Friday, November 6, 2015

Big cats hunt livestock when wild prey is scarce

by Sarah Zielinski
tiger
Tigers and other big cats will eat their natural, wild prey when it’s plentiful. Only after their prey starts disappearing do they switch to a diet of livestock, a new study finds. Eric Kilby/Flickr (CC-BY-SA 2.0)

If farmers don’t want big cats to kill their livestock, they should make sure that the kitties have enough wild prey to eat. Lions, tigers and other big cats tend to hunt cattle, goats and sheep only after their regular prey has fallen below certain thresholds, a new study finds.

The seven species that make up the big cats — lions, tigers, jaguars, cougars, leopards, snow leopards and cheetahs — are favorites for those of us who only encounter them in zoos or on safari. But people who have to live with these animals aren’t often fans. It’s not good for farmers when the cats kill animals in their herds, and it’s not good for the kitties, since people sometimes kill the big cats in retaliation or to prevent more attacks.

But studies have suggested that the cats aren’t killing livestock willy-nilly and that the animals would prefer their natural, wild diet. So Igor Khorozyan and colleagues at the Georg-August University of G√∂ttingen in Germany wondered if what the balance was between a wild diet and the easy prey of a livestock herd. They gathered data on the seven big cats from more than 100 studies and applied some statistical analyses. They report their findings in the December issue of Biological Conservation.


Even snow leopards, the smallest of the big cats, can kill cattle.
Sibylle Stofer/Flickr (CC-BY-NC-SA 2.0)
 
“The probability of livestock killing by big cats significantly increased when prey biomass fell below minimum thresholds,” the team writes. When that “prey biomass” fell below 812 kilograms per square kilometer, the cats started killing cattle in higher numbers. And when the level fell below 545 kilograms per square kilometer, cats went for the smaller goats and sheep. (The numbers aren’t easily translated into numbers of animals per area because prey come in a variety of sizes. But they will be useful for people who manage animals and lands.)
 
When the kitties’ prey starts becoming scarce, the cats start hunting the easiest and most-profitable animal alternatives — cattle. When even the cattle can’t compensate for the cats’ missing prey, then the cats go after the smaller goats and sheep. In other words, it appears that big cats don’t really want to kill livestock as a first choice for dinner, but they will if they have few other alternatives.

The researchers found a few exceptions to this trend, such as when big cats were able to supplement the lack of their regular prey with other, non-livestock species, like giant anteaters or domestic dogs. But the livestock trend held for all seven of the cats, and it showed why in some protected areas in India, Nepal and South Africa, big cats tend not to kill livestock: They have plenty of wild animals to eat.

source

No comments: