The influence of sensory information on patch residence time in wolf spiders (Araneae: Lycosidae)

Foraging models emphasize reward and/or prey capture rates as primary determinants of residence time. The influence of sensory information has rarely been examined experimentally, but may also be important in animal foraging decisions. This study examined the influence of sensory cues without food reward on residence time in wolf spiders, as well as the interaction of visual and vibratory information in foraging decisions. It also elucidated the effects of prior sensory experience on foraging decisions in wolf spiders. Sixty mature females of the common wolf spider, Schizocosa ocreata (Hentz), were tested in a four-chambered artificial foraging patch. Patches varied in the type of sensory information provided by live prey as follows: visual stimuli alone, vibratory stimuli alone, visual and vibratory stimuli together and control (no stimuli). Spiders were allowed to move freely from chamber to chamber for one hour while the duration, number and sequence of patch visits were recorded. Sensory cues, even without food rewards, are sufficient criteria to influence residence time. Spiders tended to remain longer in patches with visual cues alone or visual and vibratory cues together over those with vibratory information alone. Individuals varied significantly in both residence time and sensory biases between individuals, but none showed evidence of using prior sensory experience to choose patches or modify patch residence duration. ? 1996 The Association for the Study of Animal Behaviour Many animals forage for resources in spatially or temporally unpredictable patches and assess patch quality in numerous ways. They then use this information to decide how long to forage in a given patch before moving to another (residence time), which serves to maximize energy intake rates (Stephens & Krebs 1986) and may contribute to fitness (Morse & Fritz 1982). Most theoretical models and empirical studies of foraging behaviour have considered prey capture rates as a primary influence on residence time (Charnov 1976; Cook & Cockrell 1978; Sih 1980; McNamara 1982; Morse & Fritz 1982; Cassini et al. 1990), with fewer studies on other types of information (Valone 1991). Information on foraging patch quality can be gained by (1) sampling, i.e. as a function of prey capture rate per unit time (Stephens & Krebs 1986), or (2) estimating patch quality prior to exploitation. Pre-sampling information may be in the form of sensory cues, memory of patch quality from previous patch sampling, or knowledge of the relative distribution of resources within patch subtypes (Bayesian foraging; Valone 1991). The use of perceptual information or memory in estimating patch quality in temporally heterogeneous environments has been referred to as prescient foraging (Valone & Brown 1989). The importance of sensory cues in foraging decisions has often been assumed, but only rarely tested (Rice 1983). Many studies on foraging decisions have stressed the importance of sampling and reward rate to feeding decisions in patch-time allocation, but relatively few have addressed the influence of prescient foraging information (Valone & Brown 1989; Cuthill et al. 1990; Morse 1993; Valone & Giraldeau 1993). Most of the latter have concentrated on learning, memory and Bayesian foraging patterns (Green 1980; Johnson 1991; Kamil et al. 1993) rather than the influence of sensory cues (Young & Getty 1987; Conlon & Bell 1991; Bye et al. 1992). Integration of various forms of information about Correspondence: M. H. Persons, Department of Biological Sciences, ML 0006, University of Cincinnati, Cincinnati, OH 45221, U.S.A. (email: PERSONMH@UCBEH. SAN.UC.EDU). 0003–3472/96/061285+09 $18.00/0 ? 1996 The Association for the Study of Animal Behaviour