Based on a mix of existing research and their own case studies, Julie Young of Utah State and four other scientists conclude that feral and free-roaming dogs may be wreaking havoc on wildlife, especially imperiled species, by preying on or harassing them and by transmitting diseases.
While widely accepted that the introduction of non-native species can be harmful to natural ecosystems, dogs are not usually viewed in that light.
“Dogs occur where humans occur, but we have tended to overlook their impact on wildlife mostly because we think of them as our companions,” said Young, co-author of “Is Wildlife Going to the Dogs?” newly published in the journal BioScience.
Young cited examples from Idaho, where research showed the presence of dogs diminishing some deer populations, and in Colorado, where a study showed that wildlife like bobcats are shunning trails where people hike with pet dogs.
On the Navajo reservation in northeastern Arizona, packs of feral dogs are chasing livestock, decimating populations of small mammals such as rabbits and acting as a disease vector for rabies among people and other animals, she said.
Loose dogs also were the suspected culprits in a distemper outbreak linked to a catastrophic die-off of endangered black-footed ferrets in northwestern Wyoming in the 1980s.
The issue came to Young’s attention while studying three endangered species in central Asia: wild sheep, gazelles and antelope. The steep rate of injury and death inflicted on those animals by free-roaming dogs prompted Young and her colleagues to take a closer look at the phenomenon globally.
What they found is that dogs, their worldwide numbers estimated at 500 million, can cause more damage to wildlife and livestock than wolves and other apex predators.
One study cited by Young concluded through genetic testing that dogs — not wolves, as originally suspected — were responsible for a rash of livestock killings in the mountainous Basque country between Spain and France. Investigators also found that feral dogs were behind most domestic sheep kills tracked in the French Pyrenees in the mid-1990s.
Authors of the new study said the problem is likely to worsen as communities sprawl.
Despite widespread leash laws and state statutes permitting prosecution of dog owners whose pets chase wildlife, violators are rarely punished because enforcement agencies are understaffed and underfunded, according to the paper.
Although dog lovers may have a bone to pick about the findings, Young said low-cost, common-sense solutions are at hand. Those range from public dog-training programs to vaccinating dogs against rabies and distemper.
“Some people might think it’s cute to watch their dog flushing sage grouse (an imperiled bird in Western states) but the grouse might abandon its nest because of it,” said Young. “It’s better for people to make the change instead of having it imposed on them.”
Copyright © 2011 Reuters