Wild horses and donkeys dig desert wells in Arizona, supplying water to 57 vertebrate species

When summer heat dries up streams in the Sonoran Desert, wild horses and donkeys can do something unexpected: dig for water. Researchers began tracking these animal-made wells in 2015, mapping their water supply across four Arizona sites over three summers. By 2018, they had found that the wells could provide up to 74% of the surface water available at one site. Cameras also recorded 57 vertebrate species, from songbirds to mountain lions, visiting wells across the Sonoran and Mojave deserts. The findings, reported by Science News and Arizona State University, add a surprising dimension to the debate over animals often labelled invasive: in some places, their digging may help other species through dry spells, even as the broader impacts of horses and donkeys remain complex.Digging for waterThe study began with an observation by ecologist Erick Lundgren. In 2014, he saw wild donkeys digging into dry ground and wondered whether the holes they made could offer water to more than just the animals that excavated them. To investigate, Lundgren and colleagues mapped the surface area of water in equid wells and groundwater-fed streams at four sites in Arizona’s Sonoran Desert. They conduct...