Coexistence between Przewalski's horse and Asiatic wild ass in the desert: the importance of people.
Abstract
Przewalski's horses and Asiatic wild asses were thought to have coexisted in the past. After reintroducing the extinct-in-the-wild Przewalski's horses within the range of Asiatic wild asses around 2000, it was hoped they would coexist through different resource utilization strategies. However, equid species worldwide rarely share landscapes. The Dzungarian Gobi, with limited water availability, also seems incapable of supporting two equids even though they exhibit differentiated niches. We delimited their fundamental and realized niches in water use by captive experiments and camera traps at watering points at Kalamaili Nature Reserve, China. Using generalized linear models and circular statistics, we analysed how interspecific competition, human presence and environmental factors (temperature, precipitation, water salinity and water deficits) affected each species' daily water use patterns. The two equids exhibited distinct water-use patterns. In captivity, Przewalski's horses showed higher water dependency than wild asses-drinking more frequently, consuming more water per unit body weight (0.095 vs. 0.032 L/kg) and displaying greater sensitivity to high temperatures. Field observations from 316,556 camera trap photos over 665 days revealed that horses relied on fixed watering points and avoided saline and near-depleted watering points, unlike asses. While both could drink freely day and night when separated, their interactions in shared territories showed a clear pattern: horses primarily drank during the daytime when heat loading peaked and used physical dominance to keep smaller-bodied asses away from low-salinity, long-lasting watering points until nightfall when they left to forage. This forced asses to either drink at low-salinity watering points at night or use high-salinity ones during the day. The numerical advantage of wild asses-travelling in large herds-often results in their depleting watering points that were spring-fed. However, watering points near human settlement, though scarce, remain accessible to horses as asses avoid them, thus providing reliable drinking spots for horses, particularly harems, after night-time foraging. They serve as crucial refuges, preventing competitive exclusion by the numerically-but not physically-dominant asses. Synthesis and applications: Our findings highlight the importance of people in permitting sympatric coexistence during resource scarcity. However, human involvement requires careful management. Increased human presence may benefit horses but restrict wild asses' access to some quality water, potentially weakening their climate resilience.
Key words
- animal behaviour
- animal ecology
- climate change
- climatic factors
- diurnal activity
- drinking
- drinking water
- environmental factors
- foraging
- Geographical distribution
- Gobi Desert
- habitat selection
- habitat suitability
- habitats
- human activity
- interspecific competition
- landscape
- linear models
- nature reserves
- nocturnal activity
- precipitation
- salinity
- settlement
- species differences
- sympatric species
- temperature
- water
- water quality
- water resources
- water use
- wild animals
- wildlife conservation
- wildlife management
- zoogeography
- arid lands
- deserts