Tag Archives: herbivore

The world’s herbivores are in trouble, more so than its predators

Herbivores are facing a greater risk of extinction than predators or omnivores, a new study finds. Megaherbivores (species that grow up to more than 1000 kg) are particularly affected, and their loss will send massive ripples across ecosystems.

Image credits Penny Ash.

The Earth is no stranger to extinction. It’s a natural process, and the rate at which species disappear in the wild is known as the ‘baseline extinction rate’. It’s a bit sad to see species go, obviously, but this process helps remove under-performing actors, or those who can’t adapt, to make room for new ones to evolve.

While this natural extinction rate helps keep the world healthy, human activity is putting immense pressure on the planet, resulting in a greatly accelerated rate of extinction. And it’s disproportionately affecting plant-eaters.

Killing the middleman

“The results were somewhat shocking,” says Trisha Atwood, an Assistant Professor of Watershed Sciences at Utah State and lead author of the study.

“Our highly publicized and fraught relationship with predatory animals such as lions and wolves has led to the unfounded perception that we are losing predators more than any other trophic group.”

This isn’t the first time that human activity has led to the extinction of large herbivorous species. A similar phenomenon took place one million years ago, likely driven by human expansion and hunting, which forever changed the shape of life on our planet.

The disappearance of large herbivores reduced pressure on plantlife, changing growth and population dynamics. This altered fire regimes (there was more fuel, i.e. uneaten plant matter) and impacted nutrient cycling (nutrients are produced by plants and concentrated by herbivores). All in all, such changes lead to the Earth becoming colder — more plants and fewer plant-eaters equals less CO2 in the atmosphere.

The findings suggest that megaherbivores today could experience the same fate, and the consequences of such a change are yet unknown.

The team looked at the diets and threatened status of over 24,500 species of mammals, birds, and reptiles to see which category of animals (herbivores, carnivores, or omnivores) are most at risk of extinction. Their findings indicate that over 25% of today’s herbivore species are faced with extinction, which represents the highest risk margin for any of the studied groups. The team notes that herbivores have been experiencing a disproportionately high rate of extinction since at least the late Pleistocene 11,000-50,000 years ago.

Who needs help the most

The authors say that dispelling misconceptions (such as ‘carnivores are more at risk of extinction than herbivores’) is essential if we’re to fix the issues we’re causing. Different groups of species have different ecological functions, so the loss of each would have a different effect on the balance of nature.

The changes we’re seeing now are similar to those seen 1 million years ago, the authors note: changes to plant species and their population numbers, changes in fire regimes, disruptions in nutrient recycling.

Better management and conservation of herbivores is needed to prevent unpleasant changes in the future, such as dramatic shifts in or complete collapse of natural ecosystems. Since herbivores are a key part of global food webs (both wild and human-run), their loss isn’t an encouraging prospect.

The study highlights that herbivores are faring the worst, but predators aren’t having it easy, either. Scavengers, species that eat the remains of recently deceased animals, and species that primarily eat fish, are also facing a higher risk of extinction.

“Our results enable us to identify specialized diets within the carnivores that are associated with higher extinction risk, and also identify the habitats these species live in,” says Edd Hammill, an assistant professor of watershed sciences at Utah State University and co-author of the study.

“It would appear that seabirds across the globe suffer disproportionately high levels of extinction.”

Understanding the patterns of extinction facing different species groups is only the first step to protecting their health. Next, the team plans to examine what drives these extinctions, so we can focus our efforts on the root of the problem itself.

The paper “Herbivores at the highest risk of extinction among mammals, birds, and reptiles” has been published in the journal Science Advances.

Giant, mammal-like herbivore roamed alongside Triassic dinosaurs, new fossil reveals

What do you get when you cross a rhino with a supersized turtle? Apparently, the answer is Lisowicia bojaniThe giant, bizarre herbivore had a beak-like mouth, and was not related to the dinosaurs — in fact, it had more in common with mammals.

Artistic reconstruction of Lisowicia bojani, front view. Credit: Karolina Suchan-Okulska.

The Triassic period, which preceded the Jurassic, was a pivotal time in the planet’s biosphere. Dinosaurs slowly emerged as the leading land animal group, while the mammals and their relatives “retreated to the shadows” — at least that’s what conventional wisdom says. But this new finding “throws a wrench into that simple tale,” says Stephen Brusatte, a vertebrate paleontologist at The University of Edinburgh.

