Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103, Leipzig, Germany.
BMC Ecol. 2020 Jul 16;20(1):40. doi: 10.1186/s12898-020-00306-6.
Competition within and between social groups determines access to resources and can be inferred from space use parameters that reflect depletion of food resources and competitive abilities of groups. Using location data from 1998 to 2017, we investigated within- and between-group competition in 12 groups of wild mountain gorillas (Gorilla beringei beringei). As within-group feeding competition is expected to increase with group size, an increase in group size is predicted to lead to an increase in the size of annual home ranges and core areas, but to a decrease in fidelity (reuse of an area). Due to asymmetries in competitive abilities, larger groups are expected to have higher exclusivity (degree of non-shared space) of annual home ranges and core areas than smaller groups.
We found evidence of within-group feeding competition based on a positive relationship between group size and both annual home range and core area size as well as a negative relationship between group size and core area fidelity. Additionally, fidelity of core areas was lower than of home ranges. Between-group competition was inferred from a trend for groups with more members and more males to have more exclusive home ranges and core areas. Lastly, annual core areas were largely mutually exclusive.
Our study suggests that non-territorial, group-living animals can have highly dynamic, long-term avoidance-based spacing patterns, both temporally and spatially, to maintain annual core area exclusivity among groups while concurrently shifting these areas annually within overlapping home ranges to avoid resource depletion. Despite ranging in larger home ranges and core areas, larger groups were able to maintain more exclusive ranges than smaller groups, suggesting a competitive advantage for larger groups in between-group competition in a non-territorial species. Together, these findings contribute to understanding how social animals make behavioral adjustments to mitigate the effects of intraspecific competition.
群体内部和群体之间的竞争决定了资源的获取，而这种竞争可以通过反映食物资源消耗和群体竞争能力的空间利用参数来推断。本研究使用 1998 年至 2017 年的位置数据，调查了 12 群野生山地大猩猩（Gorilla beringei beringei）的群体内和群体间竞争。由于群体内觅食竞争预计会随着群体规模的增加而增加，因此群体规模的增加预计会导致年活动范围和核心区域的扩大，但会降低（区域的）忠实度（区域的）。由于竞争能力的不对称性，较大的群体预计会比较小的群体拥有更高的年活动范围和核心区域的排他性（非共享空间的程度）。
我们发现了群体内觅食竞争的证据，这是基于群体规模与年活动范围和核心区域大小呈正相关，以及群体规模与核心区域忠实度呈负相关的关系。此外，核心区域的忠实度低于活动范围。群体间竞争是通过具有更多成员和更多雄性的群体拥有更具排他性的活动范围和核心区域的趋势推断出来的。最后，年核心区域在很大程度上是相互排斥的。
本研究表明，非领地性、群体生活的动物在时间和空间上都可以形成高度动态的、长期的基于回避的空间格局，以维持群体之间的年核心区域排他性，同时在重叠的活动范围内每年移动这些区域，以避免资源枯竭。尽管群体在更大的活动范围和核心区域内活动，但较大的群体能够比较小的群体维持更具排他性的范围，这表明在非领地物种中，较大的群体在群体间竞争中具有竞争优势。这些发现有助于理解社会动物如何调整行为以减轻种内竞争的影响。
