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Gray's Monitor Lizard

Varanus olivaceus Hallowell 1857

Brief Summary

    Gray's monitor: Brief Summary
    provided by wikipedia

    The Gray's monitor (Varanus olivaceus) is a large (180 cm,>9 kg) monitor lizard known only from lowland dipterocarp forest in southern Luzon, Catanduanes, and Polillo Island, all islands in the Philippines. It is also known as Gray's monitor lizard, butaan, and ornate monitor. It belongs to the subgenus Philippinosaurus. It is largely arboreal and extremely shy. The Northern Sierra Madre monitor lizard was thought to be of same species with Gray's monitor until a research concluded in 2010 that northern populations of Gray's monitor was a distinct species, now known as V. bitatawa.

Comprehensive Description

    Biology
    provided by Amphibians and Reptiles of the Philippines

    Varanus olivaceus was the first frugivorous monitor species known to science. It has a greenish-gray dorsal ground color, overlain with darker transverse bands on the neck, body, limbs, and tail. Ventral coloration is gray to grayish-green or yellow, overlain with a variable number of dark brown or black longitudinal gular stripes.

    Etymology
    provided by Amphibians and Reptiles of the Philippines

    The specific epithet is likely derived from the olive-green ground color often exhibited by this species.

    Gray's monitor
    provided by wikipedia

    The Gray's monitor (Varanus olivaceus) is a large (180 cm,>9 kg) monitor lizard known only from lowland dipterocarp forest in southern Luzon, Catanduanes, and Polillo Island, all islands in the Philippines.[1] It is also known as Gray's monitor lizard, butaan, and ornate monitor.[3] It belongs to the subgenus Philippinosaurus.[4] It is largely arboreal and extremely shy. The Northern Sierra Madre monitor lizard was thought to be of same species with Gray's monitor until a research concluded in 2010 that northern populations of Gray's monitor was a distinct species, now known as V. bitatawa.

    Ecology

    Diet

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    Varanus olivaceus

    It is well known for its diet, which consists primarily of ripe fruit, especially Pandanus. A number of prey items are, however, also consumed, including snails, crabs, spiders, beetles, birds and eggs. 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.[5]

    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.[5]

    Conservation

    Threats

    It is classed as vulnerable by the IUCN because most of its habitat has been destroyed over the last 60 years, and it is now thought to live in an area as small as 20,000 km², of which only around 2,000 km² are occupied by this species. It is thought that habitat destruction is not the only cause for the decreasing population trend, but that they are also still hunted for food and collected for the pet trade.[6] It may be more threatened than initially estimated, since the northern population were confirmed to be of different species (V. bitatawa) in 2010. The range of the species has now been enclosed to the Polilo islands and the southern portions of Luzon, a very fragmented area with sparse rainforests left. A new assessment by the IUCN is highly recommended, as the species may be endangered or critically endangered already.

    In captivity

    This species is not widely kept in captivity, which is possibly partly because it is not generally bred successfully outside of the Philippines. This species is on display at the following zoos outside the Philippines:

    There are two Philippine zoos which are successfully breeding this species, which are Avilon Zoo and Paradise Reptile Zoo. 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.[8] Dallas gave their two female monitors to the Oklahoma City Zoo in May 2013.

    References

    1. ^ a b Sy, E.; Afuang, L.; Duya, M.R. & Diesmos, M. (2009). "Varanus olivaceus". The IUCN Red List of Threatened Species. IUCN. 2009: e.T22888A9396856. doi:10.2305/IUCN.UK.2009-2.RLTS.T22888A9396856.en. Retrieved 23 December 2017..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""'"'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
    2. ^ Varanus olivaceus Hallowell, 1856. ITIS.gov
    3. ^ "Common Names for Ornate Monitor (Viranus Olivaceus)". Encyclopedia of Life. Retrieved 12 December 2013.
    4. ^ Harold De Lisle. MONITORS OF THE WORLD 1998 LIST. Kingsnake.com
    5. ^ a b "Varanus olivaceus". Mampam Conservation. Retrieved 2013-02-09.
    6. ^ "Red List Entry for Varanus olivaceus". IUCN. Retrieved 2013-02-09.
    7. ^ a b "Gray's Waran". Zoo Tier Liste. Retrieved 2013-02-09.
    8. ^ https://www.earthtouchnews.com/cute-and-cool/zooborns/three-rare-grays-monitor-lizards-hatch-at-los-angeles-zoo/

