© 2009 The Authors DOI: 10.1111/j.1472-4642.2008.00554.x Journal compilation © 2009 Blackwell Publishing Ltd www.blackwellpublishing.com/ddi 513 Diversity and Distributions, (Diversity Distrib.) (2009) 15, 513– 522 BIODIVERSITY RESEARCH ABSTRACT Aim Classic island biogeographical theory predicts that reserves have to be large to conserve high biodiversity. Recent literature, however, suggests that habitat hetero- geneity can counterbalance the effect of small reserve size. For savanna ungulates, body mass is said to drive habitat selection and facilitate species coexistence, where large species use a higher proportion of the landscape than smaller species, because a wider food quality tolerance allows them to use a higher diversity of habitat types. In this case, high habitat heterogeneity would facilitate diverse assemblages of different- sized ungulates. Digestive physiology should further modify this relationship, because non-ruminants have a wider diet tolerance than ruminants. We tested this hypothesis with an empirical dataset on distribution and habitat preference of different-sized African grazers. Location Hluhluwe-iMfolozi Park, Republic of South Africa. Methods We recorded herbivore dung and habitat type on 24 line transects varying between 4 and 11 km with a total length of 190 km to determine habitat selection and landscape distribution of six grazer species, three ruminants and three non-ruminants. Results Larger ruminant grazers were more evenly distributed than smaller ruminants, had a more diverse use of habitats and used more low quality habitat. In contrast, non-ruminant grazers were more evenly distributed than similar-sized ruminants and body mass did not clearly influence diversity of habitat use and use of low quality habitat. Main conclusions We confirm that body mass influences diversity of habitat use of large herbivores but digestive strategy potentially modifies this relationship. Hence, habitat heterogeneity might facilitate herbivore diversity in savanna ecosystems and high heterogeneity might counterbalance the effects of fragmentation and declining reserve size. Concluding, processes that homogenize the landscape, such as fire (mis)management and artificial waterholes, might be as threatening to biodiversity as landscape fragmentation, especially for smaller ruminant herbivores. Keywords Community ecology, grazing lawns, habitat heterogeneity, resource partitioning, savanna ungulate diversity, species–area relationships. INTRODUCTION Biogeographical theory has played a major role in biodiversity conservation, specifically its application in reserve planning (Simberloff & Abele, 1976; Soulé & Terborgh, 1999). Island biogeography and the species–area relationship have been used to argue that bigger reserves are better suitable to maintain species diversity (MacArthur & Wilson, 1967; Brashares et al., 2001; Hansen & DeFries, 2007). However, Gurd (2006) showed, using island case studies, that small does not necessarily have to be bad, and that there are several examples of large islands losing a large proportion of their species and small islands maintaining complete species assemblages. Obviously, reserve size should not be the sole important characteristic in reserve selection. Recently, 1 Community and Conservation Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands, 2 Resource Ecology Group, Centre for Ecosystem Studies, Wageningen University, Wageningen, The Netherlands *Correspondence: Joris P. G. M. Cromsigt, Mammal Research Institute, ul. Waszkiewicza 1c, 17-230 Bialowieza, Poland. E-mail: jcromsigt@hotmail.com Blackwell Publishing Ltd Habitat heterogeneity as a driver of ungulate diversity and distribution patterns: interaction of body mass and digestive strategy Joris P. G. M. Cromsigt 1 *, Herbert H. T. Prins 2 and Han Olff 1