Nav: Home

Surviving large carnivores have far-reaching impact

August 08, 2018

Anywhere large-bodied mammalian carnivore species are present, other, smaller carnivores are less likely to occur, according to an international team of researchers that conducted the first global assessment of carnivore interactions using camera trap data.

This finding is important because populations of large mammalian carnivores are declining as habitat is lost, and often where large carnivores disappear, a chain reaction is set off that affects smaller carnivores, prey species, and even plant and insect communities.

"Large carnivores are imperiled," said David Miller, associate professor of wildlife population ecology, Penn State, whose research group in the College of Agricultural Sciences led the study. "We were able to see that this finding, with large-bodied-carnivore species, held around the globe."

Camera traps -- sites watched over by automated cameras, often called trailcams -- allowed researchers to better understand how carnivore communities are structured. They analyzed camera trap data for 108,087 trap days across 12 countries spanning five continents, and estimated local probabilities of co-occurrence among 768 species pairs from the order Carnivora -- meat-eating mammals ranging from weasels to polar bears.

Researchers evaluated how shared ecological traits correlated with probabilities of co-occurrence. Within individual study areas, species pairs co-occurred more frequently than expected at random. Co-occurrence probabilities were greatest for species pairs that shared ecological traits including similar body size, temporal activity pattern and diet.

However, co-occurrence decreased as compared to other species pairs when the pair included a large-bodied carnivore. Those results suggest that a combination of shared traits, and top-down regulation by large carnivores shape local carnivore communities globally, Miller pointed out.

"This finding, that large carnivores exclude other carnivores, is true in North America, South America, Africa, Europe and Asia. It is really important for understanding why losing big carnivores is ecologically devastating," he said. "When you lose a large-bodied species of carnivore, you have other smaller carnivores increase in density, putting pressure on other smaller carnivores, and that can lead to increases in prey species -- which might then lead to degradation of plant communities."

An example in the United States that Miller cited is the disappearance of wolves and cougars in the East. Those carnivores were critical for regulating the number of deer and controlling where other carnivores occurred, he explained. And now that they are gone, it has opened up vast areas where coyotes and bobcats roam unregulated by larger carnivores.

"Coyotes and bobcats are preying on different animals then wolves and cougars would, and that has implications for how our forests are structured. The fact that we don't have wolves and cougars means we have more deer, and those deer have overbrowsed the forests," he said.

"And having more coyotes -- because they don't tolerate foxes -- results in fewer foxes, which means we have more mice in our fields and forests," he continued. "That is affecting the prevalence of Lyme disease spread by ticks that spend much of their life on certain mice. So you see, the way these carnivores compete and co-occur has implications for all of our wildlife communities."

Many of the animals photographed in this study -- published recently in Ecology Letters -- are the charismatic species that people think of in Africa -- lions, cheetahs, leopards and hyenas -- noted lead researcher Courtney Davis, a fourth-year doctoral student in ecology. But, she pointed out the research involves many more species than those well-known carnivores, using a robust data-set pulling together data from wildlife scientists all over the world. She noted that the research concentrates on interactions between species.

"We looked at what sort of factors, not environmental factors, but more traits of the species that might either increase or decrease the probability that any two species will co-occur at the same site," Davis said.

"We focused on things like body size, temporal activity patterns, sociality of the species, and tried to understand how patterns of co-occurrence were related to whether or not they shared different ecological traits."

Trailcams have revolutionized the study of carnivores, Davis said. With the very low density of carnivores on the landscape and wide territories, monitoring their movement and behavior previously had been difficult and expensive. Researchers around the world often use the same models of cameras used by hunters and sportsmen.

Though this research did not include a Pennsylvania component, if it was done again today, it would, Miller said. Penn State doctoral student in ecology Asia Murphy has been conducting a camera-trapping study of Keystone State coyotes, bobcats and bears for the last two years. Murphy did contribute to the original international project. She participated for two years in a Virginia Tech camera-trapping effort that focused on carnivores in Madagascar's Makira National Park.
In all, 24 researchers from 12 countries contributed to the research, which was funded by government agencies, foundations, businesses and nongovernmental agencies in Botswana, Madagascar, Senegal, South Africa, United States, Belize, Argentina, Iran, Nepal, Sumatra, Indonesia and Norway.

Penn State

Related Wolves Articles:

What wolves' teeth reveal about their lives
UCLA biologist discovers what wolves' broken teeth reveal about their lives.
Fearing cougars more than wolves, Yellowstone elk manage threats from both predators
Wolves are charismatic, conspicuous, and easy to single out as the top predator affecting populations of elk, deer, and other prey animals.
Genomics of Isle Royale wolves reveal impacts of inbreeding
A new paper explores the genetic signatures of a pair of wolves isolated on Isle Royale, a remote national park in Lake Superior.
Surprisingly, inbred isle royale wolves dwindle because of fewer harmful genes
The tiny, isolated gray wolf population on Isle Royale has withered to near-extinction, but not because each animal carries a large number of harmful genes, according to a new genetic analysis.
Wolf-dog 'swarms' threaten Europe's wolves
'Swarms' of wolf-dog crossbreeds could drive Europe's wolves out of existence, according to the lead author of new research.
The return of the wolves
Researchers examine global strategies for dealing with predators.
Wolves more prosocial than pack dogs in touchscreen experiment
In a touchscreen-based task that allowed individual animals to provide food to others, wolves behaved more prosocially toward their fellow pack members than did pack dogs.
Isle Royale winter study: 13 new wolves, 20 radio-collared moose
Michigan Technological University's 2019 Isle Royale Winter Study focuses on the implications of newly introduced wolves and the movements of newly collared moose.
Origin of Scandinavian wolves clarified
There are no signs that hybrids of dog and wolf have contributed to the Scandinavian wolf population -- a matter that has been discussed, especially in Norway.
Yellowstone elk don't budge for wolves say scientists
Elk roam the winter range that straddles the northern boundary of Yellowstone National Park with little regard for wolves, according to a new study illustrating how elk can tolerate living in close proximity to the large predator.
More Wolves News and Wolves Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.