Specialist or generalist? Feeding ecology of the Malagasy poison frog Mantella aurantiaca

We studied the diet of a population of free-ranging Mantella aurantiaca, an alkaloid-containing poison frog from Madagascar. As in other poison frogs, this species is thought to sequester alkaloids from arthropod prey. Among prey, mites and ants are known to regularly contain alkaloids and mites appear to be a major source of dietary alkaloids in poison frogs. We predicted that mites and ants would constitute the most important prey item for these frogs. Prey inventories were obtained during the rainy season by stomach flushing 23 adult male and 42 adult female frogs from one population. Males had smaller body sizes than females and ate smaller prey items, but males and females displayed no differences in the number of prey items consumed. The numerical proportion of ants in most specimens was surprisingly low (11% in males and 15% in females), while mites were slightly more frequent (34% in males and 18% in females). Other prey items consumed in large proportions were flies and collembolans. Comparing the total of 5492 arthropod prey items with 1867 arthropods sampled from the frogs' leaf litter habitat, the proportion of prey classes did not significantly differ among the samples, indicating a low degree of prey electivity in this population. Our data suggest that not all poison frogs exhibit a continuous and active preference for feeding on ants and mites, but instead some may consume high proportions of ants due to a high abundance of ants in their environment.