Male calls induce egg laying in isolated female frogs

Abstract

Advertisement signals are used to attract mates and deter competitors but in some mammals and birds they also stimulate estrus or egg laying. This endocrine response could employ the same or different neural circuitry than the behavioral responses. We examined the egg laying response to calls in the túngara frog for which the behavioral responses (attraction, mate choice) are well known. Isolated females laid eggs in response to stimulation by male calls played from loudspeakers. This response was greatly diminished if the call was played backwards, which also renders it non-recognizable to females. Egg laying was induced equally by simple or complex calls although females strongly prefer complex ones. The mechanism of female reproductive state modification by male calls is therefore present in amphibians. In addition to mate attraction and male-male competition, male calls may have a role in triggering the female to lay eggs. In this study, the reproductive state response of the female to calls matched her behavioral responses in specificity but differed from them in sensitivity to signal complexity.

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