Mountain goats battle bighorn sheep for climate-constrained resources

Looking through a spyglass in Montana’s Rocky Mountains, conservation ecologist Joel Berger and his doctoral student Forest Hayes saw something strange. On a barren ridge a mile away, a herd of mountain goats and bighorn sheep prowled around “those little muddy, wet places,” Berger recalled. “It’s very unusual to see them together like this.”

The two researchers had no idea what the animals were doing, and their perplexity increased when they saw a goat approaching a group of sheep. The goat lowered its head towards the sheep in an aggressive gesture, and before it could make contact, “the sheep moved away pretty quickly,” Berger said. “Goats have these saber-shaped horns that even sheep probably know aren’t good.”

Curiosity piqued, Berger and Hayes decided to investigate these apparent interspecies tensions further. After spending days sitting in the cold and windy Alps, watching mountain goats aggressively approach and hunt bighorn sheep through binoculars and spotting scopes, they had their answer: animals fought over mineral deposits in the “muddy places” that are created accessible when mountain glaciers melt.

In a study describing their findings, published Monday in Frontiers of ecology and evolution, the researchers hypothesize that such interspecific conflicts may become more common as climate change affects the availability of unequal abiotic resources such as minerals, water and snow. “Most people think in terms of what climate extremes do to we,says Berger, a professor at Colorado State University and a senior researcher at the Wildlife Conservation Society. “But different species of animals are also dealing with this. And conflicts could intensify due to the drastic climate problems facing the planet.

Conflicts between animals, like conflicts between people, can take the form of “blood and guts” spilled in battle, Berger notes. But it also manifests itself in competition for resources, another type of conflict that drives ecological relationships. Conflicts between animals of the same species are a commonly studied phenomenon, but much less is known about hostilities between species. Berger says this lack of baseline data is particularly problematic for any researcher hoping to understand the nuances of current and future impacts of climate change on wildlife.

To begin to fill in the unknowns, Berger, Hayes and their co-author Mark Biel of Glacier National Park in Montana first comprehensively reviewed decades of studies to find documented examples of non-human animal species conflicts. . They focused on extreme landscapes such as mountains, the Arctic and deserts, environments where resources are scarce even at the best of times and where, in many cases, climate change is already having a pronounced effect.

The researchers found about two dozen examples. These included wild horses hunting pronghorns, mule deer, and bighorn sheep away from waterholes in the American West; black rhino chasing gemsbok (a type of antelope) out of shady places in the Namibian desert; and domestic yak dominating takin (a large ungulate) on the mineral deposits of the Himalayas in Bhutan. Not surprisingly, when it comes to pushing limited resources, the researchers found that larger animals tend to win.

Bighorn sheep and mountain goats are similar in size. But in field studies, Berger and his colleagues found that goats almost always win. At three alpine sites—Caw Ridge in Alberta, Glacier National Park and Mount Evans, Colorado – they observed more than 120 goat-sheep skirmishes in which one animal was chased away by the other. These clashes were mostly about mineral licks, which are deposits of salts and other essential minerals that some animals use to supplement their diets. The Goats initiated every encounter and were the winners 98% of the time. Usually the sheep would walk away or run away before a physical altercation actually broke out. Like children fleeing a playground from an approaching aggressive bully with raised fists, “in the case of the bighorn sheep, they didn’t need to be kicked by the mountain goats to get the message across. “, explains Berger.

Rather than leading to a straightforward conclusion, Berger says, these findings demonstrate the complexity of trying to understand and conserve species in a changing world. Road construction projects have destroyed many low-lying blocks of minerals that mountain goats, bighorn sheep, and other species previously depended on. So in a way it’s a positive development that retreating glaciers are opening up new resources and new habitats. However, since these new resources are limited and unequal, there will be winners and losers when it comes to access. In this case, goats are the clear winners – a finding that involves further complications because mountain goats are not native to Colorado and some other states. Wildlife officials deliberately introduced them decades ago to provide a new source of revenue from the sale of hunting licenses.

The challenge for wildlife managers is to weigh the facts and decide what steps, if any, they should take to help mitigate anthropogenic impacts – including from development, invasive species and climate change – on animals. that they wish to protect. Managers might consider adding artificial salt licks where they are lacking, for example, or exterminating goats in areas where they have been introduced. For scientists, Berger adds, his team’s new research is a call to action to fill in the many unknowns that could help inform those decisions.

“This fascinating report should be the catalyst for a burgeoning field of study, namely how climate change is driving species interactions,” says Joanna Lambert, wildlife ecologist at the University of Colorado-Boulder, who did not participate in the new study. . “There are no benchmarks here, and if we want to document change, we need starting points. These three biologists are doing just that.

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