Populations of Cane Toad, Bufo-Marinus, in Relation to Time Since Colonization

Abstract

A repeatable index of population density for cane toads active around permanent water in the dry season showed that, in the lowlands of the Gulf of Carpentaria, local populations rapidly increased in size following colonization, and remained high (up to 2138 ha-1 on a single night) for at least 19 years. Long-established populations ( ~ 47 years) around Townsville have declined to an average density of 82 ha-1 on a single night. In this area toads are in poor body condition, are smaller, and have a lower proportion of reproductive males than do younger populations. The sizes of fat bodies, and the numbers of ova carried by females, do not appear to have declined in the Townsville populations. The index of population density was found to represent approximately 20% of a Jolly-Seber, capture-recapture estimate of population density for a 2.5-year-old cane toad population. The Jolly-Seber estimate for this young population is up to 45 times the densities of native cane toads in Panama. The numbers of toads captured, toad body sizes and proportions of sexually mature toads in the Townsville populations are very similar to those in Panama.