REPTILIA: SQUAMATA: VARANIDAE: Varanus

Varanus olivaceus Hallowell, 1856

Gray's monitor / butuan

Text by Dr. Robert Sprackland.

 
Photo by Dr. Robert Sprackland, at San Diego Zoo.

Range: The Philippine island of Luzon.

Diagnosis:  

Description:  

Photo by Dr. Chip Miller, Luzon.

Natural History: It is one of zoology's interesting embarrassments that this very large lizard, long known to the local people, escaped scientific recognition until relatively late in the 20th century. The original description was based on a skin with no locality data, and a second complete juvenile that was described fifty years later under the name Varanus grayi (for John E. Gray, hence the common name). The taxonomic error was not uncovered until the 1980s, when Hallowell's older name was restored to priority. The rediscovery of the species, collection of dozens of specimens, and long term ecological studies were conducted by Dr. Walter Auffenberg of the Florida State Museum of Natural History.

Unlike any other known varanid, Gray's monitor is largely frugivorous, feeding on fruits as well as snails and large insects. A predominantly tree-dwelling species that may grow to six feet / 1.9 meters in total length.

Photo of an exceptionally beautiful specimen courtesy of John Tashjian.

Reproduction: Lays eggs.

Taxonomy & Relationships: Gray's monitor is probably closely related to the other large Asian monitors, but has traditionally been placed in its own subgenus, Philippinosaurus.

Variation: There is considerable variation seen in this species.

Additional Comments:

Type Specimen:

 Literature: Click on book to order copy.

Auffenberg, Walter. 1988. Gray's Monitor Lizard. University Presses of Florida, Gainesville. ISBN: 0-8130-0841-7.

Auffenberg, Walter. 1979. Detective Auffenberg gets his beast. Animal Kingdom 9(2): 12-15.

Auffenberg, Walter. 1976. First description of an adult Varanus grayi. Copeia 1976(3): 586-588.

Bennett, Daniel. 1998. Monitor lizards: Natural history, biology & husbandry. Edition Chimaira. ISBN: 3-930612-10-0.

Eidenmüller, Bernd. 1997. Warane: Lebensweise, Pflege, Zucht. Herpeton, Offenbach. In German. ISBN: 3-9802892-7-3. 

King, Dennis and Brian Green. 1999. Monitors: the biology of varanid lizards. 2nd edition. Krieger Publishing. ISBN: 1-57524-112-9.