Mangrove Monitor

Appearance

The monitor's body is dark green or black in color and covered with golden yellow spots, with light coloration on the top of the head and a solid, cream colored belly lacking dark markings. It has a distinct dark purple tongue and serrated teeth. The mangrove monitor attains different sizes in different parts of its range, but seldom if ever exceeds 1.5 meters in total length. Australian herpetologist Harold Cogger gives a total length of 100 cm for Australian specimens. The tail is almost two times the length of the body and laterally compressed to aid in swimming. Like the rest of the lizard's body it is covered with small, oval, keeled scales.

This monitor has the ability to increase the size of the mouth by spreading the hyoid apparatus and dropping the lower jaw in order to eat large prey, a process similar in appearance to that of snakes, although the jaw of the mangrove monitor remains rigid. Mangrove monitors possess a Jacobson's organ which they use to detect prey, sticking their tongue out to gather scents and touching it to the opening of the organ when the tongue is retracted.

The mangrove monitor is one of only two species of monitor lizard, the other being ''Varanus semiremex'', that possess salt-excreting nasal glands, which enable them to survive in saltwater conditions and to consume marine prey....hieroglyph snipped... The presence of this gland probably enabled the monitors to reach new islands and aid in its dispersal throughout the Pacific.

Distribution

The Mangrove monitor's range extends throughout Australia, New Guinea, the Solomon Islands, the Marshall Islands, the Caroline Islands and the Marianas Islands, where it inhabits damp forests near coastal rivers, mangroves, and permanent inland lakes. It also occurs on the Moluccan islands of Morotai, Ternate, Halmahera, Obi, Buru, Ambon, Haruku, and Seram. Within this range of thousands of miles across hundreds of islands there is a huge amount of variation in size, pattern and scalation. The monitors have also been introduced to Japan since the 1940s. Like the introduction to Japan, some herpetologists believe this animal's dispersal from the East Indies to smaller Pacific islands was facilitated by Polynesians in order to provide a meat supply. However, other scientists maintain this is not likely as the monitors would compete with man for food, grow slowly, and yield little meat.

Habitat

The Mangrove monitor's range extends throughout Australia, New Guinea, the Solomon Islands, the Marshall Islands, the Caroline Islands and the Marianas Islands, where it inhabits damp forests near coastal rivers, mangroves, and permanent inland lakes. It also occurs on the Moluccan islands of Morotai, Ternate, Halmahera, Obi, Buru, Ambon, Haruku, and Seram. Within this range of thousands of miles across hundreds of islands there is a huge amount of variation in size, pattern and scalation. The monitors have also been introduced to Japan since the 1940s. Like the introduction to Japan, some herpetologists believe this animal's dispersal from the East Indies to smaller Pacific islands was facilitated by Polynesians in order to provide a meat supply. However, other scientists maintain this is not likely as the monitors would compete with man for food, grow slowly, and yield little meat.

Reproduction

The species lacks distinct sexual dimorphism, however mature male monitors on Guam have been reported to be three times the mass of mature females. Males fight for females and in one observation, after mounting the female, the male used his chin to rub the dorsum of the female's head and forequarters. It was also observed that while mounted and oriented head to head, the male and female slowly rotated in a clock-wise direction through 360 degrees with the male remaining superior.

Female mangrove monitors lay 2-12 eggs that measure 3.5 to 5 cm in length. The oblong eggs are white, and hatch in about 7–8 months.

The first successful captive breeding of this species was at the Philadelphia Zoo in 1993.

The Reptilian Zoo in Vlissingen, the Netherlands , reports that they have successfully hatched eggs by a female animal that was not in any contact with a male of the same species.

Food

The Mangrove monitor is an opportunistic carnivore feeding on the eggs of reptiles and birds, mollusks, rodents, insects, crabs, smaller lizards, fish, and carrion. Mangrove monitors are the only monitor capable of catching fish in deep water. In some parts of its range it is known to eat juvenile crocodiles.

A study done in 1993 showed that mangrove monitors in the Southern Mariana Islands shifted major prey classes when their regular prey began declining. The monitors were known for eating shrews on Guam, but the introduction of the brown tree snake led to decreased shrew numbers, prompting the monitors to switch to eating invertebrates and foraging through human garbage.