The impact of a pathogenic bacterium on a social carnivore population
The impact of a pathogenic bacterium on a social carnivore population
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DOI：
10.1111/j.1365-2656.2011.01873.x
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发表时间：
2012-01-01
影响因子：
4.8
通讯作者：
East, Marion L.
中科院分区：
文献类型：
--
作者：
Hoener, Oliver P.;Wachter, Bettina;East, Marion L.
1.病原体对群体生活的大型哺乳动物种群的长期生态影响在很大程度上是未知的。我们评估了病原菌马链球菌和其他关键生态因子对坦桑尼亚恩戈罗恩戈罗火山口斑点鬣狗Crocuta crocuta种群动态的影响。我们比较了细菌感染的外部体征普遍存在（“爆发”）的两年期间以及爆发前后五年期间的关键人口统计学参数，当时这些体征不存在或罕见。我们还测试了密度依赖性并计算了细菌的基本繁殖率R-0。3.在爆发前的5年中，平均每年鬣狗死亡率为0088，每年的人口增长率相对较高（13.6%）。疫情期间，死亡率上升78%，达到0.156，导致人口年下降4.3%。疫情爆发后，在疫情爆发后的头三年，人口规模适度增加（5.1%），然后恢复到与疫情爆发前水平（13.9%）相似的增长。我们没有发现任何证据表明这些人口变化是由密度依赖或其他生态因素驱动的。大多数土狼在其领地内的猎物丰度较低时表现出感染的迹象。在爆发期间，成年雄性和一岁鸽的死亡率增加，但在社会上占主导地位的成年雌性群体成员中没有增加。这些结果表明，感染和死亡率受到与社会地位低下和营养不良有关的因素的影响。在爆发期间，我们估计该细菌的R-0为2.7，表明传播相对较快。我们的研究结果表明，短期的“自上而下”的影响，S.爆发期间的马反刍动物疫情是由对营养不良的年龄性别阶层的“自下而上”影响造成的，而爆发后较长期的种群增长下降是由爆发期间幼马存活率低以及随后繁殖雌性的招募不足造成的。这些结果表明，“自下而上”和“自上而下”的过程对主机种群动态的协同效应。
1. The long-term ecological impact of pathogens on group-living, large mammal populations is largely unknown. We evaluated the impact of a pathogenic bacterium, Streptococcus equi ruminatorum, and other key ecological factors on the dynamics of the spotted hyena Crocuta crocuta population in the Ngorongoro Crater, Tanzania.2. We compared key demographic parameters during two years when external signs of bacterial infection were prevalent ('outbreak') and periods of five years before and after the outbreak when such signs were absent or rare. We also tested for density dependence and calculated the basic reproductive rate R-0 of the bacterium.3. During the five pre-outbreak years, the mean annual hyena mortality rate was 0 088, and annual population growth was relatively high (13.6%). During the outbreak, mortality increased by 78% to a rate of 0.156, resulting in an annual population decline of 4.3%. After the outbreak, population size increased moderately (5.1%) during the first three post- outbreak years before resuming a growth similar to pre- outbreak levels (13.9%). We found no evidence that these demographic changes were driven by density dependence or other ecological factors.4. Most hyenas showed signs of infection when prey abundance in their territory was low. During the outbreak, mortality increased among adult males and yearlings, but not among adult females the socially dominant group members. These results suggest that infection and mortality were modulated by factors linked to low social status and poor nutrition. During the outbreak, we estimated R-0 for the bacterium to be 2.7, indicating relatively fast transmission.5. Our results suggest that the short- term ` top- down' impact of S. equi ruminatorum during the outbreak was driven by 'bottom-up' effects on nutritionally disadvantaged age- sex classes, whereas the longer- termpost- outbreak reduction in population growth was caused by poor survival of juveniles during the outbreak and subsequent poor recruitment of breeding females. These results suggest synergistic effects of 'bottom-up' and 'top-down' processes on host population dynamics.