Khulan (Equus hemionus), a species of wild ass living in the Gobi Desert, travel extremely long distances to meet their water needs – a strategy that will require urgent conservation interventions as local human impacts increase, says a team of scientists.

Publishing their results in the journal Scientific Reports, researchers from the University of Veterinary Medicine in Vienna, WCS, and the Norwegian Institute of Nature Research used GPS collars to track the world’s largest remaining khulan population in Mongolia’s South Gobi Region.

The researchers were able to identify 367 waterpoints, 53 of which received intensive and repeated uses by many different khulan over multiple years and thus considered to be of high importance for the entire population.  However, the large number of less-visited waterpoints are also important as they provide “stepping-stones” to switch between areas and allow for maximal movement flexibility.

The need to drink daily is an important driver of khulan movements. Khulan drink almost daily and normally require 12–15 litres of water per day and up to 24 litres on hot days. The low water content of their plant resources further increases the animals’ need to drink.

Under a warming climate (higher evaporation, increased heat stress of plants) the need to access water can be expected to increase and may reduce the radius at which khulan can graze away from water, thus reducing the pasture area that is functionally available for the khulan population. Furthermore, the frequency of extreme events like droughts and extreme winters (both with no snow or extreme amounts of snow) is expected to further increase. The high mobility of khulan and other migratory wild ungulates is the best strategy to cope with this uncertainty, but requires a high level of landscape connectivity.

In the Mongolian Gobi, khulan roam over thousands of square kilometres, a range among the largest reported for terrestrial mammals. These large nomadic movements are a consequence of the low and unpredictable resource base with both the availability of pasture and water changing within and between years. To survive and thrive in such landscapes, movement flexibility is key but may be threatened by increasing human impact on the khulan’s habitat resulting in habitat fragmentation.

Most large herbivores in arid landscapes are especially vulnerable to disturbances of their habitat. In many other of the world’s drylands, human exploitation of water for agriculture, industry, and domestic uses increasingly drives the availability and access to water for wildlife. Khulan tend to use pastures within 7 km of water and areas beyond 15-20 km of water become functionally inaccessible.

“Blocking access to water excludes khulan from the landscape and identifying important waterpoints in arid landscapes like the Gobi Desert is therefore essential for wildlife-friendly land-use planning,” said lead author John Payne of the Research Institute of Wildlife Ecology.

Until recently widespread and abundant throughout the arid landscapes of Central Asia and Mongolia, the number of khulan has declined dramatically in the 19th and 20th century.  Besides changes in land use and overhunting, the increasing difficulty in accessing water is believed to have played a major role in this development. Until now, however, there had been little data on how water availability is influencing movements.

Said co-author Chris Walzer, Executive Director of WCS’s Health Programs: “Khulan are living barometers of the health of Central Asia’s unpeopled, arid landscapes. Any human development of this fragile region must be done with extreme care or we will lose the wildlife that have called this area home for thousands of years.”

According to the researchers, the most important variable for the seasonally different use of the waterpoints is snow cover (or the lack thereof). In the deserts of Central Asia and Mongolia, a lack of snow, the low water content of the vegetation, and the freezing of small and stagnant water bodies can result in drought conditions during winter. In extreme cases, these factors can result in winter die-offs of local wildlife populations.

Khulan´s highly mobile lifestyle is a coping strategy during localized catastrophic weather events, but this requires habitats that allow large scale movements – which in turn necessitates maintaining landscape connectivity.

Said co-author Petra Kaczensky of the University of Veterinary Medicine Vienna: “Our results provide important data that can help guide a regional khulan conservation strategy, allow predictions for other khulan populations, and illustrate the overall importance of waterpoints for dryland herbivores.”