Distribution

    Distribution
    provided by Amphibians and Reptiles of the Philippines

    Varanus olivaceus is known from southern Luzon Island (Bicol Peninsula), as well as Polillo and Catanduanes islands. The northern extent of this species' distribution is limited to the southern portion of the Sierra Madre Mountain Range.

    Faunal Affinity
    provided by Amphibians and Reptiles of the Philippines

    Luzon Pleistocene Aggregate Island Complex

    Distribution
    provided by ReptileDB
    Continent: Asia
    Distribution: Philippine Islands (S Luzon, Polillo), Catanduanes Islands, elevation max. 400 m.
    Type locality: œManilla

Diagnostic Description

    Diagnostic Description
    provided by Amphibians and Reptiles of the Philippines

    Varanus olivaceus is very similar to its closest relative V. bitatawa, and has a slightly more robust head, but with less robust body and limbs. This species generally has a gray to olive ground color, overlain by dark brown to black solid transverse bands on the neck, body, limbs, and tail (most prominent in juveniles, becoming less discernible with age); head coloration often lightest anteriorly, often transitioning to a predominantly yellow-green color in labial region. Ventral coloration generally a uniform grayish-green, grayish yellow, or olive, overlain with conspicuous dark gray to black longitudinal gular stripes.

Look Alikes

    Look Alikes
    provided by Amphibians and Reptiles of the Philippines

    Varanus olivaceus would most likely be confused with its closest relative, V. bitatawa, but can be distinguished from that species by the presence of dark colored dorsal bands.

Habitat

    Habitat
    provided by Amphibians and Reptiles of the Philippines

    Varanus olivaceus is a forest obligate (as with its closest relatives V. mabitang and V. bitratawa), and is heavily dependent upon unfragmented lowland and mid-elevation forests with sufficient stands of fruiting Pandanus, Canrium, or Ficus trees.

General Ecology

    Ecology
    provided by Amphibians and Reptiles of the Philippines

    As with the other two species of frugivorous monitors, Varanus olivaceus is a predominately arboreal species, spending vast amounts of time in the canopies of fruiting trees. During dry periods, it can be expected to transition to a more terrestrial lifestyle in search of a preferred secondary food source, snails.

Behavior

    Behaviour
    provided by Amphibians and Reptiles of the Philippines

    All frugivorous monitors are highly secretive, and rarely seen through chance encounters. Varanus olivaceus is no different, and in fact has been documented spending several days at a time in the tops of fruiting trees, decending to the ground only to move to the next tree.

Life Expectancy

    Lifespan, longevity, and ageing
    provided by AnAge articles
    Maximum longevity: 15.2 years (captivity)

Conservation Status

    Conservation
    provided by Amphibians and Reptiles of the Philippines

    Despite having been considered extinct for nearly 150 years, in the past several decades Varanus olivaceus has been documented throughout its proposed range. This species has the largest distribution among frugivorous monitors, but remains characterized as vulnerable

    Conservation Status
    provided by Amphibians and Reptiles of the Philippines

    Varanus olivaceus is designated as a CITES Appendix II species. This taxon is not currently threatened by extinction, but may become so unless trade or other factors are closely monitored.

Threats

    Threats
    provided by Amphibians and Reptiles of the Philippines

    The most severe threat to this species is likely habitat loss or degradation, although collection for the pet trade and for bush meat are additional likely threats.

Management

    Management
    provided by Amphibians and Reptiles of the Philippines

    Varanus olivaceus is considered a forest obligate, requiring relatively large tracts of intact habitat. Specifically, the protection of habitat which includes dense populations of this species' prefered fruiting trees (Pandanus and Ficus) will be essential for maintaining this species in the future.