Equid tail hairs reveal dietary choices of three horse species in Asia's Gobi Desert

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What happens when different species of equids are competing for food in the same ecosystem? Researchers from the University of Vienna vet school were able to sort out who was eating what by analyzing tail hairs.

What happens when different species of equids are competing for food in the same ecosystem? Researchers from the University of Vienna vet school were able to sort out who was eating what by analyzing tail hairs.

You can tell a lot about a horse from its hair...if you happen to be a medical technician with a testing laboratory at your disposal. Hair analysis has been used for decades to de-code critical information about humans and animals in the paleobiology field. Increasingly, researchers are investigating ways that non-invasive equine medical information obtained from hair analysis, including the presence of illegal medications in racehorses.

Today we share a news story provided by the University of Vienna vet school about testing horse hair not at an archeological dig or even in a racetrack testing lab but in the desert, with real horses. At the end of the article you will find a link to the original research article, and some additional sources on horse hair testing.

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The Przewalski’s horse is a species of wild horse that has been successfully reintroduced to Central Asia's Gobi Desert. It shares its pasture grounds with wild donkey-like khulan and free-roaming domestic horses. The species became extinct in the wild in 1968. Successful breeding programs at zoos around the world have helped to reintroduce the animals in the Great Gobi B protected area in southwestern Mongolia since 1992. 

For the preservation of the wild Przewalski’s horse, it is important to understand if and how the three related species compete for food in the protected area.

Competition between Przewalski’s horses and domestic horses in the winter

Martina Burnik Šturm and Petra Kaczensky from the Research Institute of Wildlife Ecology at Vetmeduni Vienna, in cooperation with the Leibnitz Institute for Zoo and Wildlife Research in Berlin, used a special method based on the chemical analysis of tail hairs to investigate the dietary habits of the animals. The analysis allowed them to determine the composition of the diet of each of the three species, which led to the discovery of increased dietary competition in the winter months.

The chemical analysis of the tail hairs revealed that Przewalski’s horses and domestic horses are year-round grazers. Khulan, on the other hand, switch from grazing in the summer to a high proportion of shrubs in the winter. “When food becomes scarce in the long winter months, competition can be expected especially between the two species of horse,” explains Martina Burnik Šturm.

Competition considerably less in the summer



In the summer, the food supply is relatively high. At the same time, the local nomads leave the Gobi and take their horses to the high pastures of the surrounding mountains. “In the hot season, Przewalski’s horses mainly graze near sources of water. Khulan, on the other hand, also graze on pastures far from water sources as they are better able to conserve water. The potential for pasture competition in the summer is therefore relatively low among the three species in the Great Gobi B protected area,” adds Petra Kaczensky.

Chemical composition of the hairs holds information about dietary choices



The chemical analysis used by Burnik Šturm and Kaczensky measures so-called stable isotopes in the tail hairs. “Stable isotopes are atoms of of the same chemical element with the same number of protons but different number of neutrons and thus with different masses. The isotope values in the body tissue of living organisms are the result of the isotope values in the environment and of the animal’s metabolism,” explains Burnik Šturm. 

Grasses and shrubs in the Gobi Desert exhibit different values of carbon isotopes, which make it possible to differentiate between grazers and browsers.

Because the tail hairs of horses grow at a regular rate, they act as an archive storing the isotope values at each growth stage. The longer the hair, the farther back into the past the researchers can look. “If you know how fast the hairs grow, you can date specific hair segments and clearly assign them to a certain season. Consecutive hair segments therefore provide valuable information about the diet and water balance of an individual animal,” explains Burnik Šturm.

Protected area in the Gobi Desert to secure the survival of Przewalski’s horse



International research teams, under the direction of Vetmeduni Vienna and in close cooperation with the Great Gobi B protected area, have for years been committed to the reintroduction program in the Gobi Desert. The long-term goal is to establish a self-sustaining and viable population of Przewalski’s horses, but also to protect other key species such as the khulan. 

An exact understanding of the dietary behavior of the Przewalski’s horse and the khulan are important for improving the conditions in the protected area. The high potential for pasture competition between domestic and wild horses highlights the need for stricter regulation and a restriction on the grazing of domestic horses. The establishment of artificial water sources should be well considered to avoid infringing on the khulan’s areas of retreat.

The article “Sequential stable isotope analysis reveals differences in dietary history of three sympatric equid species in the Mongolian Gobi” by Martina Burnik Šturm, Oyunsaikhan Ganbaatar, Christian C. Voigt, and Petra Kaczensky was published in the Journal of Applied Ecology.

To learn more:

West, A. G., Ayliffe, L. K., Cerling, T. E., Robinson, T. F., Karren, B., Dearing, M. D., & Ehleringer, J. R. (2004). Short‐term diet changes revealed using stable carbon isotopes in horse tail‐hair. Functional Ecology18(4), 616-624.

Dunnett, M. (2005). The diagnostic potential of equine hair: A comparative review of hair analysis for assessing nutritional status, environmental poisoning, and drug use and abuse. Advances in Equine Nutrition-III, 85-106.