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Overview

Distribution

Range Description

The Spiny Chuckwalla is found on the islands of the northwestern Gulf of California. It is found on Angel de la Guarda Island, Granito, Mejía, Pond, San Lorenzo Norte, San Lorenzo Sur, and numerous islands in Bahía de los Ángeles, including Cabeza de Caballo, La Ventana, Piojo, Flecha, Mitlàn, and Smith, Gulf of California, Mexico. The area in which this species is distributed is approximately 1,200 km². The species occurs at or just above sea level.

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Continent: Middle-America
Distribution: Angel de la Guarda, Smith, Pond, Granite, Mejia, San Lorenzo Norte, San Lorenzo Sur (Gulf of California, Baja California, Mexico)  
Type locality: Angel de la Guarda Island, Gulf of California
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Physical Description

Type Information

Paratype for Sauromalus hispidus
Catalog Number: USNM 15875
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1889
Locality: Angel Island (= Isla Angel de La Guarda), Puerto Refugio, Isla Angel De La Guarda, Baja California Norte, Mexico
Vessel: U.S.S. "Albatross"
  • Paratype: Stejneger, L. 1891. Proc. U. S. Nat. Mus. 14: 409.
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Paratype for Sauromalus hispidus
Catalog Number: USNM 15874
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1889
Locality: Angel Island (= Isla Angel de La Guarda), Puerto Refugio, Isla Angel De La Guarda, Baja California Norte, Mexico
Vessel: U.S.S. "Albatross"
  • Paratype: Stejneger, L. 1891. Proc. U. S. Nat. Mus. 14: 409.
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Paratype for Sauromalus hispidus
Catalog Number: USNM 15873
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1889
Locality: Angel Island (= Isla Angel de La Guarda), Puerto Refugio, Isla Angel De La Guarda, Baja California Norte, Mexico
Vessel: U.S.S. "Albatross"
  • Paratype: Stejneger, L. 1891. Proc. U. S. Nat. Mus. 14: 409.
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Holotype for Sauromalus hispidus
Catalog Number: USNM 8563
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Locality: Angel Island (= Isla Angel de La Guarda), Isla Angel De La Guarda, Baja California Norte, Mexico
  • Holotype: Stejneger, L. 1891. Proc. U. S. Nat. Mus. 14: 409.
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Ecology

Habitat

Sierra de la Laguna Dry Forests Habitat

This taxon is found in the Sierra de la Laguna dry forests ecoregion, which was once an isolated island, containing a large number of endemic species. After sufficient mountain uplift and the joining the Baja Peninsula mainland, this ecoregion underwent significant speciation, and is thus today high in species diversity; this portion of the peninsula contains the majority of the species found in the southern part of the Baja Peninsula. The region is shaped by a vast complex of granitic mountains, running southward from the Gulf of California to the Pacific. These mountains are dissected by valleys and canyons, and surrounded by vast plateaus.

The forest is transitional both with the pine oak forests at higher elevations, and with the xeric scrub at lower portions. The dry forest of Sierra de la Laguna is characterized by abundance of low trees and scrubs, and poor vertical stratification. The dominant tree species in the subtropical forest are Mauto (Lysiloma divaricatum), Palo Blanco (L. candida), Elephant Tree (Bursera microphylla) and Palo Zorrillo (Hesperalbizia occidentalis). Herbaceous elements are poorly developed, but their representatives are Caribe (Cnidoscolus angustidens), Spiny Aster (Chloracantha spinosa var. strictospinosa), Solanum spp., and cacti such as Biznaga (Ferocactus spp).

A number of reptilian taxa are found in the ecoregion, including: the endemic Baja California Rat Snake (Bogertophis rosaliae); Hunsaker's Spiny Lizard (Sceloporus hunsakeri); Belding's Orange-throated Whiptail (Cnemidophorus hyperythrus); Spiny Chuckwalla (Sauromalus hispidus NT); San Lucan Leaf-tailed Gecko (Phyllodactylus unctus NT); Baja California Night Snake (Hypsiglena slevini), a Mexican endemic rangeing from Bahía San Juanico, in the east-central Baja California Peninsula, southward continuously Cabo San Lucas (as well as on the island of Santa Margarita and on Cerralvo and Danzante islands in the Gulf of California; and Hunsaker's Spiny Lizard (Sceloporus hunsakeri), endemic to the Cape Region of Baja California Sur and the Gulf of California islands of Espiritu Santo, Gallo, Ballena and Partida Sur.

