Black Capuchin Monkey Provisioning Study

This study was conducted in Iguazú National Park, Argentina (25°40′ S, 54°30′ W), a site with a humid semi-deciduous subtropical forest and a climate characterised by a marked seasonality in day length and temperature, but not in rainfall^{30 (link)}. Winter (May–August) represents the lean season, when the availability of fleshy fruits and arthropods, the bulk of the diet of black capuchins, drastically decreases at the site, while between October and January these items become abundant²¹ . Specifically, with pulpy fruit productivity dropping from 1000 to 1400 g in the austral summer to 50–200 g (dry weight/ha/day) in the austral winter, black capuchins may face food shortage and depend mainly on dispersed fallback food in the latter season³¹ .
At the site, black capuchin monkeys live in stable multimale-multifemale groups of 12.41 ± 7.0 (mean ± SD; n = 7) ranging from 6 to 30^{32 (link)} but occasionally reaching up to 44 individuals, with an alpha male and philopatric females that establish a linear dominance hierarchy³³ . In Iguazú, since 1991, every winter, one or two groups are provisioned with bananas on platforms for research purposes³³ . Bananas are a nutritious and highly digestible food³⁴ and have become a most preferred item for black capuchins at the study site, as indicated by the high rate of food calls given by individuals when approaching the provisioning platforms³¹ . In these capuchin groups, during provisioning on platforms, individual connections (network centrality) with other group members increase, but without any direct effect on parasitic infections (i.e. alterations of within-group spatial networks due to provisioning may have a limited influence in determining the characteristics of parasite infections in these monkeys)^{35 (link)}.
Here we collected data from adult/subadult individuals of two groups: Macuco (15–19 adult/subadults out of 23–27 individuals) and Spot (8–12 adult/subadults out of 17–21 individuals) (Supplementary Tables S1–S2). We considered females as adults when older than five years, and subadults when four to five years old, which corresponds to the average age of female first oestrus with conception³³ . We classified males as adults when older than six years, which commonly coincides with their emigration from the natal group, and subadult when five to six years old. For most individuals, we could estimate age with a precision of one to 30 days, thanks to long-term records of all births, migrations and deaths in the study groups kept by researchers at the site.