Successful adoption of an orphan infant in a wild group of brown howler monkeys.

The rarity of infant adoption in wild primates compromises our understanding of its consequences for the participating individuals. We report the first case of successful infant adoption in a wild group of brown howler monkeys (Alouatta guariba clamitans). We evaluated the potential costs of the behavior for the adoptive mother by comparing her activity budget and diet before and after the adoption. On 18 June 2013, a domestic dog killed the mother of a 2-month-old male infant (Victorio) as she attempted to cross a canopy gap. Victorio was immediately rescued from her belly by a researcher and released in a climber near another infant-carrying female (Sofia, his likely grandmother). Sofia recovered him 2 min later. She carried and breastfed both infants during the next 4 weeks, when her own infant disappeared. We monitored Victorio until he reached adulthood in March 2018. Sofia fed more (mainly on immature leaves) when she nursed only Victorio than when nursing only her own or both infants. Assuming that the disappearance of Sofia's own infant was unrelated to the adoption of Victorio, we conclude that his successful adoption may contribute to Sofia's inclusive fitness if he sires his own infants.

Fruit availability drives the distribution of a folivorous-frugivorous primate within a large forest remnant.

Understanding the ecological factors that influence the presence, abundance, and distribution of species within their habitats is critical for ensuring their long-term conservation. In the case of primary consumers, such as most primates, the availability and richness of plant foods are considered key drivers of population density at these variables influence the spatial distribution of social units within a finer, habitat patch level scale. We tested the hypothesis that the spatiotemporal availability and richness of plant foods, drive the spatial distribution of brown howler monkeys (Alouatta guariba clamitans) at a fine spatial scale. We established five line transects (2.6-4.3 km long) to census the population of brown howlers in Morro São Pedro, a 1,200 ha Atlantic forest remnant in southern Brazil, every 2 weeks from January to June 2015. We used data from tree inventories performed in sighting and control plots, and phenological surveys of 17 top food tree species to estimate bi-weekly food availability. We recorded a total of 95 sightings. The number of sightings per sampling period ranged from 2 to 12. The availability of fruit (ripe and unripe) was higher in sighting than in control plots, whereas leaf availability and the richness of food tree species was similar. We conclude that the spatial distribution of fruiting trees and the availability of fruit drive the pattern of habitat use, and spacing of brown howler groups in Morro São Pedro.