Nature is often riddled with paradoxes. On the one hand, you have species that expend a great deal of energy to embellish their appearance to attract mates or to communicate with peers. On the other hand, the same traits can make these individuals sitting ducks to predators. It’s on this tightrope, anchored by natural selection on one end and sexual selection on the other, that many species dance.
However, this is an oversimplification. New research from the University of New South Wales (UNSW) shows that standing out in appearance doesn’t necessarily invite predators for dinner. In fact, as the field experiments showed, being too flashy may actually dissuade predators.
For their study, the researchers led by Terry Ord, an evolutionary ecologist and Associate Professor at UNSW’s School of Biological, Earth and Environmental Sciences, placed a staggering 1,566 robotic lizards on trees on the campus of a university in Borneo.
The robot consisted of a box filled with motors and microelectronics, on top of which sat a plasticine draco lizard that was cast out of a realistic model. The robots performed one of three functions: a conspicuous visual display, a conspicuous ornament, or remained cryptic. The latter acted as a negative control, in that the researchers assumed that this state would be least predated by the many birds, cats, and snakes around the campus. The putty-like plasticine is great for assessing predation because you can clearly see all the pecking, biting, and scratching left by attackers.
Draco lizards are known as ‘gliding lizards’, as they have retractable gliding membranes. They communicate with extendable throat-fans, called dewlaps, which are diverse in color, shape, and size among species. Ord fitted a colorful plastic gliding membrane to each of the many robot lizards that littered the trees at the Kota Samarahan campus in Borneo, which was displayed or retracted at regular intervals by a servo motor controlled a micro-controller, mimicking real draco behavior.
Ord and colleagues embarked on this research looking for clues as to how exactly visible predator warning systems evolve in prey systems. Some animals employ bright, contrasting colors, such as the black and yellow of many wasps and the red of ladybird beetles — a phenomenon known as aposematism — as if to advertise ‘I’m not good to eat. Moreover, if you do decide to eat me, you will die in horrible pain!’
But, you see, this is a chicken or the egg dilemma. How did predators know to avoid these prey that displayed warning systems in the first place?
“There’s a paradox, when the first prey evolves a conspicuous signal, the predators are not going to know what that signal is about, the prey are going to get attacked, and they’re not going to reproduce to pass their genes onto the next generation,” Ord told Cosmos Magazine.
“How do you actually get from point A – that’s being cryptic and hiding – to point B, which is being conspicuous and deliberately advertising that you’re not profitable to predators.”
Instead of finding that the flashiest draco lizard decoys had their heads chopped off in overwhelmingly large numbers compared to controls, the researchers actually found that “robotic prey that performed a conspicuous display were equally likely to be attacked as those that remained cryptic.” Furthermore, predators avoided attacking robotic prey with a fixed, highly visible ornament, the researchers noted. In other words, the oddest animals were visited by predators the least.
Ord and colleagues refer to the deterrence of predators by stand-out features as “predator conservatism”, challenging the entrenched notion that conforming prey that looks like everyone else makes the animal safer.
Today, we know that the Basilosaurus is the first ancient whale humanity has ever found. But back when it was first described, the animal’s huge proportions earned it the name of ‘king lizard’. And although technically incorrect, the name isn’t undeserved; during its day, the Basilosaurus ruled the waters of Tethys with an iron flipper and a really impressive set of teeth.
This creature lived 40 to 35 million years ago, during a part of geologic time known as the late Eocene. The dinosaurs were quite well gone by this time, and mammals were well on the way to dominating the planet. The Basilosaurus was also a mammal — a whale, no less — and could grow up to 60 feet (a bit over 18m) in length. Needless to say, you can’t skip meals and grow so large. But this species likely had no issues getting full, as the Basilosaurus was, by all indications, a formidable apex predator.
It was first described in 1834 from fragments of a skeleton found in the US. Due to the sheer scale of the fossils, their striking similarity in shape and function to marine predatory dinosaurs, poor availability, and the limits of paleontological understanding of the day, the species was initially assumed to have been a dinosaur — and christened the ‘king of the lizards’, Basilosaurus.
The academic story of this genus starts with B. cetoides, the first ancient whale species ever discovered, which was unearthed in Louisiana around 1830 by Richard Harlan and still serves as the type species of Basilosaurus.
Details from the dig and the wider goings-on around the fossils aren’t very good from the time, but we do know that bones from this dig were sent to the American Philosophical Society by Judge Henry Bry of Ouachita County, Louisiana and Judge John Creagh of Clarke County, Alabama, according to theEncyclopedia of Alabama. Here, they were examined by Richard Harlan, one of the US’s earliest paleontologists and naturalists, who would end up christening the new species.
Upon first examination, Harlan was very excited. Comparing the bones he received to those of Plesiosaurus and Mosasaurus, two species of marine dinosaurs that were already described at the time, he concluded that the new species grew no less than 80–100 ft (24–30 m) long. Still, there were enough structural similarities between its vertebrae and those of Plesiosaurus, as well as between its skull and that of Mosasaurus, for Harlan to assume that the species were related. At the very least, he assumed, they lived around the same time.
