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Overview

Distribution

Range Description

This lizard occurs in the western United States and in northwestern Mexico. It ranges from southern Nevada, southern Utah, southeastern California, and western Arizona south to southern Baja California and west-central Sonora, Mexico; in Baja California, most of the distribution is away from the Pacific coast (Hollingsworth 1998, Grismer 2002, Stebbins 2003).
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occurs (regularly, as a native taxon) in multiple nations

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National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) This lizard ranges from southern Nevada, southern Utah, southeastern California, and western Arizona south to southern Baja California and west-central Sonora, Mexico; in Baja California, most of the distribution is away from the west coast (Hollingsworth 1998, Grismer 2002, Stebbins 2003).

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Continent: Middle-America North-America
Distribution: Espiritu Santo, Partida, San Jose, San Francisco, San Diego, Santa Cruz, San Marcos, Santa Catalina, Isla Ballena [HR 27(1)], Isla Pardo [HR 28(1)], (Gulf of California, Mexico).  australis: Mexico (SE Baja California, from Punta San Gabriel southward to La Paz)  
Type locality: restricted to (Smith & Taylor 1950): Espiritu Santo Island.
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Physical Description

Size

Length: 42 cm

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Diagnostic Description

Differs from the gila monster in having dorsal scales small and granular (vs. large and beadlike) and in having femoral pores on the underside of the thigh (pores lacking in gila monster). Differs from other U.S. iguanid lizards in being larger and more robust, lacking expanded toetips, lacking head spines (horns), lacking enlarged middorsal scales, and having nonoverlapping scales at the upper edge of the orbit (Smith and Brodie 1982).

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Type Information

Holotype for Sauromalus ater
Catalog Number: USNM 4172
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Locality: Fort Yuma, Imperial, California, United States, North America
  • Holotype: Baird, S. F. 1858. Proc. Acad. Nat. Sci. Philadelphia. 10: 253.
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Holotype for Sauromalus ater
Catalog Number: USNM 64443
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1911
Locality: La Paz, Baja California Sur, Mexico
Vessel: U.S.S. "Albatross"
  • Holotype: Dickerson, M. C. 1919. Bull. Amer. Mus. Nat. Hist. 41 (10): 463.
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Holotype for Sauromalus ater
Catalog Number: USNM 64442
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: Male;
Preparation: Ethanol
Year Collected: 1911
Locality: Tiburon Island (= Isla Tiburon), Gulf of California, Isla Tiburon, Sonora, Mexico
Vessel: U.S.S. "Albatross"
  • Holotype: Dickerson, M. C. 1919. Bull. Amer. Mus. Nat. Hist. 41 (10): 464.
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This lizard inhabits rocky desert; lava flows, hillsides, and outcrops. Creosote bush occurs throughout most of the range (Stebbins 2003). Habitats encompass subtropical thornforest in the southern part of the range. Individuals seek shelter in rock crevices (or in burrows on islands in the Gulf of California; Grismer 2002). Eggs are laid underground.

Systems
  • Terrestrial
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Comments: This lizard inhabits rocky desert; lava flows, hillsides, and outcrops. Creosote bush occurs throughout most of the range (Stebbins 2003). Habitats encompass subtropical thornforest in the southern part of the range. Individuals seek shelter in rock crevices (or in burrows on islands in the Gulf of California; Grismer 2002). Eggs are laid underground.

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Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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Trophic Strategy

Comments: Browses on a wide variety of leaves, buds, flowers, and fruit (Behler and King 1979). Occasionally eats insects (Stebbins 1985).

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: This species is represented by a large number of viable occurrences throughout the majority of the range in California, Arizona, and Sonora, Mexico.

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Global Abundance

100,000 to >1,000,000 individuals

Comments: Abundance information is not available rangewide, but total adult population size is likely more than 100,000. Coombs (1977) estimated a population size of 10,000-15,000 individuals in Washington County, Utah. The abundance in the remainder of the Utah range (Kane, Garfield, and San Juan counties) is likely to be less than in Washington County (George Oliver, pers. comm., 1998).

