Social factors driving settlement and relocation decisions in a solitary and aggregative spider.

Both ecological and social factors play an important role in determining the structure of animal settlement patterns. While the ecological factors determining animal settlement are generally well known, the relative importance of social factors in mediating fine-scale settlement choices is poorly understood. As a result, we have little knowledge of why individuals choose to settle near specific neighbors. Here we used a web-building spider (Nephila plumipes) that settles both solitarily and next to neighbors within aggregations to examine the specific social factors that influence settlement decisions. Within experimental enclosures, we observed the settlement patterns of females pre- and postmale release. This allowed us to compare two models of aggregative settlement in lekking species-the hotshot and preferences models-to examine the relative importance of a female's phenotype and mate attraction to further dissect settlement and relocation decisions. We show that mate attraction increased with aggregation size and that larger females were generally preferred, supporting both the hotshot and preference models of aggregative settlement. We further demonstrate that smaller females that attracted fewer males within an aggregation were most likely to relocate. Our results demonstrate how social feedback can affect initially state-dependent settlement decisions, thereby highlighting the dynamic nature of settlement.