Fission-fusion processes weaken dominance networks of female Asian elephants in a productive habitat
Fission-fusion processes weaken dominance networks of female Asian elephants in a productive habitat
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DOI：
10.1093/beheco/arw153
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发表时间：
2017-01-01
影响因子：
2.4
通讯作者：
Wittemyer, George
中科院分区：
文献类型：
--
作者：
de Silva, Shermin;Schmid, Volker;Wittemyer, George
预计支配等级制度的形成是为了应对社会生态压力和竞争机制。我们评估自由放养的雌性亚洲象（Elephas maximus）之间的优势关系，并将它们与非洲萨凡纳象（Loxodonta africana）进行比较，后者被认为表现出基于年龄的优势等级。这两个物种都是通才食草动物，然而，亚洲人口占据了一个更富有成效和气候稳定的环境相对于非洲萨凡纳人口。我们预计这将降低相对于非洲分类群的竞争，放松对等级的需要。我们测试了1）观察到的个体之间的优势互动是否具有传递性，2）根据4种独立的排名方法，按年龄或社会单位构建结果，3）使用大卫的评分，类之间的等级陡峭度是否显著。大象显示的优势相互作用的数量不到三分之一，在L。Africana，在统计学上，个体之间的传递性不显著。年龄层之间存在微弱但显著的有序性和陡峭性，但社会单位之间没有明确的有序性。非洲象在个体间表现出显著的传递性，在年龄级和社会单位间表现出显著的有序性和陡度。大菱象的年龄逆转优势结果的比例比L。非洲。当支配等级是弱的和非线性的，支配信号可能有其他功能，如保持社会排他性。我们认为，资源动态通过影响裂变-聚变过程来加强差异，我们称之为“生态释放”。“我们讨论了当动物受到空间限制时，这些发现对保护和管理的影响。
Dominance hierarchies are expected to form in response to socioecological pressures and competitive regimes. We assess dominance relationships among free-ranging female Asian elephants (Elephas maximus) and compare them with those of African savannah elephants (Loxodonta africana), which are known to exhibit age-based dominance hierarchies. Both species are generalist herbivores, however, the Asian population occupies a more productive and climatically stable environment relative to that of the African savannah population. We expected this would lower competition relative to the African taxon, relaxing the need for hierarchy. We tested whether 1) observed dominance interactions among individuals were transitive, 2) outcomes were structured either by age or by social unit according to 4 independent ranking methods, and 3) hierarchy steepness among classes was significant using David's score. Elephas maximus displayed less than a third the number of dominance interactions as observed in L. africana, with statistically insignificant transitivity among individuals. There was weak but significant order as well as steepness among age-classes but no clear order among social units. Loxodonta africana showed significant transitivity among individuals, with significant order and steepness among age-classes and social units. Elephas maximus had a greater proportion of age-reversed dominance outcomes than L. africana. When dominance hierarchies are weak and nonlinear, signals of dominance may have other functions, such as maintaining social exclusivity. We propose that resource dynamics reinforce differences via influence on fission-fusion processes, which we term "ecological release." We discuss implications of these findings for conservation and management when animals are spatially constrained.