Why are lions social animals?

[Sully]

From a paper I remember being posted a few years ago in what I believe was the cave lion thread: Evolution of the mane and group-living in the lion (Panthera leo): a review

The evolution of group-living:

The resource dispersion hypothesis (Macdonald, 1983)suggests that there are circumstances under which the pattern of resource availability facilitates the accommodation of additional individuals within the smallest economically defendable territory required to support reliably the primary occupants. This occurs when the overall costs owing to the presence of the additional individual(s) do not outweigh the overall benefits (Macdonald & Carr,1989). Figure 3 shows Qi values relative to the food requirements per body weight for eight extant felids (lion,tiger, jaguar, leopard, cheetah Acinonyx jubatus, puma, Canada lynx Lynx canadensis and bobcat Lynx rufus) in nine habitats, and clearly suggests that, amongst the populations tested, a parasitic female would benefit most in the Serengeti lion population. Therefore, concerning the presumably solitary early lions, in an environment like the Serengeti, forming an association with another female probably benefits a parasitic female, which is a potential additional female occupant of a lion territory. In a prey-rich environment like the Serengeti, where we suggest the initial group formation was most likely, cooperative hunting seems unlikely to increase food intake

Lion evolution 335per group member in lions (Packer et al., 1990; Creel &Creel, 2002), suggesting that this factor may not have played an important initial role in the origins of group-living further. However, from the viewpoint of the primary female that is parasitized, forming an association with another female might be beneficial straight away in terms of direct conflict, both intra- and interspecific (Packer et al., 1990; Cooper, 1991). If the parasitic female is the primary female’s kin, letting her share the kill may increase the inclusive fitness of the primary female even further if a part of the kill would otherwise be eaten by non-kin or even other species (Macdonald, 1992; Macdonald et al., in press). This intraguild conflict factor is relevant to group territoriality as well, and where either lions or their competitors live in groups, solitary individuals suffer considerable disadvantages for their survival and reproductive fitness (Packer et al., 1990; Grinnell, Packer& Pusey, 1995; Heinsohn & Packer, 1995; H¨oner et al.,2002).The foregoing argument suggests that once evolved, group-living may persist because, regardless of initial factors facilitating it, group-living is made advantageous by intraspecific and intraguild competition, forces which are unlikely to be region-specific. This multi-factor approach to sociality in lions may partly explain why lions live in groups in the Kalahari today even though this environment does not seem strongly to favour initial group formation on the basis of food resources alone(Fig. 3) (Eloff, 1973; Mills et al., 1978; Mills, 1984, 1990);rather, Kalahari lions may retain group-living partly because it evolved in a different evolutionary context. In addition, cooperative hunting of lions in a prey-scarce semi-arid environment (such as Etosha or Kalahari) seems significantly to increase food intake per capita (Stander,1992; Creel & Creel, 2002). Therefore, interestingly, lions may have been benefited by group-living to colonize prey-scarce environments where the group-living is unlikely to have evolved initially. Consideration of the selective advantage of group-living should also be mindful of the inherent scope for phenotypic variation in this trait. That is, while an evolutionarily solitary lion is, by definition, basically solitary all the time, group-living lions have the flexibility to vary their group sizes as appropriate, and do so with lionesses spanning the variation between solitariness (although usually resident solitary females cannot hold good territories) and membership of prides of >10 adult females (e.g. Schaller, 1972). Therefore, although lions with the facility for sociality probably have the capacity to cope with any circumstances to which a solitary lion can adapt, the reverse is not true. The high mobility of lions and their large, contiguous distribution would ensure that any feature with universal selective advantage spread quickly on a geological timescale, across the species range wherever it initially evolved. Reply