Impact of the black rhinoceros (Diceros bicornis minor) on a local population of Euphorbia bothae in the Great Fish River Reserve, South Africa

Abstract

In the Great Fish River Reserve, South Africa, black rhinoceros (Diceros bicornis minor) feed extensively on a local population of Euphorbia bothae. Maintaining the endangered black rhinoceros and the protected E. bothae population are both conservation priorities of the reserve. Therefore, the sustainability of this plant–animal interaction was investigated by comparing population characteristics, browsing incidence and intensity within the reserve and in an adjacent exclosure without access to rhino. Fixed‐point photographs showed that over a 2‐month period 36.6% of 213 monitored plants were browsed, with an average biomass loss of 13%, and 1% were destroyed. Of 26 plants re‐photographed after approximately 3 years, 70% showed a decrease in biomass, averaging 37.8% over this period. In this time span, 19% of the monitored plants died. Small plants (<45 cm) were over‐represented in the rhino‐browsed area, whereas the fraction of reproductively active plants and overall plant density were found to be lower than in the adjacent exclosure. No evidence of short‐term compensatory growth in response to browsing was found for E. bothae. This study indicates that, with the current population size, rhinos are overexploiting the E. bothae population and special measures should be taken to prevent local extinction.

Seasonal diet preferences of black rhinoceros in three arid South African National Parks

“…A detailed knowledge of black rhino diet has several uses: (i) estimating appropriate stocking rates for this critically endangered species (Adcock, 2001); (ii) determining key plant species as early warning indicators of food limitation and of threats to highly preferred plant species (Luske et al. , 2009); (iii) facilitate research on diet overlap with other herbivores (De Boer & Ijdema, 2007); (iv) facilitate research on nutritional requirements of black rhinos in the wild and in captivity (Atkinson, 1995); and (v) improve our understanding of diet selection by the species (Muya & Oguge, 2000).…”

Dietary Plasticity of Generalist and Specialist Ungulates in the Namibian Desert: A Stable Isotopes Approach

“…This euphorbia is highly toxic and endemic to our study area [63]. Other Euphorbia species are used by other herbivores as well, such as browsing Kudu Tragelaphus strepsiceros [64], black rhinoceros Diceros bicornis bicornis [65] or small antelopes [66] but have never been documented to be utilized by an ungulate that is traditionally considered a grazer. Hence, our result suggests that the gemsbok population of the Kunene region may have evolved physiological abilities that allow them to process or tolerate the highly toxic secondary compounds of Euphorbia damarana and consequently to benefit from its high water and nutritious content.…”

Continued decline in tree euphorbias (Euphorbia tetragona and E. triangularis) on the Great Fish River Reserve, Eastern Cape, South Africa

“…Black rhinos seek out and readily devour other low‐growing Euphorbiaceae such as Euphorbia bothae and Jatropha capensis (Brown et al. , 2003; Luske et al. , 2009), and there is no reason to suppose they would not also eat or destroy tree Euphorbia seedlings.…”