Locomotion



Varanids employ both the typical lacertilian anaerobic locomotion and an aerobic form of locomotion as well.

Walking and running (anaerobic vs. aerobic)

Typical locomotory posture is quadrupedal, the soles of the feet are placed flat on the surface and the legs are thrust to the side and then under the body in a stiff movement. The body, head, and tail undulate gently from side to side in rhythm with the moving legs. This gait is similar to that of other lizards, except that the motion normally is considerably slower. That is, the individual raises the two diagonally opposite feet and advances them while the other pair supports the body and propels it forward. The head is normally swung slowly from side to side, with the tail swung oppositely.

When running the body is held more stiffly, with less lateral undulation; the head and tail are often held fairly rigid. The hind feet are swung in a rather wide lateral arc.

Normal walking and foraging are carried on at a forward speed of approximately 0.08 m/sec. However, frightened V.bengalensis have been clocked at speeds of 0.45-4.8m/sec (max. 17.2km/hr mean 1.9m/sec, or 6.8km/hr,n 8 adults, 2 trials each) (Auffenberg 1994).

Bipedalism

Bipedal locomotion happens in varanids. It is used by curious varanids looking over tall grass or tree stumps. It can also be used for movement.

Normally seen in juveniles and subadults, bipedal locomotion is helpful when escaping over fairly level ground. When running in this fashion the two front limbs are held down and slightly posteriorly at the sides, the head is usually thrust straight ahead, and the body and most of the tail held at an angle of 45 degrees to the surface.

Males are known for bipedal combat or "wrestling". Varanids may also stand this way and lunge at intruders.

Climbing

_Varanus gilleni_ is a prime example of a climber

Varanids are devout climbers and all varanids climb at some point in their life. For most this is when young and juvenile. Adults (especially of the larger variety) generally live more terrestrial and fossorial lifestyles.

Varanus prasinus, gilleni (Greene, 1986), dumerilii, olivaceus and especially rudicollis (Barbour, 1921, 1926; W.Auffenberg, 1988) are highly arboreal. (Adaptations for this in the first two, while the other three have regularly been seen in trees).

Inhabited trees tend to be dead ones that the varanids can bore holes into. Foraging for food (insects mostly) is done here as well.

Walter Auffenberg has seen varanids survive jumps out of trees from 12m while Deraniyagla (1931 a,b) reported that they can do so from as high as 25m without injury.

Swimming

All varanids can swim, and some make a living out of it (V.salvator, komodoensis & olivaceous).

Varanids swim by tucking their legs close to their bodies and whipping their bodies rapidly from side to side. This swimming motion resembles the horizontal undulatory progression used by snakes and varanids use it to travel oversea (V.komodoensis is known to swim from island to island this way).

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Auffenberg, Walter. The Bengal Monitor, Univ. Florida Press: Gainsesville. 1994.

________ 1988 Gray's Monitor Lizard. Univ. Florida Press: Gainsesville. 419 pp.

Barbour, T. 1921. Aquatic skinks and arboreal monitors. _Copeia_ 1921(1):42-44.

______ 1926. _Reptiles and Amphibians. Their Habits and Adaptations_. Boston: Houghton-Mifflin and Co. 125 pp.

Deraniyagla, P.E.P. 1931a. Some Ceylon lizards. Spol. Zeylon. 16:139:-80.

______ 1931b. Field Notes, cited by Brongersma 1934.

Greene, H.W. 1986. Diet and arboreal adaptations in the emerals monitor, Varanus prasinus, with comments on the study of adaptation. Fieldiana, Zool. (31):1-11.