Pathologic findings in reintroduced Przewalski’s horses (Equus caballus przewalskii) in southwestern Mongolia.

The research article investigates the causes of mortality in recently reintroduced Przewalski’s horses in Mongolia, revealing diseases, harsh winters, and predator attacks as primary factors affecting the survival of the species in the wild.

Background

• The Przewalski’s horse (Equus caballus przewalskii) was extinct in the wild by the mid-1960s and survived through captive breeding only.
• To reintroduce this species into the wild, the International Takhi Group rolled out the Takhin Tal reintroduction project in Mongolia.
• The first group of captive-bred horses were released into the wild in 1997, and the first successful births in the wild happened in 1999.
• At the time of the study, Takhin Tal had 63 Przewalski’s horses, and a disease-monitoring program in place since 1998 for monitoring causes of death.

Findings

• The study evaluated a total of 28 deceased horses, collecting samples for further investigation.
• Results showed that equine piroplasmosis, a common tick-borne disease in Takhin Tal, was responsible for the death of four stallions and a stillborn foal.
• Predator attacks from wolves were initially attributed as a significant cause of death, primarily in December 2000; however, more extensive clinical and postmortem examinations unveiled strangles as a significant contributing factor to mortality in these horses.
• Harsh Mongolian winters were found to weaken the horses, rendering them more defenseless to opportunistic infections and thus easy targets for wolf predation.
• Other causes of death identified were trauma, exhaustion, wasting, urolithiasis (bladder stones), pneumonia, abortion, and stillbirth.
• However, autopsy examination of the Przewalski’s horses did not lead to a definitive cause of death in every case.

Conclusion

• The study concluded that several disease factors were significant in the initial phase of the reintroduction project, which could potentially jeopardize the establishment of a self-sustaining population.
• These diseases, coupled with other environmental and predatory factors, make the reintroduction and survival of Przewalski’s horses in the wild a continually challenging task.