An evaluation of camera traps for inventorying large- and medium-sized terrestrial rainforest mammals M. W. Tobler 1 , S. E. Carrillo-Percastegui 2 , R. Leite Pitman 3 , R. Mares 2 & G. Powell 2 1 Botanical Research Institute of Texas, Andes to Amazon Biodiversity Program, Fort Worth, TX, USA/Texas A&M University, Department of Wildlife and Fisheries Sciences, College Station TX, USA 2 World Wildlife Fund, Washington, DC, USA 3 Duke University Center for Tropical Conservation/Instituto Procarnivoros/Oxford University Wildlife and Research Conservation Unit, Durham, NC, USA Keywords camera traps; species accumulation curves; Amazon; diversity; inventory; species richness estimators; Peru; Madre de Dios. Correspondence Mathias W. Tobler Botanical Research Institute of Texas, 509 Pecan Street, Fort Worth, TX 76102-4060, USA. Email: matobler@brit.org Received 18 September 2007; accepted 8 February 2008 doi:10.1111/j.1469-1795.2008.00169.x Abstract Mammal inventories in tropical forests are often difficult to carry out, and many elusive species are missed or only reported from interviews with local people. Camera traps offer a new tool for conducting inventories of large- and medium- sized terrestrial mammals. We evaluated the efficiency of camera traps based on data from two surveys carried out at a single site during 2 consecutive years. The survey efforts were 1440 and 2340 camera days, and 75 and 86% of the 28 large- and medium-sized terrestrial mammal species known to occur at the site were recorded. Capture frequencies for different species were highly correlated between the surveys, and the capture probability for animals that passed in front of the cameras decreased with decreasing size of the species. Camera spacing and total survey area had little influence on the number of species recorded, with survey effort being the main factor determining the number of recorded species. Using a model we demonstrated the exponential increase in survey effort required to record the most elusive species. We evaluated the performance of different species richness estimators on this dataset and found the Jackknife estimators generally to perform best. We give recommendations on how to increase efficiency of camera trap surveys exclusively targeted at species inventories. Introduction Mammal inventories serve a multitude of purposes: they show the diversity at a specific site, allow for comparison among sites, help refine distribution maps for individual species and can be used to evaluate the impact of human activities on mammal communities. A good knowledge of the presence and distribution of species is crucial for plan- ning and evaluating conservation strategies for a region. However, despite years of research throughout the Amazon, there are few complete mammal inventories and our knowl- edge on the distributions of rare and elusive species is still poor (Voss & Emmons, 1996). The methods commonly used for mammal inventories are line transects, direct observa- tions, identification of tracks and feces, trapping and inter- views with local people (Voss & Emmons, 1996; Voss, Lunde & Simmons, 2001; Trolle, 2003a; Mendes Pontes, 2004; Haugaasen & Peres, 2005). While line transects can be used to survey the density of relatively abundant mammal species, they often fail to record rare and elusive species such as small carnivores, anteaters and armadillos (Voss & Emmons, 1996). The use of camera traps for studying terrestrial mammals has become increasingly popular in recent years as camera technology has improved and equipment costs have de- creased. Applications range from collecting species inven- tories (Maffei, Cu ´ellar & Noss, 2002; Silveira, Jacomo & Diniz, 2003; Trolle, 2003b; Srbek-Araujo & Garcia, 2005; Azlan & Lading, 2006) to studying activity patterns (van Schaik & Griffiths, 1996; G ´omez et al., 2005; Azlan & Sharma, 2006) and estimating animal density (Mace et al., 1994; Karanth & Nichols, 1998; Sweitzer et al., 2000; Trolle & K ´ery, 2003; Silver et al., 2004). Silveira et al. (2003) concluded that camera trap surveys were the most appro- priate and accurate method for mammal inventories in the open savannas of Emas National Park in Brazil when compared with line transects and track counts. In a study on forest antelopes in the Udzungwa Mountains of Tanzania, camera traps recorded species rarely encountered in census walks (Rovero, Jones & Sanderson, 2005). Records from camera traps in Tanzania significantly extended the known range for the endangered Jackson’s mongoose Bdeogale jacksoni (De Luca & Rovero, 2006). Photographs from camera traps provide reliable records of a species presence, Animal Conservation 11 (2008) 169–178 c  2008 The Authors. Journal compilation c  2008 The Zoological Society of London 169 Animal Conservation. Print ISSN 1367-9430