Saturday, March 14, 2020

How khulans get water

Khulan, a species of wild ass living in the Gobi Desert, travel over extremely long distances to find food and water, a recent study has shown.

The asiatic wild ass or khulan (Equus hemionus) used to be found throughout the arid lands of Central Asia and Mongolia, but their range is being limited by encroaching human activity.

As part of a long-term study into these animals, researchers at the Research Institute of Wildlife Ecology (FIWI, Conservation Medicine Unit) at Vetmeduni Vienna have been tracking their activity. Analysis of the data has not only revealed new insights into the behaviour of these animals, but it has also provided a new way of identifying water sources. The work has been published in Scientific Reports.

The world’s largest remaining khulan population, in Mongolia’s South Gobi Region, provided the subjects for the study. Using GPS collars to track the animals in the 100,000 km² study area, the researchers identified 367 waterpoints. Of these, 53 received intensive and repeated uses by many different khulan over multiple years and so seem to be of high importance for the entire khulan population.

However, the researchers point out that 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.

According to the researchers, khulan drink nearly every day, with daily requirements of 12-15 litres, rising to 24 litres on hot days. The low water content of their plant resources further increases the animals’ need to drink. 

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 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. The researchers point out that, as in many other of the world’s drylands human exploitation of water for agriculture, industry, and domestic uses increasingly affects the availability of 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. “Hence, 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,” says John Payne.

According to the researchers, the most important variable for the seasonal variation in choice of water sources is snow cover (or the lack of it). 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. 

The 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. The researchers emphasise the urgent need for regional conservation strategies so the khulan can continue to find the hidden liquid treasure of the Gobi Desert in the future.

Petra Kaczensky concluded: “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.”

For more details, see:

Hidden treasure of the Gobi: understanding how water limits range use of khulan in the Mongolian Gobi
John C. Payne, Bayarbaatar Buuveibaatar, Diana E. Bowler, Kirk A. Olson, Chris Walzer & Petra Kaczensky
Scientific Reports (2020) vol 10, Article number: 2989

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