Many eyes or many ewes: vigilance tactics in female bighorn sheep Ovis canadensis vary according to reproductive status
Many eyes or many ewes: vigilance tactics in female bighorn sheep Ovis canadensis vary according to reproductive status
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DOI：
10.1111/j.0030-1299.2008.16274.x
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发表时间：
2007-11
期刊：
影响因子：
3.4
通讯作者：
G. Rieucau;Julien G. A. Martin
中科院分区：
文献类型：
--
作者：
G. Rieucau;Julien G. A. Martin
在群居动物中，个体警惕性和群体规模之间通常存在负相关关系。群体规模的这种影响通常可以通过增加发现捕食者的概率（多眼假说）和减少较大群体中发生的风险来解释。很少有研究试图检验这两种假设对动物预期警惕模式的具体影响。在这里，我们研究了繁殖状况是否影响大角羊加拿大绵羊的警惕模式。我们还测试观察到的警惕模式是否与警惕稀释或检测模型的预测一致。尽管警惕性随着群体规模的增加而降低，但不育雌性和哺乳期雌性之间的警惕策略有所不同。哺乳期母羊完全依赖于捕食者的检测。相比之下，当群体规模增加并根据群体中泌乳母羊的比例调整警惕性时，不育母羊受益于检测和稀释效应。人们普遍认为合群可以提高安全性。在这里，我们进一步表明，繁殖状态影响动物如何降低捕食风险，并且一些个体利用其他个体提供的警惕努力。
In gregarious animals, there is usually a negative relationship between individual vigilance and group size. This effect of group size is generally explained by increasing probability of predator detection (the many-eyes hypothesis) and by the dilution of risk occurring in larger groups. Few studies have attempted to examine the specific implications of either hypothesis on the expected vigilance pattern of an animal. Here we examine whether reproductive status affects vigilance patterns in bighorn sheep Ovis canadensis ewes. We also test whether the observed vigilance patterns are consistent with predictions from dilution or detection models of vigilance. Although vigilance decreased with increasing group size, vigilance tactics differed between barren and lactating females. Lactating ewes relied solely on predator detection. In contrast, barren ewes benefited from both detection and dilution effects when group size increased and adjusted vigilance effort according to the proportion of lactating ewes in their group. It is generally assumed that gregariousness increases safety. Here we further show that reproductive status influenced how animals reduce predation risk and that some individuals take advantage of the vigilance effort provided by others.