There are a number of mammalian species occurring in the Sierra de la Laguna dry forests. Among the mammals found here are: Eva's Desert Mouse (Peromyscus eva), endemic to Baja California Sur;  Mexican Funnel-eared Bat (Natalus stramineus); the near-endemic Peninsular Bat (Myotis peninsularis EN), chiefly found in Baja California Sur; Dalquest's Pocket Mouse (Chaetodipus dalquesti VU), known only from the Cape Region of Baja California Sur.

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San Lucan Xeric Scrub Habitat

This taxon is found in the San Lucan xeric scrub, an ecoregion situated at the southern-most part of the Baja Peninsula of Mexico; this diverse landscape of mountains, valleys, and plateaus is covered with a variety of species of xeric vegetation. This neotropical ecoregion is classifed within the Deserts and Xeric Scrublands biome. Plants and animals of this region evolved independently before the Baja Peninsula, a previous island during the Miocene, joined the mainland. An arid climate supports a number fauna and species, about ten percent which of which are endemic.

The ecoregion took shape in the Miocene as an isolated landform prior to joining the peninsula, and thus can be considered an biogeographical island of vegetation. This arid landscape is composed of a vast, rugged complex of granitic mountains, valleys, canyons, and plateaus. The ecoregion occupies the plateaus between the coast and the lower limits of the dry forests, which begin around 250 meters. Precipitation is about 400 millimetres annually.

Some elements of dry forest habitat are present in this ecoregion, but xeric elements are dominant and include Chain-link Cholla (Opuntia cholla); Elephant Tree (Bursera microphylla), at the southern limit of its range here and extending north to the Waterman Mountains in the USA; Mauto (Lysiloma divaricata); Organ Pipe Cactus (Stenocereus thuberi), Mala Mujer (Cnidoscolus angustidens), Yucca spp., and Barrel Cacti (Ferocactus spp). Herbaceous elements in the ecoregion include Plantago linearis, Bouteloua hirsuta, and Commelina coelestis.

The San Lucan xeric scrub harbours 31 of 48 of the reptile species for the Cape Region. Almost a third of the wider regional recorded species of collembola arthropods and spiders (30 of 138 species, respectively) occur in this ecoregion. In general, over ten percent of animal and plant species found here are endemic.

Within the San Lucan xeric scrub ecoregion, reptilian taxa include: the endemic Island Burrowing Sand Snake (Chilomeniscus punctatissimus); the endemic Isla Cerralvo Snake (Chilomeniscus savagei), restricted solely to Cerralvo Island; the Cape Arboreal Spiny Lizard (Sceloporus licki), a near-endemic restricted to the southern portion of the Baja Peninsula; the near-endemic Spiny Chuckwalla (Sauromalus hispidus NT), found only on Angel de la Guarda Island, Granito, Mejía, Pond, San Lorenzo Norte, San Lorenzo Sur, and other islands in Bahía de los Ángeles, including Cabeza de Caballo, La Ventana, Piojo, Flecha, Mitlàn, and Smith, Gulf of California; the near-endemic San Lucan Leaf-toed Gecko (Phyllodactylus unctus NT), found only on southern Baja Peninsula and some islands within the Gulf of California: Gallo, Partida Sur, Espiritu Santo, Ballena, Gallina and Cerralvo. There are only a small number of anuran species present in the ecoregion: Red-spotted Toad (Anaxyrus punctatus); and Pacific Chorus Frog (Pseudacris regilla).

The Espiritu Santo Island Antelope Squirrel (Ammospermophilus insularis) is endemic to the San Lucan xeric scrub ecoregion and is found only on the island of Espiritu Santo in the Gulf of California. Among threatened mammals occurring in the ecoregion are: the near-endemic Dalquest's Pocket Mouse (Chaetodipus dalquesti VU), known from the Cape Region of the Baja California Peninsula.

Threatened mammals in the ecoregion include: the near-endemic Peninsular Myotis (Peninsular Myotis EN), found only on southern Baja Peninsula; Fish-eating Bat (Myotis vivesi VU), a near-endemic occurring chiefly on the near-shore islands off of the southern Baja Peninsula and mainland Sonora; Mexican Long-tongued Bat (Choeronycteris mexicana NT); and the Lesser Long-nosed Bat (Leptonycteris yerbabuenae VU).

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Habitat and Ecology

Habitat and Ecology

This species is diurnal, often returning to the same burrow or rock crevice each night. Juveniles have a preference for rocky areas, while adults utilize hillside burrows (Grismer 2002). The islands inhabited by S. hispidus often receive little rain, and as noted above, population size often varies as a result of the fluctuating food supply. Daily activity is reduced during drier periods which likely reduces water requirements and water loss rates (Smits 1985a,b). S. hispidus shows one of the lowest water loss rates of any vertebrate (Smits 1985a). This species is the most arboreal species in the genus Sauromalus and is often found on tree branches where it climbs to eat the flowering stems. A variety of food items are eaten including, in order of frequency, shrubs, forbs, tree leaves and fruits, cactus flowers and fruits, and grasses (Sylber 1988).


