| I conducted a 14-month study of the foraging behavior, nutrient intake, energy budgets, ranging patterns, and social behavior of mantled howling monkeys (Alouatta palliata) living in Finca La Luz, a shade coffee plantation on Mombacho Volcano, Nicaragua. The shade coffee forest has relatively low tree density and diversity. Annual diets comprise 28.0% mature leaves, 27.7% young leaves, 34.8% fruits, 7.9% flowers, and 1.6% other plant parts. At least 57 tree species are used as food sources, with leaves and fruits of Ficus costaricana dominating the diet at 32% of total feeding time. The howlers spend 57.0% of daylight hours resting, 27.4% traveling, 13.6% feeding, 1.5% socializing, and 0.5% vocalizing. Abundant tree species were important food sources and provided relatively high-quality foliage. The consumption of seasonally-available phenophases shows only a weak relation to availability; however, on a species-by-species basis, consumption of preferred parts closely tracks abundance. Average diets contain 41.7% NDF, 38.7% ADF, 14.0% crude protein, 9.5% water-soluble carbohydrate, and 0.1% crude fat. Mean caloric intake was estimated at 440 kcal metabolizable energy/day. Estimates of average daily metabolic needs based on activity budgets suggest that pregnant and lactating females may frequently experience negative energy balance. Home ranges varied from 13 to 20 ha in size, and the howlers traveled an average of 617 m daily. Ranging variables increase with group size, providing indirect evidence of within-group scramble competition. Seasonal variation is seen in patterns of feeding, activity, and ranging, with foraging effort (i.e., time spent feeding and traveling, range area, and day journey length) increasing during the rainy season, when fruits and mature leaves are consumed more frequently. Contest competition is relatively rare, and occurs at a rate of only 0.25 events per focal hour; females engage in agonistic behavior more frequently than males or immatures. The results suggest a less selective foraging strategy, which may be an adaptation to the high abundance of high-quality forage; contest competition for feeding and social resources may be reduced in this population, and shade coffee plantations may be more favorable habitat for howlers than initially hypothesized. |
