Anurans can represent important trophic pathways between water and land owing to their amphibious nature and biphasic life cycles, but there remains much to learn about the feeding dynamics of different species. We investigated the feeding ecology of four co-occurring anurans in a small South African river using several approaches (stomach content, stable isotope and fatty acid analyses), with the aims of determining diet compositions and the relative contributions of aquatic- versus terrestrial-derived resources to the anuran diets. We collected anurans in 2012 and 2013 at an upstream and a downstream site in the river. The proportions of aquatic-derived fatty acids were generally higher in tadpoles and a predominantly aquatic species of frog (Xenopus laevis), lower in the semi-aquatic species (Strongylopus grayii and Amietia fuscigula), and lowest in a toad that favours terrestrial habitats (Sclerophyrs capensis) at both sites. Stomach analysis of adult specimens confirmed that X. laevis had recently ingested only aquatic prey, S. grayii and A. fuscigula recently ingested combinations of aquatic and terrestrial prey, and Sc. capensis ingested primarily terrestrial prey. Stable isotope models indicated some differential contributions of aquatic vs terrestrial resources to the species at the different sites. Our results have important implications on the transfer of physiologically-important nutrients from water to land, as tadpoles and adult frogs are consumed by a variety of terrestrial predators.

Primary Presenter: Nicole Richoux, Rhodes University (n.richoux@ru.ac.za)

Authors:

Nicole Richoux, Rhodes University  (n.richoux@ru.ac.za)

Likho Sikutshwa, African Climate and Development Initiative  (sikutshwa.likho@gmail.com)

Sydney Moyo, Rhodes College  (sydmoyo@gmail.com)

Daniel Parker, University of Mpumalanga  (daniel.parker@ump.ac.za)