ANT-EATING AND TERMITE-EATING IN AUSTRALIAN MAMMALS AND LIZARDS - A COMPARISON

Relative abundance is one factor that influences selection of prey by insectivorous mammals and lizards. Ants and termites are extremely abu ndant over most of inland Australia. Their patterns of abundance are a lso broadly similar across climatic gradients, being most and least ab undant in seasonally arid (tropic and sub-tropic) and temperate mesic regions, respectively. All else being equal (e.g. mechanisms of prey d efence, palatability, availability), animals that eat many termites sh ould also eat many (adult) ants. The present study asks three question s: (i) What is the diversity of specialized ant-eaters (>50% volume)!; (ii) Does specialization vary with climate?; and (iii) Are ants and t ermites eaten in broadly similar proportions (using an earlier study o n termites). Of the mammals, only the echidna (Tachyglossus aculeatus) in mesic regions, and probably the marsupial mole (Notoryctes typhlop s) in the arid zone and the striped possum (Dactylopsila trivirgata) i n mesic regions are ant-specialized. Ant-specialization in mammals sho ws no pattern with regard to climate. Of the lizards, only four agamid lizards are ant-specialized: Moloch horridus (arid, semi-arid), Cteno phorus fordi (arid, semi-arid), Ctenophorus isolepis (arid) and Ctenop horus maculatus (arid). Specialization on ants by lizards is greatest in the arid zone (4 spp.); no lizard species were found to be ant-spec ialists in mesic regions. In the arid and semi-arid zone, two mammals each specialize on termites and one on ants; in mesic regions, two mam mals specialize on ants and one on termites. Specialized insectivorous mammals thus demonstrate no marked preference for either termites or ants. Lizards, in contrast, are markedly termite-specialized (4 ant-sp ecialist spp., 16 termite-specialist spp.), and specialization is grea test in the arid zone (16 spp.). Greater specialization on termites th an on (adult) ants in lizards is explained with reference to differenc es in prey defence and palatability between ants and termites. Consump tion of ant brood (eggs, larvae, pupae) appears to be associated with a fossorial foraging mode (the marsupial mole N, typhlops; spp. of Apr asia lizards; spp. of blindsnakes Ramphotyphlops).