Food and Parasitism of the Cane Toad, Bufo-Marinus, in Relation to Time Since Colonization

Abstract

Food habits and parasitism of cane toad, Bufo marinus, populations are documented in relation to time since the populations were first established. Toads from populations less than 2 years old consume greater dry weights of animal prey and greater numbers of prey items per unit time than do those from populations 3-47 years old. There are no significant differences among the dry weights of animal food and numbers of prey items consumed by toads from areas colonized 3-47 years before the study. There are significant regional and interpopulation differences in the taxonomic composition of prey consumed; these appear independent of the age of particular cane toad populations. Rates of parasitism by protozoans and helminths are low in a 2-year-old population, higher in populations 4-19 years old and low in a population approximately 47 years old. Parasitism by Saccamoeba and the opalinate Zelleriella appears to promote parasitism by other taxa. The rates of parasitism by particular taxa are independent of the age and size of the cane toad population. Neither food shortage nor parasitism by helminths or protozoans appears a likely cause for the decline in body condition in populations 47 years old. If this is due to the presence of a microbial pathogen, the low rates of helminth and protozoan parasitism may reflect continuing development of an interactive parasitic community in cane toad populations; isolation of the microbe might provide a mechanism for slowing the rate of spread of cane toads, and reducing their impact on the native fauna.