Experience influences male-male contests in the spider Argyrodes antipodiana (Theridiidae:Araneae)

Fighting is costly. Therefore, it is to an animal's advantage to assess the abilities of its opponent and compete more strongly against weaker competitors and avoid contests with stronger competitors. However, assessment may also be difficult or costly, making it sometimes advantageous for the animal to avoid direct assessment. This study examines male-male contests over access to females in the spider Argyrodes antipodiana. Pairs of naive males in their first contest were more likely to escalate that contest if the pair consisted of large males. Thus large males were inherently more likely to escalate contests than small males. Second, males that had had experience at winning contests were more likely to win subsequent contests against spiders of the same size who had had experience at losing contests. These trained spiders responded differently from the onset of the contest suggesting that their experience had altered their perception of their chance of winning the current contest. These two results suggest means by which direct assessment may be reduced, and yet observed interactions could still follow predictions from game theory models. Mechanisms by which experience may reduce assessment are discussed. (C) 1997 The Association for the Study of Animal Behaviour.