While everyone has been worrying about saving the lions and tigers and bears, a collection of scientist studying threatened and extinct species have concluded that herbivores – many an animal’s tasty treat – have been taking a beating.
“In both recently extinct species and late Pleistocene extinct mammals, we found herbivores to have the greatest proportion of extinct species,” they reported at the American Association for the Advancement of Science Ecology on Wednesday. “In contrast, predators had lower proportions of extinctions compared to herbivores and, except for recently extinct birds, had lower levels of extinction compared to the background proportion.”
The authors from six U.S. universities and the Imperial College London admitted their work flies in the face of conventional wisdom.
“As a result of their extensive home ranges and slow population growth rates, predators have often been perceived to suffer higher risks of extinction than other trophic groups,” they noted.
“(But) our study challenges this extinction-risk paradigm by quantitatively comparing patterns of extinction risk across different trophic groups of mammals, birds, and reptiles.”
Some believe Alaska’s major predators – wolves and grizzly bears – are persecuted to boost populations of plant eating moose and caribou, but the Alaska Department of Fish and Game claims the populations of those animals are healthy.
When independent reseachers looked at the big, global picture, what they found, they said, is that the extinction threats stem not from whether an animal is predator or prey but instead its position in the food chain and its body size.
On multiple levels, they said, “herbivorous reptiles and large-bodied herbivores consistently have the highest proportions of threatened species.”
About 25 percent of the word’s herbivores are in danger, according to the study. Some are now teetering perilously close to extinction. Live Science reports the population of Javan rhinos is down to 68 animals.
“They once lived throughout northeast India and Southeast Asia, but can now only be found in Java’ Ujung Kulon National Park in Indonesia,” the website said.
“At the moment the national park is the Javan rhinos’ only chance of survival.”
Adult rhinos – like healthy adult moose – are largely safe from wild predators, but calves are vulnerable to tigers and crocodiles. And then there are humans.
“The Javan rhino showed the most dramatic decline of all three Asian rhino species, and by about 1930 Javan rhinos were restricted to…the westernmost tip of Java and a few small isolated populations in Vietnam and possible Laos and Cambodia,” according to the Save the Rhino organization.
“By the time the first naturalists ventured into the Southeast Asian forests, the Javan rhino was already very rare, and not much is known about its behaviour and ecology outside the single remaining viable population, which may not even be located in ideal or typical habitat.”
The last rhino in Vietnam was poached in 2011. Like the Javan rhino, most of the world’s rhinocerouses are now threatened with extinction.
“Rhinos once roamed many places throughout Europe, Asia, and Africa and were known to early Europeans who depicted them in cave paintings,” according to the World Wildlife Federatoin. “At the beginning of the 20th century, 500,000 rhinos roamed Africa and Asia. By 1970, rhino numbers dropped to 70,000, and today, as few as 29,000 rhinos remain in the wild.”
Elephants – the world’s largest hervivore – are also in trouble in many places as are hippopatamuses.
The 49th state is lucky in that its populations of large-bodied herbivoes are generally well managed although there are endless debates about what ratios of predator and prey should be maintained in the nation’s last, true wilderness state.
In oppostion to those who believe wolves and grizzly bears are over hunted, others contend the numbers of bears and wolves are so high they’re suppressing populations of moose and caribou.
There is no easy middle ground.
“Carbone and Gittleman estimated that 10,000 kilograms (22,046 pounds) of prey is needed to support just 90 kilograms (198 pounds) of a given carnivore species,” the lastest study noted, “and prey depletion has been linked to declines of many large carnivores, including tigers, dholes, and several species of leopard.
“Declining populations of natural prey combined with retracting home ranges also increase human-predator conflicts as predators expand into human-occupied areas. The tenuous relationship between humans and predators is exemplified by the fact that hunting and trapping has, at least in part, been implicated in the decline of 80 percent of threatened species in the order Carnivora.”
As the competition between humans and predators increases, the fallout in some cases lands on prey, and the consequences can ripple through an ecosystem.
“….Declines in large-bodied frugivores (fruit eaters) in tropical forests are reshaping tree communities, which, in turn, is predicted to lead to an overall reduction in forest carbon storage,” the study said.
“…We found that consumers of fruit and general plant parts (e.g., leaves, roots, and stems) all had higher proportions of threatened species….”
Alaska, fortunately, has done a good job in maintaining its herbivore populations by controlling both natural and human kills. That is the not the case everywhere.
The scientists concluded there was a herbivore of some sort threatened with extinction “in 80 percent of marine regions and 85 percent of land regions. Herbivorous reptiles, followed by herbivorous mammals, contributed the majority of this risk.”
Herbivorous omnivores were the second most at-risk group with an elevated risk in 80 percent of marine regions and 46 percent of land regions.
Bears fall in the omnivore category. Black bear populations are now healthy in much of the U.S. and grizzly bear populations have been restored in parts of the West.
“Last, predators had elevated levels of risk in only 23 percent of land regions and 40 percent of the marine regions,” the study said. “Predatory reptiles and predatory birds (e.g., seabirds) drove the geographic patterns observed in at-risk predators. Overall, sub-Saharan Africa and the Atlantic Ocean had the highest numbers” of animals at threat.