Barking Spider Monkeys

Barking spider monkeys that fight off unwelcome human invaders are dominant animals in the “green mansions” of Panama jungles. They live in semi-nomadic troops, each of which occupies a fairly restricted area of the forest, sometimes overlapping slightly with areas of other groups. Within their territory members of a troop wander freely, but their activities tend to center around food and lodge trees.

In reporting on his observations of their activities Dr. C. R. Carpenter of Columbia stated: “Almost every night the group slept within earshot of camp. For eight successive nights they returned to the same group of trees. Throughout the day the troop travelled, in general, over the same routes from one food tree to another and from favorite places in the deep forest where the midday siesta occurred. Several other groups were regularly located in their own particular home areas.”

The monkeys resent intrusion of their territories by anything that looks like another monkey, such as a man. When approached they start barking. The usual terrier-like bark of great excitement may change to a metallic chatter repeated with great frequency. When males, and sometimes adult females are approached closely they growl in a strikingly vicious manner. Typically they come to the terminal ends of branches, often within 40 to 50 feet of the observer, and vigorously shake these branches. Both hands and feet may be used while the animal hangs by its tail.

Throwing of branches is a conspicuous part of the reactions to men. Quite frequently they break off and drop limbs close to the intruder. Green branches sometimes, but most often large dead limbs weighing up to ten pounds may be dropped. “This behavior,” according to Dr. Carpenter, “cannot be described as throwing although the animal may cause the object to fall away from the perpendicular by a sharp twist of its body or a swinging circular movement of its powerful tail. This dropping of objects from trees may be considered as a defensive adaptation arising from the more generalized habit of shaking branches. A significant variation occurs when the animal breaks off a limb and holds it for a time—from a second to half a minute—before letting it fall.”

Normally the monkeys travel along the upper surfaces of limbs, using all four feet and carrying the tail arched over the back. When crossing from one tree to another they use their powerful tails to support themselves from limbs. During such movements hands, arms and tails are used at the same time to make contacts with supports. The monkeys have a strong tendency to keep their heads upward. Therefore, when coming down a perpendicular limb, vine or tree trunk they go backwards rather than head foremost. They frequently make long jumps outward and downward, covering at times more than thirty feet