Heloderma suspectum 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Squamata Helodermatidae

Scientific Name: Heloderma suspectum Cope, 1869
Common Name(s):
English Gila Monster
French Lézard perlé, Monstre de gila
Spanish Monstruo de Gila

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2007
Date Assessed: 2007-03-01
Assessor(s): Hammerson, G.A., Frost, D.R. & Gadsden, H.
Reviewer(s): Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)
Listed as Near Threatened because this species is probably in significant decline (but probably at a rate of less than 30% over three generations), especially because of habitat loss throughout much of its range, thus making the species close to qualifying for Vulnerable under criteria A2, A3 and A4.
Previously published Red List assessments:

Geographic Range [top]

Range Description:The Gila Monster occurs in southwestern United States and northwestern Mexico. It ranges from extreme southwestern Utah, southern Nevada, and adjacent southeastern California south through southern Arizona, southwestern New Mexico, and much of Sonora to extreme northern Sinaloa, Mexico (Stebbins 2003). The core of the range is in Arizona and Sonora. Its elevational range extends from near sea level in Sonora and 30 m in Arizona to at least 1,545 m in southeastern Arizona (Lowe et al. 1986), and 1,180 to 1,950 m in New Mexico (Degenhardt et al. 1996).
Countries occurrence:
Mexico; United States
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species is never very abundant, but its abundance varies greatly. It is represented by well over 100 collection/observation sites that are well distributed throughout the range (e.g., see Campbell and Lamar 2004). The total adult population size is unknown but is probably at least several thousand; the species is fairly common in at least some parts of the range. Lowe et al. (1986) stated that Gila monsters are infrequently seen but not rare or uncommon in Arizona. In New Mexico, the species is commonly encountered in the Redrock Wildlife Area in Grant County and at Granite Gap in Hidalgo County; a density of approximately five individuals per sq. kilometre was estimated for one area (Degenhardt et al. 1996). Populations are declining over most of the United States range (Campbell and Lamar 2004), but the rate of decline is unknown (probably less than 30% over the past three generations). Beck (1985) estimated that the population in Utah included 450 to 800 individuals, down from an estimated 2,000 to 5,000 before the 1930s. It is probably declining even more seriously in Mexico.
Current Population Trend:Decreasing
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:Occupied vegetation types include desert grassland, Mohave and Sonoran desert scrub, and thorn scrub (Sonora); less often oak or pine-oak woodland. In Mexico, it occurs on lower mountain slopes and adjacent plains and beaches (Stebbins 2003), sometimes in irrigated areas. Canyon bottoms, arroyos (dry creeks), and rocky slopes may support relatively dense populations in some parts of Arizona and Sonora. In southern Arizona, the Gila Monster is more abundant in wetter and rockier palo verde-sahuaro desert than in drier and sandier creosote-bursage desert, where it occurs mainly in or near rocky buttes or mountains (Lowe et al. 1986). In New Mexico, the species is most commonly associated with desert scrub vegetation in rocky regions of mountain foothills and canyons; sometimes it is found along the lower fringes of pinyon-juniper woodland or oak woodland; rarely encountered in agricultural areas (Degenhardt et al. 1996). Gila monsters are mainly terrestrial but infrequently climb into vegetation. Refuges include spaces under rock, dense shrubs, burrows, or woodrat nests. Sub-surface shelters are important components of the habitat, and certain ones are used with a high degree of fidelity (particularly in winter), sometimes by multiple individuals concurrently (Beck and Jennings 2003). In Arizona, Gila monsters spend about 98% of the year under cover (Lowe et al. 1986). In Utah, individuals spent over 95% of active season underground; occasionally they basked near shelters in spring; shelters were burrows or crevices in rocky areas; hibernacula faced south (Beck 1990).

