Near Cities, Pumas Kill More but Eat Less

A mother puma and two cubs on a hillside above San Jose, California. The image was captured by a motion-detecting camera. Chris Wilmers

When people move near cities, they become more likely to use mass transit and shop at Whole Foods. When pumas do, they become more deadly, hunting and killing more prey but eating less of each carcass.

That's because, scientists suggest in a study published this month in the journal Proceedings of the Royal Society B, pumas, also known as mountain lions or cougars, are unnerved by the presence of people. Humans are, after all, the only species that regularly kills adult pumas—they have hunted and trapped the creatures almost completely to nonexistence in eastern North America, where they were once plentiful.

But the animals' numbers have rebounded somewhat in recent years. And human developments in areas where the animals are found, like Northern California, continue to expand. Those two factors mean that more pumas are living closer to humans.

Researchers from the University of California, Santa Cruz, attached tracking collars to 30 pumas that lived at varying distances from developed areas near that West Coast town. Animals that abutted developed areas killed 36 percent more deer but spent 42 percent less time feeding on these prey, compared with pumas in undeveloped areas, according to the study. As a result, the animals likely need to kill more because they get less food energy from each one.

"Increased kill rates may lead carnivores to waste energy and also influence prey survival rates in human-modified landscapes," said Justine Smith, a doctoral student at UC Santa Cruz and one of the authors of the paper, in a statement.

Pumas killing more deer in semideveloped areas could actually be advantageous for humans and the environment, since deer overabundance—in the absence of natural predators—can cause serious problems, from hampered forest regeneration (from eating saplings), to vehicle collisions, to the spread of Lyme disease.

But when pumas can't finish their meals, the authors speculate, it's harder for them to survive and reproduce.