Size-dependent variability in the formation and trade-offs of facultative aggregations in golden orb-web spiders

Animals within a population can show variability in a range of behaviors, such as foraging and predator avoidance, and at times, the ideal way of behaving depends on individual or environmental conditions. E. Ferree and her students have asked why some female golden orb-web spiders (Nephila clavipes) form groups, while in the same population, others are solitary. This is an interesting question given how rare aggregations are among spiders (<0.01% of species). By collecting data on over 1500 spiders across 4 years at Pitzer’s Firestone Center for Restoration Ecology, they found that small spiders benefited most from clustering in terms of higher survival when aggregated compared to when solitary. At the same time, spiders of all sizes captured less prey when aggregated, although this cost was only detected in years with relatively abundant prey. Together, these findings suggest that trade-offs that vary individually and over time could influence a spider’s decision to cluster and, hence, explain the optional nature of aggregating in this population.
https://link.springer.com/article/10.1007%2Fs00265-018-2574-7