Gauntlet Behaviour as a Male Sexual Tactic in the American Toad (Amphffiia: Bufonidae)

Abstract

1. Toads comprising the Towson population are characterized by a prolonged breeding season (> 5 weeks), and some males remained at the site for at least 23 days. 2. During the breeding season, sexually active males may be classified as terrestrial or aquatic. 3. Although we did not observe males switching tactics during the same calling session, we recorded within and between season shifts. 4. On any given night, a few aquatic males engage in vocalization to attract females, while the majority actively swim about the pond surface attempting to intercept females or to displace males that have achieved amplexus. 5. Terrestrial males are smaller (on average) than pond males and are consistently positioned a few meters from the rim of the pond, facing the forest. 6. Terrestrial males intercept approximately 70% of the females approaching the pond, and 60% of these remain in amplexus after an hour, despite numerous displacement attempts by conspecific rivals. 7. Except for the first few nights of migratory activity, males achieving terrestrial amplexus are significantly smaller than would be expected by chance. 8. We hypothesize that male toads exploit a terrestrial tactic of mate capture if their advertisement call is relatively unattractive to females, and if they are too small to displace successful males from amplexus. 9. As males increase in size (with age), they move to the pond and switch to a mating tactic involving both vocalization and sexual parasitism. 10. In most instances, terrestrial males integrate visual, chemical and seismic cues to identify females.