Threats [top]

Major Threat(s): Populations have been exploited (illegally) by commercial and private collectors, and they have suffered from habitat destruction due to urbanization and agricultural development (New Mexico Department of Fish and Game 1985). Concrete-lined canals are barriers to movement (Brown and Carmony 1999), as are busy highways. Mortality on roads likely is increasing as traffic volume increases on established highways and new roads are built. The most important reason for the decline is habitat loss resulting from development (Campbell and Lamar 2004). It is probably decreasing in southern Sonora due to expanding commercial agriculture.

Conservation Actions [top]

Conservation Actions: Collection of Gila monsters is prohibited by laws and regulations throughout the range in the United States and Mexico. Sizable areas of habitat are protected from development in national parks and monuments and in federal wilderness areas (Brown and Carmony 1999). It is listed on CITES Appendix II.

Classifications [top]

1. Forest -> 1.4. Forest - Temperate
3. Shrubland -> 3.4. Shrubland - Temperate
3. Shrubland -> 3.5. Shrubland - Subtropical/Tropical Dry
8. Desert -> 8.1. Desert - Hot
8. Desert -> 8.2. Desert - Temperate
1. Land/water protection -> 1.1. Site/area protection
2. Land/water management -> 2.1. Site/area 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
1. Residential & commercial development -> 1.1. Housing & urban areas
♦ 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

4. Transportation & service corridors -> 4.1. Roads & railroads
♦ timing:Ongoing    
→ Stresses
  • 2. Species Stresses -> 2.1. Species mortality

4. Transportation & service corridors -> 4.3. Shipping lanes
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.3. Indirect ecosystem effects

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

8. Invasive and other problematic species, genes & diseases -> 8.1. Invasive non-native/alien species/diseases -> 8.1.1. Unspecified species
♦ timing:Past, Unlikely to Return    

1. Research -> 1.2. Population size, distribution & trends
1. Research -> 1.3. Life history & ecology
1. Research -> 1.5. Threats
3. Monitoring -> 3.1. Population trends
0. Root -> 4. Other

Bibliography [top]

Baillie, J. and Groombridge, B. (eds). 1996. 1996 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

Beck, D.D. 1985. The natural history, distribution, and present status of the gila monster in Utah. Department of Biology and Ecology Center, Utah State University, Logan, Utah. Report submitted to Utah Division of Wildlife Resources.

Beck, D.D. and Jennings, R.D. 2003. Habitat use by Gila monsters: the importance of shelters. Herpetological Monographs 17: 111-129.

Brown, D.E. and Carmony, N.B. 1999. Gila Monster: Facts and Folklore of America's Aztec Lizard. University of Utah Press, Salt Lake City, Utah. 129 pp.

Campbell, J.A. and Lamar, W.W. 1989. The Venomous Reptiles of Latin America. Cornell University Press, Ithaca, New York.

Campbell, J.A. and Lamar, W.W. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock, Ithaca, New York and London, UK.

Degenhardt, W.G., Painter, C.W. and Price, A.H. 1996. Amphibians and Reptiles of New Mexico. University of New Mexico Press, Albuquerque, New Mexico. Xix + 431 pp.

Groombridge, B. (ed.). 1994. 1994 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

IUCN. 1990. IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

IUCN. 2007. 2007 IUCN Red List of Threatened Species. Available at: www.iucnredlist.org. (Accessed: 12th September 2007).

IUCN Conservation Monitoring Centre. 1986. 1986 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

IUCN Conservation Monitoring Centre. 1988. IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

Lowe, C.H., Schwalbe, C.R. and Johnson, T.B. 1986. The Venomous Reptiles of Arizona. Arizona Game and Fish Department.

New Mexico Department of Fish and Game. 1985. Handbook of Species Endangered in New Mexico.

Stebbins, R.C. 1985. A Field Guide to Western Reptiles and Amphibians. Second Edition. Houghton Mifflin Company, Boston, Massachusetts.

Citation: Hammerson, G.A., Frost, D.R. & Gadsden, H. 2007. Heloderma suspectum. In: . The IUCN Red List of Threatened Species 2007: e.T9865A13022716. . Downloaded on 19 June 2018.
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