Feeding strategies of red Howler monkeys in a montane forest of the Colombian Andes.

The phenology of trees in tropical forests shapes the temporal distribution of resources such as fruits and leaves. In montane forests (> 1000 m altitude), tree diversity and primary productivity tend to decline with elevation, correlating with lower temperatures and resulting in low food availability for herbivorous and frugivorous consumers. In such environments, wild animals often rely on adaptive food choice strategies to cope when preferred resources are scarce, shifting to less preferred but more available items. This research examines the feeding strategy of red howler monkeys (Alouatta seniculus) inhabiting a montane forest in the Colombian Andes (2,500-3,000 m asl) by analyzing their food intake (grams of dry weight) and their response to resource availability and food species aggregation over an annual cycle. We recorded 1,277 h of continuous focal animal sampling of two howler groups and monitored 28 phenological plots within their home range. Fruit availability varied throughout the year, with asynchronous fruiting patterns observed both within and between species, while leaves remained available all year-round. Montane howlers maintained a predominantly folivorous diet; however, only the daily intake of young leaves and ripe fruits was significantly explained by their availability. Overall, total daily food intake increased with ripe fruit and flower availability but decreased with that of unripe fruits, even though did not explain ripe fruit consumption. In contrast, the aggregation of food species had no effect on daily food intake. Although availability varied among items, montane howler monkeys adjusted their consumption patterns to specific resources availability (e.g., increasing intake of ripe fruits and young leaves during periods of higher availability), within the context of their primarily folivorous feeding strategy.