Typically, anuran amphibians favor larger females as mates because larger females lay more eggs; thus, males in amplexus can increase the number of eggs fertilized, and fitness. However, males may also prefer those females that were closest to the norm for their population in overlapping populations, and these individuals do not receive the benefits of enhanced fertilization success. In this study, we test how male Bufo gargarizans choose mates in the presence and absence of an invasive species, bullfrogs (Rana catesbeiana). When given a simultaneous choice between a small male and a large female toad, males discriminated between the sexes and attempted to clasp a large female. However, when one male toad was presented with a large female bullfrog and a small female toad, the males chose both with equal frequency. Therefore, male B. gargarizans appears to trade-off between species and mate-quality recognition, such that those toads co-occurring with heterospecifics do not blindly prefer mate-quality to ensure conspecific matings.
Intrasexual selection and alternative mating behaviour. In:
Amphibian BiologyVol. 2: Social behaviour pp.
419-468. Surrey Beatty and SonsChipping Norton.