Male Reproductive Tactics in an Explosive Breeding Toad Population

Abstract

American toad ( Bufo amencanus ) males use one of two different reproductive tactics. Some males are stationary and call. Others are silent and mobile. Based on field studies, I developed a computer program that simulates the behavior of females and males to determine the probability of mating success of males engaging the different tactics and the factors that effect male reproductive success. Field studies indicate that non-calling males can be successful. Non-calling males were more numerous and smaller than calling males. Population size changed greatly both between and within nights. Contact rates for non-calling males were greater than those for calling males. The results of the preliminary simulations indicate that male mating success is a function of the population size and the operational sex ratio. In small populations, contact rate has no effect on male success. The effect of contact rate on male success has not been tested in large populations. In large populations, mating success is also a function of the ratio of calling to non-calling males. Generally, in small populations (n > 20) calling males are more successful than non-calling males. In large populations (n > 40) the success of noncalling males is equal to or greater than the success of calling males.