The Gray's monitor (''Varanus olivaceus'') is a large (180 cm, >9 kg)

monitor lizard Monitor lizards are lizards in the genus ''Varanus,'' the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and West African Nile monitor, one species is also found in south America as an invasive species. A ...

known only from lowland

dipterocarp Dipterocarpaceae is a family of flowering plants with 22 genera and about 695 known species of mainly lowland tropical forest trees. Their distribution is pantropical, from northern South America to Africa, the Seychelles, India, Indochina, Indo ...

forest A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...

in southern

Luzon Luzon ( , ) is the largest and most populous List of islands in the Philippines, island in the Philippines. Located in the northern portion of the List of islands of the Philippines, Philippine archipelago, it is the economic and political ce ...

Catanduanes Catanduanes (; ), officially the Province of Catanduanes (), is an island province located in the Bicol Region of Luzon in the Philippines. It is the 12th-largest island in the Philippines, and lies to the east of Camarines Sur, across the M ...

, and

Polillo Island Polillo () is an island in the northeastern region of the Philippine archipelago. It is the largest island and the namesake of the Polillo Islands. It is separated from Luzon Island by the Polillo Strait and forms the northern side of Lamon ...

, all islands in the

Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...

. It is also known as Gray's monitor lizard, butaan, and ornate monitor. It belongs to the subgenus ''Philippinosaurus''. It is largely

arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally (scansorial), but others are exclusively arboreal. The hab ...

and extremely shy. The population of northern Luzon was formerly included in the Gray's monitor, but has been recognized as a separate species, the

northern Sierra Madre forest monitor The Northern Sierra Madre forest monitor (''Varanus bitatawa''), also known by the local names ''bitatawa'', ''baritatawa'', and ''butikaw'', is a large, arboreal, frugivorous lizard of the genus ''Varanus''. Description The forest monitor liz ...

(''V. bitatawa''), since 2010.

Ecology

Diet

It is well known for its diet, which consists primarily of ripe

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

, especially ''

Pandanus ''Pandanus'' is a genus of monocots with about 578 accepted species. They are palm-like, dioecious trees and shrubs native to the Old World tropics and subtropics. Common names include pandan, screw palm and screw pine. The genus is classified ...

''. A number of prey items are, however, also consumed, including

snail A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

spider Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...

beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s and

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...

s. Monitors are generally carnivorous animals, which makes the Gray's monitor somewhat of an exception amongst the varanid family. Such an unusual diet may be as a result of competition over food with the water monitors, which share their range. One of the only fruits readily eaten by this species in captivity is grapes, with these and fruit powder supplementing a captive diet of insects and rodents.

Reproduction

Details of the breeding habits of this species, certainly in the wild, are very limited due to the secretive nature of this species. The optimum egg-laying time for this species is known to be between July and October, when a clutch of up to 11 eggs will be laid. Rather than digging a nest, the most likely place for this species to lay eggs is thought to be in tree hollows, where they also spend much of their days resting. Young are often observed at their smallest in May to July, and as such estimates of incubation time lay at around 300 days. In captivity, however, incubation has been recorded over 219 days.

Conservation

Threats

It is classed as vulnerable by the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

because much of its

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

has been destroyed over the last century, and it is now thought to occupy a highly fragmented area smaller than . In addition to habitat destruction, they are threatened by hunting for food and illegal collection for the pet trade.

In captivity

This species is regularly observed being illegally sold in the Philippine pet trade. Among others, this species is on display at the following zoos outside the Philippines: *

Los Angeles Zoo The Los Angeles Zoo and Botanical Gardens is a zoo founded in 1966 and located in Los Angeles, California, United States. The city of Los Angeles owns the zoo, its land and facilities, and the animals. History Eastlake Zoo, opened in Eastlak ...

Oklahoma City Zoo and Botanical Garden The Oklahoma City Zoo and Botanical Garden is a zoo and botanical garden located in Oklahoma City's Adventure District in northeast Oklahoma City, Oklahoma. The zoo covers and is home to more than 2,000 animals of more than 500 species. It is ...

* Protvin Krokozoo * Plzen Zoo *

Brookfield Zoo Brookfield Zoo Chicago, known until 2024 as simply Brookfield Zoo, and also known as the Chicago Zoological Park, is a zoo located in Brookfield, Illinois. Brookfield Zoo is owned by the Forest Preserve District of Cook County and is managed ...

San Diego Zoo The San Diego Zoo is a zoo in San Diego, California, United States, located in Balboa Park (San Diego), Balboa Park. It began with a collection of animals left over from the 1915 Panama–California Exposition that were brought together by its ...

Bronx Zoo The Bronx Zoo (also historically the Bronx Zoological Park and the Bronx Zoological Gardens) is a zoo within Bronx Park in the Bronx, New York City. It is one of the largest zoos in the United States by area and the largest Metropolis, metropol ...

* Fresno Chaffee Zoo One Philippine zoo,

Avilon Zoo Avilon Zoo is a zoo located in Barrio San Isidro, Rodriguez, Rizal, Philippines. It is operated by the Avilon Wildlife Conservation Foundation, which also operated the Ark Avilon Zoo in Pasig. Zoo Avilon Zoo is currently the largest zoological ...

, has achieved successful breeding of this species. For many years, the only report of a breeding outside of the Philippines was a single baby hatched at the Dallas Zoo in 1994, until the LA Zoo hatched them for the first time in 2015. Dallas gave their two female monitors to the Oklahoma City Zoo in May 2013.Bronx Zoo The Bronx Zoo (also historically the Bronx Zoological Park and the Bronx Zoological Gardens) is a zoo within Bronx Park in the Bronx, New York City. It is one of the largest zoos in the United States by area and the largest Metropolis, metropol ...

Ecology

Diet

Reproduction

Conservation

Threats

In captivity

References

Bibliography

External links