Conservation of Neotropical game species must take into account the livelihood and food security needs of local human populations. Hunting management decisions should therefore rely on abundance and distribution data that are as representative as possible of true population sizes and dynamics. We simultaneously applied a commonly used encounter-based method and an infrequently used sign-based method to estimate hunted vertebrate abundance in a 48,000-km2 indigenous landscape in southern Guyana. Diurnal direct encounter data collected during three years along 216, four-kilometer -long transects consistently under-detected many diurnal and nocturnal mammal species readily detected through sign. Of 32 species analyzed, 31 were detected by both methods; however, encounters did not detect one and under-detected another 12 of the most heavily hunted species relative to sign, while sign under-detected 12 never or rarely collected species relative to encounters. The six most important game animals in the region, all ungulates, were not encountered at 11–40% of village and control sites or on 29–72% of transects where they were detected by sign. Using the sign methodology, we find that tapirs, one of the terrestrial vertebrates considered most sensitive to overexploitation, are present at many sites where they were never visually detected during distance sampling. We find that this is true for many other species as well. These high rates of under-detection suggest that behavioral changes in hunted populations may affect apparent occurrence and abundance of these populations. Accumulation curves (detection of species on transects) were much steeper for sign for 12 of 16 hunted species than for encounters, but that pattern was reversed for 12 of 16 species unhunted in our area. We conclude that collection of sign data is an efficient and effective method of monitoring hunted vertebrate populations that complements encounter and camera-trapping methods in areas impacted by hunting. Sign surveys may be the most viable method for large-scale, management-oriented studies in remote areas, particularly those focused on community-based wildlife management.

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Biodiversity affects many ecosystem functions and services, including carbon cycling and retention. While it is known that the efficiency of carbon capture and biomass production by ecological communities increases with species diversity, the role of vertebrate animals in the carbon cycle remains undocumented. Here, we use an extensive dataset collected in a high-diversity Amazonian system to parse out the relationship between animal and plant species richness, feeding interactions, tree biomass and carbon concentrations in soil. Mammal and tree species richness is positively related to tree biomass and carbon concentration in soil-and the relationship is mediated by organic remains produced by vertebrate feeding events. Our research advances knowledge of the links between biodiversity and carbon cycling and storage, supporting the view that whole community complexity-including vertebrate richness and trophic interactions-drives ecosystem function in tropical systems. Securing animal and plant diversity while protecting landscape integrity will contribute to soil nutrient content and carbon retention in the biosphere.