Group living in animals occurs in diverse lineages including birds, mammals and fishes. The numerous potential benefits of group living have resulted in the evolution of animal societies that differ in social complexity. For example, social group composition may vary from single sex to mixed sex groups, as well as containing individuals of varying ages, relatedness and breeding status. Social groups may also vary in the type and extent of cooperation that they exhibit, with different cooperative behaviours associated with different benefits. In small mammals, notable benefits of group living include increased survival though cooperative group antipredator behaviours, and increased reproductive output resulting from allocare from group members.
Cape ground squirrels (Xeris inauris) are an arid-zone adapted species that live in Southern Africa.
A non-aggressive species
Compared to temperate ground squirrels, Cape ground squirrels have unusually low levels of aggression (no physical aggression, non-territorial) and and docile personalities. They engage in a variety of cooperative behaviours such as vigilance, predator mobbing, allocare and cooperative breeding.
Warrington, Miyako H.; Beaulieu, Sienna; Vos, Sjoerd; Jellicoe, Riley; Bennett, Nigel C; Waterman, Jane M. 2022. Personalities are not associated with different reproductive tactics in male Cape ground squirrels (Xerus inauris), Animal Behaviour, 193, 63–74. https://doi.org/10.1016/j.anbehav.2022.08.014
Cape ground squirrels exhibit two types of social groupings: 1) Mixed-sexed matrilineal family groups consisting of plurally breeding related adult females, and subadults of both sexes, and sexually mature males that have delayed dispersal (‘natal males’); 2) all-male bands (of up to 19 individuals) of dispersed sexually mature males (‘band males’). These all-male bands (of up to 19 individuals) are a fission-fusion social system with males forming ephemeral foraging sub-bands of two to eight individuals. The type and extent of cooperative and collective behaviours exhibited in these two types of social associations (female, natal male, band male) varies. I am currently examining the variation in social associations and behaviours of Cape ground squirrels to address how these social features increases fitness and survival, and thus, contribute towards the maintenance of social living in this species.
Effects of climate change
Cape ground squirrels live in open grasslands throughout southern Africa and have typical arid adaptations such as concentrated urine, high thermal conductance and a low resting metabolic rate. They face thermoregulatory challenges dealing with cold night-time temperatures and hot daytime temperatures. Cape ground squirrels deal with heat in several different ways. They dig large burrow clusters (aggregations of burrows), and sleep with their groups at night in shared burrows. And during the day individuals may shade themselves with their tails while exposed to the sun or may retreat to underground burrows during unfavourable weather conditions. As arid environments incur large variations in daily and seasonal ambient temperatures, and Southern Africa is experiencing rapid changes in climatic conditions, Cape ground squirrels may be affected by changing climatic and ecological conditions in their habitat. At our field site, daily maximum air temperatures at have risen by more than 2°C. So far, we have found that the relative size of ground squirrel feet has increased, while their bodies have become smaller. It seems that ground. These proportionally bigger feet may help the ground squirrel cool off by allowing them to shed more heat even faster than those squirrel with smaller feet. Likewise, smaller bodies are predicted to help animals shed heat at a faster rate than larger-bodied animals. This result suggests that ground squirrel bodies may be changing in response to the greater heat stress that these animals are experiencing in recent years.
Warrington, Miyako H., & Waterman, J.M. 2022. Temperature driven morphological changes in an African arid-zone ground squirrel. Journal of Mammalogy, https://doi.org/10.1093/jmammal/gyac107.
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