Fruit as a key factor in howler monkey population density: Conservation implications

Howler monkeys (Alouatta) are widely regarded as the most folivorous of the neotropical monkeys and the ability of howlers to live in a wide range of environments including highly disturbed forests has been linked to this ability. Generally categorized as energy minimizing folivores leaves comprise at least half and as much as 90 % of annual feeding time. All howler species also consume fruit; however, this amount is quite variable both within and between species, and across different months of the year. Seasonality in fruit consumption in Alouatta appears to be directly tied to its availability, suggesting that for all species fruit is a preferred food item. A study of population density and diet in A. pigra following a severe hurricane suggests that frugivory may be more crucial to population stability and growth than previously thought. This chapter considers the effects of this hurricane on A. pigra in relation to what is known about frugivory in the Mesoamerican clade of Alouatta (A. palliata and A. pigra), focusing on relationships between diet, population density, group size, behavior, ranging, and reproduction. These data suggest that frugivory is an important part of the feeding ecology of these species and that periods of prolonged fruit shortage may have significant impacts on their population dynamics and survival. Given that both natural and anthropogenic habitat disturbance generally have a negative effect on fruit production, this could have important conservation implications for this primate genus.