Research shows that wells dug by feral donkeys and horses benefit other species and the environment.
Erik Lundgren and others studied the behaviour of feral equids in the Sonoran desert in the south-western United States. A report of the work has been published in the journal Science.
They found that feral horses and donkeys dig their own wells, which are sometimes up to two metres deep. The wells provide benefits for other species and lead to an increase in biodiversity in the surrounding area.
As part of their research, Erick Lundgren and his colleagues monitored four separate streams in part of the Sonoran desert in Arizona, using camera traps to observe the activity around the wells.
|Feral donkey (left and horse digging for water. Photo (c) Erick Lundgren|
The streams usually fill with groundwater but dry up in the summer. The research team surveyed each stream every few weeks over three summers and found that horses and donkeys in the area dig wells there to access the groundwater.
“It’s a very hot, dry desert and you’ll get these pretty magical spots where suddenly there is surface water,” said Lundgren.
"The donkey wells kept water in the system. And these features were used by pretty much every species you could picture, including some surprising ones like black bears, that we didn't expect to see in the desert."
Apart from the donkeys and horses, the team saw 59 other vertebrate species at the wells, 57 of which were recorded drinking from the wells.
Other species that they caught on camera visiting the wells included mule deer, bobcats, Woodhouse's scrub jay and javelinas.
The team even spotted some river tree species sprouting from abandoned wells, indicating they also serve a role as plant nurseries.
The researchers also found some riparian tree species (ie those that grow alongside water courses) sprouting from abandoned wells, indicating a wider environmental benefit.
Equids engineer desert water availability
Erick J. Lundgren, Daniel Ramp, Juliet C. Stromberg, Jianguo Wu, Nathan C. Nieto (deceased), Martin Sluk, Karla T. Moeller, Arian D. Wallach