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General Ecology

Southeastern California: first-year survivorship varied greatly among years, influenced mainly by egg mortality; annual survivorship about 75% for older individuals; large adults apparently most susceptible to predation; population density 15-30/ha; life expectancy about 15 years; summer rainfall promoted early maturity and successful reproduction (Abts 1987).

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Life History and Behavior

Cyclicity

Comments: Basks on rocks during the day. Inactive in cold temperatures or extreme heat. In southeastern California, may be active throughout most of year when winters relatively mild and summer rainfall frequent (Abts 1987).

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Life Expectancy

Lifespan, longevity, and ageing

Maximum longevity: 9.3 years (captivity)
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Reproduction

Mating apparently occurs May to June. Lays clutch of 5-16 eggs (clutch size increases with female body size), June perhaps to August. In Colorado Desert of southeastern California, oviposition occurs during first 3 weeks of July, just prior to summer rainfall (Abts 1988). Females may lay only every second year (Behler and King 1979). In Colorado Desert of southeastern California, males typically sexually mature at 2 years, females at 2-3 years if conditions optimal or at about 5 years if drought occurs; over several years, mean annual frequency of reproduction ranged from 0 to 95%; In Mojave Desert, females mature apparently in 5 years (Abts 1987). In southeastern California, first hatchling sighted in late September; hatchlings observed more frequently after early November (if climate mild) (Abts 1988).

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Sauromalus ater

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 6
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2007

Assessor/s
Hammerson, G.A.

Reviewer/s
Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)

Contributor/s

Justification
Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.
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National NatureServe Conservation Status

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

Reasons: Fairly common in many areas in a restricted range in the deserts of southwestern North America; little information is available on populations and trends, but apparently secure rangewide; threatened by collecting in some isolated areas, but probably not very threatened rangewide.

Intrinsic Vulnerability: Moderately vulnerable

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Population

Population
This species is represented by a large number of viable occurrences throughout the majority of the range in California, Arizona, and Sonora, Mexico. Abundance information is not available rangewide, but the total adult population size is probably more than 100,000. Coombs (1977) estimated a population size of 10,000-15,000 individuals in Washington County, Utah. The abundance in the remainder of the Utah range (Kane, Garfield, and San Juan counties) is likely to be less than in Washington County (G. Oliver pers. comm. 1998). Populations may vary with environmental conditions. According to Abts (1987), annual densities are variable with higher densities after relatively mild winters and the occurrence of summer rainfall. During a seven-year study in the Colorado Desert of southwestern California, densities ranged from 15 to 30 individuals per hectare (Abts 1987). Nevertheless, the area of occupancy and population size appear to be relatively stable over most of the range.

Population Trend
Stable
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Global Short Term Trend: Relatively stable (=10% change)

Comments: The Utah Heritage Program states that the population trend there is unknown but perhaps stable (George Oliver, pers. comm., 1998). Populations in Sonora, Mexico are considered stable (Andres Villareal Lazarraga, pers. comm., 1998).

Global Long Term Trend: Increase of 10-25% to decline of 30%

Comments: Populations may vary with environmental conditions. According to Abts (1987), annual densities are variable with higher densities after relatively mild winters and the occurrence of summer rainfall. During a seven-year study in the Colorado Desert of southwestern California, densities ranged from 15 to 30 individuals per hectare (Abts 1987). Nevertheless, area of occupancy and population size appear to be relatively stable over most of the range.

