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Abstract:The Neotropics house two guilds of large arboreal vertebrate seed predators: parrots and the pitheciin primates. Both have diets dominated by immature fruits. The possibility of members of the Pitheciinae (genera Cacajao, Chiropotes and Pithecia) acting as occasional seed dispersers has been mooted, but not experimentally shown. We combined primate behavioural data and seed germination data from three separate field studies in the Brazilian states of Amazonas and Pará to analyse patterns of post-consumption seed survivorship for seeds discarded by three pitheciin species (Cacajao melanocephalus ouakary, Chiropotes chiropotes and Chiropotes albinasus). We then calculated the frequency of dispersal events for four species eaten by C. m. ouakary. All three primate species dropped intact seeds while feeding, and 30.7% of 674 dropped seeds germinated ex situ. Undamaged seeds from unripe and ripe samples germinated (29.3% and 42.7%, respectively), and all three primate species carried some fruits up to 20 m from the parent tree before consuming them. Potential seed-dispersal events varied from 1 (Macrolobium acaciifolium) per fruiting cycle to more than 6500 (Duroia velutina), suggesting that there are differences in dispersal potential. In summary, although they are highly specialized seed predators, these primates may also act as important dispersers for some plant species, and effective dispersal is not restricted to ripe fruits, as immature fruits removed from a tree may continue to mature and the seeds later germinate, a much-neglected aspect of dispersal ecology. The possibility that similar events occur in parrots should be experimentally investigated.

Although primate predation is rarely observed, a series of primate anti-predation strategies have been described. Energetic costs of such strategies can vary from high-cost mobbing, via less costly alarm calling, to low-cost furtive concealment. Here we report the anti-predation strategies of red-nosed cuxiú, Chiropotes albinasus, based on direct observations from four study sites in southeastern Brazilian Amazonia. Over a collective period of 1255 fieldwork hours, we observed nine direct interactions between raptors (all potential predators) and red-nosed cuxiús. Of these, one (11%) resulted in predation. Raptors involved were: Harpia harpyja (four events), Leucopternis sp. (two events), Spizaëtus tyrannus (one event), and unidentified large raptors (two events). Predation attempts occurred in flooded-forest and terra firme rainforest, were directed at both adult and non-adult cuxiús, and involved both adult and juvenile raptors. Anti-predation strategies adopted by the cuxiús included: (1) group defence and mobbing behaviour (two occasions), (2) dropping into dense sub-canopy (seven occasions), (3) alarm calling (eight occasions), and (4) fleeing to, and hiding in, dense vegetation (eight occasions). During each encounter at least two of these behaviours were recorded. These are the first published records of predation, predation attempts, and anti-predator behaviour involving red-nosed cuxiú.

Neotropical monkeys of the genera Cacajao, Chiropotes, and Pithecia (Pitheciidae) are considered to be highly arboreal, spending most of their time feeding and traveling in the upper canopy. Until now, the use of terrestrial substrates has not been analyzed in detail in this group. Here, we review the frequency of terrestrial use among pitheciin taxa to determine the ecological and social conditions that might lead to such behavior. We collated published and unpublished data from 14 taxa in the three genera. Data were gleaned from 53 published studies (including five on multiple pitheciin genera) and personal communications of unpublished data distributed across 31 localities. Terrestrial activity was reported in 61% of Pithecia field studies (11 of 18), in 34% of Chiropotes studies (10 of 29), and 36% of Cacajao studies (4 of 11). Within Pithecia, terrestrial behavior was more frequently reported in smaller species (e.g. P. pithecia) that are vertical clingers and leapers and make extensive use of the understory than in in the larger bodied canopy dwellers of the western Amazon (e.g. P. irrorata). Terrestrial behavior in Pithecia also occurred more frequently and lasted longer than in Cacajao or Chiropotes. An apparent association was found between flooded habitats and terrestrial activity and there is evidence of the development of a "local pattern" of terrestrial use in some populations. Seasonal fruit availability also may stimulate terrestrial behavior. Individuals also descended to the ground when visiting mineral licks, escaping predators, and responding to accidents such as a dropped infant. Overall, the results of this review emphasize that terrestrial use is rare among the pitheciins in general and is usually associated with the exploitation of specific resources or habitat types.