Life Underground: Food Habits and Reproductive Biology of Two Amphisbaenian Species from Southern Africa

Abstract

Examination and dissection of 216 museum specimens of two species of amphisbaenians (the shovel-snouted Monopeltis anchietae and round-headed Zygaspis quadrifrons) from southern Africa provided data on morphology, sexual dimorphism, reproduction, and dietary habits. The two species differed considerably in absolute size, in body proportions (eg, head width relative to snout-vent length), and in the degree of sexual dimorphism in these traits. In the relatively heavy-bodied Monopeltis both sexes attained similar body lengths, but females had wider heads than conspecific males. Conversely, in the thin-bodied Zygaspis, females attained larger body sizes than conspecific males, and there was no sexual dimorphism in head size. Clutch sizes were small in both species (means of 2.4 neonates in Monapeltis, 3.3 eggs in Zygaspis) and were not correlated with maternal body size. Termites were the most common prey far both taxa, but a wide variety of other soft-bodied invertebrates (beetle larvae, caterpillars) was also consumed. The two species differed in dietary composition, mean prey size, and in the numbers of prey items per stomach. Stomachs of Monopeltis contained more prey items than stomachs of Zygaspis (means of 72.2 versus 13.0 prey items) and prey ingested by Monopeltis were larger than those of Zygaspis. In Monopeltis, there was a significant positive correlation between predator size and prey number, but larger lizards continued to feed on relatively small prey. The reverse pattern was found in Zygaspis. The substantial differences in trophic biology between these two taxa and other sympatric fossorial reptiles, suggest that adaptations to fossoriality do not constrain ecological diversity within burrowing squamates.