Arboreal locomotion small branches, as they may wrap too far around and prick the animal's own paw. Adhesion is an alternative to claws, which works best on smooth surfaces. Wet adhesion is common in tree frogs and arboreal salamanders, and functions either by suction or by capillary adhesion. Dry adhesion is best typified by the specialized toes of geckos, which use van der Waals forces to adhere to many substrates, even glass. Frictional gripping is used by primates, relying upon hairless fingertips. Squeezing the branch between the fingertips generates a frictional force that holds the animal's hand to the branch. However, this
Sexual dimorphism in non-human primates to the likelihood of higher vulnerability to predators. Another hypothesis suggests that arboreal primates have limitations on their upper body size, given that larger body size could disrupt their usage of terminal branches for locomotion. However, among some species of guenons ("Cercopithecus"), arboreal blue monkeys ("C. mitis") appear to be more sexually dimorphic than terrestrial vervet monkeys ("C. aethiops"). It has been hypothesized that niche divergence between the sexes attributes to the evolution of size dimorphism in primates. Males and females are known to have different preferences for ecological habitat due to different reproductive activities, which could possibly lead to