. Among the main causes hypothesized by paleontologists are natural climate change and overkill by humans. Image: Wikimedia Commons

Humans can be beautifully creative, yet brutally inconsiderate at the same time of the world they live in and share with other creatures. It’s precisely our uncanny intellect and creativity – which we’re so proud of and which are often trumpeted as key differential qualities that separate us from beasts – that is dooming this planet. Because our technology and means of manipulating resources have evolved so rapidly, few species can keep up. A growing number of ecosystems are faced with situations where the environment is no longer predictable, either because of direct human interference (deforestation, loss of habitat, pollution) or indirect, through global warming (shorter seasons, droughts, ocean acidification, and so on).

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Biologists and paleoecologists estimate that humans have driven roughly 1,000 species extinct in our 200,000 years on the planet. Since 1500 we have killed off at least 322 types of animals, including the passenger pigeon or the Tasmanian tiger. Only yesterday ZME Science reported how the Northern White Rhino is down to only five specimens as a result of human poaching. Another 20,000 or more species are now threatened with extinction according to the International Union for the Conservation of Nature, which keeps a list of all the known endangered plants and animals on the planet. The population of any given animal among the five million or so species on the planet is, on average, 28 percent smaller, thanks to humans.

extinction

A thought experiment

As if this wasn’t bad news enough, there’s another chilling prospect that might make the whole event even more frustrating: no one might ever know that most of these species existed. Say a doomsday event was to shatter human knowledge and civilization as we know it, forcing the survivors to start from square one. Within a couple of generations, common knowledge about the world we take for granted today (like the existence of lions, rhinos or turtles) might vanish. No problem, post-meltdown paleontologist will be able to piece together the puzzle of past existence on Earth by studying fossil remains. According to Roy Plotnick, a palaeontologist at the University of Illinois at Chicago, this might be useless for most animals on Earth.

extinction1

One study found that although human population has doubled in the past 35 years, the number of invertebrate animals – such as beetles, butterflies, spiders and worms – has decreased by 45% during that same period. “We were shocked to find similar losses in invertebrates as with larger animals, as we previously thought invertebrates to be more resilient.” said Ben Collen of the U.K.’s University College London, one of the study authors. Image: Science

 

Of the 715 mammal species listed on the International Union for the Conservation of Nature (IUCN) Red List only 90 of them are represented in the fossil record or 13%. The rest of them will be gone without a trace.

“We assume a lot about the persistence of human recordings. Who can read an 8-inch floppy disk these days? The rock record is a much more persistent way of recording information. I’m a reader of science fiction, and I think about post-apocalyptic worlds. What would we make of what had happened in the long-ago past?” said Plotnick in an interview for Nature.

According to Plotnick, rodents and bats are the most vulnerable at becoming completely forgotten. Body size is an important factor as far as fossils go, but geographical distribution is by far the most significant. You have much less chance of getting caught in the fossil record if you’re only found in one place. Birds and reptiles are also particularly vulnerable, especially island species.

“As a palaeontologist I think about the appearance and extinction of species — that shows how we do geological time. One big signal is the mass extinction of mammals in North America, Europe and Australia, when hunters arrived. That would be the stratigraphic marker.” Plotnick says.

Plotnick ends his interview by striking a humorous chord – we’ve bred so many pigs all over the world and, consequently, scattered their bones all over the place that a post-current era civilization might conclude this planet was once dominated by hogs. They wouldn’t be that far away from the truth.

ancient mammoth

Diversity is what helped mammals survive through deep time

ancient mammoth

After the great dinosaur extinction some 65 million years ago, mammals finally had their big shot as numerous niches became free for the taking. Thus, from mouse size, some mammal species surfaced which were as large as a bus, the so called mammal megafauna, like mammoths, giant sloths or saber-tooth tigers. However, a dire trial of their own was to come. Through out millions of years, mammals were challenged by a series of alternating climate cycles. According to a recent study by scientists at Vanderbilt University, diversity was the key to their survival.

