Changes in large herbivore populations across large areas of Tanzania Chantal Stoner 1 *, Tim Caro 1,2 , Simon Mduma 2 , Charles Mlingwa 2 , George Sabuni 2 , Markus Borner 3 and Christiane Schelten 3 1 Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, CA 95616, U.S.A., 2 Tanzania Wildlife Research Institute, PO Box 661, Arusha, Tanzania and 3 Frankfurt Zoological Society, PO Box 14935, Arusha, Tanzania Abstract We collated aerial census data collected during the late 1980s to early 2000s for large herbivore populations in eight large census zones in Tanzania. Of the ungulate populations that showed significant changes in densities at the start versus end of this decade, most declined; very few populations increased significantly. Thomson’s gazelle, Grant’s gazelle, hartebeest, reedbuck, roan antelope, sable antelope, warthog and zebra, for example, declined in over 50% of the zones where they were surveyed. Interestingly, small-bodied species fared particularly poorly in many census zones, whereas elephant and giraffe generally fared well across the country. Most populations of all herbivores declined in some portions of the country (e.g. Burigi- Biharamulo, Katavi, Greater Ruaha and Tarangire census zones). These surveys suggest that, even in a country renowned for its protected areas and conservation com- mitment, some large herbivore populations need more conservation attention in order to remain stable. Key words: aerial surveys, East Africa, large mammals, population dynamics Re ´sume ´ Nous avons rassemble ´ les donne ´es re ´colte ´es entre la fin des anne ´es 1980 et le de ´but des anne ´es 2000 lors de recens- ements des populations de grands herbivores dans huit vastes zones de Tanzanie. La plupart des populations d’ongule ´s qui pre ´sentaient des changements de densite ´ significatifs entre le de ´but et la fin de ces recensements avaient diminue ´; tre `s peu avaient augmente ´ significative- ment. La gazelle de Thomson, la gazelle de Grant, le bubale, le cobe des roseaux, l’antilope rouanne, l’antilope sable, le phacoche `re et le ze `bre, par exemple, avaient de ´cline ´ dans plusieurs zones. Il est inte ´ressant de remar- quer que les espe `ces de petite taille avaient des re ´sultats pluto ˆt me ´diocres dans de nombreuses zones de recense- ment alors que les e ´le ´phants et les girafes s’en sortaient bien dans tout le pays. La plupart des populations de tous les herbivores ont baisse ´ dans certaines parties du pays (ex. les zones de recensement de Burigi-Biharamulo, Katavi, le Grand Ruaha et Tarangire). Ces e ´tudes montrent que, me ˆme dans un pays renomme ´ pour son engagement en- vers ses aires prote ´ge ´es et la conservation, certaines pop- ulations de grands herbivores ont besoin d’une attention de conservation plus grande pour rester stables. Introduction Monitoring changes in population size over time is critical for effective conservation. Long-term monitoring data reveal how changing abiotic and biotic factors influence popula- tion dynamics, and therefore are of great help in allocating conservation efforts (Hafner & Fasola, 1997). Investigations that focus on the impacts of land development (e.g. Briggs et al., 1996; McCarthy et al., 1999), invasive species (Fitzgerald & Gibb, 2001), restoration projects (e.g. Luke & Zack, 2001), and sustainable harvest efforts (e.g. Forsyth, 1999) on native flora and fauna all reiterate the necessity for assessing long-term trends in populations. In a review of tools for managing diversity within forests, Lindenmayer (1999) noted that though a growing number of publications hint at the many advantages of long-term data, relatively few long-term monitoring programmes exist. In Tanzania, a megadiversity country with an extensive network of reserves, herbivore populations have been *Correspondence: Tel.: 1-530-752-5196; E-mail: cjstoner@ucdavis. edu 202 Ó 2006 The Authors. Journal compilation Ó 2006 Blackwell Publishing Ltd, Afr. J. Ecol., 45, 202–215