Varanus Salvadorii - Biology and Morphology

Biology and Morphology

The most characteristic feature of this monitor is its blunt bulbous snout, which makes this species look different than every other monitor on New Guinea and lends to its common name of tree crocodile. The body of the lizard is dark green with rings of yellow spots. The tail is banded yellow and black and is extremely long, being more than twice as long as the snout-to-vent length. It has long straight teeth and prominent curved claws. There is no external sexual dimorphism.

Unique among living varanid species, the animal's tail is two-thirds longer than the snout-to-vent length in both juveniles and adults. Herpetologist Robert Sprackland gives the proportion as the tail being 210% of the animal's body length. At birth V. salvadorii is about 45 cm (18 in) long, while a sexually mature female may grow to 150 cm (4.9 ft). This is possibly the longest living species of lizard, although considerably less massive and heavy than the Komodo Dragon. Specimens are known to reach at least 244 cm (8.01 ft) in length. but it has been speculated that it may grow longer. A specimen reportedly measuring 323 cm (10.60 ft) was caught in Konedobu by Dr. F Barker. Several reported specimens have been claimed to exceed 350 cm (11.5 ft), some even to 610 cm (20.0 ft), but most of these were second-hand reports and there are no museum specimens in this size range. Weight in the species has been reported at up to 90 kg (200 lb), but a more typical specimen of under 200 cm (6.6 ft) will probably weigh a fifth or a sixth as much as this.

Varanus salvadorii has what physiologists refer to as mammal-like aerobic abilities; this is accomplished by means of a positive pressure gular pump in the animal’s throat to assist lung ventilation. The majority of lizards cannot run and breathe at the same time due to Carrier's constraint, but monitor lizards are exceptions to this rule. The development of this ventilatory pump is analogous to the evolution of the diaphragm in mammals, which ventilates the lung independently of locomotion; scientists place Varanus salvadorii as the species with the highest endurance in this regard. This would suggest that the lizard is at an evolutionary midpoint, relying on both forms of breathing.