Kingma Sjouke A, Komdeur Jan, Hammers Martijn, Richardson David S
School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK Behavioural and Physiological Ecology, GELIFES, University of Groningen, PO Box 11103, 9700CC Groningen, The Netherlands
Behavioural and Physiological Ecology, GELIFES, University of Groningen, PO Box 11103, 9700CC Groningen, The Netherlands.
Biol Lett. 2016 Jun;12(6). doi: 10.1098/rsbl.2016.0316.
Understanding why individuals delay dispersal and become subordinates within a group is central to studying the evolution of sociality. Hypotheses predict that dispersal decisions are influenced by costs of extra-territorial prospecting that are often required to find a breeding vacancy. Little is known about such costs, partly because it is complicated to demonstrate them empirically. For example, prospecting individuals may be of inferior quality already before prospecting and/or have been evicted. Moreover, costs of prospecting are mainly studied in species where prospectors suffer from predation risk, so how costly prospecting is when predators are absent remains unclear. Here, we determine a cost of prospecting for subordinate Seychelles warblers, Acrocephalus sechellensis, in a population where predators are absent and individuals return to their resident territory after prospecting. Prospecting individuals had 5.2% lower body mass than non-prospecting individuals. Our evidence suggests this may be owing to frequent attacks by resident conspecifics, likely leading to reduced food intake by prospectors. These results support the hypothesis that energetic costs associated with dispersal opportunities are one factor influencing dispersal decisions and shaping the evolution of delayed dispersal in social animals.
理解个体为何延迟扩散并在群体中成为从属者是研究社会性进化的核心。假说是，扩散决策受寻找繁殖空缺时常需的领地外探索成本的影响。对此类成本知之甚少，部分原因是通过实证证明它们很复杂。例如，探索个体在探索前可能质量就较差和/或已被驱逐。此外，探索成本主要在探索者面临捕食风险的物种中进行研究，所以在没有捕食者时探索的成本有多高仍不清楚。在此，我们确定了在一个没有捕食者且个体探索后返回其居住领地的种群中，从属塞舌尔莺（Acrocephalus sechellensis）的探索成本。探索个体的体重比未探索个体低5.2%。我们的证据表明这可能是由于常住同种个体的频繁攻击，可能导致探索者食物摄入量减少。这些结果支持了以下假说：与扩散机会相关的能量成本是影响扩散决策和塑造群居动物延迟扩散进化的一个因素。
