Imagine a grassy island inhabited almost entirely by a small group of wild horses. Now imagine that same island, several years later, inhabited almost entirely by a large group of wild horses. How will their use of habitat on the island have changed?

That’s the question Canadian researchers set out to answer, working with real feral horses on a real grassy island known as Sable Island. Located about 200 miles southeast of Canada’s Nova Scotia, Sable Island is home to around 500 horses—entirely independent of human handling and management—and only about five humans.

Philip McLoughlin, PhD, associate professor of biology at the University of Saskatchewan in Saskatoon, and colleagues have been tracking the Sable Island horses’ movement patterns and population density (number of horses in the same area) for the past five years. He recently confirmed that feral horses choose their habitat depending on population density. In other words, McLoughlin said, the horses appear to “shop around” for the best place to live under the circumstances.

“Horses can graze in the best grassland when density is low, but then they are forced to move and use poorer habitat when density increases,” McLoughlin said. This happens at two different levels: along the whole island as well as within regions of the island