Western black widow spiders (Latrodectus hesperus) remember prey capture location and size, but only alter behavior for prey caught at particular sites

Abstract

AbstractAnimals form memories and use them to guide future behaviors. The information stored in memory is selected to include only details that result in adaptive decision‐making. Understanding the contents of animal memories can provide insight into an animal's ecology and evolution. In this paper, we use an assay of searching behavior to reveal the contents of West black widow spiders’ memory. We provided prey in two major components of black widow webs and then stole the prey to elicit searching behavior. We used search effort, in terms of likelihood of searching and the number of bouts of searching, to determine whether spiders form memories of their prey, and whether their memories include any specific features of their prey. Black widows were significantly more likely to search after experiencing prey theft, which demonstrates the spiders form memories of their prey. Black widows were also more likely to search for relatively larger prey, but this effect depended on the site of prey capture within the web (only for prey snared at the web's gumfooted lines). This indicates that black widows also form memories of the relative size of their prey and its capture location. Further, their natural history helps interpret when these details are stored or used, and when not. Our results underscore the importance of behavioral observations for understanding the contents of animal memories.