The study focused on the various ups and downs in range and diversity of families of mammals that inhabited the continental U.S. during  the period that began with the Eocene and ended 12,000 years ago with the terminal Pleistocene extinction. The scientists involved in the study looked at a myriad of fossil records, however its almost impossible to distinguish highly related species between one another, so instead they concentrated on performing a family-level analysis. They analyzed 35 different families, such as Bovidae (bison, sheep, antelopes); Cricetidae (rats, mice, hamsters, voles); Equidae (horses, donkeys); Ursidae (bears); Mammutidae (mammoths); and Leporidae(rabbits and hares).

What their analysis showed was that the range and distribution of mammalian families stayed surprisingly consistent, despite major climate changes through out the 56 million year period, which saw temperature differences of several degrees, in alternating warm/cold cycles, and finally ended with the Ice Ages that alternated between relatively cold glacial and warm interglacial periods.

“These data clearly show that most families were extremely resilient to climate and environmental change over deep time,” said Larisa R. G. DeSantis, assistant professor of earth and environmental studies at Vanderbilt University who directed the study.

The scientists’ research shows that families retained more or less similar niches through out millions of years and is consistent with the idea that family members may inherit their ranges from ancestral species. However, the biggest takeaway is the fact that the researchers observed a highly important link  between a family’s diversity and its range – the greater diversity a family has, the better the stability and range.

“Diversity is good. The more species a family has that fill different niches, the greater its ability to maintain larger ranges regardless of climate change,” says DeSantis.

Mammals have demonstrated a remarkable ability to adapt to their environmental conditions, re-sizing and migrating easily. Understanding how mammalians have adapted through out deep geological time is highly important to understanding how they will adapt in the future, especially considering that one in four species of land mammals in the world faces extinction.

“Before we can predict how mammals will respond to climate change in the future, we need to understand how they responded to climate change in the past,” says DeSantis.

“It is particularly important to establish a baseline that shows how they adapted before humans came on the scene to complicate the picture.”

The findings were published in the journal PLoS One

source: Futurity  / image credit : Wikimedia Commons.

Scanning electron microscope image showing the ‘tectonic' effects of the collision of one spherule with another during the cosmic impact. (c) UCSB

Comet might have catastrophically collided with Earth 13,000 years ago

A recently published study suggests that the Earth might have been visited by a giant space rock 13,000 years ago, an event which might have sparked an unusual cold period in the planet’s climate history.

The Younger Dryas, also known as the Big Freeze, was a brief period of cold climatic conditions and drought which occurred some 13,000 years ago. Scientists are still debating what exactly caused this sudden shift in climate, and one highly controversial theory has it that a major cosmic impact with Earth might be to blame for the onset of this unusual cold climatic period. Suspicions of such an event have been voiced for a few years now, but up until now no clear evidence to support this hypothesis was found.

Recently, an international team of researchers  has identified a nearly 13,000-year-old layer of thin, dark sediment buried in the floor of Lake Cuitzeo in central Mexico. This layer is filled with an eclectic geological mix of materials, including nanodiamonds, impact spherules, and more, which, according to the researchers, are the result of a cosmic body impacting Earth.

Scanning electron microscope image showing the ‘tectonic' effects of the collision of one spherule with another during the cosmic impact. (c) UCSB

Scanning electron microscope image showing the ‘tectonic' effects of the collision of one spherule with another during the cosmic impact. (c) UCSB

The theory was long dismissed since no impact crater could be found, but the researchers involved in the study argue that a lot of cosmic bodies simply disintegrate into the atmosphere before even getting the chance to reach the ground. They claim the hypothetical comet event might have actually exploded in mid-atmosphere.

“If you don’t have a crater, you’re a little bit lost,” said space scientist Ted Bunch of Northern Arizona University, a member of the research team. “Here what we have is something similar to an aerial bomb blast. With these aerial bursts, with time all the evidence is wiped away unless it’s buried.”

Apart from the Mexican site, the researchers also identified sediment layers of the same age, dating back 13,000 years ago,  in Canada, the United States, Russia, Syria and various sites in Europe. The same  family of nanodiamonds, including the impact form of nanodiamonds called lonsdaleite, which is unique to cosmic impact, and high velocity collided spherules were found. These features are impossible to form through geologically natural processes here on Earth, and seem to lead to the conclusion of a cosmic impact. Since evidence has been scattered through the world, including Mexico and the tropics, with this latest find, it seems a large, previously fragmented body, greater than several hundred meters in diameter entered the atmosphere at a relatively shallow angle.

