Games spiders play. III: Cues underlying context-associated changes in agonistic behaviour

In this paper I consider the proximate cues underlying context-associated variation in the agonistic behaviour of the spider Agelenopsis aperta (Gertsch). At the initiation of a contest, individual opponents are shown to assess their relative weights; the subsequent behaviour of each is adjusted according to the result of the assessment. Escalation to potentially injurious behaviour early in the contest, for instance, is a threshold effect of weight bias. Several lines of evidence indicate, that only the territory Owner (resident) has information about the quality of a site at the initiation of a territorial dispute. (1) Owners of poor-quality sites that received food supplements exhibited significantly greater persistence and estimated energy expenditure in contests over these sites than unsupplemented individuals did over theirs. (2) A significant correlation was observed between web area and the behaviour of Owners, but not between web area and the behaviour of Intruders (individuals that encroach on occupied webs). (3) No correspondence was observed between spider body temperature and agonistic behaviour. (4) The presence or absence of prey on the web during the dispute did not affect the agonistic behaviour of either opponent. I conclude that the Intruder's behaviour is in some way adjusted to that of the Owner rather than directly to some aspect of the disputed site. Partial correlation analysis show site quality to have a greater influence on agonistic behaviour than weight bias, although both are important determinants of spider behaviour in territorial disputes.