Abstract:
The study of reproductive strategies is central to understand the demography of populations and the energetic relationships of the species with their ecosystem. Documenting the reproductive natural history of the species is pressing in groups, like amphibians, that are threatened with extinction at a global scale. Herein, we describe the reproductive ecology and spawning behavior of the leptodactylid frog Engystomops pustulatus. In addition, we report observations that suggest the existence of an alternative mating strategy. Our results show that reproduction in E. pustulatus is characterized by high maternal investment (15% egg mass relative to body mass). We found evidence of size-assortative mating with a tendency of larger females to mate with larger males. Clutch size was correlated with female weight, female condition and male size. Larger females showed a tendency to lay larger foam nests and larger nests contained more eggs. At reproductive choruses, there was a male-biased operational sex ratio, indicative of high variance in male reproductive success. We observed an amplectant couple spawning while an additional male was embedded in the foam. We hypothesize that this behavior is evidence of an alternative mating strategy where a small non-amplectant male attempts to fertilize the eggs that are extruded by the amplectant female.
