Abstract
The degree to which terrestrial vertebrate populations are depleted in tropical forests occupied by human communities has been the subject of an intense polarising debate that has important conservation implications. Conservation ecologists and practitioners are divided over the extent to which community-based subsistence offtake is compatible with ecologically functional populations of tropical forest game species. To quantify depletion envelopes of forest vertebrates around human communities, we deployed a total of 383 camera trap stations and 78 quantitative interviews to survey the peri-community areas controlled by 60 semi-subsistence communities over a combined area of over 3.2 million hectares in the Médio Juruá and Uatumã regions of Central-Western Brazilian Amazonia. Our results largely conform with prior evidence that hunting large-bodied vertebrates reduces wildlife populations near settlements, such that they are only found at a distance to settlements where they are hunted less frequently. Camera trap data suggest that a select few harvest-sensitive species, including lowland tapir, are either repelled or depleted by human communities. Nocturnal and cathemeral species were detected relatively more frequently in disturbed areas close to communities, but individual species did not necessarily shift their activity patterns. Group biomass of all species was depressed in the wider neighbourhood of urban areas rather than communities. Interview data suggest that species traits, especially group size and body mass, mediate these relationships. Large-bodied, large-group-living species are detected farther from communities as reported by experienced informants. Long-established communities in our study regions have not “emptied” the surrounding forest. Low human population density and low hunting offtake due to abundant sources of alternative aquatic protein, suggest that these communities represent a best-case scenario for sustainable hunting of wildlife for food, thereby providing a conservative assessment of game depletion. Given this ‘best-case’ camera trap and interview-based evidence for hunting depletion, regions with higher human population densities, external trade in wildlife and limited access to alternative protein will likely exhibit more severe depletion.
Highlights
Conservationists from across all major tropical and subtropical regions have voiced concerns that vast tracts of apparently intact forest mask large-scale faunal extirpation [1,2,3,4,5,6,7,8,9,10,11]
The importance of habitat fragmentation and degradation are recognised [17], hunting is often implicated as the main driver of defaunation [18] and heavily hunted sites have been shown to retain less than 20% of the crude vertebrate biomass of unhunted sites [5]
We provide a snapshot of the status of forest vertebrate populations
Summary
Conservationists from across all major tropical and subtropical regions have voiced concerns that vast tracts of apparently intact forest mask large-scale faunal extirpation [1,2,3,4,5,6,7,8,9,10,11]. Where human communities extract tropical forest vertebrates, an “empty forest” scenario [12] may result, in which species larger than 2kg are virtually absent [13]. These defaunated forests may be subject to gradual degradation as the key functional roles played by megafauna are lost [14,15,16]. The importance of habitat fragmentation and degradation are recognised [17], hunting is often implicated as the main driver of defaunation [18] and heavily hunted sites have been shown to retain less than 20% of the crude vertebrate biomass of unhunted sites [5]. The consumption by humans of hunted wild animals (bushmeat) has been implicated in the transmission of zoonotic diseases, with wide-ranging deleterious consequences for human health [20]
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