SOME LIFE-HISTORY PARAMETERS OF A DECLINING POPULATION OF SOUTHERN ELEPHANT SEALS, MIROUNGA-LEONINA
SOME LIFE-HISTORY PARAMETERS OF A DECLINING POPULATION OF SOUTHERN ELEPHANT SEALS, MIROUNGA-LEONINA
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DOI：
10.2307/5449
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发表时间：
1991-02-01
影响因子：
4.8
通讯作者：
HINDELL, MA
中科院分区：
文献类型：
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作者：
HINDELL, MA
(1)对1951年至1965年麦夸里岛南象海豹种群数量下降的13个群体进行了标记-观察数据分析。(2)在20世纪50年代，第一年存活率基本稳定，雌性约为46%，雄性约为42%。在20世纪60年代，第一年的存活率急剧下降，到1965年，男女存活率都下降到不到2%。从1950年代到1960年代，1年后的存活率没有变化。(3)与南乔治亚稳定种群相比，麦夸里岛种群的第一年和成年存活率都较低。在研究期间，麦夸里岛海豹首次繁殖的年龄没有变化，但平均比南乔治亚岛晚1年。(4)据推测，目前在几个主要的象海豹繁殖地，象海豹数量的下降是由于本世纪初随着商业开发的结束，象海豹数量上升到异常高的水平，现在又回到了封印前的水平。(5)对这一假设的可能检验包括研究南象海豹的饮食和觅食行为，以了解捕食者和猎物之间的关系；继续对麦考瑞岛的海豹种群进行普查，以确定种群数量是否在封印前的估计水平附近，并监测同样受到严重剥削但目前正在迅速增加的北象海豹种群。
(1) Mark-resight data were analysed for thirteen cohorts from a declining population of southern elephant seals branded at Macquarie Island between 1951 and 1965.(2) First year survival was essentially stable during the 1950s at about 46% for females and 42% for males. There was a dramatic fall in first year survival during the 1960s, declining to less than 2% for both sexes in 1965. Post-year-1 survival did not change between the 1950s and the 1960s.(3) Comparisons with a stable population of southern elephant seals at South Georgia indicated that both first year and adult survival were lower in the Macquarie Island population. There were no changes in the age at first breeding of the Macquarie Island seals during the study, but this was on average 1 year later than at South Georgia.(4) It is hypothesized that the current decline in elephant seal numbers at several of their major breeding islands is due to the populations returning to pre-sealing levels after they had risen to abnormally high levels with the end of commercial exploitation early this century.(5) Possible tests of the hypothesis include studying the diet and foraging behaviour of southern elephant seals to gain an understanding of the predator-prey relationships, continuing to census the Macquarie Island population to determine if the population levels out at around the estimated pre-sealing levels, and monitoring northern elephant seal populations which were also severly exploited but are currently increasing rapidly.