When endangered wild animals try to mate with domestic relatives, both wildlife and people lose

Fatal attractions are a standard movie plotline, but they also occur in nature, with much more serious consequences. As a conservation biologist, I’ve seen them play out in some of Earth’s most remote locations, from the Gobi Desert to the Himalayan Highlands.

In these locales, pastoralist communities graze camels, yaks and other livestock across wide ranges of land. The problem is that often these animals’ wild relatives live nearby, and huge, testosterone-driven wild males may try to mate with domestic or tamed relatives.

Both animals and people lose in these encounters. Herders who try to protect their domestic stock risk injuries, emotional trauma, economic loss and sometimes death. Wild intruders can be displaced, harassed or killed.

These clashes threaten iconic and endangered species, including Tibetan wild yaks, wild two-humped camels and Asia’s forest elephants. If the wild species are protected, herders may be forbidden from chasing or harming them, even in self-defense.

Human-wildlife conflict is a widely recognized challenge around the world, but clashes in these remote outposts receive less attention than those in developed areas, such as pumas ranging into U.S. exurbs. As I see it, protecting threatened and endangered species won’t be possible without also helping herders whose lives are affected by conservation policies.

The drive to mate

The force driving these raids is pure biology. All domestic animals are descended from wild ancestors. Steeped in evolution, natural selection has favored males who inseminate the most females – and females who leave reproductive offspring of their own. Attractions can go both ways: Sometimes smaller or less aggressive domestic males may mate with wild females.

Many herding societies contend with this challenge. In the Hindu Kush mountain system of Central Asia and farther east, Tibetans, Uyghurs, Changpa and Nepalis raise domestic yaks, which provide meat, milk, transportation and shaggy hides for clothing.

Wild yaks were once thought extinct in Nepal, until a team led by wildlife biologist Naresh Kusi rediscovered them in 2014. Now aggressive contests between domestic and wild yaks are headaches for local herders.

In Africa, Namib Desert mountain zebras, a vulnerable species, have been bred by donkeys. In northern China and Mongolia, domestic and reintroduced Przewalski horses coexist in tense zones where herders work to prevent genetic exchanges. In Southeast Asia, wild cattle species, such as gaur and banteng, have mixed extensively with domestic cattle and buffaloes.

In northern realms, caribou and reindeer, which are the same species, Rangifer taranadus, both occur in wild forms. Reindeer have also been domesticated and are central to Indigenous herding cultures in Scandinavia, Russia, Canada and Alaska. Caribou slaughters and separation efforts have not prevented mixing.

In temperate zones of Europe and Asia, native species such as ibex, or wild goats, and argali, the world’s largest wild sheep, cause trouble by mingling with domesticated goats and sheep. In South America, guanacos – relatives of wild camels – range from sea level to the snow line in the Andes and attempt to interbreed with domestic llamas.

The wild and the tame

Across Earth, humans raise about 5 billion head of livestock. In most places, wild ancestors are long gone, so herders don’t have to contend with interbreeding.

The wild relatives that survive typically are rare or endangered. For example, there are about 43 million domestic donkeys, also known as asses, worldwide. But in the Horn of Africa, the sole remaining spot with native ancestors, fewer than 600 wild asses survive today.

The same asymmetry exists in the Himalayan Highlands, where wild yaks – a critically important species for Tibetan people – are estimated to number perhaps 15,000 to 20,000, compared with 14 million domestic yaks. Globally, for each wild Bactrian camel, there are about 2,500 domesticated brethren.

Even in protected areas of northern India, western Mongolia and western China, the abundance of domestic livestock outnumbers that of hoofed wildlife by a factor of about 19 to 1.

As wild populations shrink, the remaining males have smaller mating pools, which makes them more likely to pursue domestic females. But hybridizing with domestic animals could lead to some wild animals’ extinction as genetically distinct species.

No easy resolution

For pastoralists, earning a living along Earth’s rarified edges is hard enough without wild animals raiding their herds. Frequently, the only legal weapons herders can use to defend their livestock or themselves are sticks and stones. Guns are rare and often illegal, either because the wild species is protected or because the nation bans or restricts gun ownership.

Global conservation policy recognizes herders’ plight. The International Union for the Conservation of Nature, a network of governments and nongovernmental organizations that work to conserve life on Earth, affirms that Indigenous peoples play key roles in protecting threatened species and maintaining these wild animals’ genetic purity.

Many relevant national governments also support both protecting wild species and aiding nomadic herders, at least in principle. These broad goals aren’t always upheld at the local level, however, especially when the people in question are pastoralists living in remote areas where it’s hard to access government help.

Coexistence in a crowded world

When pastoralists need to protect their herds from other threats, such as snow leopards, brown bears or wolves, their main options are putting up fences, avoiding areas where carnivores are known to be present or killing the predators. Herders also castrate their domestic animals to keep them from fighting with other animals in the herd or attacking humans.

None of these options work well for dealing with wild progenitors of species such as yaks and camels. Castrating wild males or reducing their geographic ranges makes it harder to protect and increase threatened species.

Fencing is harmful because it can keep wild grazers from moving seasonally to different habitats. Wildlife migrations aren’t just important for the herd: As the animals roam and graze across broad areas, they fertilize grasslands. Arming pastoralists against wayward and aggressive wild males may seem justified, but destroying endangered species is a poor conservation path.

Respect for Indigenous peoples’ traditional cultural practices is important. So are international agreements to protect biodiversity. In my view, these human-wildlife clashes demand serious discussions that bring together herders, conservationists and local and national governments to develop pragmatic strategies.

Without creative solutions to prevent intermingling, more iconic animals will follow the disappointing paths of wild reindeer, bison and other wild species struggling to thrive as they increasingly collide with human societies.