Reproduction and Mortality of Re-introduced Przewalski＇s Horse Equus przewalskii in Hustai National Park, Mongolia

The reproduction rate of Equus przewalskii in this study increased from year to year showing that the wild horses have already felt comfortable in the new environment and became acclimatized successfully. Of the mares which were born in Hustai National Park and successfully reached reproductive age, 24.7% first gave birth at age 3 and 55.6% of them first gave birth at age 4. The most effective age range within the breeding population was 5 to 15, 25%-89% of them giving birth and an average during 2002-2011 of 72.9%. Of the Przewalski＇s horses which died, 65% were foals, 9.4% subadult male, 7.7% subadult female, 7.2% adult male and 10.6% were adult females. Causes of mortality differed by age and sex although wolf attacks accounted for the predominant number of deaths among foals and subadults. Stallions usually died of bad condition and injuries but parturition problems were common causes of death among mares. The mortality rate of foals （40% in 1993-2011） is a matter of great concern since foals born in Hustai National Park are the only gain component now after the active reintroduction period came to an end. A total of 109 foals were killed by wolves in 1993-2011 but 52% of them were younger than one month.

Analysis on the relationship between winter precipitation and the annual variation of horse stomach fly community in arid desert steppe, Northwest China (2007–2019)

Gasterophilus spp.have been found to be widespread in reintroduced Przewalski’s horses in the Kalamaili Nature Reserve(Northwest China).However,data on the annual variation in Gasterophilus infections are lacking.To analyze the epidemiological features and determine the cause of the annual variation in Gasterophilus infections,we treated 110 Przewalski’s horses with ivermectin and collected Gasterophilus larvae from fecal samples each winter from 2007 to 2019.All 110 Przewalski’s horses studied were found to be infected by Gasterophilus spp.,and a total of 141379 larvae were collected.Six species of Gasterophilus were identified with the following prevalence:G.pecorum(100%),G.nasalis(96.36%),G.nigricornis(94.55%),G.haemorrhoidalis(56.36%),G.intestinalis(59.09%),and G.inermis(3.64%).The mean infection intensity of Gasterophilus spp.larvae in Przewalski’s horses was 1285±653.G.pecorum(92.96%±6.71%)was the most abundant species.The intensity of Gasterophilus spp.(r=–0.561,P<0.046)was significantly correlated with winter precipitation.Our findings confirmed that,in the Kalamaili Nature Reserve,gasterophilosis is a severe parasitic disease in Przewalski’s horses.Winter precipitation at the beginning of the year can indirectly affect the intensity and composition of Gasterophilus spp.in Przewalski’s horses at the end of the year.Therefore,the water-related ecological regulation should be carried out to help reduce the parasite infection of Przewalski’s horses.