Mechanisms of Mate Investment in the Polygamous Fowl, Gallus gallus

Male fowl (Gallus gallus) that have recently mated invest in their mates by producing antipredator alarm signals at a higher rate. It remains unclear, however, whether these males are investing judiciously in their mates, or responding more generally to recent mating success. Here, we manipulated each male's mating experience with two different females to test whether males invest selectively in their mates. For 1 wk, males could interact with both females, but could mate with only one of them. In the second week, we removed either the mated or the unmated female and measured the male's rate of alarm calling. Males did not invest preferentially in their mates, suggesting that increased alarm calling is a more general response to recent mating experience. This relationship could be based on a relatively simple cognitive rule of thumb or on an underlying physiological mechanism. Testosterone and corticosterone are associated with reproduction and antipredator behaviour in other species and so could provide the necessary physiological link in fowl. To test this, we measured plasma levels of testosterone and corticosterone before, during and after mating. Results show that hormone levels did not change as a function of male mating status and hence cannot provide the link between mating and calling behaviour. Instead, we suggest that a general cognitive mechanism is more likely to explain prudent mate investment in this species.