VN June 2021

Vetnuus | Junie 2021 6 Leading Article Erick Lundgren, PhD Student, Centre for Compassionate Conservation, University of Technology Sydney; Arian Wallach, Lecturer, Centre for Compassionate Conservation, University of Technology Sydney; Daniel Ramp, Associate Professor and Director, Centre for Compassionate Conservation, University of Technology Sydney In the heart of the world’s deserts – some of the most expansive wild places left on Earth – roam herds of feral donkeys and horses. These are the descendants of a once-essential but now-obsolete labour force. These wild animals are generally considered a threat to the natural environment, and have been the target of mass eradication and lethal control programs in Australia. However, as we show in a new research paper in Science, these animals do something amazing that has long been overlooked: they dig wells — or “ass holes”. In fact, we found that ass holes in North America — where feral donkeys and horses are widespread — dramatically increased water availability in desert streams, particularly during the height of summer when temperatures reached near 50℃. At some sites, the wells were the only sources of water. The wells didn’t just provide water for the donkeys and horses, but were also used by more than 57 other species, including numerous birds, other herbivores such as mule deer, and even mountain lions. (The lions are also predators of feral donkeys and horses.) Incredibly, once the wells dried up some became nurseries for the germination and establishment of wetland trees. Ass holes in Australia Our research didn’t evaluate the impact of donkey-dug wells in arid Australia. But Australia is home to most of the world’s feral donkeys, and it’s likely their wells support wildlife in similar ways. Across the Kimberley in Western Australia, helicopter pilots regularly saw strings of wells in dry streambeds. However, these all but disappeared as mass shootings since the late 1970s have driven donkeys near local extinction. Only on Kachana Station, where the last of the Kimberley’s feral donkeys are protected, are these wells still to be found. In Queensland, brumbies (feral horses) have been observed digging wells deeper than their own height to reach groundwater. Feral horses and donkeys are not alone in this ability to maintain water availability through well digging. Other equids — including mountain zebras, Grevy’s zebras and the kulan — dig wells. African and Asian elephants dig wells, too. These wells provide resources for other animal species, including the near-threatened argali and the mysterious Gobi desert grizzly bear in Mongolia. These animals, like most of the world’s remaining megafauna, are threatened by human hunting and habitat loss. Feral desert donkeys are digging wells, giving water to parched wildlife Feral donkeys and horses dig wells to desert groundwater. Erick Lundgren Numerous species use equid wells. This includes mule deer (top left), scrub jays (middle left), javelina (bottom left), cottonwood trees (top right), and bobcats (bottom right). Erick Lundgren Some of the last feral donkeys of the Kimberley. Arian Wallach