Comparative diet and habitat selection of puku (Kobus vardonii) and lechwe (Kobus leche) on the Chobe River floodplain, Botswana

Abstract

The influence of ecological change on the populations of select herbivores is of concern to national parks and wildlife managers in many regions of the world. Impacts of burgeoning elephant (Loxodonta africana) populations recovering from early 20th century hunting pressure have been well documented. Puku (Kobus vardonii) antelope within the Chobe National Park, Botswana, are believed to be at risk of local extinction due to ecological change resulting from an increasing elephant population. In this study, I sought to compare the low density puku population to the high density, congeneric lechwe (Kobus leche) population that inhabits the floodplains adjoining the Chobe River. With this project I aimed to improve our understanding of forage selection, nutritional status, and habitat selection of puku in relation to the more regionally distributed, high density lechwe. Theories of feeding specialization, competition, and patterns of species abundance suggested that the low density puku would be more selective in forage and habitat resources as well as being more constrained nutritionally than the high density lechwe. My results showed puku to feed on a wider range of grass species than lechwe, but to be more narrowly selective of grasses in terms of phenotypic features. Puku were more narrowly selective of grass greenness, height, and cover than were lechwe. Puku and lechwe shared high levels of dietary overlap across seasons, only differing in contributions of a few key grass species. There was no distinction between puku and lechwe nutritionally with both species appearing to remain above critical thresholds for faecal nitrogen and phosphorus. The two grazers show slight partitioning of habitat use during the low water season. During the high water season, puku and lechwe showed near complete partitioning of habitat use by implementing differing strategies of selection in response to the inundation of the floodplains. Overall, results showed slight partitioning of food resources, but more definitive differentiation in habitat use between puku and lechwe. My findings suggest that due to the close similarities in diet, nutrition, and habitat selection between the low density puku and high density lechwe,some other factor, such as predation, may be limiting the population density of puku within the Chobe National Park.