Abstract
In the Western Cape three species of mole-rat occur in sympatry, however, little is known about differences in their dietary preferences. Dietary composition of the three species; the common mole-rat (Cryptomys hottentotus hottentotus), the Cape mole-rat (Georychus capensis) and the Cape dune mole-rat (Bathyergus suillus) were examined using stable isotope analysis. Blood, fur and claw samples were collected from 70 mole-rats, in addition to several potential food items, to assess food selection of the three species under natural conditions. Overall there was a significant difference in the isotopic composition (δ13C and δ15N) between all three species and significant differences in their diet composition. There were also significant differences between tissues in all three species suggesting temporal variation in diet. The small size and colonial lifestyle of C. h. hottentotus allows it to feed almost 100% on bulbs, while the solitary and larger species G. capensis and B. suillus fed to a greater extent on other resources such as grasses and clover. B. suillus, the largest of the species, had the most generalized diet. However, overall all species relied most heavily upon geophytes and consumed the same species suggesting competition for resources could exist. We also showed a high level of individual variation in diet choices. This was most pronounced in B. suillus and G. capensis and less so in C. h. hottentotus. We demonstrate that stable isotope analysis can successfully be applied to examine dietary patterns in subterranean mammals and provide insights into foraging patterns and dietary variation at both the inter and intra population level.
Highlights
In the Western Cape of South Africa three species of mole rat, the common mole rat (Cryptomys hottentotus hottentotus), the Cape mole rat (Georychus capensis) and the Cape dune mole rat (Bathyergus suillus) occur in sympatry
During the summer of 2010 a total of 70 mole rats (9 Batherygus suillus, 17 Cryptomys hottentotus hottentotus and 44 Georychus capensis) were trapped using modified Hickman live traps baited with sweet potato [26].Once captured, tissues samples were collected from all animals
We found there was a significant difference in the isotopic composition of the three species of mole-rat on both the d13C and d15N axes, and that these differences were maintained over different temporal scales
Summary
In the Western Cape of South Africa three species of mole rat, the common mole rat (Cryptomys hottentotus hottentotus), the Cape mole rat (Georychus capensis) and the Cape dune mole rat (Bathyergus suillus) occur in sympatry. Mole-rats are subterranean and harvest the majority of their resources from below ground. All three species are thought to be herbivorous, feeding on underground food resources such as geophytes which they gather by excavating their burrow systems, little detailed knowledge is known about their dietary habits. Geophytes have been shown to be high in nutritional value and are available as a resource for most of the year [1]. B. suillus and G. capensis have been reported to supplement their diet with aerial vegetation such as grasses, by pulling the plants down into the burrow [3]
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