Information-content of morphological and behavioural sexual traits in the Palmate newt (Lissotriton helveticus)

•Few studies investigating multiple traits considered both morphological and behavioural sexual traits.•We explored the information-content of both morphological and behavioural multiple traits in the Palmate newt, Lissotriton helveticus.•Morphological sexual traits were positively inter-correlated and were correlated to body condition.•Courtship activity was not correlated to male body condition.•Multiple traits may evolve because redundant message, unreliable signals (and possibly multiple messages) can coexist.

The question of why females evaluate more than one sexual trait to choose their mates has received increasing attention in recent years. Here, we investigated the information-content of both morphological and behavioural sexual traits that have been identified as predictors of male reproductive success in the palmate newt, Lissotriton helveticus. We examined the co-variation of multiple traits with one aspect of male quality, the male body condition, using both a correlative study and an experimental diet restriction. We found that the development of the three morphological sexual traits (filament length, hind-foot-web size, and crest size) was positively inter-correlated, and was correlated to body condition. In contrast, courtship activity, an important indicator for male reproductive success, was uncorrelated to male body condition. Our results suggest that females likely obtain redundant information on male condition when evaluating filament length, hind-foot-web size and crest size during mate choice. Contrary to our expectations, display activity was not a reliable indicator of male condition, leaving the information-content of this trait unraveled. Our results further suggest that complex, multiple traits may evolve because redundant message, unreliable signals and, possibly, multiple messages can coexist.