Foraging Decisions During Nectar Feeding by Tamarin Monkeys (Saguinus mystax and Saguinus fuscicollis, Callitrichidae, Primates) in Amazonian Peru

Abstract

A 12-month field investigation was conducted on the diet and foraging activities of moustached (Saguinus mystax) and saddleback (Saguinusfuscicollis) tamarin monkeys in the Amazon Basin of northeastern Peru. Throughout most of the year insects, fruits, and plant exudates are the primary components of the tamarin diet. However, during the dry season months of July and August, from Symphonia globulifera (Guttiferae) accounted for 22-31 percent of tamarin feeding time. These primates are highly destructive in their nectar-feeding activities: a single adult tamarin may destroy 6-14 Symphonia flowers per feeding minute. Foraging activities associated with feeding are reminiscent of traplining behavior and characterized by goal-directed travel to particular feeding trees. S. mystax and S. fuscicollis appear to be aware of the distribution and location of flowering Symphonia trees in their home range and select sites largely on the basis of proximity. In 86 percent of all cases, the tree nearest the previous feeding tree was also visited. The mean distance between these feeding sites was 107 m. Expectations regarding the amount and variance of the food reward were also important factors in tamarin foraging decisions. It is argued that by minimizing random foraging movements and bypassing trees with limited food rewards, these small-bodied primates are able to exploit widely scattered but predictable resources. FIELD DATA COLLECTED over the past 20 years indicate that is an important seasonal component in the diet of a number of strepsirhine primates (Petter 1962, Coe & Isaac 1965, Sussman & Tattersall 1976, Hladik 1979, Hladik et atl. 1980). Despite the fact that these primates often destroy flowers in the process of procuring nectar, Sussman and Raven (1978) have suggested that, in areas of Africa and Madagascar depauperate in plant-visiting bats, small-bodied nocturnal prosimians may play a significant role in the pollination of certain plant species . . . , and that such ecological relationships may have existed since the Eocene. The evidence for nectar-feeding by diurnal primates is less clear. This may result from the fact that the quantity of produced by flowering plants that attract diurnal feeders (e.g., hummingbirds) is generally far below that available in bator hawkmoth-adapted species (Cruden et al. 1983, Opler 1983). For example, Opler (1983) reports that in a dry tropical Costa Rican forest the mean maximum amount of available in bat-pollinated flowers (1310 Al) is approximately 75 times greater than the quantity present in hummingbird-pollinated flowers (17 ,ul). Although in certain species may be produced continuously or after the activity period of the primary pollinator (Cruden et al. 1983), Rourke and Wiens (1977) suggest that, in general, nectar secretion is synchronized temporally for visitation by the established pollinators coadapted to that particular flower. Thus, for many species of larger-bodied primates, the availability and production of diurnal is limited and probably below some minimum value needed to stimulate habitual nectar-feeding behavior. Following are described extensive observations of feeding by two species of small-bodied diurnal primates, S. mystax (moustached tamarin, mean adult body weight 594 gm) and S. fuscicollis (saddle-back tamarin, mean adult body weight 412 gm; Garber and Teaford, 1986). This research was part of a 12-month field investigation of the feeding ecology of mixed-species troops of tamarins at the Rio Blanco Research Station in the Amazon Basin of northeastern Peru (72?10'W, 4?05'S). In this region of the Amazon, moustached and saddleback tamarins form stable, mixed-species assemblages in which individuals of each species travel, forage, and cooperatively defend a common home range and set of resources. Eleven S. mystax and eight S. fuscicol/is constituted the main study troop. Throughout most of the year, insects, ripe fruits, and plant exudates were the major components of the tamarin diet. However, during the dry season months of July and August, from S. globulifera (Guttiferae) accounted for 22-31 percent of tamarin feeding time. The intensity of these feeding bouts and the manner in which Saguinus ranged to encounter flowering Symphonia trees suggest that is an important seasonal part of the diet of moustached and saddle-back tamarins.