Stable isotope ecology of the common hippopotamus

The diet of African hippopotamids can be documented through stable carbon isotope ratios (13C/12C) analyses of enamel and other tissues. The common hippopotamus Hippopotamus amphibius is widely assumed to be a pure grazer; however, the 13C/12C ratios of modern H. amphibius show a higher fraction of dietary C3 biomass than estimated from traditional observations. Isotope profiles of modern hair and modern tooth enamel confirm that H. amphibius has a variable diet in both the short‐ (seasonal) and long‐ (sub‐decadal) time scales. Isotopic analyses of extant mammals from the same parks as the analyzed hippos provide comparative examples for diets of C3‐browsers and C4‐grazers. Oxygen isotope ratios (18O/16O) show that the hippo is consistently the most 18O‐depleted mammal in any one ecosystem; this directly reflects its semi‐aquatic habitat.