A matter of choice: substrate preference by burrow-digging males of a sand-dwelling spider

Abstract

Animals may build refuges to avoid predation, to communicate, to mate, and to protect against extreme temperatures, among other factors. Allocosa senex is a wolf spider that constructs burrows in the coastal sand dunes of South America. The distribution of A. senex includes beaches with different granulometry, which could affect burrow characteristics and energetic costs of excavation. Males are the digging sex and their burrows are mating and oviposition sites. We aimed to test substrate preference of males of A. senex simultaneously exposed to coarse- (CS) and fine-grain sand (FS) (n = 30) and study digging behavior in both substrates. Regardless of their substrate of origin, males significantly preferred CS for digging (males from CS habitat, 23/30, P = 0.001; males from FS habitat, 20/30, P = 0.02). Males from the FS habitat showed higher weight and better body condition. Digging behavior showed similar patterns in both types of substrate but resting duration was longer when males dug in CS. Although males of A. senex can dig in both substrates, this study shows their preference for digging in CS, a substrate that is possibly less energetically demanding for that behavior.