Mangrove goanna, Western pacific monitor lizard
The Mangrove monitor (Varanus indicus) is a member of the monitor lizard family with a large distribution. It was first described by the French herpetologist François Marie Daudin in 1802. The Mangrove monitor is also known as Mangrove goanna or Western Pacific monitor lizard and wbl yb in the Kalam language of Papua New Guinea.
The body of the Mangrove monitor is dark green or black in color and covered with golden-yellow spots, with light coloration on the top of its head and a solid, cream-colored belly lacking dark markings. It has a distinct dark purple tongue and serrated teeth. The tail is almost twice 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 its mouth by spreading the hyoid apparatus and dropping the lower jaw to eat large prey, a process similar in appearance to that of snakes, although the jaw of the mangrove monitor remains rigid. The Mangrove monitor is one of only two species of monitor lizards that possess salt-excreting nasal glands, which enables it to survive in saltwater conditions and to consume marine prey. The presence of this gland probably enabled the monitors to reach new islands and aid in its dispersal throughout the Pacific.
Mangrove monitors are found throughout northern Australia, New Guinea, and the Solomon Islands. They also occur on the Moluccan islands of Morotai, Ternate, Halmahera, Obi, Buru, Ambon, Haruku, and Seram in Indonesia. Within this range, these monitors inhabit damp forests near coastal rivers, mangroves, and permanent inland lakes. They have also adapted to plantations and other areas close to human habitations.
Mangrove monitors are at home both on land and in water. They are also good climbers and frequently can be found in trees near bodies of water. Mangrove monitors are usually seen singly and maintain large territories. They employ active-pursuit hunting techniques. Monitors have a Jacobson's organ, which they use to detect prey. They stick their tongue out to gather scents and touch it to the opening of the organ when the tongue is retracted. Being strong swimmers they often hunt in the water and are the only monitor species capable of catching fish in deep water. Mangrove monitors are fast and when feeling threatened they become very aggressive. When biting they release venom which affects their prey but is not deadly to humans.
Mangrove monitors are carnivores that feed on the eggs of reptiles and birds, mollusks, rodents, insects, crabs, smaller lizards, fish, and carrion. In some parts of their range, they are known to eat juvenile crocodiles.
Little is known about the mating system of Mangrove monitors. During the breeding season, males are known to fight for females. Female monitors are oviparous and lay between 2 and 12 eggs. The oblong eggs are white in color, and hatch in about 7 to 8 months.
Mangrove monitors are hunted in many places for their skin, which is used for leather in making drum heads. Although international trade in this species is small, it was referred to be one of the most heavily exploited monitor lizards. In 1980, trade in over 13,000 monitors was declared. However, in many remote places, Mangrove monitors are used as a food source and are killed because of their reputation for preying on domestic animals.
According to the IUCN Red List, the Mangrove monitor is locally common throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List.
