In African savannas, browse-based resources (@3 plants) are isotopically distinct from grasses (@4 plants). The carbon isotopic composition of the basic plant diet is recorded in animal tissues. Mammal faeces are a readily accessible, non-invasive, sample material for temporally resolved dietary reconstructions. Faeces, however, include both undigested plant matter and waste, hence accuracy of dietary calculations could potentially be compromised by shifts in plant isotopic values related to seasonal or spatial differences, or by variability in the isotopic differences between faeces and diet. A controlled feeding study of four ungulate species showed a small, consistent difference between diet and faeces of-0.9 o, irrespective of whether the diet was @3 or C4-based. Results from faeces oftaxa known to be pure grazers, pure browsers, and mixed-feeders from the Kruger National Park were entirely consistent with their diets, but the accuracy of dietary reconstructions is enhanced with data from local plant communities

Impala are known to exhibit dietary flexibility, relying primarily on browse in some areas and graze in others. In this study we use stable isotope analysis of faeces and hair to examine the diets of impala in Kruger National Park. As expected, the data show that impala are mixed-feeders and highly distinct from grazing buffalo and browsing kudu. Moreover, impala, buffalo, and kudu faeces contain 2.1 %, 1.4 %, and 2.9 % nitrogen respectively, suggesting that impala diets are of intermediate quality. There are also marked differences between impala populations in the northern and southern regions of the park. The northern impala graze less than their southern counterparts. This difference probably reflects decreased availability of herbaceous forage in the mopane-dominated north. Males and females also have different diets, with males grazing more than females.

Species’ partitioning of resources remains one of the most integral components for understanding community assembly. Analysis of stable carbon and nitrogen isotopes in animal tissues has the potential to help resolve patterns of partitioning because these proxies represent the individual’s diet and trophic niche, respectively. Using free-ranging rodents in a southern African savanna as a model community, we find that syntopic species within habitats occupy distinct isotope niches. Moreover, species with strongly overlapping isotope niches did not overlap in their spatial distribution patterns, suggesting an underlying effect of competitive exclusion. Niche conservatism appears to characterize the behaviour of most species in our sample - with little or no observed changes across habitats - with the exception of one species, Mastomys coucha. This species displayed a generalist distribution, being found in similar abundances across a variety of habitats. This spatial pattern was coupled with a generalist isotope niche that shifted across habitats, likely in response to changes in species composition over the same spatial gradient. The case for M. coucha supports contentions that past competition effects played a significant evolutionary role in shaping community structures of today, including the absence of strong interspecific niche overlaps within particular habitats. Our study highlights the value of stable isotope approaches to help resolve key questions in community ecology, and moreover introduces novel analytical approaches to quantifying isotope niche breadths and niche overlaps that are easily comparable with traditional metrices.

Many herbivore species expand their dietary niche breadths by switching from browse-rich diets in dry seasons to grass-rich diets in rainy seasons, in response to phenological changes in plant availability and quality.Weanalyzed stable isotope series along tail hairs of captive and free-ranging African elephant (Loxodonta africana (Blumenbach, 1797)) to compare patterns of seasonal dietary variability across individuals. Results from elephants translocated from the wild into captivity, where their diets are semicontrolled, revealed tail hair growth rates of 0.34 mm/day, on average, and relatively rapid isotope turnover through the transition from wild into captivity. Sampling hairs at 10 mm increments thus archives dietary chronologies at a resolution suitable for tracking diet switches at seasonal, and even subseasonal, scales. Hairs of free-ranging elephants showed extensive carbon isotopic variability within individuals, consistent with seasonal switches between C3-browsing and C4-grazing. Similarly extensive, but asynchronous, shifts in nitrogen isotope ratios were also observed, suggesting an influence of factors other than seasonality. Across individuals, switching patterns differed across habitats, and across age classes, with older, larger animals including increasing amounts of C3 browse into their diets. These results demonstrate how stable isotope approaches characterize complex patterns of resource use in wildlife populations. ARTICLEStable isotope turnover and variability in tail hairs of captive and free-ranging African elephants (Loxodonta africana) reveal dietary niche differences within populations Jacqueline Codron, Kevin Kirkman, Kevin J. Duffy, Matt Sponheimer, Julia A. Lee-Thorp, Andre Ganswindt, Marcus Clauss, and Daryl Codron Abstract: Many herbivore species expand their dietary niche breadths by switching from browse-rich diets in dry seasons to grass-rich diets in rainy seasons, in response to phenological changes in plant availability and quality. We analyzed stable isotope series along tail hairs of captive and free-ranging African elephant (Loxodonta africana (Blumenbach, 1797)) to compare patterns of seasonal dietary variability across individuals. Results from elephants translocated from the wild into captivity, where their diets are semicontrolled, revealed tail hair growth rates of ϳ0.34 mm/day, on average, and relatively rapid isotope turnover through the transition from wild into captivity. Sampling hairs at 10 mm increments thus archives dietary chronologies at a resolution suitable for tracking diet switches at seasonal, and even subseasonal, scales. Hairs of free-ranging elephants showed extensive carbon isotopic variability within individuals, consistent with seasonal switches between C 3 -browsing and C 4 -grazing. Similarly extensive, but asynchronous, shifts in nitrogen isotope ratios were also observed, suggesting an influence of factors other than seasonality. Across individuals, switching patterns differed across habitats, and across age classes, with older,...

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