Globally, dogs have caused about 10 extinctions and continue to threaten another 150 species. In the United States alone, some 78,000 dogs roam habitats close to urban and suburban development. From marine shores and grasslands to woodlands and coniferous forests, dogs chase and attack wild birds and deer and terrorize native predators such as gray foxes and even pumas.
Even the scent of a dog is enough to compel wildlife to flee and hide. The presence of dogs accelerates heartbeats in bighorn sheep and causes marmots to be more hesitant to reemerge from their burrows. Some animals will abandon living in an area altogether if dogs visit frequently, forcing them to give up precious opportunities to feed and travel.
Elsewhere, dogs serve as reservoirs for a host of diseases — such as rabies, canine parvovirus and leishmaniasis (also known as black or dumdum fever). Studies from Brazil reveal that wildlife and livestock in proximity to dogs are particularly at risk of leishmaniasis, which infects roughly 1.6 million people a year. In China’s Wolong Reserve, free-roaming dogs share at least four microparasites with the reserve’s giant pandas, threatening Wolong’s precious pandas with several pathogens.
In poor countries such as Nepal, dog populations — originally used to ward off snow leopards — have exploded. Unwanted dogs are left roaming villages, living on food scraps or hunting wildlife in forest habitats. Inevitably, conflicts mount. In the Annapurna Conservation Area, villagers routinely poison dogs with strychnine, a readily available poison that induces a long, painful death. It’s not uncommon to find dog carcasses in rivers and landfills. Sadly, when vultures and other scavengers eat the carrion, they are poisoned, too.
— Dogs are man’s best friend — but one of wildlife’s worst foes, Debby Ng and Joel Berger, The Washington Post. 24 March 2017.