Choosy males court both large, colourful females and less colourful but responsive females for longer

Abstract

Male mate choice based on female secondary sexual traits is increasingly reported, even in species with otherwise conventional sex roles. However, empirical evidence of male mate preference remains scarce for vertebrate species other than birds and fish. Here we examined male mating investment in response to female coloration in the Alpine newt, Ichthyosaura alpestris. In our experiment, males had a choice between females that varied in the redness of the belly (red versus yellow). We recorded five parameters indicative of male preference, and the female's response. Additionally, we performed these preference trials in different light conditions (control and blue filter) to test whether male choosiness depends on the female's colour signal. We found that males adjusted their mating investment according to the encountered female. Males courted red females longer than yellow females, regardless of the red female's response. Nevertheless, if yellow females were responsive, males invested as much courtship time as for red females. Males might have a guaranteed insemination with responsive females regardless of belly colour. In addition, redder females might provide quality advantages when an insemination is successful. We further detected that less colourful males tended to invest more spermatophores for red females than males that were colourful themselves. Both effects, however, were evident in both light conditions. Since larger females had redder bellies, body size and belly colour may confer similar information about female quality. Taken together, our results provide evidence that males choose a specific female coloration and size, but also reveal potential behavioural compensation mechanisms by less colourful females to obtain similar male effort. Our findings are thus consistent with the idea of mate choice based on colourful ornaments but highlight that interactions may be complex and multiple cues as well as female responses should be considered when investigating male mate choice.