Population Density and Ecological Traits of Highland Woolly Monkeys at Cueva de los Guacharos National Park, Colombia

Colombian woolly monkeys (Lagothrix lagothricha lugens) are critically endangered because they occur in the Northern Andean region, where a high deforestation rates have happened. The populations living in highlands, which comprise a large proportion of their original geographical range, are particularly poorly known. For 13 months, we used linear transects to estimate the population density of woolly monkeys, and focal animal sampling to gather information on their behavior, diet, and ranging patterns at Cueva de los Guacharos National Park. In addition, we estimated variations in fruit productivity, using phenological transects. We calculated a population density of 20.5 individuals/km2 in Sub-Andean forests, but we did not observe woolly monkeys in black oak forests. Our main study group (ca. 30 individuals) was observed to use approximately 300 ha and the daily path length was estimated to be 1,580 m. We observed woolly monkeys resting in 29.5 % of the records, moving in 42.3 %, feeding in 25.5 % and in social behavior is 2.7 %. They fed preferentially more on fruits (42.6 %) and arthropods (39.5 %) than on leaves (11.3 %) and flowers (6.7 %). The most striking behavioral difference of this population is that they move and look for arthropods more frequently than in lowlands populations. Since frequent movement does not represent longer daily path lengths, our results suggest that woolly monkeys in mountains move and spend more time looking for arthropods than other populations, mainly using epiphytes as substrate. Therefore, the conservation of healthy populations in high altitudes should take into account areas with high fruit production and epiphyte cover.