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Threats

Major Threats
Chuckwalla populations are locally threatened by excessive collecting and habitat degradation (New Mexico Department of Game and Fish 1997). Collectors not only remove individuals from the habitat which thus may reduce population viability but also often cause microhabitat destruction when tools are used to move or break rocks and exfoliations to expose the reptiles (New Mexico Department of Game and Fish 1997). Some subpopulations have been hard hit by collectors. For example, the easily accessible South Mountain subpopulation, near Phoenix, Arizona, has a unique colour pattern and is highly desired by the pet trade; exploitation of this subpopulation and destruction of its habitat are on the rise (Gergus et al. 1998). Historical populations in the Glen Canyon area of Utah have been reduced or eliminated by the damming of the Colorado River. Habitat degradation due to grazing activities of goats, sheep, and burros is also a potential threat. Overall, however, the species appears to be moderately to not very threatened across most of its range. The species is regarded as not very threatened in Sonora, Mexico (A. Villareal Lazarraga pers. comm. 1998).
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Degree of Threat: Medium

Comments: Chuckwall populations are locally threatened by excessive collecting and habitat degradation (New Mexico Department of Game and Fish 1997). Collectors not only remove individuals from the habitat may thus may reduce population viability but also often cause microhabitat destruction when tools are used move or break rocks and exfoliations to expose the reptiles (New Mexico Department of Game and Fish 1997). Some populations have been hard hit by collectors. For example, the easily accessible South Mountain population, near Phoenix, Arizona, has a unique color pattern and is highly desired by the pet trade; exploitation of this population and destruction of its habitat are on the rise (Gergus et al. 1998). Historical populations in the Glen Canyon area of Utah have been reduced or eliminated by the damming of the Colorado River. Habitat degradation due to grazing activities of goats, sheep, and burros is also a potential threat.

Overall, however, the species appears to be moderately to not very threatened across most of its range. The species is regarded as not very threatened in Sonora, Mexico (Andres Villareal Lazarraga, pers. comm., 1998).

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Management

Conservation Actions

Conservation Actions
Habitat is protected from development in several national parks and monuments and in federal wilderness areas in the United States, and the species occurs within protected sites in Sonora, Mexico (A. Villareal Lazarraga pers. comm. 1998). Many sites outside formally protected areas are rugged and remote and thus protected from most potential threats.
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Global Protection: Many to very many (13 to >40) occurrences appropriately protected and managed

Comments: Habitat is protected from development in several national parks and monuments and in federal wilderness areas in the United States, and the species occurs within protected sites in Sonora, Mexico (Andres Villareal Lazarraga, pers. comm., 1998). Many sites outside formally protected areas are rugged and remote and thus protected from most potential threats.

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Wikipedia

Sauromalus ater

The Common Chuckwalla (Sauromalus ater) is a species of lizard in the family Iguanidae. It inhabits the Sonoran and Mojave Deserts of the southwestern United States and northwestern Mexico. Its range extends from Eastern California, Utah, and Nevada south to Baja California and Sonora.[2]

Taxonomy[edit]

The common name "chuckwalla" (or chuckawalla) is derived from the Shoshone word "tcaxxwal" or "caxwal," the form used by the Cahuilla of southeastern California.[3]

Its generic name, sauromalus, is a combination of two Ancient Greek words:σαῦρος (sauros) meaning "lizard". and ομαλυς (omalus) meaning "flat".[3] Its specific name is ater, Latin for "black" or "dark"

Its original epithet was Sauromalus obesus; and although that name is no longer officially recognized, it is still very common in the literature and it remains in many standard natural history references for North America. In 1998, Bradford D. Hollingsworth examined variations in Sauromalus and concluded that only five species should be recognized. He regarded S. obesus as conspecific with S. ater, and he used S. ater, which has priority, as the specific name of the combined taxon.[4] No subspecies of S. ater are currently recognized.[4] Based primarily on the extensive use of the name S. obesus, a petition to give that name precedence over that of S. ater was submitted to the ICZN.[4] However this reasoning was dubious and the priority of S. ater was maintained.[4] In 2004, ICZN ruled that the name Sauromalus ater was first described by zoologist Auguste Duméril in 1856 and thus had precedence over the name Sauromalus obesus which was not named until 1858 by Baird.[4]

Description[edit]

