Influence of body size and level of cooperation on the prey capture efficiency of two sympatric social spiders exhibiting an included niche pattern

Abstract

Summary 1. Body size and other morphological traits play key roles in an animal’s performance and thus their ability to locate, capture and handle different resources. For species that live and forage in groups, group-level characteristics, such as foraging group size and level of cooperation, may also influence performance and further shape resource use. 2. We explored the simultaneous role of individual (body size) and social traits on performance (i.e. prey capture efficiency) in two sympatric social spiders in Ecuador. 3. Given a fivefold difference in body size, the large species captured on average significantly larger insects than the small species. However, because the large species captured both small and large insects, its prey size range included that of the small species, which is thus said to exhibit an included niche. 4. The small species compensated for its small body size by having greater density of individuals within the nests, faster reaction times, and greater participation of individuals of all age classes in prey capture. As a result, the smaller species had a steeper increase in the size of the insects it captured with increasing colony size than the larger species. As predicted by included niche theory, the small species was also more efficient within the shared range as it was less likely to miss or ignore small prey than the large species. 5. Our study contributes to our understanding of how social traits may jointly interact with individual-level traits to shape foraging performance and resource use in communities of social organisms, a problem little explored in the past.