“If you have an event like this in a 1- or 2-inch layer that dates to exactly the same age over a very large area, and you have high-temperature materials and nanodiamonds in there, the evidence pretty well points to an event that as pretty disastrous,” Bunch said.

A heat flash fireball in the sky might have caused an ice age

Images of single and twinned nanodiamonds show the atomic lattice framework of the nanodiamonds. Each dot represents a single atom. (c) UCSB

Images of single and twinned nanodiamonds show the atomic lattice framework of the nanodiamonds. Each dot represents a single atom. (c) UCSB

Currently, there are only two known continent-wide layers with abundance peaks in nanodiamonds, impact spherules, and aciniform soot. One is the Younger Dryas layer, and the other is 65-million-year-old Cretaceous-Paleogene boundary layer, which sets it on par with the current leading dinosaur extinction theory of a giant asteroid impact. The Younger Dryas period is associated with the extinction of a large number of mammals, including Mammoths and Saber-toothed cats.

“The timing of the impact event coincided with the most extraordinary biotic and environmental changes over Mexico and Central America during the last approximately 20,000 years, as recorded by others in several regional lake deposits,” said James Kennett, professor of earth science at UC Santa Barbara. “These changes were large, abrupt, and unprecedented, and had been recorded and identified by earlier investigators as a ‘time of crisis.’ “

A comet impacting Earth’s atmosphere at a typical velocity of 30 miles/second would have caused a deadly heat flash reaching about 3,000 to 4,000 degrees Fahrenheit (1,600 to 2,200 degrees Celsius), obliterating any sings of life across a wide radius around it – like a deadly ball of fire. The researchers aren’t claiming, however, that this celestial impact event actually started the Younger Dryas  ice age, but rather argue that it surely had a significant effect on Earth’s climate.

“We’re not going to come out and say it did do it, but it’s more than a coincidence that the timing happened exactly the time that a lot of climatic conditions occurred and you had the loss of various species,” Bunch said.

The researchers’ findings were published in the journal Proceedings of the National Academy of Sciences.

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A mouse skull relative to an elephant's skull. (c) Alistair Evans

24 million generations later, a mouse grows into an elephant

A mouse skull relative to an elephant's skull. (c) Alistair Evans

A mouse skull relative to an elephant’s skull. (c) Alistair Evans

Around 140 millions years ago, mammals didn’t even outsize a modern day mouse, as dinosaurs dominated Earth’s crowded surface. As the latter became extinct, a myriad of free ecosystems and niches opened up, including those once dominated by giant plant eating dinosaurs, and mammals where quick to fill these up. After compiling and analyzing a fossil record data set of mammal body size during the last 70 million years, researchers established some very fascinating growth rates, of great interest to the study of evolution. For instance, scientists found that it took 24 million generation for a mammal to grow in size from mouse to elephant proportions.

“Big animals represent the accumulation of evolutionary change, and change takes time,” said evolutionary biologist Alistair Evans of Australia’s Monash University.

As modifications occurred in their diet, environment, metabolism and so on, mammals naturally evolved. But how fast does evolution occur, and does the rate differ for certain types of mammals? Well size-wise, it’s been found that odd-toe ungulates (horse, sheep, rhinos) have the highest rate of growth, rodents are somewhere in between, carnivores at the bottom, while primates have an even lower rate of growth in size. In the oceans, however, body size could change twice as fast.

To come to these conclusions, the researchers analyzed the teeth, skulls and limb bones of ancient animals to estimate their size, and then compared them with current day species. It took whales 5 million generations, or 30 million years, to go from 25 kilograms to 190 tons, or the weight of blue whale. Actually, marine life, whales in particular, are the only mammals getting bigger nowadays. As habitat loss, global warming and human hunting are rampant, it doesn’t pay to be big anymore – size can be lost 100 times faster than it’s gained, according to the study published this week in Proceedings of the Royal Academy of Sciences.

In a previous study we showcased on ZME Science, researchers found that for every degree Celsius added in temperature, a variety of plants lose between 3-17% in size, while fish shrink by 6-22%.

UPDATE: a recent massive study that analyzed hundreds of living and extinct mammal species, coupled with thousands of images, found that the earliest placental mammal surfaced some 200,000 years after the dinosaurs went extinct , roughly 65 million years ago.