 Reference Base  Cleaning symbiosis involving pied crows and white rhino |
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| Location: |
Africa - Southern Africa - South Africa |
| Subject: |
Ecology - Interspecific Relations |
| Species: |
White Rhino |
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The pied crow Corvus albus has been recorded in feeding associations with large mammals (Brooke & Grobler, 1973). Hitchins (1962) recorded a pied crow perching on the back of a black rhino Diceros bicornis while feeding on ectoparasites, while Owen-Smith (1973) mentioned that pied crows ?commonly' settled on white rhino Ceratotherium simum in Umfolozi Game Reserve, picking off food morsels. None of these observations however, give quantitative data on the occurrence of this clearing symbiosis. Remains of ectoparasites were not found in pellets analyzed by Siegfried & Grindley (1967) and Brooke & Grobler (1973).
In a 33-day study period during May and June 1977 in the HluhluweUmfolozi Game Reserve complex, four instances of feeding associations were observed between pied crows and white rhino from a total of 197 white rhino observed over a counting distance of 2,097 km. In all four cases the rhino were lying down in open areas. Two feeding strategies were observed i.e. walking on the back of the animal to probe in the ears and around the anus and walking on the ground around the animal and probing between the hind legs and around the anus. Their actions suggested that they were removing ticks but this could not be positively confirmed even with the aid of 7 x 50 binoculars. The mean time spent on the animals was 12,5 min (range 8-17 min). No intolerance was shown towards the attentions of the crows. The crows seemed to have problems balancing themselves while standing on the back of the animal and probing in the ear or around the anus. This is probably due to the fact that crows are not adapted to exploit this niche to the same extent as oxpeckers (Buphaginae) in the sense of having curved claws.
On two occasions the crows settled on a rhino with associating redbilled oxpeckers Buphagus etythrorhynchus. The oxpeckers immediately gave the alarm call and flew away. These observations suggest possible interspecific competition between crows and oxpeckers in the Complex. However, during the same count a total of 89 oxpeckers were associating with the 197 white rhino observed. The proportion is therefore 0,452 oxpeckers/ rhino compared to a very low association of 0,036 crows/ rhino. These results suggest that ectoparasites are not a very important food source for the Pied crow.
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