摘要
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.
