Does dietary β-carotene influence ontogenetic colour change in the southern corroboree frog?

Captive diet does not influence exploration behavior upon reintroduction to the wild in a critically endangered amphibian

Exploration behavior can have profound effects on individual fitness. Consequently, knowledge of the proximate mechanisms underpinning exploration behavior may inform conservation breeding programs (CBPs) for threatened species. However, the environmental factors that influence exploration behavior in captivity and during the reintroduction process remain poorly understood. Dietary micronutrients, such as carotenoids, are known to affect the expression of energetically costly behavioral traits, and theoretically may also influence the degree of exploration behavior in various contexts. Here, we investigate whether dietary β-carotene supplementation in captivity influences exploration behavior upon reintroduction to the wild in the critically endangered southern corroboree frog, Pseudophryne corroboree. We conducted a manipulative dietary experiment where captive bred P. corroboree were supplemented with different doses of β-carotene for 40 weeks prior to release. Frogs (n = 115) were reintroduced to the wild using a soft-release approach, where they were released into field enclosures specifically designed for this species. Upon reintroduction, the frogs’ initial exploration behavior was measured using a standardized behavioral assay. There was no effect of diet treatment on any measure of exploration behavior (mean latency to leave the initial refuge, time spent mobile within the release apparatus and latency to disperse into the field enclosure). However, there was a significant relationship between individual body size and latency to leave the refuge, whereby smaller individuals left the refuge more rapidly. While these findings provide no evidence that β-carotene at the dosages tested influences P. corroboree exploration behavior in a reintroduction context, the effect of body size draws attention to the potential for bodily state to influence exploration behavior. We discuss the need for ongoing research investigating the influence of captive diet on post release behavior, and highlight how knowledge concerning state-dependent behavior might help to inform and direct reintroduction programs.

Multiple phenotypic traits predict male mating success in a critically endangered frog

Abstract

Complex sexual signals spanning multiple sensory modalities may be common in nature, yet few studies have explored how combinations of phenotypic traits influence male attractiveness and mating success. Here, we investigate whether combinations of multiple male phenotypic traits (both within and across sensory modalities) predict male mating and fertilization success in the critically endangered southern corroboree frog, Pseudophryne corroboree. We conducted breeding trials in a standardized captive environment where females were given the opportunity to choose between multiple males over the duration of the breeding season. For each male, we measured multiple call traits, aspects of coloration, body size, and age. We found that complex interactions between multiple traits best predicted male mating and fertilization success. In general, males with lower call frequency, lower call rate, and shorter call duration had the highest mating and fertilization success. Fertilization success was additionally linked to male body size and age. These findings suggest that female P. corroboree select mates based on a suite of acoustic traits, adding to a growing body of evidence that females use multiple traits to assess male quality. Our results also suggest that females may combine information from multiple signals non-additively. Moreover, our results imply that females gain direct fertility benefits from their mate choice decisions. We argue that understanding female mate choice based on various signals across multiple sensory modalities has important implications for the integration of mate choice into conservation breeding programs and needs to be considered when developing behavior-based captive breeding strategies.

Significance statement

Sexual signals are often highly complex, yet we know little about how multiple signal components both within and across various sensory modalities predict male mating success. We investigated whether combinations of multiple phenotypic traits (within and across sensory modalities) predicted male breeding success in threatened corroboree frogs. We conducted captive breeding trials in a homogeneous environment, where females could choose between multiple males over the duration of a single breeding season. We found that interactions between multiple male traits predicted mating and fertilization success. Males with lower call frequency, call rate, and duration had higher mating success. Fertilization success was also linked to acoustic signals, body size, and age. Understanding mate choice for multiple traits further elucidates the complexity of female mate choice. This study is one of the first to consider the conservation implications of multimodal signaling in mate choice.