Parâmetro demográficos de populações de duas espécies ameaçadas de macacos-aranha, Ateles chamek e Ateles marginatus, no ecótono Cerrado-Amazônia

Abstract

Ateles spp. are among the largest Neotropical primates, and occupy mainly lowland evergreen rainforests. They feed on a great amount of large-seeded fruits and therefore are important seed dispersers of tropical plants. Spider monkeys are threatened by anthropic actions, such as habitat loss and hunting. Estimating demographic parameters of spider monkey populations is key to understanding their ecological needs, assessing anthropic impacts on populations, and qualifying conservation measures for the species. Between 2016 and 2018, we recorded encounter rates, average group sizes, and estimated population density of A. chamek and A. marginatus along eight 5 km -transects, in the riparian forest of the Teles Pires River, four on each side of the river bank. There was no significant difference between the encounter rates of A. cha- mek and A.marginatus between the dry and wet seasons. We recorded mean group size of 5.6±4.9 individuals and an encounter rate of 0.84 group/10 km of A. marginatus on the right bank of the Teles Pires River. And on the left bank, groups of A.chamek with mean group size of 3.8±3.0 individuals and encounter rate of 0.75group/10km. We confirmed the Teles Pires River as a geographic barrier separating these two species of spider monkeys, but we recorded mixed groups on both banks, indicating scattered dispersal events of some individuals. The Amazon-Cerrado ecotone needs conservation and mitigation measures, especially for forest species. We recommend a continuous monitoring of demographic parameters for populations of A. chamek and A. marginatus to assess their population viability and detect local threats.