It gets quite hot and dry in the southwest part of the United States and animals get thirsty! To reach groundwater, wild donkeys and horses dig into the dirt to reach cool and clear groundwater. New research suggest that equid wells, dug up by the donkeys and horses, are very valuable and beneficial to the ecosystem.
Wild donkeys and horses are often looked down upon because they can trample over native vegetation, erode creeks beds, and compete with native animals. They were introduced to North America in the last 500 years. When Erick Lundgren, a field ecologist at Aarhus University in Denmark, "first observed wild donkeys digging wells in 2014, he wondered whether these holes might benefit ecosystems, similar to the way elephant-built water holes can sustain a community in the African savanna."
Lundgren and his colleagues wanted to see if these holes increase accessible water. Over the summers between 2015-2018, they mapped out the surface area of water in wells at four sites in Arizona's Sonoran Desert. According to the study, "water availability was highly variable among sites, but equid wells generally increased accessible water, especially as temperatures rose. At one site, wells were the only source of drinking water once the stream completely dried up. Elsewhere, wells provided up to 74 percent of available surface water. Wells also decreased the distance between water sources by an average of 843 meters, making this essential resource more accessible and easing tensions that can escalate among drinkers at isolated water holes", Lundgren says.
Once the wells were dug, all sorts of animals came up for a drink. They documented 57 vertebrate species including birds, mountain lions, even a black bear! The study “clearly shows that equids can alter these ecosystems in ways that can benefit other species,” says Clive Jones, an ecologist at the Cary Institute of Ecosystem Studies in Millbrook, N.Y.