Abstract
The relationship between the spatiotemporal distribution of resources and patterns of sociality is widely discussed. While the resource dispersion hypothesis (RDH) was formulated to explain why animals sometimes live in groups from which they derive no obvious benefits, it has also been successfully applied to species that benefit from group living. Some empirical tests have supported the RDH, but others have not, so conclusions remain equivocal and further research is required to determine the extent to which RDH predictions hold in natural systems. Here, we test four predictions of the RDH in an African lion population in the context of their fission–fusion society. We analyzed data on group composition of GPS‐collared lions and patterns of prey availability. Our results supported the first and second predictions of the RDH: Home range size (a) was independent of group size and (b) increased with distance between encounters with prey herds. Nonetheless, the third and fourth RDH predictions were not supported: (c) The measure of resource heterogeneity and (d) resource patch richness measured through prey herd size and body size had no significant effect on lion group size. However, regarding the fourth prediction, we added an adaptation to account for dynamics of fission–fusion society and found that the frequency of pride fission increased as group size increased. Our data set restricted us from going on to explore the effect of fission–fusion dynamics on the relationship between group size and patch richness. However, this should be investigated in future studies as including fission–fusion dynamics provides a more nuanced, realistic appreciation of lion society. Our study emphasizes the importance of understanding the complexity of a species' behavioral ecology within the framework of resource dispersion. Whatever larger theoretical framework may emerge to explain lion society, incorporating fission–fusion dynamics should allow the RDH to be refined and improved.
Highlights
The selective advantage of group living is, in many social animals, attributed to the direct benefits of cooperation, such as cooperative foraging, alloparental care, or territorial defense (Krause & Ruxton, 2002)
Resource richness and heteroge‐ neity have been described as part of the environmental parameters that determine the probability with which additional group members can be sustained in a territory (Carr & Macdonald, 1986). This leads to the resource dispersion hy‐ pothesis (RDH) third and fourth predictions: Group size is determined by the heterogeneity of available resources, and group size is de‐ termined by the richness of available resources (Carr & Macdonald, 1986; Macdonald, 1983; Macdonald & Johnson, 2015)
Knowing that lions live in prides that can exhibit fission–fusion dy‐ namics, we expected RDH principles to lead to relationships be‐ tween measures of patch richness and group size, but we saw no apparent reason to predict whether that relationship would manifest with respect to total pride size or to the size of fissioned hunting par‐ ties
Summary
The selective advantage of group living is, in many social animals, attributed to the direct benefits of cooperation, such as cooperative foraging, alloparental care, or territorial defense (Krause & Ruxton, 2002). The resource dispersion hy‐ pothesis (RDH) describes how groups may form even in the absence of any functional advantage to any individual from the presence of another It links ecological factors, such as spatiotemporal pat‐ terns in the richness and dispersion with which resources become available, with sociological characteristics, such as the size of social groups and the extent of their territories (Carr & Macdonald, 1986; Macdonald, 1983). River confluences in the Serengeti National Park, Tanzania, and waterholes in Hwange National Park, Zimbabwe, have emerged as important resource patches for lions (see Mosser, Fryxell, Eberly, & Packer, 2009; Valeix, Loveridge, & Macdonald, 2012, respectively) These studies found resource patch heterogeneity to be a prerequi‐ site to the development of group territoriality and that in poor qual‐ ity habitats; animals exclude each other from richer patches. (v) Fission–fusion dynamics is influ‐ enced by group size
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