The first signs that this name wasn’t really spot-on came when Harlan took his specimens to the UK for consultation with his peers there. Richard Owen, a controversial figure but a superb paleontologist, observed that the animal’s molars were two-rooted. No known fish or reptile at the time showed the same structure, and Owen suggested the animal might have been a whale instead. The two even agreed to rename it Zeuglodon cetoides (“whale-like yoke teeth”).
A few years later the other known species, B. isis, would be described based on fragments of bone recovered from Egypt. Although the first full skeleton of B. isis wouldn’t be unearthed until 2016, the discovery of this species and its fossil association with species that were known to have been whales at the time further suggested that all Basilodons were, in fact, mammals. This was helped by the fact that Basilosaurus fossils actually became quite common over time, so much so that in the 19th century they were even used as andirons, furniture, or decoration.
Over the years, paleontologists have wisened up to the fact and tried to change the genus’ name. However, zoological naming conventions meant that the original name stuck. Today, the Basilosaurus is the state fossil for Alabama and Mississippi.
How did it used to live?
One thing that Harlan got right about the Basilosaurus was that it was large. This whale was bigger even than some predatory dinosaurs that came before it, and it undoubtedly threw its weight around the ancient, lost sea of Tethys.
Another thing it definitely threw around were bites. Unlike most whales today, Basilosaurus didn’t filter feed, it hunted. Its jaws were lined with several types of teeth, including molars and canines, which are specialized for chewing and ripping, respectively. Such teeth are characteristic of meat-eating species.
Two other important characteristics of the species are a skull asymmetry and a relatively low intracranial volume. The first is a trait it shares with modern toothed whales such as orcas. Today, this asymmetry is associated with whales’ ability to produce high-frequency sounds for echolocation; Basilosaurus likely didn’t have this ability, however, and its skull was asymmetrical in order to house a fatty sensory organ meant to help it hear underwater. The lack of room for a big brain inside its skull likely means that Basilosaurus was not a social species, like whales are today, and that it also wasn’t as capable from a cognitive standpoint.
Such traits can be indicative of an evolutionary ‘work-in-progress’. The Basilosaurus seems to have been the first whale species to live entirely underwater, marking the point where the lineage of walking whales finally took the plunge.
It most likely spent its day as a solitary hunter, or at most, one that lived in small groups. Social interactions are extremely demanding, from a cognitive point of view, and Basilosaurus’ brain just seems to have been too small to adequately navigate living in a group.
Still, who needs big brains when you have big brawns? Analysis of fossilized, scarred Dorudon skull bones — this is another genus of prehistoric whale that was the preferred prey of Basilosaurus — suggests that the king of lizards could bite down with 3,600 pounds per square inch (PSI).
To put things into perspective, that’s 233 times more pressure than a fully-loaded M1A2 main battle tank exerts on the ground under its tracks. Most industrial hydraulic presses in use today exert between 1,000 to 3,000 PSI, which is still under the estimated high ofr Basilosaurus. You do not want to get bitten by one of these.
With big bites, however, also comes good manners. Wear patterns on Basilosaurus teeth suggest that the animal bit and then chewed its food, unlike most predators today, whose teeth are specialized in ripping chunks of meat off the bone, that are then gulped up whole. In regards to what they ate, stomach contents seem to indicate that B. cetoides hunted fish and large sharks exclusively, while we know from Dorudon skulls that B. isis would also hunt these. Dorudon was a larger animal, related to today’s dolphins, and B. isis likely focused on delivering a killing blow to its head before tearing it apart while feeding (many Dorudon skeletons, especially those showing signs of predation from Basilosaurus, are found disarticulated).
King no more
The Basilosaur genus went extinct, with our last fossil evidence of them hailing from around 40 million years ago. They didn’t leave behind any direct descendants which, judging from their teeth, isn’t the worst thing to have ever happened.
We’re not entirely sure why they disappeared. Sometime around 40 million years ago, something happened to bring these toothy kings low. However, the fact that other toothed and baleen whales are around today suggests these smaller relatives of the Basilosaurus out-competed them in the end. It might have been their big brains, it might have been their social nature, it could even have been their more modest appetites; for now, it remains a mystery.
The fossil of a 15-meter-long extinct species of dolphin is helping us better understand how different lineages of marine mammal independently evolved the same characteristics.
The species, christened Ankylorhiza tiedemani lived about 25 million years ago during the Oligocene in what today is South Carolina. It belonged to a group of large dolphins (Odontoceti) whose best-known modern representative is the orca (killer whale).
The anatomy of this fossil suggests that it was likely a top predator in its day. It shares several features with today’s baleen and toothed whales despite not being directly related to these groups, the authors report. This suggests that these animals evolved their shared swimming adaptations independently from one another, a phenomenon known as parallel evolution.
Like whales in a pod
“The degree to which baleen whales and dolphins independently arrive at the same overall swimming adaptations, rather than these traits evolving once in the common ancestor of both groups, surprised us,” says Robert Boessenecker of the College of Charleston in Charleston, South Carolina, first author of the paper describing this fossil.
“Some examples include the narrowing of the tail stock, increase in the number of tail vertebrae, and shortening of the humerus (upper arm bone) in the flipper.
Comparison with lineages of seals and sea lions reveal that the two families went down very different evolutionary paths as they transitioned from a land- to a marine-based lifestyle. The initial differences between these lineages were slight, the team explains: Ankylorhiza’s ancestors had one extra row of finger bones in their flippers and a “locking elbow joint”. Still, these factors lead to them developing different swimming styles and skeletal structures.
