Impala, Aepyceros melampus: does browse quality influence their use of sites originally utilised as short-duration kraals in a southern African savanna?

Abstract

In eastern and southern Africa, some ranch owners are now keeping cattle overnight in temporary corrals (hereafter referred to as kraals) within rangelands for short durations to improve grass production. However, this has profound effects on the woody plant community. For instance, cattle break woody plant stems and strip them of foliage, initiating resprouting. The resprouts produced have high foliar nitrogen (N) and reduced condensed tannin (CT) concentrations, making them attractive to herbivores. The aim of this study was to determine the key nutrient-quality parameters of resprouts that make previously kraaled sites attractive to impala soon after cattle removal at Debshan Ranch in central Zimbabwe. We determined resprout length, foliar N, phosphorus (P), potassium, CT, fibre and rumen fermentation of three browse species, viz. Grewia monticola Sond., Terminalia sericea Burch. ex DC. and Dichrostachys cinerea (L.) Wight and Arn., and related them to impala use of previously kraaled sites. We used impala dung density to determine the use patterns of previously kraaled sites 2, 4, 12 and 24 weeks after cattle removal and compared them with the surrounding vegetation. Impala use of previously kraaled sites was highest 4 weeks after cattle removal and lowest in the surrounding vegetation. Resprout length increments were 6-fold over a 10-week growth period in all three woody species. Foliar N and P were generally higher, whereas CT was lower, in previously kraaled sites than the surrounding vegetation in all three of the plant browse species. Impala use of previously kraaled sites showed a strong negative relationship with foliar CT. We conclude that kraaling initiates strong resprout responses by woody plants soon after cattle removal, to produce resprouts of high nutrient quality, which attract herbivores such as impala.