Here’s a great article by Liza Gross in KQED’s Quest. It ties our recent puma work nicely together with other work on predator effects on ecosystem function.
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These “top down” trophic cascades, which the ecologists dubbed “trophic downgrading,” have been documented from the poles to the equators and every major biome in between, making the loss of top predators, they wrote, “arguably humankind’s most pervasive influence on the natural world.” Earth has weathered five mass extinctions but never before at the hands of one species—human beings. And we humans seem hell bent on clearing the Earth of larger bodied apex predators.
I considered all this as I read a new paper from wildlife ecologist Chris Wilmer’s lab (published last week in PLOS ONE) that looks at how human development affects pumas. Like most large carnivores, pumas need vast territories to hunt, find mates and raise young. Pumas living in the San Francisco Bay Area have no such luck. Wilmers, an associate professor of environmental studies at the University of California-Santa Cruz, has been studying the effects of habitat fragmentation on the behavior, ecology and even the physiology of pumas around the Santa Cruz Mountains. He develops cutting-edge GPS collars to track both the location and behavior of his animals.
Fragmented landscapes often pave the way to extinction for wide-ranging large carnivores like pumas, with cascading effects. Freed from the threat of top predators, smaller carnivores like foxes increase in number, driving declines in birds and small mammals. But habitat fragmentation can produce effects similar to extinction because large predators tend to avoid small fragmented parcels. Given the heterogeneous patterns of human developments—with houses and other structures interspersed among natural areas—predicting how animals might respond, and with what consequences, presents a serious challenge.
Read the full article here.