A learned response to sperm competition in the field cricket, Gryllus bimaculatus (de Geer)

While, historically, studies of classical conditioning have been concerned mainly with the rules and mechanisms of stimulus association, more recent work is providing evidence of its adaptive value to the animal. Much of this has focused on reproductive advantages, such as learning to predict the availability of a potential mate or competitor. We looked at classically conditioned stimulus association in the novel context of sperm competition. Using field crickets, Gryllus bimaculatus, we looked at the ability of adult males to associate topographical features of the environment (configurations of toy bricks) or olfactory cues (artificial odours) with the presence or absence of an apparent competitor (another male on the other side of a clear partition). Males were able to learn associations between apparent competition and one of two spatial configurations or odours, in that they transferred larger spermatophores to a female in the conditions associated with another male, both during training (when another male was present) and during testing (when it was not). Males thus appeared to modulate sperm transfer in relation to learned environmental predictors of sperm competition. However, while males began stridulating sooner after the introduction of a female, stridulated more often and were quicker to transfer a spermatophore in some conditions associated with the presence of another male, these differences were apparent only during training, and not during testing. (c) 2006 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.