The common chuckwalla is a large, flat-bodied lizard with a large rounded belly, and a wide-based blunt-tipped tail.[3] Reaching a total length of 20 inches and a weight of .9 kilograms (2.0 lb).[5] Small scales cover its body, with larger scales protecting the ear openings.[3] The coloration of these lizards varies by location and between juveniles and adults, as well as among males and females.[3] In adult males, the head, shoulder, and pelvic regions are black while the mid-body is light tan speckled with brown.[3] Adult females are brownish in color with a scattering of dark red spots. Young chuckwallas have four or five broad bands across the body, and three or four on the tail which are lost in adulthood by males, but retained somewhat by females.[3]

Common Chuckwalla Sauromalus ater at Bristol Zoo, England

Behavior[edit]

Harmless to humans, these lizards are known to run from potential threats.[5] When disturbed, the Chuckwalla will gulp air, distend its body and wedge itself into a tight rock crevice.[5] The Chuckwalla will inflate its body with air in order to entrench itself.[5]

Males are seasonally and conditionally territorial; an abundance of resources tends to create a hierarchy based on size, with one large male dominating the area's smaller males.[5] Chuckwallas use a combination of colour and physical displays, namely "push ups", head-hobbing, and gaping of the mouth to communicate and defend their territory (see animal communication).[5]

Chuckwallas are diurnal animals and as they are ectothermic, spend much of their mornings and cooler days basking.[5] These lizards are well adapted to desert conditions; they are active at temperatures of up to 102°F (39°C).[5] Chuckwallas brumate during cooler months and emerge in February.[5]

Mating occurs from April to July, with 5-16 eggs laid between June and August. The eggs hatch in late September.[5]

Diet[edit]

Primarily herbivorous, the chuckwalla eats creosote bush flowers, leaves, fruit, and occasionally insects.[5]

Gallery[edit]

References[edit]

  1. ^ "Sauromalus ater". Integrated Taxonomic Information System. Retrieved 15 September 2008. 
  2. ^ Grismer, L. Lee (2002). Amphibians and Reptiles of Baja California, Including its Pacific Islands, and the Islands in the Sea of Cortés. University of California Press. p. 130. ISBN 978-0-520-22417-9. 
  3. ^ a b c d e f g Schwenkmeyer, Dick. "Sauromalus ater Common Chuckwalla". Field Guide. San Diego Natural History Museum. Retrieved 17 September 2008. 
  4. ^ a b c d e Hollingsworth, Bradford D. (2004). "The Evolution of Iguanas an Overview and a Checklist of Species". Iguanas: Biology and Conservation (University of California Press). p. 42. ISBN 978-0-520-23854-1. 
  5. ^ a b c d e f g h i j k Stebbins, Robert C.,(2003) A Field Guide to Western Reptiles and Amphibians, 3rd Edition. Houghton Mifflin Company, ISBN 0-395-98272-3
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Names and Taxonomy

Taxonomy

Comments: Hollingsworth (1998) examined variation in Sauromalus and concluded that five species should be recognized. He regarded S. obesus as conspecific with S. ater, and he used S. ater, which has priority, as the specific name of the combined taxon. No subspecies of S. ater were recognized. Based primarily on the extensive use of the name S. obesus, a petition to give that name precedence over that of S. ater was submitted to the ICZN. However, McDiarmid et al. (2002) questioned this reasoning and argued that the priority of S. ater should be maintained. In 2004, ICZN ruled that the name Sauromalus ater Duméril 1856 has precedence over the name Sauromalus obesus (Baird 1858) (Bulletin of Zoological Nomenclature 61:74-75). Hence, Sauromalus obesus is no longer the correct name for the chuckwallas of the United States (or Mexico).

See Petren and Case (1997) for a phylogenetic analysis of Sauromalus based on mtDNA variation. Patterns of mtDNA variation show geographic patterns but do not exhibit a phylogenetic break at the Colorado River valley (in contrast to the pattern found in the desert tortoise) (Lamb et al. 1992).

MtDNA data indicate that Cyclura is monophyletic and not closely releated to any other genus, whereas Iguana is strongly supported as the sister taxon to Sauromalus (Malone et al. 2000). Wiens and Hollingsworth (2000) concluded that Cyclura is the sister taxon of Iguana and that Sauromalus probably is the sister taxon of the Cyclura-Iguana clade.

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