Diet in relation to prey of Cape clawless otters in two rivers in the Western Cape Province, South Africa
The annual and seasonal diet of Cape clawless otters (Aonyx capensis (Schinz, 1821)) in the Olifants and Eerste rivers, Western Cape Province, South Africa, is described. Seasonal diet is discussed in relation to the availability of river crabs (Potamonautes perlatus) and fish. Crabs were found to be the main prey and fish the second most common prey of Cape clawless otters in the rivers during all seasons. Plant material ranked third in the diet of the otters from the Olifants River but only seventh in the Eerste River. Other prey included frogs, insects, birds and mammals. In terms of the number of prey, crabs again dominated the diet in both rivers. There was no significant difference between the relative numbers of crabs in spraints (faeces) from the two rivers. The percentage occurence of prey of Cape clawless otters in both rivers shows an increase in the amount of crab in summer and a corresponding decrease in the number of fish eaten. There was a significant seasonal difference in size of crabs eaten by the otters in the Olifants and Eerste rivers. The seasonal fluctuation in crab and fish corresponded to the expected frequencies as determined by trapping.