Humans kill non-human animals for all sorts of reasons, many of them not good. But we don’t feel the same way when we think about animals killing other animals, That’s part of a perfect, harmonious system. But, as with most things, we’ve found a way to corrupt that system, too. Now animals are killing other animals for bad reasons.
Researchers working on a new study of pumas in the Santa Cruz Mountains of California studied the behavior of 30 electronically tagged big cats across hundreds of locations, analyzing how the animals behaved the closer they came to housing developments. Male pumas killed about the same amount of prey as normal. But the females killed 36% more prey, compared to areas with little housing. The research raises the possibility that humans could have a widespread impact on animal numbers even when they don’t kill the animals themselves.
“Our results could have implications on the population trends of multiple species,” says lead author Justine Smith, a doctoral student at the University of California, Santa Cruz.
The study shows that when female pumas kill deer near housing, they spend less time than normal eating the carcass. That in turn leads them to chase and kill more animals, which means using more energy and more killing to eat. “Our results [show] that when pumas exhibit avoidance behaviors in highly disturbed areas, the loss of food therefore forces pumas in these habitats to kill more often to compensate for food loss,” Smith says in an email.
The males seemed less concerned about the presence of humans, and in any case they spend less time eating. They range further away from kill sites, patrolling and marking territory.
Smith hasn’t researched the effect on deer numbers, but thinks they could fall in line with the pumas’ more aggressive behavior. More generally, it’s possible humans increase animal kill-rates just by building houses.