Varanus olivaceus 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Squamata Varanidae

Scientific Name: Varanus olivaceus Hallowell, 1859
Common Name(s):
English Gray's Monitor, Gray's Monitor Lizard
French Varan De Gray
Varanus grayi Boulenger, 1885
Varanus olivaceus Hallowell, 1857
Varanus ornatus Gray, 1845
Taxonomic Notes: There is a need to review the taxonomic status of animals from the Northern Sierra Madre of Luzon currently allocated to Varanus olivaceus.

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2d; B1ab(i,ii,iii)+2ab(i,ii,iii) ver 3.1
Year Published: 2009
Date Assessed: 2007-04-22
Needs updating
Assessor(s): Sy, E., Afuang, L., Duya, M.R. & Diesmos, M.
Reviewer(s): Cox, N. & Hoffmann, M. (Global Reptile Assessment Coordinating Team)
Listed as Vulnerable, in view of its extent of occurrence of less than 20,000 km² and area of occupancy of less than 2,000 km² (excluding provisionally assigned populations from northern Luzon), with a severely fragmented habitat. There is a continuing decline of individuals, resulting from heavy hunting pressure, believed to be greater than 30% over a ten year period.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is endemic to the Philippines, where it is knonw only from southern Luzon, Catanduanes and Pollilio. Animals collected during recent surveys from the Northern Sierra Madre Range of Luzon may be allocated to this species, but it is possible that they may represent a distinct species and further taxonomic studies are needed to resolve this issue (E.L. Rico, M.R. Duya, D. Bennett, A. Diesmos and R. Brown pers. comm. 2007). It is a lowland species ranging from around sea level to 400 m asl.
Countries occurrence:
Additional data:
Upper elevation limit (metres):400
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:It appears to be moderately common within its limited range (Bennet 1995). Animals possibly allocated to this species, appear to be moderately common in the Northern Sierra Madre Range.
Current Population Trend:Decreasing
Additional data:
Population severely fragmented:Yes

Habitat and Ecology [top]

Habitat and Ecology:This arboreal species has been recorded from both primary and secondary tropical moist forests, often with rocky outcrops or cliffs (Bennet 1995). Juvenile animals have a diet of snails or crabs, but animals change to a largely frugivorous diet as they mature (Bennet 1995). Little is known about reproduction in this species.

Threats [top]

Major Threat(s): This species is threatened by habitat loss and fragmentation, through conversion of land to agricultural use and logging operations. It is also threatened by hunting for food by local people and collection for the pet trade (hatchlings and juveniles are targeted for the international market).

Conservation Actions [top]

Conservation Actions: The species is present within the Sibulan Protected Watershed on Polillo, and has been recorded from other protected areas within its range. A research programme is in place for the population of this species on Polillo Island (the Polillo Butaan Project). Further taxonomic studies are needed for animals recorded from the Northern Sierra Madre on Luzon. This species is listed on Appendix II of CITES.

Classifications [top]

1. Forest -> 1.6. Forest - Subtropical/Tropical Moist Lowland
2. Land/water management -> 2.1. Site/area management
3. Species management -> 3.1. Species management -> 3.1.1. Harvest management
3. Species management -> 3.1. Species management -> 3.1.2. Trade management

In-Place Research, Monitoring and Planning
In-Place Land/Water Protection and Management
  Occur in at least one PA:Yes
In-Place Species Management
In-Place Education
  Included in international legislation:Yes
  Subject to any international management/trade controls:Yes
2. Agriculture & aquaculture -> 2.1. Annual & perennial non-timber crops -> 2.1.1. Shifting agriculture
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

2. Agriculture & aquaculture -> 2.1. Annual & perennial non-timber crops -> 2.1.2. Small-holder farming
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

5. Biological resource use -> 5.1. Hunting & trapping terrestrial animals -> 5.1.1. Intentional use (species is the target)
♦ timing:Ongoing    
→ Stresses
  • 2. Species Stresses -> 2.1. Species mortality

5. Biological resource use -> 5.3. Logging & wood harvesting -> 5.3.5. Motivation Unknown/Unrecorded
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

1. Research -> 1.1. Taxonomy
1. Research -> 1.2. Population size, distribution & trends
3. Monitoring -> 3.1. Population trends

♦  Food - human
 Local : ✓ 

♦  Pets/display animals, horticulture
 National : ✓  International : ✓ 

Bibliography [top]

Auffenberg, W. 1988. Gray's Monitor Lizard. University of Florida Press., Gainesville.

Bennett, D. 1995. A Little Book of Monitor Lizards. Viper Press., Aberdeen, UK.

Hallowell, E. 1857. Notes on the reptiles in the collection of the museum of the Academy of Natural Sciences. Proceedings of the Academy of Natural Sciences Philadelphia 8(4): 146-153.

IUCN. 2009. IUCN Red List of Threatened Species (ver. 2009.2). Available at: (Accessed: 3 November 2009).

Citation: Sy, E., Afuang, L., Duya, M.R. & Diesmos, M. 2009. Varanus olivaceus. The IUCN Red List of Threatened Species 2009: e.T22888A9396856. . Downloaded on 20 September 2018.
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