Success breeds success in mating male reed frogs (Hyperolius marmoratus).

Studies of the distribution of mating success among males in frog choruses typically seek to identify specific phenotypic attributes that confer a higher mating success on certain individual males. These attributes invariably relate to competition among males: either direct competition in the form of aggression, or competition to attract and be chosen by females. In this paper, we present evidence that an additional factor may operate in frog choruses. We show that individual males who mate on a given night enjoy a higher probability of being successful on the next night, and we suggest that this is because successful mating enables males to conserve energy.

Selective phonotaxis by males in the Majorcan midwife toad.

Males are expected to exhibit mating preferences when there is high variance in the quality of females or when males are limited to a small number of matings. In the Majorcan midwife toad, Alytes muletensis, the male performs parental care by carrying the eggs wrapped in a string around his hind legs. Both sexes possess courtship vocalizations which they use to advertise receptivity. We looked for evidence of male mating preferences in a phonotaxis arena in which males were presented with two alternative synthetic female calls. We predicted that males should prefer to mate with large females because of maternal effects on egg size, and that this preference would be manifest by selective phonotaxis toward low frequency calls. We also predicted that males should prefer high intensity calls as indicators of the energetic or motivational state of the female. Contrary to our prediction, males did not exhibit a preference for low frequency calls. The results suggest that there is stabilizing selection on call frequency and directional selection on call intensity.

Testosterone binding sites in the brain, plasma sex hormones and reproductive behaviour in males of the toad Bufo bufo.

The central action of steroid hormones of the regulation of reproductive behaviour has been recognized in Amphibia, as in, other Vertebrates. Central and peripheral endocrine aspects of reproductive behaviour were studied in the toad Bufo bufo during the breeding aspects of reproductive behaviour were studied in the toad Bufo bufo during the breeding (DHT) and estradiol (E) levels. In the first experiment the effect of early and late entrance into the breeding pond and the difference between animals entering and leaving was established: DHT and E plasma levels, as well as T binding capacity in the brain were lower in animals leaving the pond at the end of the breeding season; animals entering early in the season showed higher levels of E than those entering late. In the second experiment the hormonal effect of amplexus and spawning was established: single males showed lower plasma DHT, higher plasma E and higher T binding values in the brain than males paired with a female. Males in amplexus with a non-spawning female showed higher plasma E levels than those with a spawning female. These results show that it is possible to relate the different reproductive success to different T binding in the brain. The effect of amplexus on potential responsiveness to steroid hormones at the central level and on peripheral hormone concentrations suggests the presence of a regulatory mechanism which is more active when both amplexus and spawning occur. On the other hand, the data concerning animals entering and leaving the pond indicate that the hormonal variations are not due solely to the end of sexual behaviour since the difference is already significant between groups entering early and late in the breeding season.