Leaf nutritional quality as a predictor of primate biomass: further evidence of an ecological anomaly within prosimian communities in Madagascar

The correlation between the biomass of forest primates and a chemical index of the average nutritional quality of leaves in tropical forests has been repeatedly documented since 1990. We tested the role played by protein : fibre on lemur biomass in a gallery forest in southern Madagascar. Plant species abundance was determined based on transect censuses. We calculated an average ratio of protein-to-fibre in leaves and an abundance-weighted ratio, i.e. the mean weighted by the basal area of tree species, to be compared with the figures available for other forest ecosystems in Madagascar and a number of anthropoid habitats. Lemur densities were evaluated through compilation of previous studies made from prior to 1975 and up until 2011 based on strip censuses and/or identification of all groups supplemented with new censuses. A high mean ratio of protein to fibre (> 0.4) supports high folivore biomass at 390 kg km−2 (reaching 630 kg km−2 in the closed-canopy forest area) compared with primate communities in other Malagasy forests (protein : fibre: < 0.5; folivore biomass: < 440 kg km−2), as predicted. However, the data corroborate the finding that the total biomass of lemur communities as well as the biomass of folivorous lemur species are low compared with those of African and Asian primate communities for a given protein : fibre ratio. Tree diversity and leaf production do not consistently explain this pattern. In contrast, the extinction of large folivorous lemurs during the past two millennia presumably allowed too little time for smaller-sized species to evolve equally effective morphological and physiological specializations for processing a large range of fibrous foods.

Ecological consequences of hunting in Atlantic forest patches, São Paulo, Brazil

This paper evaluates the ecological consequences of hunting by comparing mammalian densities, biomass, relative energy consumption and community structure between sites with different levels of hunting pressure. Hunting is carried out mainly by colonists who farm on the edge of Atlantic forest fragments in the State of São Paulo, Brazil. Mammals were studied over a period of 18 months, along 2287 km of line transects. Transects were distributed among two protected sites, one slightly hunted site and two heavily hunted sites. Tapirs, the two peccary species, brocket deer, armadillos and agoutis are preferred by hunters in the region. Primates are not hunted in the region. Hunting has affected community structure, with ungulates dominating mammalian biomass at protected sites and primates dominating at hunted sites. This has caused an ecological inversion in the hunted areas of the Atlantic forests. In Amazonian regions of the Neotropics hunting is more evenly distributed among primates, large rodents, and ungulates and has resulted in an opposite inversion, with hunted sites having lower primate biomass. Atlantic forests are very susceptible to the possible ecological imbalances induced by hunting by humans, and this must be considered for management and conservation programmes.