Diets of savanna ungulates from stable carbon isotope composition of faeces

Abstract

Hypotheses to explain diversity among African ungulates focus largely on niche separation along a browser/grazer continuum. However, a number of studies advocate that the browser/grazer distinction insufficiently describes the full extent of dietary variation that occurs within and between taxa. Disparate classification schemes exist because of a lack of uniform and reliable data for many taxa, and failure to incorporate spatio-temporal variations into broader assessments of diet.In this study, we tested predictions for diet and dietary niche separation of African savanna ungulates using stable carbon isotope evidence from faeces for proportions of C 3 (browse) to C 4 (grass) intake among 19 species from the Kruger National Park, South Africa. Dietary predictions from the literature are confirmed in the case of browsers (black rhinoceros Diceros bicornis, giraffe Giraffa camelopardalis, bushbuck Tragelaphus scriptus, kudu Tragelaphus strepsiceros), mixed-feeders (impala Aepyceros melampus, nyala Tragelaphus angasii), and most grazers (white rhinoceros Ceratotherium simum, Burchell's zebra Equus burchellii, warthog Phacochoerus africanus, hippopotamus Hippopotamus amphibius, blue wildebeest Connochaetes taurinus, tsessebe Damaliscus lunatus, waterbuck Kobus ellipsiprymnus). In contrast, several species showed results differing from most expectations derived from the available literature, including eland Taurotragus oryx, steenbok Raphicerus campestris, grey duiker Sylvicapra grimmia, buffalo Syncerus caffer, roan antelope Hippotragus equinus and sable antelope Hippotragus niger. Many of these discrepancies can be accounted for by seasonal and/or regional dietary differences. Cluster analysis based on a data matrix that incorporates the extent of spatio-temporal dietary variation among Kruger Park ungulates reveals several distinct categories of feeding preferences that extend beyond a two-edged browser/grazer dichotomy, such as mixed-feeders with a preference for either forage class, and spatial/seasonal shifts between uniform and mixed-feeding styles among variable browsers (e.g. grey duiker) and variable grazers (e.g. buffalo). These results highlight the need for approaches that are sensitive to spatio-temporal variations and the continuity of diet.

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

“…Mabinya et al (2002), also working in GFRR, used a chemical analysis of dung analysis and reported a roughly similar proportion of grasses in black rhino diets from GFRR. Hall- Martin et al (1982) also found that overall, the diet of black rhinos in Addo Elephant National Park comprised 2-10% grass using faecal analysis, and similar values are reported for the Kruger National Park in a carbon isotope study (Codron et al 2007). Hence, the failure of backtracking to detect grass consumption and the underestimation of herbs is an important shortcoming of the method.…”

Stable Carbon Isotope Analysis of the Diets of West African Bovids in Pendjari Biosphere Reserve, Northern Benin

“…The model endpoints were based on seasonallyspecific medians of Ç 13 C values from the local C 3 and C 4 vegetation collected over the same time periods as the faeces. The equation above provides an estimate of C 4 -intake, but is not an accurate index of diet because of variation in Ç 13 C, in carbon isotope composition of dietary baselines (plants), and stochasticity (Post 2002;Cerling et al 2003;Codron et al 2005Codron et al , 2007b.To account for this variation in our analysis, we varied a 13 C values randomly between the published maximum and minimum values reported by Codron et al (2011a), and C 3 and C 4 plant endpoint values between their respective 25th to 75th interquartile ranges. We report on means and 95% confidence limits derived from 1000 iterations.…”

“…Several studies in Africa have used the stable isotope technique to investigate diets of diverse herbivore taxa including antelope (Tieszen et al 1979;Cerling & Harris 1999;Codron et al 2006Codron et al , 2007bCodron et al ,c, 2011a, elephants (Koch et al 1995;Codron et al 2011a), and suids (Cerling & Viehl 2004). Most of this research has focused on East and southern African savannas (Cerling et al 2003;Sponheimer et al 2003a;Codron et al 2006Codron et al , 2007aCodron et al , 2011a, with little emphasis placed on savannas in West Africa.…”

“…C 3 plants are consistently depleted in 13 C relative to C 4 plants (Ehleringer et al 1991;Ehleringer & Monson 1993;Codron et al 2005), and this difference is recorded in the body tissues and faeces of the herbivores that feed on them. The application of stable isotopes in feeding ecology has emerged as a powerful tool for partitioning herbivore diets into browsing and grazing components, and testing ecological/evolutionary hypotheses related to browsing and grazing (Tieszen et al 1979;Cerling et al 2003;Sponheimer et al 2003b;Codron et al 2007b).…”

Ruminants as Part of the Global Food System: How Evolutionary Adaptations and Diversity of the Digestive System Brought them to the Future

“…Many plants have used animals as vectors for seed dispersal, and several animals have adapted their requirements according to the environmental food availability [25]. Conjectures that changes in the resource-use specialization rate of ungulates, more precisely the evolution and incorporation of the grazing, were pushed by the expansion of C4 grasslands in Africa during the early Pliocene [26,27]. Palaeoecological evidences claim that the ancestral ruminant was a small and forest-dwelling species [28] with feeding characteristics of a browser/mixed feeder, and therefore with a leaf-eating style, rich in intracellular carbohydrates [29][30][31].…”