Another thing the authors note is that Ankylorhiza is the first echolocating whale to become an apex predator. According to the team, it was “very clearly preying upon large-bodied prey like a killer whale”. Its extinction cleared an ecological niche that sperm whales and a lineage of shark-toothed dolphins (both extinct) evolved into. Later still, killer whales would evolve into the same niche around 1 or 2 million years ago.
Ankylorhiza was first described from a skull fragment found during dredging of the Wando River, South Carolina, in the 1880s. A nearly-complete skeleton was later unearthed in the 1970s. The one described in this paper was found in the 1990s by commercial paleontologist Mark Havenstein at a building site and donated it to the Mace Brown Museum of Natural History to allow for its study.
“Whales and dolphins have a complicated and long evolutionary history, and at a glance, you may not get that impression from modern species,” Boessenecker says. “The fossil record has really cracked open this long, winding evolutionary path, and fossils like Ankylorhiza help illuminate how this happened.”
Boessenecker says that there are “many other unique and strange early dolphins and baleen whales from Oligocene aged rocks in Charleston, South Carolina,” including fossils of juvenile Ankylorhiza and specimens of related species. Both filter-feeding and echolocation first appeared during the Oligocene, he adds, so these fossils should give us a very good peek into how they came to be.
The paper “Convergent Evolution of Swimming Adaptations in Modern Whales Revealed by a Large Macrophagous Dolphin from the Oligocene of South Carolina” has been published in the journal Current Biology.
The vast majority of U.S. households own at least one pet and according to a national pet owners survey, there were approximately 95.6 million cats living in households in the United States in 2017. Along with dogs, cats are the most popular pets — but while many of us truly adore these sweet fur balls, pet felines are natural-born killers that can wreak havoc on ecosystems.
Researchers at North Carolina State University and the North Carolina Museum of Natural Sciences distributed GPS trackers to pet owners in six countries, most of which were used in the U.S., U.K, Australia and New Zealand.
By the end of the study, the researchers had collected data on the movements and prey-catching of 925 house cats — and the results were gruesome.
The cats killed up to 10 times more wildlife than a comparable predator in the wild. Most of the carnage took place close to home, around a 100-meter radius of the household where cats spend most of their time outside.
“Since they are fed cat food, pets kill fewer prey per day than wild predators, but their home ranges were so small that this effect on local prey ends up getting really concentrated,” said Roland Kays, the study’s lead author. “Add to this the unnaturally high density of pet cats in some areas, and the risk to bird and small mammal population gets even worse.”
Previously, a 2013 study found that pet cats kill between 1 and 4 billion birds each year and up to 22 billion other mammals.
“We knew cats were killing lots of animals – some estimates show that cats in North America kill from 10 to 30 billion wildlife animals per year – but we didn’t know the area in which that was happening, or how this compared with what we see in nature,” Kays said.
The researchers computed the number of animals killed every year by house cats — with some adjustment since not all prey is brought home by cats — and then divided this number of the surface area in which the cats hunted. They found that house cats killed 14.2 to 38.9 animals per 100 acres, or hectare, per year, depending on how lazy or active the house cat is. Most of the ecological damage is done in disturbed habitats, such as housing developments, the researchers reported in the journal Animal Conservation.
For comparison, a jungle cat kills around 400 prey per month. However, its range is around 600 hectares while a house cat’s range is around 3.5 hectares. When the researchers did the math, house cats actually killed 4 to 10 times more prey per unit area than their wild counterparts.
“Because the negative impact of cats is so local, we create a situation in which the positive aspects of wildlife, be they the songs of birds or the beneficial effects of lizards on pests, are least common where we would appreciate them most,” said study co-author Rob Dunn from NC State. “Humans find joy in biodiversity, but we have, by letting cats go outdoors, unwittingly engineered a world in which such joys are ever harder to experience.”
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Killifish in Trinidad that live with predators in their environment grow more brain cells than their less-stressed peers, a new paper found.
What doesn’t kill you makes you stronger — but it seems they also make you brainier. New research suggests that animals living in predator-heavy environments grow more brain cells than animals that face little to no predation. The findings were made using a group of killifish in a river in Trinidad that is separated into individual populations by waterfalls. These waterfalls block predators from swimming upstream.
Outsmarting the competition
“The killifish living downstream live among predatory fish, while the fish upstream do not,” Josh Corbo, Cancer Research Training Award (CRTA) Fellow at the National Cancer Institute and co-author of the study, told Andrew Concatelli. “Our central question was: how does negative stimuli—predation—in the environment affect the rate of brain cell proliferation?”
“The implication of our research reaches much farther than the Northern Mountain Range of Trinidad. The topic of how the environment we live in affects our health concerns many disciplines, from public health to sociology. Our research draws more attention to our understanding of the relationship we as organisms have with our environment.”
The team writes that while environmental factors are known to influence brain cell proliferation, contributing to brain plasticity and a greater ability to adapt to these factors, there is no research to date on whether environmental factors trump genetic ones in this regard. In other words, on whether the conditions we live in can shape our brain more than our genetics.
