Wild horses and donkeys are often considered a problem in the American West, but the team found that the average number of species around a horse or donkey well was 64 percent higher than in dry surrounding areas observed at the same time periods.
Image: © Petra Kaczensky
Wild horses and donkeys are often considered a problem in the
American West, but new research suggests their penchant for digging
wells with their hooves offers benefits to the ecosystems they
inhabit, reports Douglas Main for National Geographic.
The study, published this week in the journal Science, shows that
when wild or feral horses and donkeys dig wells, they increase the
availability of water for other species living in the parched desert
landscape. These wells can be up to six feet deep and provide access
to groundwater to species including badgers, mountain lions, deer
and birds.
Donkeys and horses were introduced to North America roughly 500
years ago, and the Bureau of Land Management currently estimates
there are more than 95,000 wild donkeys and horses roaming the West.
That figure is more than triple what land managers say the landscape
can sustain, and the growing population can “trample native
vegetation, erode creek beds and outcompete native animals,” writes
Jonathan Lambert for Science News.
In 2014, however, Erick Lundgren, a field ecologist at Aarhus
University in Denmark, saw wild donkeys digging wells and wondered
if other animals in the environment might use them in much the same
way that animals from far and wide take advantage of elephant-dug
watering holes in the African savannah, per Science News.
To investigate, Lundgren and his co-authors kept an eye on four
dried-up streams in the Sonoran Desert of Arizona. The team
monitored the streams during the summers of 2015, 2016 and 2018 and
made note of any new wells dug by horses and donkeys.
Researchers found that the wells drew 59 other vertebrate species,
57 of which were seen drinking from the equine waters. Some wells
even appeared to provide a boost to desert trees such as willows and
cottonwoods, which researchers observed germinating from the
moistened soil.
“These resources are in fact used by all other animals—there was a
cacophony of organisms,” Lundgren tells Karina Shah of the New
Scientist.
In fact, the team found that the average number of species around a
horse or donkey well was 64 percent higher than in dry surrounding
areas observed at the same time periods.