Seiler Nicole, Boesch Christophe, Stephens Colleen, Ortmann Sylvia, Mundry Roger, Robbins Martha M
Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany.
Am J Primatol. 2018 Apr;80(4):e22754. doi: 10.1002/ajp.22754. Epub 2018 Apr 10.
Space use patterns determine access to resources necessary for survival and reproduction. Although it is recognized that the interplay between social and ecological variables shapes spacing patterns, few studies in group-living animals have simultaneously assessed their importance in a comprehensive approach using different spatiotemporal space use measures. In territorial species, such patterns are strongly determined by between-group competition, but its impact in non-territorial species is poorly understood. To better understand the role of social and ecological variables in non-territorial mountain gorillas (Gorilla beringei beringei), we simultaneously evaluated the impact of between-group competition (local gorilla population density and frequency of intergroup encounters) and within-group competition (group size) on space use patterns in 13 gorilla groups in Bwindi Impenetrable National Park, Uganda, while also examining variation in food availability (herbaceous food availability and level of frugivory). We found evidence of between-group competition, indicated by a decline of both monthly home range size and frequency of revisits to each part of the home range as the local gorilla population density increased and by an increase in daily travel distance on days when intergroup encounters occurred. Within-group feeding competition was inferred by a decrease in the frequency of revisits as group size increased. Lastly, food availability influenced the gorillas' spacing patterns, as indicated by a decline in monthly home range size as herbaceous food availability increased and by an increase in daily travel distance as the degree of frugivory increased. In sum, our results suggest that Bwindi gorillas adapted their space use according to the constraints of intraspecific competition and the availability of food resources. We provide some of the first evidence of between-group competition influencing spacing patterns in a non-territorial species. This study suggests a gradient between territoriality and non-territoriality, along which the level of between-group competition varies.
空间利用模式决定了获取生存和繁殖所需资源的途径。尽管人们认识到社会和生态变量之间的相互作用塑造了空间分布模式，但在群居动物中，很少有研究使用不同的时空空间利用测量方法，以综合的方式同时评估它们的重要性。在领地性物种中，这种模式很大程度上由群体间竞争决定，但它在非领地性物种中的影响却鲜为人知。为了更好地理解社会和生态变量在非领地性山地大猩猩（Gorilla beringei beringei）中的作用，我们同时评估了群体间竞争（当地大猩猩种群密度和群体间相遇频率）和群体内竞争（群体大小）对乌干达布温迪难以穿越国家公园13个大猩猩群体空间利用模式的影响，同时还研究了食物可利用性的变化（草本食物可利用性和食果性水平）。我们发现了群体间竞争的证据，表现为随着当地大猩猩种群密度的增加，每月家域大小和对家域各部分的重访频率均下降，以及在发生群体间相遇的日子里每日旅行距离增加。随着群体大小增加，重访频率降低，由此推断存在群体内觅食竞争。最后,食物可利用性影响了大猩猩的空间分布模式，表现为随着草本食物可利用性增加，每月家域大小减小，以及随着食果性程度增加，每日旅行距离增加。总之，我们的结果表明，布温迪大猩猩根据种内竞争的限制和食物资源的可利用性来调整它们的空间利用。我们提供了一些首批证据，证明群体间竞争会影响非领地性物种的空间分布模式。这项研究表明了领地性和非领地性之间的一种梯度变化，群体间竞争的程度沿此梯度变化。