To find out, they examined free-living populations of Trinidadian killifish (Rivulus hartii) exposed to very different environmental conditions. Together with Margarita Vergara, now earning a master’s in clinical embryology at the University of Oxford, Corbo sectioned brain tissues used a procedure known as immunohistochemistry to quantify the formation of new brain cells in these animals. The research was carried out while both authors were majoring at Trinity College, Connecticut.
The fish that lived in predatory-heavy areas showed higher rates of brain cell proliferation (roughly twofold higher) and faster brain growth relative to body size than their peers. “Cell proliferation differs among brain regions but is correlated across brain regions,” the authors note, showing that this effect is brain-wide but not necessarily uniform. However, wild-caught fish from predator-heavy areas also had a smaller relative brain size in their early adulthood.
In order to check whether the effect was genetic or environmental in nature, the team also reared a new generation of fish from members in both (predatory-heavy and predatory-free) environments in uniform lab conditions for between 54 and 82 days.
Animals descended from predation-heavy environments also showed a higher rate of brain cell proliferation and faster brain growth compared to those descended from predator-free areas. Furthermore, they found that wild-caught fish had greater cell proliferation in the forebrain than laboratory-reared fish, but very similar everywhere else. This, they explain, suggests that the effect is environmental, not genetic.
“However, both populations showed similar patterns of divergence in the wild and in captivity, indicating that the predator environment per se does not contribute to the enhancement of cell proliferation by the natural habitat,” the team writes.
“The differences in cell proliferation observed across the brain in both the field and [laboratory] studies indicate that the differences are probably genetically based and are mediated by evolutionary shifts in overall brain growth and life-history traits.”
The team says that the observed changes among the two populations could be explained through several different mechanisms. Either individuals are increasing the rate at which they generate new brain cells as a response to predators, or we could be seeing the effects of natural selection at work — in essence, that brainy fish go on to reproduce while the rest get eaten. Alternatively, the presence of predatory fish could improve conditions for the killifish that evade capture, for example by making food more readily available to them through lower competition, which could lead to changes in brain cell proliferation.
The paper “Predation drives the evolution of brain cell proliferation and brain allometry in male Trinidadian killifish, Rivulus hartii” has been published in the journal Royal Society B: Biological Sciences.
New research at Western University shows that animals can suffer post-traumatic stress disorder-like symptoms following exposure to predators.
Black-capped chickadee. Image via Skitterphoto.
Fear, especially strong fear such as that generated by life-threatening events, can cause significant and long-lasting changes in the circuitry of our brains. These neural changes lead to a host of shifts in behavior that we collectively refer to as post-traumatic stress disorder (PTSD).
Wild animals also experience these same changes in traumatic situations, new research shows. Fear of predators can lead to enduring neural changes that induce fearful behavior, comparable to effects seen in human PTSD patients.
“These results have important implications for biomedical researchers, mental health clinicians, and ecologists,” explains Liana Zanette, a biology professor in Western’s Faculty of Science and lead author of the paper.
“Our findings support both the notion that PTSD is not unnatural, and that long-lasting effects of predator-induced fear with likely effects on fecundity and survival, are the norm in nature.”
The team worked with wild-caught black-capped chickadees at Western’s Advanced Facility for Avian Research (AFAR). The birds were individually exposed to audio recordings of either predators or non-predator species for two days. Afterward, all birds were allowed to flock together in outdoor conditions for a week, during which they were not exposed to any further audio recordings.
They gauged ‘enduringly fearful behavior’ after this week-long period by measuring each individual’s reaction to hearing a chickadee alarm call distinct from those they were exposed to seven days previously. The team estimated each bird’s levels of fearfulness by measuring how long they remained ‘vigilant and immobile’ (i.e., ‘freezing’) upon first hearing the alarm calls. They used freezing as a proxy as it is an anti-predator behavior demonstrated in almost every type of animal, they explain.
“To assess effects on behaviour, individuals were again housed solitarily in acoustic isolation chambers, and all were exposed for 15 minutes to playbacks of conspecific alarm calls, a signal which, like hearing predator vocalizations, alerts the hearer to a predator danger,” the paper explains.
The long-term effects of exposure on the brain were assessed by measuring ∆FosB protein levels in the amygdala and hippocampus, two areas of the brain involved in PTSD in humans. The amygdala is responsible for fear processing and the acquisition and expression of fear memories, the team explains, whereas the hippocampus is involved in memory formation. ∆FosB is a transcription factor, meaning it can turn other genes on or off. It is “unusually stable” for a transcription factor (i.e. has long-lasting effects) and, among other things, is known to promote resistance to the consequences of chronic stress.
Zanette’s team is the first to show that the effects of predator exposure on the neural pathways that govern fear in animals can persist far beyond the initial ‘fight or flight’ response. They showed that this response remains measurable over one week later even for animals that have been allowed a peaceful, quality life after exposure.
They explain that retaining a powerful and enduring memory of a life-threatening predator encounter might seem crippling, but it’s actually evolutionarily-rewarding if it helps the individual avoid such events in the future. The team says their findings support the view that PTSD is the cost of inheriting an evolutionarily primitive mechanism that prioritizes survival over the quality of life.
The results suggest predator exposure could impair the behavior of prey species much more, and for longer than previously assumed. They also tie in well with past research in which Zanette and her collaborators show that scared parents are less able to care for their young.
