Species: Lumholtz’s Tree Kangaroo

Species: Lumholtz’s Tree Kangaroo (Dendrolagus lumholtzi)

Use: Activity cycle and non-social behavior

Authors: Elizabeth Procter-Gray, Museum of Comparative Zoology, Harvard University and Udo Ganslosser, Zoologishes Institut

Methods: Focal sampling

Publications/Presentations: Elizabeth Procter-Gray, Udo Ganslosser (1986). The Individual Behaviors of Lumholtz’s Tree-kangaroo: Repertoire and Taxanomic Implications, Journal of Mammology, 67(2): 343-352.

Behavioral Repertoire

Locomotion on the ground:

Tree kangaroos go to the ground to move from one tree to another.

Bipedal leaping (Bipedes H¸pfen) the comparable German term used by Ganslosser (1977): This was the only locomotion that was observed in tree-kangaroos moving on the ground, either in normal traveling from tree to tree or during attempts to escape capture. The body was bent far forward, the back being nearly horizontal. Arms were bent and held in front of the chest. The tree-kangaroo hopped on the balls of its feet, and the tail bobbed up and down with each hop, apparently not serving a supporting function. This gait in terrestrial kangaroos was termed Bipedal Hop by Windsor and Dagg (1971).

Moving up a bole

Springing up (Anspringen): To begin the climb up a vertical bole, the tree- kangaroo sprang up about 0.5-1 m with power from the back legs. The back was not arched. The tree-kangaroo landed on the bole on its arms and arms simultaneously. The feet pointed upward and were about hip-width apart. The arms wrapped around the bole.

Climbing (Stemmklettern): From the position reached after springing up, with the back curved only slightly, the arms slid up the bole, either alternately or simultaneously. Then the feet hopped up together. The actions were repeated in quick succession, and the animal proceeded up the tree with this ratchet-like mechanism. Tree-kangaroos preferred to climb trees smaller than 40 cm diameter-breast-height.

In the trees

Hopping (Hoppeln): The preferred locomotion on large (>10 cm) horizontal or slightly upward-sloping branches consisted of extending the arms forward together in front of the body, placing them on the substrate to support the body, and then hopping the feet forward together.

Quadrupedal walking (Quadrupes Schreiten): When moving on small branches the most frequent locomotion was a slow, careful placing of each hand and foot separately. The claws of the hands could wrap around twigs (<2cm), but the claws of the feet usually did not. The feet pointed in the direction of movement.

Galloping hop (Hoppelgalopp): This was similar to hopping except that the hands were put down one after the other, not simultaneously. The feet hopped forward together after the hands. This movement was observed only once in a tree-kangaroo on a 30 cm horizontal limb.

Springing from branch to branch: This behavior was rare in calm adults except over very short distances (<1 m). It was most often seen in the young-at-foot or in animals attempting to escape from capture. Power for the jump came from the hind legs. In mid-air the animalís back was slightly forward curved, not arched. The arms were not extended far forward. The individual landed on its feet first, with hands touching down immediately thereafter. The movement was generally confined to large (>10 cm) branches.

Chin-up (Klimmzug): Observed once in a young-at-foot. To move up and forward the animal put its hands on a 2 cm branch above it, and using arm power, pulled its body up so that the feet could get onto the branch between the hands.

Hand-over-hand: Observed in an adult when dislodged from a branch during a capture attempt. Hanging below a 7 cm horizontal branch, one hand on each side of the branch, the tree-kangaroo pulled itself along the branch with hand-over-hand movement.

Quadrupedal hanging: Observed once in a young-at-foot. While hanging by all four limbs from the horizontal branch (feet somewhat supinated to press soles and claws against the sides of the branch), the tree-kangaroo moved one limb at a time to proceed along the branch.

Turning around (Umdrehen): To reverse direction on a large branch, the tree-kangaroo would sit up, weight on hind feet, move one foot around to the new direction and then the other.

Descending:

Descent was always tail-first on vertical boles. Tree-kangaroos moved backwards down inclines of 35°or more.

Quadrupedal walking descent: The animal backed down the bole, moving one limb at a time. The arms were usually, wrapped around the sides of the bole. The feet could be parallel to the bole or turned outward slightly. When it had descended to approximately 2 m above ground, it usually leaped to the ground, twisting in the air and landing on feet and then hands.

