Pithecia pithecia's behavioral response to decreasing fruit abundance

Abstract

In this article we describe the behavioral responses of a group of white-faced sakis' (Pithecia pithecia) to fruit and water scarcity. Six sakis were observed on Round Island in Guri Lake, Venezuela, between March and May 1996. These months are considered the dry season and the beginning of the wet season. Sakis specialize in eating seeds. During the present study only one tree species, Licania discolor (Chrysobalanaceae), fruited in substantial numbers. Licania seeds accounted for 88% of the time the sakis spent eating fruit in March, 87% in April, and 80% in May. We estimate that the sakis' intake of Licania seeds dropped from 2,573 seeds in the 15-day observation period in March to 956 seeds in the 16-day observation period in May. The sakis not only spent less time eating Licania, they ate the seeds at a much slower rate. The drop in the sakis' feeding rate was probably due to increased local search and inspection times. In response to the scarcity of fruit, the sakis ate more young leaves, insects, and flowers. Feeding bouts became more frequent but shorter. Mean distances between feeding bouts fell significantly and the sakis revisited trees less often.

Integrating information about location and value of resources by white-faced saki monkeys (Pithecia pithecia)

“…They averaged 25 feeding and drinking bouts per day. The average straight-line distance from starting locations to feeding and drinking bouts was 57 m during P1 and 63 m during P2 (Cunningham and Janson 2006). Figure 1 shows two representative day paths, locations of the focal animal's feeding and drinking bouts and the distribution of Licania trees.…”

“…A small Capparis weighed 61.3 g. Water in tree holes was an important resource for the sakis, especially in April when there was almost no rain. (See Cunningham 2003;Cunningham and Janson 2006 for detailed discussion of resource availability and the study group's socioecology. )…”

“…The Pithecia study group, examined here, inhabited a small home range and traveled short distances (averaging about 60 m) between feeding and drinking bouts, most of which were brief and seemed relatively insigniWcant (Cunningham and Janson 2006). Several times a day, however, they had longer feeding bouts; usually in large Licania discolor (Chrysobalanaceae) trees or (less frequently) Capparis muco (Capparidaceae) trees.…”

Diet and Food Choice in Peruvian Red Uakaris (Cacajao calvus ucayalii): Selective or Opportunistic Seed Predation?

“…Similarly, in white-faced sakis (Pithecia pithecia) and bearded sakis (Chiropotes satanas) the ripening of the most-eaten resources brings about a switch from unripe seeds to ripe pulps (Norconk 1996). Contrary to these studies, black uakaris (Cacajao melanocephalus) at Pico da Neblina, Brazil, eat proportionally more ripe pulps and arils and fewer seeds when fruits are scarce in the forest (Boubli 1999), and Pithecia pithecia at Guri Lake, Venezuela eat fewer seeds and more leaves, insects, and flowers when fruits are scarce (Cunningham and Janson 2006). In all of these studies on pitheciins, the proportions of seeds and pulps in the diet varied seasonally and the authors related this to the relative availability of the plant parts, but they did not measure the selectivity for the fruit species concerned compared to their availability in the environment.…”

“…Among the Old World primates, seeds make up a large proportion of the diets of colobine monkeys (subfamily Colobinae : Dasilva 1994;Kool 1993;Maisels et al 1994), mangabeys (Cercocebus: Waser 1984, mandrills (Mandrillus sphinx : Lahm 1986), orangutans (Pongo pygmaeus : Ungar 1995), and sifakas (Propithecus diadema : Hemingway 1998;Yamashita 1996). Of the New World primates, brown capuchins (Cebus paella : Peres 1991;Terborgh 1983), woolly monkeys (Lagothrix lagothricha: Peres 1994), and titis (Callicebus personatus: Heiduck 1997) show some dependence on seeds, but the sakis (Pithecia), bearded sakis (Chiropotes), and uakaris (Cacajao), collectively the tribe Pitheciini (Rosenberger et al 1996), are unique among Neotropical primates in that they are specialized seed predators (Aquino 1995, Aquino andEncarnación 1999;Ayres 1986Ayres , 1989; Barnett et al 2005;Boubli 1999; Buchanan et al 1981;Cunningham and Janson 2006;Johns 1986;Kinzey and Norconk 1993;Norconk and Conklin-Brittain 2004;Peres 1993;Setz 1994;van Roosmalen et al 1988). Large, palatable seeds are often protected by hard shells (Fischer and Chapman 1993;Norconk et al 1998), and pitheciins are equipped to open such fruits.…”