The paper “Predator-induced fear causes PTSD-like changes in the brains and behaviour of wild animals” has been published in the journal Scientific Reports.
Ohio University paleontologists have discovered a new species of extinct carnivore. Its lineage has been severed by the ages but, while it was alive, this massive predator was likely the terror of the eastern stretches of Africa.
Simbakubwa kutokaafrika, a gigantic carnivore known from most of its jaw, portions of its skull, and parts of its skeleton, was a hyaenodont that was larger than a polar bear. Illustration by Mauricio Anton.
Larger than any big cat today — larger, in fact, than a polar bear — with a skull as large as that of a rhinoceros and dagger-long canine teeth, Simbakubwa kutokaafrika was a really scary part of the ecosystems occupied by early apes and monkeys 22 million years ago. The species is described in a new paper published by paleontologists from the University of Ohio based on most of its jaw, portions of its skull, and parts of its skeleton.
“Opening a museum drawer, we saw a row of gigantic meat-eating teeth, clearly belonging to a species new to science,” says study lead author Dr. Matthew Borths, who is currently the Curator of the Division of Fossil Primates at the Duke Lemur Center at Duke University.
The fossils used in this study aren’t exactly freshly-recovered. They were unearthed in Kenya decades ago by teams looking for ancient ape fossils. Simbakubwa’s fossils were placed in a drawer at the National Museums of Kenya for safekeeping and then kind of… forgotten about. Borths, alongside his Ohio University colleague Dr. Nancy Stevens recognized the significance of the fossils and set about analyzing them properly.
Simbakubwa is Swahili for “big lion”, because the animal was likely at the top of the food chain in Africa, as lions are in modern African ecosystems. The species name, kutokaafrika, is Swahili for “coming from Africa”. Yet Simbakubwa is not closely related to big cats or any other mammalian carnivore alive today. It is the oldest of the gigantic hyaenodonts. Hyaenodonts were a lineage of giant carnivores likely originated on the African continent which moved northward to flourish for millions of years.
Simbakubwa kutokaafrika mandible (A throguh C), with Panthera leo (lion, D) mandible for comparison. Scale bar equals 5 cm. Image credits Matthew Borths, Nancy Stevens, (2019), JoVP.
They were the first mammalian carnivores in Africa, the team explains. For roughly 45 million years after non-avian dinosaurs disappeared, they were also the apex predators of the continent. After millions of years of near-isolation, however, Africa drifted into contact with the northern continents, enabling flora and fauna to exchange between these (previously-isolated) landmasses.
Around this time, the relatives of cats, hyenas, and dogs began to arrive in Africa from Eurasia. Meanwhile, Simbakubwa’s kin was making their way north. This would not prove to be a very savvy decision — in time, hyaenodonts worldwide went extinct.
“It’s a fascinating time in biological history,” Borths says. “Lineages that had never encountered each other begin to appear together in the fossil record.”
“We don’t know exactly what drove hyaenodonts to extinction, but ecosystems were changing quickly as the global climate became drier. The gigantic relatives of Simbakubwa were among the last hyaenodonts on the planet,” he adds.
The paper “Simbakubwa kutokaafrika, gen. et sp. nov. (Hyainailourinae, Hyaenodonta, ‘Creodonta,’ Mammalia), a gigantic carnivore from the earliest Miocene of Kenya” has been published in the Journal of Vertebrate Paleontology.
Our microplastics are a much more important factor in the health of the ocean than suspected. And they’re up to no good.
Microplastics. Image credits Oregon State University / Flickr.
Researchers at the French National Centre for Scientific Research report that microplastics can disrupt predator-prey relationships in the wild. In a new study, the group describes the impact of microplastic consumption on the common periwinkle (Littorina littorea).
Micropastics, macro effects
Periwinkles are a kind of sea snail. They’re not… particularly exciting. They sit on algae-encrusted rocks all day, munching on the plants. They are, however, considered to be a keystone species — they’re prey for many other species, especially crabs (we also eat them sometimes).
The authors wanted to find out what would happen should these periwinkles dine on algae that have absorbed microplastics. Prior research has shown that algae absorbing such products become enriched in hazardous chemicals and metals. Microplastics are porous and soak up these chemicals as they flute around (we’re dumping those chemicals there, too).
The team’s hypothesis was that when a periwinkle eats the algae, it is also eating the hazardous materials present in the algae. In order to test if this results in any adverse changes for the snails, the team gathered a few periwinkles and brought them into the lab for testing. They also brought along a few crabs to use as predators.
They report that periwinkles which consumed the toxic materials did not react to the crabs in an expected way. Normally, upon spying the predator, the snails pull into their shells or try to hide in the surrounding environment. Those exposed to the toxic materials did not attempt to avoid capture, however, suggesting that they suffered nerve damage of some sort. This is likely due to the ingestion of heavy metals, the team adds.
They note that the levels of toxicity in the microplastics they used for the study were equivalent to those on a typical beach. The findings are thus broadly applicable in real-world conditions — and they point to major changes in the marine environment due to the microplastics we’ve introduced.
The paper “Microplastic leachates impair behavioural vigilance and predator avoidance in a temperate intertidal gastropod” has been published in the journal Biology Letters.
“You asked for it punk!” Image credits Shane Black.
