Dynamics of an Insularized and Compressed Impala Population: Rainfall, Temperature and Density Influences
Dynamics of an Insularized and Compressed Impala Population: Rainfall, Temperature and Density Influences
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孤立和压缩的黑斑羚种群的动态：降雨、温度和密度的影响
DOI：
10.2174/1874213001205010001
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
E. Kanga
中科院分区：
文献类型：
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作者：
J. Ogutu;H. Piepho;E. Kanga
了解不同生活史阶段对种群丰度变化的相对贡献，是了解种群动态以及有效管理和保护大型食草动物的基础。我们研究了从1994年6月到2011年12月，每天监测211个月(17.6年)的压缩和孤立黑斑羚种群的出生率、招募和死亡率以及性别比的时间变化。我们将这些速率与过去降雨量、温度和先前丰度的即刻和累积的同期变化联系起来。在这17.6年的时间里，种群数量在22到52只之间波动。共记录了213只出生，96只羔羊死亡，33只雄性和58只雌性；55只少年被招募到雌性类别，40名少年被招募到雄性类别。年平均自然死亡率为2.3%，其中羔羊占52.3%，雄性26.6%，雌性21.2%。羔羊的死亡率在干旱月份最高，这意味着食物短缺，但雌性羔羊的死亡率在最潮湿的月份和炎热潮湿的季节达到峰值，这表明在炎热潮湿的天气条件下更容易发生疾病和病原体。雄性、雌性和总体种群死亡率与先前的丰富度呈正相关，意味着种群增长的负密度反馈。出生是季节性的，出人意料地与怀孕前后和区域5年一次降雨周期的湿润阶段的降雨量呈负相关。这意味着，相当令人惊讶的是，高降雨量抑制了黑斑羚的繁殖成功。幼体招募随着5个月平均降雨量的增加而增加，但在(1)年降雨量过高时，(2)随着先前密度的增加而减少，(3)在炎热、干燥的季节。这意味着在高密度下对有限资源和营养压力的竞争加剧，在高降雨量下对疾病和病原体的脆弱性增加，以及栖息地干燥和高环境温度下活动水平降低的不利后果。
Understanding the relative contributions of different life history stages to changes in population abundance is basic to understanding population dynamics and effective management and conservation of large herbivores. We examined temporal variation in natality, recruitment and mortality rates and sex ratio in a compressed and insularized impala population monitored daily for 211 months (17.6 years), spanning June 1994-December 2011. We related the rates to contemporaneous variation in immediate and cumulative past rainfall, temperature and prior abundance. Over the course of this 17.6-year period, the population size fluctuated between 22 and 52 individuals. A total of 213 births, mortality of 96 lambs, 33 males and 58 females; recruitment of 55 juveniles into the female category and 40 juveniles into the male category were recorded. Natural mortality averaged 2.3% of the population annually with lambs contributing 52.3%, males 26.6% and females 21.2%. Lamb mortality was highest in dry months, implicating food scarcity, but female mortality peaked in the wettest months and in hot, wet seasons, suggesting increased susceptibility to diseases and pathogens in hot, damp weather conditions. Male, female and overall population mortality rates were positively correlated with prior abundance, implicating negative density feedbacks on population growth. Births were aseasonal and were surprisingly negatively correlated with rainfall around the time of conception and during wet phases of a regional 5-year rainfall cycle. This implies, quite surprisingly, that high rainfall depressed reproductive success in impalas. Juvenile recruitment increased with increasing 5-month running mean of monthly rainfall but declined (i) at excessively high values of annual rainfall, (ii) with increasing prior density and (iii) in hot, dry seasons. This implicates heightened competition for limiting resources and nutritional stress at high density, increased vulnerability to diseases and pathogens at high rainfall and adverse consequences of habitat desiccation and reduced activity levels at high ambient temperatures.