In a new study published in Science, a team of Polish scientists describes a finding that challenges all that theory. The “new” fossil, a partial skeleton, is a called a dicynodont — herbivorous creatures, with two tusks (hence the name), a strong, barrel-shaped body, and powerful limbs. Dicynodonts are part of a larger group called synapsids, which mammals and all animals belong to.

A highlight of the geologic timescale when was living.

They were dominant in the Permian (before the Triassic) but were thought to have faded away after that.

“We used to think that after the end-Permian extinction, mammals and their relatives retreated to the shadows while dinosaurs rose up and grew to huge sizes,” said Grzegorz Niedzwiedzki, a paleontologist at Uppsala University in Sweden who co-authored the paper.

During the Triassic period (252-201 million years ago) mammal-like reptiles called therapsids co-existed with ancestors to dinosaurs, crocodiles, mammals, pterosaurs, turtles, frogs, and lizards. One group of therapsids are the dicynodonts. The new species Lisowicia bojani is presented above. Credit: Tomasz Sulej.

But this finding does more than force us to rewrite an important chapter in evolutionary history — it may point to the factors that drove dinosaurs to evolve into the giants they came to be. A dinosaur group called the sauropods also lived at the time, and sauropods gave produced species such as the long-necked Diplodocus, which could measure over 24 meters (79 feet) and was so big that it probably required auxiliary hearts and potentially even an auxiliary brain. Since two giant groups lived around the same time, it may be that the environmental conditions of the Late Triassic are what spurred the evolution of gigantism, the researchers said.

Researchers have hypothesized that sauropods grew big to avoid getting eaten, and the same might be true of L. bojani.

The creature’s posture is also intriguing. Most dicynodonts had a seemingly awkward posture, with straight hind limbs (much like mammals), but sprawled, lizard-like forelimbs. Given the way that L. bojani‘s upper bone is connected to its shoulder, it seems like it might have walked like modern reptiles, which would have helped support its massive weight.

Journal Reference: T. Sulej el al., “An elephant-sized Late Triassic synapsid with erect limbs,” Science (2018).

 

Vegetarian dinosaurs sometimes feasted on crustaceans

The idea of a strictly vegetarian dinosaur has been called into question as researchers found evidence of shellfish eating.

Skin impressions are known in Parasaruolophus, a hadrosaur. The hadrosaurs are known for their particular skull shape. Image credits: Steveoc 86 / Wikipedia.

Our understanding of how and what dinosaurs ate is still simplistic. Largely speaking, we have the plant-eaters and the meat-eaters, but things might be much more nuanced than what we originally thought. Now, researchers have found evidence of Hadrosaurs eating crabs and other crustaceans, a behavior linked to mating behaviors.

Hadrosaurs are a kind of duck-billed dinosaur and one of the most common herbivores of the Cretaceous. Hadrosaur fossils are so common and so well-preserved that paleontologists have been able to calculate their muscle mass, learning that hadrosaurs were very muscular, likely having the ability to outrun predators. The so-called “Dakota” specimen was in such good condition that researchers were even able to analyze its ligaments, tendons, and possibly some internal organs through a CT scan. If anything, “Dakota” is more a mummy than a fossil. But we still have a long way to go before we can say we get hadrosaurs.

Dr. Karen Chin of the University of Colorado, Boulder, US, led a team which discovered and analyzed hadrosaur droppings which contained pieces of crabs and other crustaceans — but only during some times of the year.

“I immediately said, ‘Oh, no, no, it can’t be crustaceans.’ That was my knee jerk reaction,” Karen Chin tells The Two-Way. She’s the curator of paleontology at University of Colorado Boulder’s Museum of Natural History and a co-author of the paper published today in Scientific Reports.

“I was very surprised but I think it reminds us that there’s a lot we just don’t know about the behavior of ancient animals,” she said.

The surface of knobby crustacean shell fragment embedded in fossilized feces samples from Grand Staircase-Escalante National Monument in Utah. Karen Chin/Denver Museum of Nature & Science.

The crustaceans weren’t accidentally ingested. Crustaceans were found in 10 of the 15 studies places, spread over a 20-kilometer area and potentially over hundreds of years. “This was definitely a recurring diet,” Chin says. The droppings also contained wood pieces, which indicates that the crustaceans lived around (probably rotting) logs. They were also “good-sized crustaceans,” measuring at least five centimeters, which indicates that hadrosaurs chose to eat them.