Skinks in the genus Tiliqua are pretty inconspicuous as far as lizards go. They don’t really like to draw attention to themselves, and they’re decidedly lizard-shaped. New research shows that when their unassuming nature fails to garner the peace of mind they desire (from predators), the skinks fall back to a surprising — and surprisingly effective — last-ditch defense: their tongues.
Their what now?
Bluetongued skinks are fairly widely spread throughout Australia, eastern Indonesia, and Papua New Guinea. They’re omnivorous, mediumly-sized lizards that primarily rely on their camouflage to keep out of sight. When under attack by a determined predator, however, they make an effort to stand out: the skinks open their mouth suddenly, as wide as they can, to reveal a brightly-colored blue tongue. Not to make them self-conscious but these tongues must be a sight to recoil from — because that’s exactly what predators do.
The behavior is used as a last line of defense to protect the skinks from attack, writes Martin Whiting, the study’s corresponding author, in a press release. The research revealed that the tongues are very reflective in the UV spectrum, and that they are more UV-luminous towards the back. Some of the lizards’ main predators, such as birds, snakes, or monitor lizards, are thought to be able to see UV light, suggesting the skinks might use this light to startle predators into breaking off their attack.
The study focused on the northern bluetongue skink (Tiliqua scincoides intermedia), the largest species of the group. The species sports good camouflage: broad brown bands across their backs to blend them into their surroundings. However, some of its main predators can still spot them, likely due to their ability to perceive UV light — so the team aimed to determine what tactics it uses to deter attackers.
First, they used a portable spectrophotometer to measure the color and intensity across different areas of the tongues of 13 skinks. This revealed that the blue tongues actually reflect UV light. Further data crunching in the lab later revealed that the tongues were almost twice as bright at the rear compared to the tip.
Mean spectra of different regions of the tongue. Associated illustration by Courtney Walcott of a Bluetongue skink performing a full-tongue display. Image credits A. Badiane et al., 2018, Behavioral Ecology and Sociobiology.
The next part of the study was to identify how this bright tongue benefited the skinks. The team observed that skinks in the wild would open their mouths and stick their tongues out at would-be attackers. To find out more, the team simulated attacks on the lizards using models of their natural predators — the team used a snake, a bird, a goanna (monitor lizard), a fox — and a piece of wood as a control.
Skinks will rely on concealment for as long as they possibly can, the team reports. Should this fail, however, the lizards open their mouths widely at the last moment, revealing their UV-reflective tongues. One particularly amusing paragraph of the study suggests that the more intense attacks elicited a stronger tongue-response: the more risk the skinks felt exposed to, the more tongue they would poke at their enemies. I can relate to their fighting style.
Northern Bluetongue skink performing a ‘full-tongue’ display in response to a simulated attack by a model predator. The face of a true warrior. Image credits Peter Street / A. Badiane et al., 2018, Behavioral Ecology and Sociobiology.
“The lizards restrict the use of full-tongue displays to the final stages of a predation sequence when they are most at risk, and do so in concert with aggressive defensive behaviours that amplify the display, such as hissing or inflating their bodies,” explains lead author Arnaud Badiane.
“This type of display might be particularly effective against aerial predators, for which an interrupted attack would not be easily resumed due to loss of inertia.”
Finally, the team notes that tongue-displays were most often triggered by the fake bird and fox models, rather than by those of snakes or monitor lizards.
“The timing of their tongue display is crucial,” adds Badiane. “If performed too early, a display may break the lizard’s camouflage and attract unwanted attention by predators and increase predation risk. If performed too late, it may not deter predators.”
If you’re ever caught between a rock and a hard knuckle, stick your tongue out. It likely won’t be as effective as those of the skinks, but maybe you’ll confuse people enough to make your (brave and honorable) escape. Worth a shot.
The paper “Why blue tongue? A potential UV-based deimatic display in a lizard” has been published in the journal Behavioral Ecology and Sociobiology.
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.
The snow leopards is buckling under pressure from human killings, with hundreds of the cats falling prey to farmers and poachers in the remote mountains of central Asia each year.
There might be less than 4,000 of them still alive in the wild. Image credits Marcel Langthim / Pixabay.
Fluffy, adorable, and exceedingly deadly, there are an estimated 4,000 snow leopards still living in the world. While getting an accurate head count of the elusive, solitary felines is pretty difficult, we’re pretty confident that the species has lost a fifth of its members in the last 16 years. Now, a report looking into the state of the endangered snow leopard estimates between 220-450 annual deaths of the big cats, putting the species in a precarious position. It also warns that this number is likely even higher, as killings by farmers and poachers in remote mountain areas of central Asia often go undetected.
The report comes from wildlife monitoring network Traffic and was published last Friday, in anticipation of a UN meeting on the subject which will be held in New York. The animals naturally prey on Himalayan blue sheep and ibexes, but these animals are under pressure from farmers encroaching on their habitat. So, the leopards turn towards livestock for food. Traffic estimates that over half of the killings are done by farmers to stem further attacks on livestock. Around 20% of the total number are caught in snares set out for other animals, and roughly 20% are killed specifically for the illegal fur trade. Pelts from animals killed for other reasons are often sold, though, from example by farmers looking to make up for their losses — the pelts, claws, and fangs of the animal can fetch a good price on the black market.
