Information use in anurans: how conspecifics and predators influence reproductive decisions

The choice of breeding habitat is integral to offspring survival and reproductive success, and can ultimately influence species distributions and population dynamics. Many factors are likely involved in location and evaluation of habitat, including biotic factors such as the presence of conspecifics and predators. Increasingly, organisms in a variety of taxa have been found to incorporate information on conspecifics and predators in their habitat selection decisions, but the degree to which this occurs in anuran amphibians is still not well-known. My research sought to first synthesize our current understanding of how conspecifics and predators influence reproductive decisions in anurans by reviewing the literature on this topic. Through experimental studies, I then examined how conspecific cues in the form of chorus sounds influenced breeding habitat selection in seven species of anurans (wood frog, Lithobates sylvaticus; Cope’s gray treefrog, Hyla chrysoscelis; American toad, Anaxyrus americanus; green frog, Lithobates clamitans; spring peeper, Pseudacris crucifer; Mexican spadefoot, Spea multiplicata; and Arizona treefrog, Hyla wrightorum). I then further examined how the presence of conflicting cues, in this case conspecific cues and predators, influenced breeding habitat selection in a single anuran species (western chorus frog, Pseudacris triseriata). A review of over 40 studies examining the influence of conspecifics, heterospecifics and/or predators on temperate and tropic anuran reproductive decisions found that in the majority of cases (75%), individuals avoid depositing offspring in sites with predators and conspecifics or heterospecifics. From my own experiments in Illinois, Indiana, and Arizona, I found that some species were attracted to breeding ponds with conspecific chorus sounds (Cope’s gray treefrog and Mexican spadefoot), while others showed weak or no response to conspecifics (wood frog, American toad, green frog, spring peeper, Arizona treefrog). Response was not predictably correlated with particular life history traits, but the tendency to breed in more seasonal or temporary ponds was a characteristic of the two species that did respond more strongly to conspecific cues. Regarding the influence of predator cues on breeding pond selection of western chorus frogs, chorus frogs exhibited predator avoidance at the Illinois field site but did not vary their behavior at the Indiana field site when presented with both predators and conspecific egg-mass cues. My results provide support for the idea that some species of anurans can and do use conspecific social information in locating and selecting breeding habitat, but that social information use may vary by breeding ecology, landscape matrix, and environmental characteristics