“The fact that these crustaceans were a fair percentage of the width of the skull of the dinosaurs [means] they would have had a choice to reject it if it wasn’t either a desired or acceptable food source.”

The team proposes that the dinosaurs ate the crustaceans to complement their diet during the mating season, when they need large amounts of both protein and calcium, especially during the egg laying period. If this is the case, it could mean that the behavior is also shared by other herbivores, such as the mighty triceratops or the mace-tailed stegosaurus. Perhaps this isn’t really that surprising when you think about. This behavior is also common in today’s herbivores. Usually, they feast on plants but every now and then, they eat something else to complement their diet (either accidentally or intentionally).

“And knowing that at least some of them – we can’t say all of them at this point – but at least some of them occasionally varied their diet to eat more animal products is really intriguing.”

Whatever the case may be, we definitely have to fine tune our idea of herbivore dinosaurs. The classic image of a gentle giant munching on foliage all day long might simply not be true.

Journal Reference: Karen Chin, Rodney M. Feldmann & Jessica N. Tashman. Consumption of crustaceans by megaherbivorous dinosaurs: dietary flexibility and dinosaur life history strategiesdoi:10.1038/s41598-017-11538-w

60% of large herbivores on the verge of extinction, bleak study finds

The 74 largest terrestrial herbivores are on the verge of extinction, a new worrying study has found. All in all, over half of all large terrestrial herbivores are on the verge of extinction – and we’re to blame.

The Sumatran rhinoceros is the smallest of the rhino species. Image via Wikipedia.

They don’t eat other animals, and they’re some of the most peaceful creatures out there – but they’re facing a gruesome fate, vanishing from the Earth at startling rates. Researchers from the Oregon State University conducted the study in different regions of Asia and Africa and were surprised at just how barren the landscapes are, without many of the herbivores we’ve been used to seeing.
Authors were clear about this, we’re dealing with “empty landscapes” in some ecosystems “across much of the planet Earth” and we’re the reason why this is happening.  Professor William Ripple said:
”I expected that habitat change would be the main factor causing the endangerment of large herbivores. But surprisingly, the results show that the two main factors in herbivore declines are hunting by humans and habitat change. They are twin threats.”
The problem is not only that we are wiping out some of the planet’s more iconic and loved animals, but we are creating huge beaches in ecosystems – without the activity of these herbivores, entire ecosystems may collapse. As scientists have known for a long time but much of the general public is still unaware, protecting herbivores is important not just in itself, but because of the invaluable environmental services they provide.

Giraffe at the Nairobi Park. Image via Wikipedia.

“The big carnivores, like the charismatic big cats or wolves, face horrendous problems from direct persecution, over-hunting and habitat loss,” David Macdonald, an Oxford scholar and co-author, told the BBC, “but our new study adds another nail to their coffin — the empty larder. … It’s no use having habitat if there’s nothing left to eat in it.”
Indeed, threatening herbivores threatens all the animals above them in the food chain.
“Growing human populations, unsustainable hunting, high densities of livestock, and habitat loss have devastating consequences for large, long-live, slow-breeding, and, therefore, vulnerable herbivore species,” Ripple added, expressing his hopes that policymakers will step in and prevent further damage. “We hope this report increases appreciation for the importance of large herbivores in these ecosystems,” Ripple added in the release. “And we hope that policymakers take action to conserve these species.”

Kenyan ranger stands by as authorities burn down 15 tonnes of ivory. Image via South African Times Live.

The problem isn’t only humans killing animals for meat – organized crime and the endless hunt for animal body parts, such as elephant tusks and rhinocerous horns has reached unprecedented heights. Between 2002 and 2011 alone, the number of forest elephants in central Africa declined by 62 percent. Some 100,000 African elephants were poached between 2010 and 2012. And the western black rhinoceros in Africa was declared extinct in 2011.
“This slaughter is driven by the high retail price of rhinoceros horn, which exceeds, per unit weight, that of gold, diamonds, or cocaine,” according to the study.
The article ends on a motivational note, urging for action now. After all, it may be the last chance we get.
“Now is the time to act boldly,” the article concluded. “Saving the remaining threatened large herbivores will require concerted action,” the study concluded. “The world’s wealthier populations will need to provide the resources essential for ensuring the preservation of our global natural heritage of large herbivores. A sense of justice and development is essential to ensure that local populations can benefit fairly from large herbivore protection and thereby have a vested interest in it.”
The research was published in the latest edition of Science Advances.