Snow leopards’ range includes 12 nations, but over 90% of reported poaching takes place in five countries: China and Mongolia (where most snow leopards live), along with Pakistan, India, and Tajikistan (each having a population of a few hundred leopards). One of the leopards’ most powerful (and surprising) allies throughout their habitat are Buddhist monks, which patrol the grounds near their monasteries to keep an eye out for poachers.
Still, they cannot save the species alone, although they’re definitely the most awesome monks in my book. The report calls for stronger law enforcement on the issue, citing that less than a quarter of known poaching cases are investigated, with just one in seven being prosecuted. They also recommend a push for wider usage of leopard-proof corrals for yaks and horses, and insurance coverage for farmers. Such schemes are already being tested, for example in a village in the Indian state of Himachal Pradesh.
But the insurance you really need is for one of them stealing your heart, awwww! Image credits Tambako The Jaguar / Flickr.
Around 200 pelts are illegally traded each year, the report found, with China, Russia, and Afghanistan being the major destinations. The number has thankfully been falling sharply in the last few years, however, especially in China, due to increasing police enforcement.
“Even if there is reduced demand for snow leopard skins, the killing will continue unless we all work together to drastically reduce human-wildlife conflict and ensure that mountain communities can co-exist with snow leopards,” said co-author Rishi Sharma of WWF.
“Compensation schemes and innovative predator-proof corrals are making a difference but we urgently need to expand these to benefit communities – and snow leopards – across Asia’s high mountains.”
Not only are the cats being hunted, but they’re also at risk from climate change — they will have to abandon roughly one third of their habitat as the treeline advances further up the mountain slopes and farmers move in to claim the land.
Hopefully, we’ll leave the animals time to recover until this happens.
Though humans might not be as fierce as a lion or white shark, we’re definitely the greatest predatory species in the world, ever. The extent of humanity’s super-predation was assessed by a team at University of Victoria in British Columbia which compared our hunting abilities to those of both land and marine predators in all the oceans and continents, besides Antarctica. The findings reveal humans lack any real competition preying on adults of other species at rates up to 14 times higher than other predators, especially marine ones.
Starting with the 1970s, Thomas Reimchen noticed some disturbing patterns while studying predator-prey relationships in the Haida Gwaii, an archipelago on the North Coast of British Columbia. In this particular ecosystem, 22 species of trout, loons and other predators fed on stickleback fish. He found that the ecosystem was at balance with stickleback numbers remaining fairly constant despite the large number of competing predators who collectively didn’t prey on more than 5% of the adult fish population. In contrast, human fishing in nearby marine waters seized “40 to 80 percent of the biomass of salmon and herring, and then predominantly the reproductive-age classes,” Reimchen found.
This study was the footing ground for a much broader analysis. Chris Darimont, a professor of geography at the University of Victoria, joined Reimchen to create a huge database of 2,200 data points on 399 prey species around the world on both land and sea, and devised models of the predator-prey relationships. Some key findings from the paper:
predators other than human target juveniles. This allows more adults to breed and increases the chance that they lay their eggs.
human hunting, especially fishing activities, mainly target adults since these contain more meat. Juveniles are generally avoided since it’s more important for them to grow into adulthood when they become a better catch, but also have the chance to reproduce. This isn’t always true, especially for fish. Heavily targeting adults causes widespread consequences like changing mating patterns and even the biology of fish. For instance, Cod starts breeding when its six years old. In area where over-fishing is cornering Cod, the fish start breeding at four and half years of age, but they also produce fewer offspring.
on land, humans kill as much adult prey – mainly herbivores – as non-human predators.
in the water, this ratio is heavily skewed in the humans’ favor. Marine predators eat as much as 1 percent of the adult biomass each year. Humans, on the other hand, take a median of 14%. In some cases, this was found to be 80%.
the over-predation effect was most felt in the Atlantic Ocean. This can be attributed to the long history of fishing in the area and the ever higher population density.
Advanced hunting tools and, in the case of fishing, massive industrialization allows just a handful of individuals to secure food for thousands. In fact, this may very well be the main factor that leads to over-predation: that all people enjoy the spoils of predation even though only a small fraction of the population actually does the hunting or fishing.
Rate of exploitation. Image: Science
“If future generations of people are to see large carnivores, then this requires cultivating new tolerance for living with them. This might include increasing revenues to local communities derived from nonconsumptive ‘uses,’ such as eco-tourism [and] shooting carnivores with cameras, not guns,” Darimont told Smithsonian.
Now, if humans were to be dependent on this prey which we hunt, then we’d see our numbers stabilize at the same time. But humans also practice agriculture, which basically has had us “set for life”, offering a constant and predictable stream of food. This combination means that humans can hunt entire species to extinction without necessarily driving their own demise, since they always have veggies or grain to makeup for any shortage in meat. As you might notice, being a super-predator isn’t a good thing and as the world grows – in needs and numbers – it’s becoming increasingly clear that we should move to a more sustainable predation pattern.
“Some might argue that humanity’s dominance is entirely natural and that any other predator would dominate prey if they could,” Darimont told Discovery News. “While this might be true, it does not justify the behavior. In other words, just because something is ‘natural’ does not mean it’s justified.”
