EVALUATION OF THE TOXICITY OF EGGS, HATCHLINGS AND TADPOLES OF THE INTRODUCED TOAD BUFO-MARINUS (ANURA, BUFONIDAE) TO NATIVE-AUSTRALIAN AQUATIC PREDATORS

The early life history stages of anurans in the Family Bufonidae often possess chemicals that are noxious or toxic to predators. Predators w ith no evolutionary history of exposure to bufonids may be particularl y susceptible to these toxins. We conducted a series of laboratory exp eriments to investigate the toxic effects of eggs, hatchlings and tadp oles of the introduced toad, Bufo marinus (Linnaeus), on native Austra lian aquatic predators. There was considerable interspecific and intra specific variation in these effects. Bufo marinus were highly toxic to some predator species, but were readily consumed by other species wit hout apparent in effect. Interspecific variation in toxic effects was not related to predator feeding mode or the number of B. marinus inges ted by predators, and there was no clear pattern of distribution of vu lnerability among species within higher taxa. Intraspecific variation in responses to toxins may result from individual variation in the res istance of predators to B. marinus toxins, or from individual variatio n in toxicity among B. marinus. Some native species adversely affected by B. marinus appeared unable to detect and avoid B. marinus toxins. This may result from a general inability to assess the toxicity of foo d items or from a lack of evolutionary exposure to B. marinus toxins.