Comparative locomotion of six sympatric primates in Ecuador

Primates exhibit a great variety of arboreal locomotor modes associated with their size and postcranial morphology. The study of sympatric primates is interesting in that it may reveal how primates of different sizes and anatomies move and select for forest structure. This study reports on preliminary data on the locomotion of six non-ateline platyrrhines found in the Yasuni National Park, Napo Province, Ecuador. Pygmy marmosets are confined to the understory using scansorial locomotion and quadrupedalism, preferring large vertical supports. Golden-mantled tamarins, common squirrel monkeys and dusky titis also range in the understory, moving by quadrupedal walk and leap, mainly on small horizontal supports. Monk sakis are found in the main canopy and use quadrupedal walk and less leap on medium-sized horizontal supports. Whitefronted capuchins use the understory and the main canopy equally often, walking quadrupedally and leaping on small and medium-sized oblique supports. In general, smaller species occupy lower strata while larger species tend to spend more time in the upper strata. Small tegulae-bearing monkeys showed the highest proportions of large vertical support use. For all species, leaping was the main gap-crossing mode, though decreasing in proportion with a higher use of the upper forest layers.