“In fact,” he added, “humans are blessed with the ability to understand the consequences of our deviant behavior and have the capacity to change.”
When herbivorous dinosaurs went to sleep, they had bad dreams about Tyrannosaurs. But what where Tyrannosaurs afraid of? If you’re thinking “Nothing”, then you’re really wrong. A new species of carnivorous dinosaur (one of the three largest ever discovered in North America) competed with them 98 million years ago – the newly discovered species, Siats meekerorum; as a matter of fact, the species was the apex predator for millions of years, bullying pretty much all other species – Tyrannosaurs included.
This is an illustration of Siats meekerorum. (Credit: Artwork by Jorge Gonzales)
Named after a cannibalistic man-eating monster from the Ute Indian tribe, Siats was a member of the Carcharodontosauridae – a group of dinosaurs which includes some of the largest predators ever discovered. They lived in the Cretaceous, from about 127 million years to 89 million years ago. After that, they started being overcome by smaller, more niched predators. The discovery of Siats comes after a long period of wait.
“It’s been 63 years since a predator of this size has been named from North America,” says Lindsay Zanno, a North Carolina State University paleontologist with a joint appointment at the North Carolina Museum of Natural Sciences, and lead author of a Nature Communications paper describing the find. “You can’t imagine how thrilled we were to see the bones of this behemoth poking out of the hillside.”
The described individual measured more than 15 meters in length and weighed at least four tons – but despite its giant size, it was still a juvenile! Zanno and colleague Peter Makovicky, from Chicago’s Field Museum of Natural History believe that a full grown specimen would have easily measured over 10 meters.
Siats terrorized what is now Utah during the Late Cretaceous period, showing that the reign of the Carcharodontosaurids lasted much longer than previously believed. This fossil fills in a huge 30 million year gap in the fossil record; only after they started to decline did the Tyrannosaurs finally start to claim the top spot.
“The huge size difference certainly suggests that tyrannosaurs were held in check by carcharodontosaurs, and only evolved into enormous apex predators after the carcharodontosaurs disappeared,” says Makovicky. Zanno adds, “Contemporary tyrannosaurs would have been no more than a nuisance to Siats, like jackals at a lion kill. It wasn’t until carcharodontosaurs bowed out that the stage could be set for the evolution of T. rex.”
The team is confident that they will soon find other fossils which will help them understand the Cretaceous environment.
“We have made more exciting discoveries including two new species of dinosaur,” Makovicky says.
“Stay tuned,” adds Zanno. “There are a lot more cool critters where Siats came from.”
Lindsay E. Zanno, Peter J. Makovicky. Neovenatorid theropods are apex predators in the Late Cretaceous of North America. Nature Communications, 2013; 4 DOI:10.1038/ncomms3827
The king of all predators, the godfather of his time, la creme de la creme – Tyrannosaurus Rex (T. Rex) was the ultimate predator… or was he? When Jurassic Park came out, even though the cinema crowd went wild as T. Rex smashed and ate velociraptors (and the occasional human), at the time, there was no compelling proof that the dinosaur actually hunted – some teams actually claimed that he was a scavenger.
“It is effectively impossible for Tyrannosaurus rex to have fed solely or almost completely on carcasses of dead animals. T. rex lived in an ecosystem with a large number of smaller-bodied carnivorous dinosaur species and it couldn’t have relied on carcasses for its diet,” said Sam Turvey, a co-author of the study published in Proceedings of the Royal Society B.
It seemed obvious that T. Rex was a hunter. But few doubts still remained. Now, another study seems to pin the final nail in the scavenger theory.
The researchers found a T. rex tooth stuck between vertebrae in the tail of a herbivorous duck-billed hadrosaur. The fossils came from a famous area in South Dakota – the Hell Creek Formation.
This CT scan of a duck-billed hadrosaur’s vertebra shows an embedded T. rex tooth crown with bone tissue that regrew around it.
The finding is very significant because the T. rex tooth is surrounded by bone that clearly grew after the tooth became lodged there. This could only happen if the predator bit the herbivore’s tail, lost its tooth there, as well as the prey.
“It’s a smoking gun. We finally have Tyrannosaurus rex caught in the act,” says Bruce Rothschild, a palaeopathologist at the University of Kansas in Lawrence and a co-author of the paper. “We’ve seen plenty of re-healed bite marks attributed to Tyrannosaurus rex, but it’s hard to confirm identity with those,” says Thomas Holtz, a vertebrate palaeontologist from the University of Maryland in College Park. “Actually having the broken tooth makes it easy to determine who was doing the hunting here,”
But even with this, some are hard to convince.
“I’ve long argued that Tyrannosaurus rex was an opportunist like a hyena, sometimes hunting and sometimes scavenging. This provides no evidence to the contrary,” says Jack Horner, a palaeontologist at the Museum of the Rockies in Bozeman, Montana, who served as scientific adviser on the Jurassic Park films.
But even as a few argue that he wasn’t a pure predator, and more argue that he in fact was, even a larger group is just fed up by this debate.
“Great galloping lizards!” exclaims John Hutchinson, an evolutionary physiologist at the Royal Veterinary College in London. “It is so frustrating to see provocative half-baked ideas about celebrity species like Tyrannosaurus rex drawing the public’s attention when there is so much more interesting palaeontology to be talking about.”