Locomotion in Some East African Viverrids

1. What they did

Viverrids (the civets, genets and mongooses, as the family was classified at the time) are very varied in East Africa, yet in 1970 almost nothing had been published on how they move. This paper was meant as an introduction to the subject.

The author observed 12 species from nine genera in Kenya. Because most are nocturnal or elusive, most observations were of captive animals, though some were also photographed in the wild.

• Filming. He filmed the animals on 8 mm cine film at 16 and 64 frames per second, walking, trotting, running, galloping, jumping, climbing, swimming and burrowing.
• Tracing. He projected the film frame by frame onto a ground-glass viewing box and traced each frame as a cartoon figure, noting the frame number so the position of each limb could be matched to the phase of the stride. Where the film was blurred, he studied other sequences, and where the feet or claws could not be seen, he studied the animals closely in captivity.
• Analysis. He followed Hildebrand’s methods for the cheetah, and described each gait with Hildebrand’s gait formulae and gait diagrams showing when each foot is on the ground.

2. What they found

Walking

• Walking is the only way of moving shared by all the East African viverrids. The terrestrial species walk with the head low and the shoulder nearer the ground than the base of the tail.
• The white-tailed mongoose used a slow, single foot, lateral sequence walk (gait formula 73-20), each stride taking about 1.7 seconds. As in dogs, the hind limbs give the main push and the forelimbs act more as struts.
• The mongooses studied are digitigrade (walking on their toes). Genets have a palmigrade forefoot (walking on the whole sole) and a semi-digitigrade hind foot. On branches, genets keep their legs more flexed and swing them out in a sideways arc, which allows a faster correction if they slip. They walked more slowly, at about 3.5 seconds per stride.
• The palm civet walks like a genet but hugs the branch, with a low center of gravity that gives better control on slippery branches. Its long, heavy tail serves for balance and is held above the horizontal, often upright. Genets carry their tails straight out behind, and mongooses generally drag theirs on the ground.
• The pygmy and banded mongooses have short legs for their body size, which the author suggests may be an adaptation to living in termite holes.

Trotting, running and galloping

• Few mongooses trot; mainly the larger terrestrial species. Unlike the horse, the trotting white-tailed mongoose has no moment with all four feet off the ground. A moderate walking trot (63-45, about 1.1 seconds per stride) was the fastest gait seen in this species.
• A banded mongoose sped up from a fast walking trot through a slow run to a running gait (35-60) with never more than two feet on the ground, always a diagonal pair, and two moments per stride with all feet off the ground. Its stride time fell from 0.92 to 0.75 seconds.
• The banded mongoose also galloped using the half-bound: the hind feet give the main thrust, one forefoot lands just before the other, and the body flexes to about 60% of its stretched-out length. Each stride took 0.65 seconds.

Jumping and climbing

• Larger mongooses jump about 90 cm to reach food, but awkwardly. Banded mongooses may jump straight up about 50 cm. Genets rarely jump much higher than a meter but will jump down 1.8 m without hesitating. A genet jumping 22 cm up a branch took about one second.
• The palm civet is the best jumper: in captivity it often jumps up 1.8 m, sometimes carrying up to 850 g of meat, and can leap gaps of about a meter, but prefers to climb rather than jump down.
• The palm civet is the most skilled climber. On vertical posts up to 20 cm across it climbs down head first in a series of loops, gripping with the forefeet and bringing both hind feet up together, moving about 50 cm with each stride. The author named this “vertical looping”. A genet was twice seen trying a rushed version under stress, with little control. The black-tipped mongoose is the only East African mongoose seen to climb with any skill, but it rushes up and usually falls down.

Swimming and burrowing

• The marsh mongoose is the only good swimmer. It swims with sideways movements of the body and its back partly out of the water, and captive animals stayed under water for 15 seconds. Its toes can spread widely, which the author suggests may help on soft mud. Gray and white-tailed mongooses and the genet G. tigrina are known to swim occasionally.
• Banded and pygmy mongooses live in groups in old termite mounds. They dig only to enlarge holes, scraping with their long front claws and throwing earth back between their hind feet.

3. What they concluded

• The ways different viverrids move reflect their different habitats and food preferences.
• Trotting is the most common gait of the larger species of savannah and light woodland, and seems linked with larger feeding territories: from his trapping results, about 1 km² for the black-tipped mongoose and about 8 km² for the white-tailed mongoose. Running and galloping are typical of the smaller banded and pygmy mongooses.
• Three or more species usually live in the same place, but their foraging overlaps little: black-tipped mongooses are active by day, genets at dusk and dawn, hunting by sight in trees or on the ground, and white-tailed mongooses are fully nocturnal and terrestrial, hunting mainly by scent.
• Vertical looping down a post reflects the palm civet’s adaptations to life in trees.

6. Other technologies, skills or innovations

• Frame-by-frame analysis of 8 mm cine film (Eumig PS projector with zoom lens) traced on a homemade viewing box with a mirror at 45 degrees, which avoided the reversed image of back projection.
• Gait formulae and gait diagrams in the system of Hildebrand.