Spatio-temporal shifts of the dynamic Cape fur seal population in southern Africa, based on aerial censuses (1972-2009)
Spatio-temporal shifts of the dynamic Cape fur seal population in southern Africa, based on aerial censuses (1972-2009)
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DOI：
10.1111/j.1748-7692.2012.00584.x
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发表时间：
2013-07-01
影响因子：
2.3
通讯作者：
Underhill, L. G.
中科院分区：
文献类型：
--
作者：
Kirkman, Steve P.;Yemane, D.;Underhill, L. G.
对跨越四十年（1972-2009年）和三个国家（南非、纳米比亚和安哥拉）的海狗种群空中普查的时间序列进行了分析，以评估种群数量的时空变化。使用加权分位数回归方法估计幼仔计数的趋势，幼仔计数用作繁殖群中较年长动物数量的替代。在研究期间，繁殖群落的数量增加了74%，从1973年的23个增加到2009年的40个。繁殖种群的分布也有明显的北移。这在很大程度上是由于种群分布范围的北方部分发生的事件与纳米比亚的情况相吻合，纳米比亚南部的大多数种群海豹数量下降，而纳米比亚北方和安哥拉南部则出现了几个新的繁殖种群。根据幼仔数量模型，尽管范围扩大和新殖民地的发展，2009年的总体人口规模与20世纪90年代初相似。观察到的变化，其管理的影响，潜在的机制进行了讨论。
A time series of aerial censuses of Cape fur seal colonies, spanning four decades (1972-2009) and three countries (South Africa, Namibia, and Angola), was analyzed to assess spatio-temporal changes in population numbers. A weighted quantile regression approach was used to estimate trends in pup counts that were used as proxies for numbers of older animals at breeding colonies. There was a 74% increase in the number of breeding colonies over the study period, from 23 in 1973 to 40 in 2009. There was also a significant northward shift in the distribution of the breeding population. This was largely attributable to events in the northern part of the population's range coinciding with Namibia, where seal numbers declined at most colonies in the south of Namibia while several new breeding colonies developed in the northern part of Namibia and one in southern Angola. Despite range expansion and the development of new colonies, the overall size of the population in 2009 was similar to that of the early 1990s, according to the pup count models. Potential mechanisms for the observed changes, and their management implications, are discussed.