Population Constraints Associated with the Use of Black Rhinos as an Umbrella Species for Desert Herbivores

Abstract

The numerous tactics used to conserve biodiversity include the designation of protected areas, political change, and research and education, the latter involving paradigms such as insular biogeography and the “umbrella species concept.” In Namibia lands removed from national park status in 1970 and currently under the jurisdiction of indigenous people now contain one of the few unfenced populations of black rhinos (Diceros bicornis) remaining in Africa. Theory predicts that the protection of umbrella species will ensure the survival of other biota that require(s) less space. To gauge how well biodiversity might be retained by examining the spatial needs of a small population of black rhinos, I used data gathered under various ecological conditions to estimate mean and minimum population sizes of six large herbivores of the Namib Desert ranging in size from giraffe (Giraffa camelopardalis) to springbok (Antidorcas marsupialis) and ostrich (Struthio camelus). My results indicate that annual differences in rainfall, both within and between seasons, resulted in wide fluctuations in herbivore population sizes for all species except rhino. Although other herbivores switched to areas of higher rainfall, rhinos did not. The data suggest that under conditions of extreme environmental variance the space used by rhinos alone was unlikely to assure the existence of populations of other species in excess of 250 individuals. Fifty percent of the species failed to exceed 150 individuals 50% of the time and one third of the species never attained populations in excess of 50 individuals. However, by employing assumptions about the spatial needs of rhino populations numbering up to 100 individuals, the mean minimum population sizes attained by any of four desert herbivores is 535. A future challenge in using rhinos and other large‐bodied species as umbrellas for organisms of either similar or dissimilar trophic levels will be the refinement of estimates of population viability.

Is research effort allocated efficiently for conservation? Felidae as a global case study

“…Many of these species might also act as effective umbrella species, facilitating the conservation of their smaller brethren (Karanth 2003;Thorne et al 2006). Though large-bodied species are often useful umbrella species, this cannot always be assumed a priori; for example, Berger (1996) showed that black rhinoceros (Diceros bicornis) in Namibia, despite their large size, do not actually serve as umbrella species for smaller ungulates due to different seasonal distributions. Finally some research on large cats continues to generate extremely useful insights with broad applications.…”

Eciton Army Ants—Umbrella Species for Conservation in Neotropical Forests

“…Species categorised as an umbrella require large areas of habitat for their survival and, therefore, by protecting their habitat, many other species will be protected [16,165], including those that share similar ecology [166,167] or those species more directly interacting with them [168]. However, the conservation of these other species is strongly dependent on the appropriate selection of the umbrella species [169,170].…”

Hippos alter their aggregations to mitigate density‐dependent drought effects

“…As a result of long‐distance movements, drought can increase the spatial heterogeneity in herbivore abundance, with individuals aggregated in areas less affected by drought (Pople et al, 2007). Alternatively, the demographic characteristics of megaherbivore populations, for example, high survival during drought, may buffer demographic variability in response to extreme weather events (Berger, 1997; Trimble et al, 2009). These relationships among resource availability, movement and local density are thus critical to understanding the response of megaherbivores to extreme weather events (Chamaillé‐Jammes et al, 2008).…”