Frog eat frog: exploring variables influencing anurophagy

Abstract

Background. Frogs are generalist predators of a wide range of typically small prey items. But descriptions of dietary items regularly include other anurans, such that frogs are considered to be among the most important of anuran predators. However, the only existing hypothesis for the inclusion of anurans in the diet of post-metamorphic frogs postulates that it happens more often in bigger frogs. Moreover, this hypothesis has yet to be tested.Methods. We reviewed the literature on frog diet in order to test the size hypothesis and determine whether there are other putative explanations for anurans in the diet of post-metamorphic frogs. In addition to size, we recorded the habitat, the number of other sympatric anuran species, and whether or not the population was invasive. We controlled for taxonomic bias by including the superfamily in our analysis.Results. Around one fifth of the 355 records included anurans as dietary items of populations studied, suggesting that frogs eating anurans is not unusual. Our data showed a clear taxonomic bias with ranids and pipids having a higher proportion of anuran prey than other superfamilies. Accounting for this taxonomic bias, we found that size in addition to being invasive, local anuran diversity, and habitat produced a model that best fitted our data. Large invasive frogs that live in forests with high anuran diversity are most likely to have a higher proportion of anurans in their diet.Conclusions. We confirm the validity of the size hypothesis for anurophagy, but show that there are additional significant variables. The circumstances under which frogs eat frogs are likely to be complex, but our data may help to alert conservationists to the possible dangers of invading frogs entering areas with threatened anuran species.

Overland movement in African clawed frogs (Xenopus laevis): a systematic review

“…Migration from permanent to temporary water-bodies for spawning would allow the spatial separation of adults from larvae which might otherwise be cannibalised (e.g., Measey, 1998a; Measey et al, 2015; Schoonbee, Prinsloo & Nxweni, 1992) as temporary waters are likely to have reduced densities of occupants. Similarly, temporary waters are likely to be high in nutrients, sometimes experiencing algal blooms and having reduced predator pressure, making them ideal habitats for developing larvae.…”

A global assessment of alien amphibian impacts in a formal framework

“…The most frequently recorded ecological impacts were with respect to the GISS category predation. These mostly relate to dietary studies which are relatively numerous for amphibians (Measey et al, 2015). However, it is noteworthy that articles about the capacity of the cane toad to intoxicate predators were also scored in the predation subcategory.…”

“…Larger amphibians may be more likely to have a higher impact through predation, related to the larger range of prey items available to them (e.g. Caldwell & Vitt, 1999;Toledo et al, 2007;Measey et al, 2015). In addition, large (and vocally prominent) alien amphibians may drive an investigation bias that leads to publication bias resulting in higher GISS scores.…”

Global realized niche divergence in the African clawed frog Xenopus laevis

“…Among invasive amphibians, X. laevis has one of the highest recorded impacts on native fauna (Measey et al., ). These comprise competition for resources, direct predation of native amphibians (Amaral & Rebelo, ; McCoid & Fritts, ; Measey et al., ), a negative impact to the reproduction of native amphibians (Lillo et al., ) and has been shown to be an asymptomatic carrier of the chytridiomycosis fungus Batrachochytrium dendrobatidis (Fisher & Garner, ).…”