Heloderma suspectum 

Scope: Global
Language: English

Translate page into:

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
Needs updating
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.

Citation: Hammerson, G.A., Frost, D.R. & Gadsden, H. 2007. Heloderma suspectum. The IUCN Red List of Threatened Species 2007: e.T9865A13022716. . Downloaded on 22 July 2018.
Disclaimer: To make use of this information, please check the <Terms of Use>.
Feedback: If you see any errors or have any questions or suggestions on what is shown on this page, please provide us with feedback so that we can correct or extend the information provided