摘要
欧洲水獭自50年代来明显减少,正在从许多河流消失。本研究基于对英国西部3个自然建群的集水区和英国东部2个通过人工投放加速建群的集水区的长期监测(从1977年以来)结果。到2002年,在每条河流至少收集了16年的数据,在每条研究河上设置一系列研究点,记录水獭出现点的百分率、痕迹点的痕迹数,并通过结合以上2个参数计算年种群指数。在一条自然建群的西部河流,头5年水獭种群生长快速增长,接着生长缓慢。但在2个研究开始就已经有水獭的集水区,其生长比较稳定。东部河流水獭建群的速度缓慢,随时间有巨大的波动。年种群生长率约为1%～7%,在早期较高。对水獭的年度监测计划提出了建议。
European otters declined dramatically from the 1950s,disappearing from many rivers.We report here on long-term monitoring (from 1977)in 3 catchments in western Britain that were recolonized naturally and in 2 catchments in eastern England that were reinforced by captive-bred otters.A minimum of 16-years data was collected on each river until 2002.At a series of sites in each study river,the percentages which were positive for otters and the number of spraints per sprainting site were recorded and combined to produce an annual index of population.One western river,naturally recolonized,showed rapid early population growth for 5 years, followed by slower growth,while growth was steadier in 2 catchments which already held some otters at the beginning of the study.Colonization on the eastern rivers was slower,with greater fluctuations over time.Annual population growth rates were estimated at 1 -7%,higher in the earlier years.A strategy for annual monitoring of otters is recommended.
