MONKEY LOCOMOTION ON INCLINED SURFACES

Motion pictures were taken of a subadult, female squirrel monkey moving on level and inclined surfaces. The gaits for the various degrees of incline were compared. The noncontact periods were not affected by changes in inclination. The contact periods, which were inversely related to speed, were affected, by changes in slope and intersect constants. When the incline was steep the animal was forced to jump and zig‐zag to retain its progression. The affect of inclination was advantageous at 16° and disadvantageous at higher and lower inclines. At the 16° inclination the animal's short fore legs and long hind legs held the body horizontal, cancelling the effect of the incline. It is reasoned that limb proportions may be adaptive for progression on inclined surfaces and that the locomotor niches for the various arboreal primates may be usefully categorized in terms of the inclinations of their substrates. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company