Reproductive behaviour of spadefoot toads (Pelobates fuscus): daily sex ratios and males' tactics, ages, and physical condition

International audienceIn anuran competition over mates, disadvantaged (i.e., less competitive) males are generally known to be the smallest ones, but ages of those males have rarely been documented. In the context of a high level of male competition for mates, disadvantaged males were expected to use alternative mating tactics. To test for alternative tactics in a territorial toad (the spadefoot toad, Pelobates fuscus, Pelobatidae), daily breeding migration patterns were observed during 3 consecutive years. Relationships between migration pattern, operational sex ratio (OSR), and male's age (inferred from skeletochronological analysis), size, and mass were analysed. During 2 of the study years, OSRs were highly male-biased at the beginning of the breeding season and then gradually decreased when male numbers increased. Males with a low body condition index (CI) tend to arrive later and to lose relatively more mass than males with a higher CI. There was a negative relationship between percent mass loss per day and CI as well as length of stay in the breeding area, which suggests that a high energetic cost tactic was adopted by males with a higher CI. A negative relationship between length of stay and age was also observed. We conclude that based on competition for mates, male P. fuscus seem to adopt reproductive behaviour that differs according to body condition and age