Intergroup food transfers in wild golden lion tamarins (Leontopithecus rosalia)

Transfers of food between adults are uncommon in primates. Although golden lion tamarins (Leontopithecus rosalia), are unique among primates in the extent of food transfers, reports of food transfers between adults have so far been restricted to captive or reintroduced individuals. Here, I report the first six recorded events of adult-adult food transfers between individuals belonging to different groups. Given that individuals emigrate from their natal group to find reproductive opportunities, I suggest that those intergroup food transfers could be a way for individuals to estimate the quality or availability of potential mates or social partners. Here I propose an additional function of food transfers in wild golden lion tamarins: to create and strengthen social bonds outside of the family group.

Yellow fever in Brazil threatens successful recovery of endangered golden lion tamarins

The golden lion tamarin is an endangered primate endemic to Brazil’s Atlantic Forest. Centuries of deforestation reduced numbers to a few hundred individuals in isolated forest fragments 80 km from Rio de Janeiro city. Intensive conservation action including reintroduction of zoo-born tamarins into forest fragments 1984–2000, increased numbers to about 3,700 in 2014. Beginning in November 2016, southeastern Brazil experienced the most severe yellow fever epidemic/epizootic in the country in 80 years. In May 2018, we documented the first death of a golden lion tamarin due to yellow fever. We re-evaluated population sizes and compared them to results of a census completed in 2014. Tamarin numbers declined 32%, with ca. 2,516 individuals remaining in situ. Tamarin losses were significantly greater in forest fragments that were larger, had less forest edge and had better forest connectivity, factors that may favor the mosquito vectors of yellow fever. The future of golden lion tamarins depends on the extent of additional mortality, whether some tamarins survive the disease and acquire immunity, and the potential development of a vaccine to protect the species against yellow fever.