Diet and travel costs for spider monkeys in a nonseasonal, hyperdiverse environment

I studied the effects of a nonseasonal environment with a high diversity of plant species in a community of white-bellied spider monkeys (Ateles belzebuth belzebuth) in the Yasuni National Park, Ecuador. During 10 2-wk follows of focal individuals across 1 yr, I collected 1268 h of observation data on ranging and foraging. The environment had strong effects on both the foraging and ranging behavior of the monkeys. Yasuni spider monkeys are similar to spider monkeys in more seasonal environments in that ripe-fruit consumption dominates the diet. However, Yasuni spider monkeys exhibit an extremely diverse diet that parallels the variety of foods available to them, consuming more than 238 species of fruits. The impressive dietary variety increased even more with increased observation time, as I had not previously observed in the spider monkeys' diet 40% of the fruit species the subjects consumed during the final follow. Ripe fruits remain the most important item in the diet year-round, supplemented with decayed wood or leaf flush. Local rarity of plant species means that fruiting patches are an average of 420 m apart, and mean patch residence times are short, only 8.1 min. Visits to an average of 11.5 feeding patches/d lead to a mean daily path length of 3311 m, longer than reported for any other Ateles species, and long compared to most other primate species. The long daily paths of Yasuni spider monkeys reflect travel costs resulting from foraging in a hyperdiverse nonseasonal environment.