Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
The Dian Fossey Gorilla Fund International, Atlanta, USA.
Sci Rep. 2018 Nov 13;8(1):16718. doi: 10.1038/s41598-018-35255-0.
The effect of feeding competition on foraging efficiency is an important link between ecological factors and the social organization of gregarious species. We examined the effects of group size on daily travel distances, activity budgets, and energy intake of mountain gorillas in Rwanda. We measured daily travel distances of five groups, activity budgets of 79 gorillas in nine groups, and energy intake data for 23 adult females in three groups over a 16-month period. Travel distances and the proportion of time spent traveling increased with size for most groups, which would be expected if their foraging efficiency is limited by intragroup feeding competition. However, travel distances and times decreased for the largest group, which also had higher energy intake rates than intermediate sized groups. The improved foraging efficiency of the largest group may be explained by advantages in intergroup contest competition. The largest group had much lower home range overlap than the other study groups which may be due to groups avoiding one another as a result of male mating competition. Collectively, our results indicate that intermediate sized groups had the lowest foraging efficiency and provide a new twist on the growing evidence of non-linear relationships between group size and foraging efficiency in primates.
摄食竞争对觅食效率的影响是生态因素与群居物种社会组织之间的重要联系。我们研究了群体大小对卢旺达山地大猩猩每日旅行距离、活动预算和能量摄入的影响。我们在 16 个月的时间里，测量了 5 个群体的每日旅行距离、9 个群体中 79 只大猩猩的活动预算以及 3 个群体中 23 只成年雌性的能量摄入数据。对于大多数群体来说，旅行距离和旅行时间随着群体规模的增加而增加，如果它们的觅食效率受到群体内摄食竞争的限制，这是可以预期的。然而，最大的群体的旅行距离和时间减少了，其能量摄入率也高于中等规模的群体。最大群体的觅食效率提高可以用种间竞争优势来解释。最大群体的家域重叠度远低于其他研究群体，这可能是由于雄性交配竞争导致群体相互回避。总的来说，我们的研究结果表明，中等规模的群体的觅食效率最低，这为越来越多的证据表明灵长类动物的群体大小与觅食效率之间存在非线性关系提供了一个新的视角。
