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

Abstract

Investigations were conducted to study the effects of browse availability and quality on black rhinoceros (Diceros bicornis michaeliGroves 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.

A comparison of faecal analysis with backtracking to determine the diet composition and species preference of the black rhinoceros (Diceros bicornis minor)

“…The preference for Grewia spp. has also been reported in other studies (Hall-Martin et al 1982;Emslie andAdcock 1994, Muya andOguge 2000), but although other studies (Emslie and Adcock 1994;Joubert and Eloff 1971;Mukinya 1977) reported a preference for Acacia spp., this was not observed in the GFRR.…”

“…The underestimation of grasses in the diet from backtracking data was also reported by Hall-Martin et al (1982). Backtrack or observational studies (Joubert and Eloff 1971;Mukinya 1977;Oloo et al 1994;Pole 1995;Muya and Oguge 2000;Winkel 2004) all reported a very low proportion of grass in the diet (<1%) or detected no grasses at all. Therefore, one important bias in the backtracking study might be that certain bites are missed (e.g.…”

“…Secondary metabolite content (e.g. polyphenols or condensed tannins) might also be important, as Muya and Oguge (2000) found a negative correlation between phenol and alkaloid content and rhino utilisation, although Loutit et al (1987) could not find any effect of soluble tannins on plant preference. Therefore, before further conclusions can be drawn, browse species should be analysed for their plant secondary metabolite content and, additionally, acid detergent fibre and lignin so that the role of plant secondary compounds on the diet choice of black rhino can be investigated (Bryant and Kuropat 1980;Cooper and Owen-Smith 1985;Clauss et al 2007a).…”

“…The diet of individual rhinos can be determined by tracking backwards and locating distinctive bite marks (a scissorlike cut stump) left by feeding animals (Muya and Oguge 2000). A bite mark was identified as any isolated severed shoot or branch that was bitten off.…”

“…Previous studies of black rhinoceros (Diceros bicornis minor) diet have largely depended upon direct observation or backtracking techniques (Goddard, 1968;Schenkel and Schenkel-Hullinger 1969;Joubert and Eloff 1971;Mukinya 1977;Loutit et al 1987;Emslie and Adcock 1994;Oloo et al 1994;Atkinson 1995;Pole 1995;Muya and Oguge 2000;Ausland et al 2002;Brown et al 2003;Winkel 2004;Ganqa et al 2005). Microhistological analysis of faeces (Stewart, 1967;de Boer et al 2000;de Jong et al 2004) has rarely been attempted, and comparisons of both methods have only been reported previously by Hall-Martin et al (1982).…”