安西极旱荒漠国家级自然保护区重引入普氏野马繁殖成效与种群生存力分析

Re-introduced Przewalski's horses's breeding success and population viability analysis in Anxi National Nature Reserve

安西自然保护区放归的普氏野马是一个孤立封闭的小种群,种群数量增长极其缓慢,同时,面临着严峻的捕食压力和近交衰退。因此,对这个种群制定长期的自然保护计划是当务之急。本研究通过对重引入普氏野马种群繁殖力和种群生存力进行分析,结果表明:(1)安西保护区野马种群数量增长缓慢是由低生育率(44.3%)和高幼驹死亡率(43.4%)造成,天敌捕食(35.3%)和疾病(26.5%)成为影响野马繁殖存活率的主要因素;普氏野马的繁殖具有明显的季节性特征,80.9%的幼驹出生在5月和6月;(2)种群生存力分析(PVA)预测本放归野马种群未来100年的灭绝概率是60%,野马种群数量达200匹以上才能保证100年后90%的存活率;(3)参数敏感度分析显示,外部因素——狼袭对保护区野马种群的灭绝和种群数量最具影响力,其次是决定生殖成功的内部因素——生育率、最大繁殖年龄;(4)保护区野马小种群效应明显,疾病和幼驹羸弱而死亡的比例高(分别为26.5%和8.8%),合理的补充新个体是降低种群灭绝风险长期的管理对策;同时,减小狼对野马的捕食压力,加强幼驹的保护,是目前改善本区内普氏野马小种群生存状态的有效手段。

The Przewalski＇ s horse （Equus przewalskii） population re-introduced in the Anxi Extra-arid Desert National Na- ture Reserve in northwest China, is a relatively isolated population with an extremely low growth rate. In addition, they are facing severe predation pressure as well as inbreeding recession. Hence, to develop a long-term protection strategy is of high urgency. In this study, the reproduction and population viability of reintroduced Przewalski＇ s horse have been ana- lyzed. The results showed that, （ 1 ） the low population growth of reintroduced Przewalski＇ s horse was caused by both low fertility rate （44. 3% ） and high foals mortality rate （43.4%）. Low reproductive survival rate is mainly influenced by nat- ural enemies＇ predation and diseases. The Przewalski＇ s horses exhibited seasonal breeding, 80. 9% of foals were born in May and June; （2） We used the Population Viability Analysis model VORTEX in this case and predicted that the extinc- tion risk of this population is 60% after 100 years. A minimum population of 200 is required to guarantee a risk less than 10% ; （3） The sensitivity analysis showed that wolf attacks have the greatest influence on the extinction risk and final pop- ulation size, followed by intrinsic factors such as maximum breeding age and fecundity rate ; （4） This Przewalski＇ s horse population was trapped in a small population effect. The mortality caused by diseases and foal weakness was relatively high （26. 5% and 8. 82%, respectively）. Hence, it is necessary to supplement the population with new individuals to prevent extinction. Some additional strategies, like mitigating wolves＇ predation pressure and strengthening foals＇ s security, can also effectively improve the Przewalski＇ s horse living condition.