Mountain lion leftovers feed — and house — thousands

Analysis by Dr. Karen Shaw Becker

mountain lion role in ecosystem

Story at-a-glance -

  • Researchers located 18 carcasses of elk and mule deer left behind by mountain lions in Bridger-Teton National Forest and returned weekly for six months to collect data
  • They found a thriving ecosystem of beetles dining on the carcasses and collected 24,000 individual beetles from 215 different species — far more than the 4,000 beetle species found just 65 feet away
  • About half of the beetles they collected were meat-eating northern carrion beetles, but they found a large number of beetles that typically eat either plants or slugs and snails
  • The research emphasizes the importance of how mountain lion kills positively impact a wider variety of species in their environments than, say, a wolf pack might because of the number of other species that benefit
  • Mountain lions are “subordinate apex predators,” meaning that although they may be forced to leave behind a carcass for other carnivores, a kill as large as an elk might mean there’s enough left over for them to go back for leftovers

Sometimes the circle of life involves the demise of animals less able to protect themselves against other animals that call them prey. It's disturbing to some, that some animals must die to fulfill the law that says only the fittest survive.

But even when prey falls by the wayside and becomes sustenance for mountain lions, the circle of life continues in ways that are fascinating and even awe-inspiring. That's what researchers found as they looked at carcasses left behind by these large cats in Bridger-Teton National Forest in northwestern Wyoming.

Weighing an average of 150 pounds, mountain lions routinely tackle animals like 700-pound elk. While that may seem surprising, the fact that they leave behind large portions of meat earns them the designation of "ecosystem engineers."

In a study published in Oecologia,1 biologist Mark Elbroch, Ph.D. Puma Program director for Panthera, an organization devoted to conserving the world's biggest cats, explained that a number of animal species, from mammals to birds to insects and other invertebrates, take advantage of the free meals left behind by the mountain lions (also called pumas, catamounts or panthers, depending on the area they roam).

The scientists found 18 mule deer and elk carcasses in May of 2016, set up beetle traps nearby, then visited the sites every week for six months to collect data and peruse the changes taking place.

Imagine their surprise to find a thriving ecosystem of beetles dining on the carcasses. The researchers collected 24,000 individual beetles from 215 different species, but they found something else: As little as 65 feet away where there were no carcasses, there was only an average of 4,000 beetles. In addition, Smithsonian Magazine reports:

"They discovered beetles in the Curculionidae family, which normally eat plants that may have been dining out on the stomach contents of the deer. They also found beetles that snack on slugs and snails, which are often found under the animal carcasses. The dead deer weren't just passing snacks for the beetles. For many of these insects, the rotting meat pile was their permanent address."2

For some insects, rotting meat is a 'permanent address'

Carcasses of dead deer and other large prey taken down by mountain lions aren't just snacks to the beetles and other insects that find their way to them. For many, the carcasses become their new residence for generations. "These carcasses are their homes," Elbroch says. "They are the places where they seek their mates. They're the places where they raise their young and where they hide from predators." He adds, "This is habitat. This is not just food resource. It's more than that."3

Cannon says the research helps emphasize the importance of how mountain lion kills positively impact a wider variety of species in their environment than, say, a wolf pack might. In fact, a study published in Biological Conservation4 reported that carcasses left behind by mountain lions are visited by 39 species of birds and mammals, the largest number of scavenger species ever recorded around a carcass.

While they are large predators in the whole scheme of things, mountain lions aren't at the top of the food chain. Depending on the circumstances, these lone hunters are often forced to leave behind their kills to be devoured by wolves, grizzly bears or other carnivores.

That makes them "subordinate apex predators," Elbroch explains; if the prey is big enough, there might still be some left over after the carcass has been picked over. A kill as large as an elk might mean there's enough left over for them to go back for leftovers a number of times over several days.

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How animals change their ecosystems to benefit other species

John C. Cannon, writing for Mongabay, a nonprofit organization providing conservation and environmental science news, explains that animals sometimes change their ecosystems in profound ways by inadvertently providing resources that benefit other species.

"These ecosystem engineers typically function as the bulldozers and earthmovers of the natural world: Think of elephants excavating waterholes that then slake the thirst of other animals, or beavers constructing dams to form ponds that ultimately house a wide range of fish. Mountain lions, Elbroch's team has shown, manipulate their environment in their own unique way."5

Although they fit into the same category, woodchucks that excavate burrows used by other species don't have the ecological impact that mountain lions do. Elbroch returned often to kill sites and noticed countless times "how deep into the ecological web the effect of that carrion penetrated."6

Besides animals small and large picking apart the carcass for meat, he noticed small birds darting about the carcasses catching flying insects for food, and vultures hovered for a chance to sample the maggots proliferating inside. But mountain lions aren't the only large cats participating in the phenomenon that makes them movers and shakers in their respective ecosystems.

Six other felids, or wild cats, including the cheetah (Acinonyx jubatus) in Africa's savannas, Sunda clouded leopards (Neofelis diardi) of Borneo and Sumatra, clouded leopard (Neofelis nebulosa), Eurasian lynx, leopard (Panthera pardus) and the snow leopard (Panthera uncia)7 make similar marks in their territories.

Other than Antarctica, all together, these big cats have similar habits in regard to leaving large portions of uneaten kill behind — and are distributed over an estimated 43% of the Earth's surface, the 2017 study asserts.8 Elbroch's team wrote:

"Together with pumas, these seven felids may provide distinctive ecological functions through their disproportionate production of carrion and subsequent contributions to biodiversity. We urge conservation managers to increase support for these species, as a means of prioritizing resources to best ensure the persistence of carrion in natural systems."9

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