Influência das características físico-químicas e disponibilidade dos frutos na ecologia dos primatas em uma floresta no norte da Amazônia

Abstract

The fluctuation of food resources limits plants and animals. Although well studied among small frugivores in temperate regions, such as birds and rodents, the relationship among the fluctuation of resources, quality, and their effects on the ecology of large tropical frugivores in seasonal forests remains largely unknown. The exuberance and high diversity of tropical forests give a faux idea of continuous abundance of food resources, but as seen in other environments, these forests also go through relatively long periods of shortage, imposing limitations to frugivores. Here, I investigate the effects of fruit shortage on the ecology of frugivorous primates at Maracá Ecological Station (MES), a highly seasonal forest in the northern Amazonia, mainly concerning the feeding ecology of an endangered primate, Ateles belzebuth. Surveys on primate and fruit abundance and frugivory was carried out concomitantly through line-transect method. Fruit samples were collected to the assessment of morphological and nutritional assays. Additionally, a detailed study on the feeding ecology of a well habituated group of A. belzebuth was carried out. The abundance of fruits, especially those of Sapotaceae, positively influences primate abundance, which concentrates in spots with high abundance of fruits, but only during fruit shortages. Lipid and ash content significantly determines whether or not a fruit was eaten by spider monkeys during shortage periods. Although these nutrients influenced fruit choices, a comparison of the nutritional profile of fruits consumed by spider monkeys and that of fruits available in the local plant pool indicated that nutrients were consumed according to their local availability. A natural experiment concerning pulp variation in four fruits often consumed by several frugivores in the study site, including A. belzebuth, showed that unusual droughts do not appear to affect the amount of pulp produced. Finally, a relatively large sampling effort is needed to reach survey completeness in species-poor sites such as in the study site than required in other Amazonian sites, possibly due to the relatively large number of low abundant species in this assemblage. Although limited during relatively long periods of fruit shortage, the frugivorous primates at MES appear to adopt both strategies of energy maximization and time minimization to circumvent such critical periods. Primates invest their foraging efforts in places with high fruit supply of abundant species, and consume high energy fruits in an opportunistic way.