Dogs may be a human’s best friend, but can be a deadly menace to wildlife, including endangered species, according to a survey in India, home to the world’s fourth-biggest population of dogs.
The findings, reported in a new study published in Animal Conservation, highlighted dog attacks on some 80 species, including threatened ones dwindling in numbers, such as the golden langur (Trachypithecus geei), the great Indian bustard (Ardeotis nigriceps) and the green sea turtle (Chelonia mydas). Nearly half of these attacks took place in or around protected areas, the survey found.
India is home to about 60 million of the world’s estimated 1 billion dogs. In a bid to understand the impacts of free-ranging dogs on native wildlife in the country, which many experts claim is an “underreported” fact, Chandrima Home of the Bangalore-based Ashoka Trust for Research in Ecology and the Environment (ATREE) and colleagues zoomed in on dog-wildlife interactions in India through an online survey and scrutinized reports from national print media.
“We found it is largely a problem across India, despite the limitations of an online survey,” Home told Mongabay-India. “Dogs were reported to attack nearly 80 species of wildlife and most of the attacks were on mammals, largely ungulates like cattle and small carnivores. In some places, respondents reported multiple attacks. Majority of these attacks were by free-ranging dogs unaccompanied by humans and in packs. Nearly half of the attacks led to the death of the animal.”
Of the species that dogs reportedly attacked, 31 are listed under a threatened category on the IUCN Red List, including four critically endangered species. These include the great Indian bustard and the Bengal florican (Houbaropsis bengalensis), as well as the Chinese pangolin (Manis pentadactyla). Others include the green sea turtle, Himalayan goral (Naemorhedus goral), Asiatic wild ass (Equus hemionus), red panda (Ailurus fulgens) and the golden langur.
Some 73 percent of the 249 responses to Home’s online survey reported seeing domestic dogs attack wildlife, while nearly 78 percent of the respondents perceived the presence of dogs in and around wilderness areas to be harmful to wildlife.
Globally, cats, dogs and even rodents and pigs are known to disrupt wildlife, endangering about 600 species that are classed as vulnerable to critically endangered in the IUCN Red List. Studies show dogs have contributed to 11 vertebrate extinctionsand imperiled 188 threatened species worldwide.
The high dog density in India is attributed to poor dog ownership rules and a lack of sustained efforts in population control, exacerbated by increased availability of food waste. Home said she believed a combination of all these factors influenced the negative impact of dogs on wildlife.
“Since domestic dogs occur at densities higher than natural predators, the frequency of attacks on prey species is also likely to be high, especially in and around protected areas which are generally small in size in India,” she said. “Large mammals find it difficult to fight back when dogs charge in packs.”
In India, most free-ranging dogs are loosely associated with humans, Home said. Even if they are pets, they are generally off the leash and therefore have a propensity to interact with wildlife in several cases, due to their proximity to buffer zones and protected areas.
Dogs can venture out into these areas even if they are being fed at home. It is important to recognize the fact that a large proportion of these attacks occur without an accompanying human present, indicating that whether they are owned or not, these dogs’ free-ranging nature can have significant impacts on wildlife, Home said.
“The effects of these attacks on populations that are actually in decline could be disastrous,” she said. “It’s almost like the final nail in the coffin. When a species such as the great Indian bustard has shown already serious decline due to numerous reasons, predation by domestic dogs can push the species to extinction.”
However, the researchers cautioned against an “observation bias” in the data accumulated, since larger-sized species tend to get reported more.
About 48 percent of the attacks were reported within protected areas and the buffer areas around them, pointing to, as Home says, a “pervasive threat” to biodiversity. This highlights the role of dogs in driving changes at the boundaries of habitats, also called the edge effect, which has important implications for forest fragmentation and conservation.
“When habitats are fragmented, there are several edge impacts,” Home said. “For example when a road passes through a protected area, there are impacts on the species that are at the boundaries. Similarly the movement of dogs within such areas and longer forays can extend the impact of the edge.”
As an example, primatologist Parimal Bhattacharjee cites a recorded aggression in a small forest fragment in the northeastern state of Assam, in which a troop of six endangered Phayre’s leaf monkeys (Trachypithecus phayrei) were forced to abandon their regular areas following intense barking by domestic dogs.
“Coupled with the fact that there is large scale destruction of habitat for the procurement of agricultural land and setting up new human settlements, high dependency of locals on fuel wood, the aggression between the Phayre’s leaf monkeys and dogs may result in expulsion of the monkeys from their native area,” Bhattacharjee, who was not associated with the study, told Mongabay-India.
“These [golden langurs] are non-urban species and when they enter villages at the edge of forests, they are subjected to aggression by dogs owned by villagers to protect livestock from predators,” Bhattacharjee said. “In certain areas, canopy construction was carried out to protect them from a combination of road kills and dog attacks.”
Conservation biologist Sanjay Gubbi says domestic dogs have both direct and indirect impacts on wildlife, competing for prey with wild carnivores.
“They hunt wild animals from smaller wildlife such as hare, monitor lizards to large mammals such as chital and sambar,” Gubbi of the Nature Conservation Foundation, who was not associated with the study, told Mongabay-India. “We see this regularly in our camera traps where domestic dogs are carrying or chasing wild prey. Hence they compete for prey with wild carnivores. Lowered wild prey density affects species such as leopards and can cause leopards to shift to domestic prey leading to increased human-wildlife conflict.”
The experts also underscored domestic dogs as carriers of diseases that can be transmitted to wild animals such as the dhole, wolf, jackal, fox and other canids and felids.
About 87 percent of the people responding to the online survey felt the need to control dog populations around wilderness areas — an observation that underscores the need to rethink population management and address the threat of dogs as a conservation problem for wildlife, experts say. Some of the population control methods the respondents suggested using included trap-neuter-release, euthanasia, reducing food availability, or translocation of dogs to dog shelters.
“When it comes to dog population management nobody actually wants to look at one of the most important problem in India, that is, dog ownership policies,” Home said. “People like to feed dogs (easy way to show compassion) but do not want to be responsible pet owners. Also sterilisation is considered the only way to curb population.
“Restricting free-ranging behaviour is very important and that can only come with strong laws,” Home added. “In certain cases, hard decisions also have to be taken but in a humane way. One cannot have dogs around sensitive conservation areas. Disowned and feral ones should be removed. Animal welfare should not just be about dogs but also the gamut of wildlife being affected by the dogs themselves.”
Andrew Rowan, chief scientific officer for The Humane Society of the U.S. and former president and CEO of Humane Society International, said the issue of stray dogs killing wildlife in India is very similar to complaints in the U.S. by conservation biologists that cats are responsible for a huge proportion of bird mortality.
“The core problem is the encroachment of human communities into protected areas and the humans are then accompanied by dogs who may, or may not, remain close to their human commensals as they explore their environment,” Rowan said.