Effects of browse availability and quality on black rhino (Diceros bicornis michaeli Groves 1967) diet in Nairobi National Park, Kenya

Investigations were conducted to study the effects of browse availability and quality on black rhinoceros (Diceros bicornis michaeli Groves 1967) diet in Nairobi National Park, Kenya, between September 1994 and February 1995. Line intercept method was used to assess availability of browse. The ratios of browsed crowns to the total crown were applied in the estimate of browse use. Proximate analysis and extraction methods were used, respectively, to appraise browse nutritional quality and phytochemical status of twelve species. Thirty-four plant species were identified as potential black rhino browse, whose availability differed significantly (P < 0.001). Lippia javanica (20.581 +/- 3.101, n = 544) and Lannea cornuta (0.963 +/- 0.529, n = 544) were the most and least available species, respectively. Only 32 species, however, were utilized, as L. cornuta and Rhynchosia hirta did not show any level of rhino feeding activity. Browse use was found to vary significantly (P < 0.001) during the study period. Grewia similis was most (20.564 +/- 2.764, n = 544) and Commelina africana least (0.974 +/- 0.974, n = 544) exploited, respectively. Differences in total alkaloids and phenols, crude fibre, crude protein and total ash contents among species investigated were highly significant (P < 0.001). Ether extract values were similar (P = 0.0933) across plant taxa. The study shows that the black rhino is a selective browser feeding on plants with low phenol and alkaloid contents and high fibre values. Of the nutritionally similar species, browsing was driven by availability. These findings suggest that a key habitat factor important in black rhinoceros conservation include diverse plant species with low levels of phenols and alkaloids.