Sliding descent: There were many variations on this most frequent form of descent. Grasping the vertical bole, tail downward, the animal might slide backwards with all four feet, slide the hind feet while walking the hands down, or slide the hands while walking the feet down. Again, it usually leaped off the bole when it reached about 2 m in height.

Crash: This form of descent was usually heard, not seen. In reaction to perceived danger (e.g. a human passing by with a spotlight), a tree-kangaroo could leap to the ground from heights of up to 15 m. It landed on its feet on all fours, and was immediately able to begin bi-pedal leaping on the ground. Never did a tree-kangaroo appear injured or stunned after the crash.

Rest and alert postures

Curled rest posture: This was the most common resting position, usually located in forks of branches of varying sizes. Resting on the ground was never observed. Typically the rump rested on one branch, the feet on another. The arms were held close to the chest, and the head was tucked in towards the belly, so that the back was strongly curved, withers uppermost. The proximal part of the tail passed forward between the legs, and the distal end hung straight down below the animal. The tree-kangaroo sometimes rested its chin and/or hands on nearby branches instead of holding them close to the body, but the back remained curved.

Quadrupedal rest posture: This was another frequent position. The animalís body extended along a branch (>10 cm), feet parallel to the branch, weight on all fours and, if pressed against the branch, on the chest. The tail hung down behind the rump. The nose pointed down and forward, usually not touching the branch.

Easter-bunny posture (Osterhasenstellung- Schneider, 1954): This very common alert posture was also used during feeding. The tree-kangaroo sat up, weight on hind feet (usually on the heels) and sometimes on the rump. The back was held nearly vertical. Hands rested in front of the body or grasped nearby branches.

Feeding:

The diet of D.lumholtzi, consisting almost exclusively of leaves, was described by Procter- Gray (1984). Feeding was generally done in the Easter-bunny posture. The use of hands was variable. If the leaf was close to the tree-kangarooís head, it might simply chew it on the twig, not touching it with the hands. More commonly, the animal reached out to a twig with both hands (or less often with one), pulled it toward the mouth, bit a leaf, and tore it from the twig with a quick upward jerk of the head. It continued to hold the twig with its hands while chewing, and brought it to the mouth again for the next bite. Occasionally, an individual would pull a leaf from a twig using only the hand (perhaps accidentally). Then it would move the hand to the mouth in order to eat the leaf. Tree-kangaroos were able to hold small objects in the hand by pressing the long claws against the palm.

Drinking:

Drinking of water was never observed. There was no standing water within the home ranges of the study animals, so they probably satisfied their requirements through water contained in and on their food.

Comfort movements
Yawning (Gähnen): Yawning was observed occasionally in resting or alert animals.

Ear flicking: It was very frequently observed that tree kangaroos flick their ears (separately or simultaneously), presumably to ward off insects. Shaking the whole head for the same purpose was much less common.

Shaking (Schütteln): This action was observed almost exclusively when tree kangaroos were wet from rain. The shake began at the head and passed down through the whole body. Its duration was approximately 1 second.

Licking (Lecken): This was a very frequent grooming action. To lick the tail, the animal passed it forward between the legs and held it in its hands. To lick the lower back, the upper body was twisted around 180 º to one side, with the arm reaching up over the back. To lick the pouch, a female held it open with two hands. The face was washed by licking both hands, then wiping them from brow to nose three or four times. Both hands were used simultaneously in face washing.

Nibbling: This gentle biting of the skin often accompanied scratching.

Scratching (Kratzen): Like licking, this frequent grooming action took place at irregular intervals during rest. Scratching was generally performed with one hand or one foot, depending on the spot to be scratched, but when scratching the ventral midline (chest, belly or tail) a tree-kangaroo might use both hands in rapid succession. To scratch the neck or head, the foot was brought around the outside of the arm (henterherum), not beneath it. The animal often licked the foot or hand after scratching with it.

Tail swatting and clutching: For a period of about 4 days, 2 weeks after her joey had vacated the pouch, one adult female lashed her tail from side to side for bouts of up to 30 minutes. She alternated this behavior with clutching of the tail, pulled forward between her legs by one or both hands. Sometimes she draped the tail over the back of the joey who was resting in front of her. Tail lashing, when seen in captive tree-kangaroos is generally associated with arousal or annoyance (Ganslosser, 1977). No motive for tail swatting was obvious in this case.

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