Locomotion, Postures, and Habitat Use by Pygmy Marmosets (Cebuella pygmaea)

Abstract

Abstract Pygmy marmosets (Cebuella pygmaea) are the smallest representatives of the Callitrichidae and are characterized by morphological correlates to extensive exudativory and to frequent claw climbing, clinging, quadrupedalism, and leaping on vertical supports. This morpho-behavioral complex is unique and crucial for understanding the evolutionary history of the family. I studied the positional behavior and habitat use of a group of pygmy marmosets in a terra-firme rainforest in Amazonian Ecuador. During the study period, the pygmy marmosets confined their movements to the understory of a dense liana forest, where they largely utilized lianas and tree trunks, showing a strong preference for the latter. In addition, they extensively used and preferred supports > 10 cm in diameter, and almost two thirds of these supports were vertical. Feeding bouts (finding, manipulating, and eating plant foods) on exudates and foraging (finding, manipulating, and eating arthropod prey) occurred at around 5 m above ground. The dominant feeding posture was claw clinging on vertical trunks. In contrast, the dominant foraging postures were quadru-tripedal stand and cantilever, with extensive use of small and medium sized lianas. Traveling occurred lower to the ground than did foraging or feeding, and locomotion was dominated by claw climbing and terminal leaping, and low pro- portions of quadrupedal activities and vertical leaps. Claw climbing was mainly used for movements within trees while the other forms of locomotion were usedfor crossing between trees. Landing support use was similar for both short and long terminal leaps. However, both short and long vertical leaps initiated from and ended on larger supports more frequently than terminal leaps. In addition, long vertical leaps were initiated on larger supports than were shorter vertical leaps. Field observations show that pygmy marmosets use claw climbing, claw clinging, and vertical supports more than any other callitrichid, but they use less leaping and vertical leaping than Callimico. In general, these positional data are not entirelycoupled with morphological predictions for pygmy marmosets, but likely reflect adaptations that evolved recently within the evolutionary radiation of callitrichids.