Systems
  • Terrestrial
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Life History and Behavior

Life Expectancy

Lifespan, longevity, and ageing

Maximum longevity: 17.2 years (captivity)
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
NT
Near Threatened

Red List Criteria

Version
3.1

Year Assessed
2010

Assessor/s
Montgomery, C.E. & Mayer, G.C.

Reviewer/s
Grant, T.D. & Hoffmann, M.

Contributor/s

Justification
There is no evidence of extreme fluctuations in abundance or recent population declines in this species. The extent of occurrence is roughly 1,200 km² comprised of at least 12 subpopulations fragmented among isolated islands. No current information on total population size is available, but there are likely fewer than 10,000 mature individuals based on suitable habitat and size of known islands of occurrence. The species is therefore listed as Near Threatened as it almost qualifies for listing as Threatened under criteria B1a and C2.
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Population

Population

The species undergoes population fluctuations according to rainfall; densities are low during and following drought years. This species is physiologically well adapted to arid environments and normal drought cycles do not appear to effect long-term population health. There is no current information on the total population size or its trends.


Population Trend
Unknown
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Threats

Major Threats

Fluctuations in population numbers are caused by rainfall and the Spiny Chuckwalla suffers in periods of prolonged drought. This lizard is threatened by the international pet trade and from disease transmission, though it is uncertain if these threats have a negative effect on the population size.

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Management

Conservation Actions

Conservation Actions

This species occurs on Angel de la Guarda Island which is uninhabited and is a biological reserve. The other islands on which this lizard can be found are also protected as part of the Área de Protección de Flora y Fauna Islas del Gulfo de California. The region is part of the global network of UNESCO Biosphere Reserves. Further research into threats and ongoing monitoring is required.

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Wikipedia

Angel Island chuckwalla

The Angel Island chuckwalla (Sauromalus hispidus) (also known as the spiny chuckwalla) is a species of chuckwalla lizard belonging to the Iguanidae family endemic to Isla Ángel de la Guarda (Angel Island) in the Sea of Cortés. The species was transported to other islands by a tribe of the Seri as a potential food source.

Taxonomy and etymology[edit]

The generic name, sauromalus, is a combination of two Ancient Greek words:σαῦρος (sauros) meaning "lizard". and ομαλυς (omalus) meaning "flat".[3] Its specific name hispidus is Latin for "coarse" or "thorny" in reference to the spines on the chuckwalla's tail.[4][5]

The common name chuckwalla derives from the Shoshone word "tcaxxwal" or Cahuilla "caxwal", transcribed by Spaniards as "chacahuala".

Description[edit]

The Angel Island chuckwalla is the second largest species of chuckwalla reaching 44 centimetres (17 in) in body length, 64 centimetres (25 in) overall length and weighing up to 1.4 kilograms (3.1 lb).[4] It is considered a gigantic species as it is two to three times the size of its mainland counterparts.[4][6] Its body color is a dark brown color with tranverse black bands which fade into a solid darker brown to black color as the animal ages.

Distribution and habitat[edit]

The Angel Island chuckwalla is endemic to Isla Ángel de la Guarda (Angel Island) and ten smaller islands in the Sea of Cortés.[4]

Behavior and reproduction[edit]

Harmless to humans, these lizards are known to run from potential threats.[7] When disturbed, the chuckwalla will inflate its lungs, distend its body and wedge itself into a tight rock crevice.[7][8]

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.[7] Chuckwallas defend their territory and communicate with one another using a combination of colour and physical displays, namely "push ups", head-hobbing, and gaping of the mouth.[7]

Angel Island chuckwallas are diurnal animals and as they are exothermic, spend much of their mornings and winter days basking.[7] These lizards are well adapted to desert conditions; they are active at temperatures of up to 102°F (39°C).[7]

Mating occurs from April to July, with 5–16 eggs laid between June and August. The eggs hatch in late September.[7] Chuckwallas may live for 25 years or more.

Human use[edit]

The Comca’ac considered this species of chuckwalla an important food item.[9] So much so, that the lizards were translocated to most of the islands in Bahia de los Angeles: Isla San Lorenzo Norte, Isla San Lorenzo Sur, and Tiburón Island by the Seri people for use as a food source in times of need.[4]

References[edit]

  1. ^ "Sauromalus hispidus". Integrated Taxonomic Information System. Retrieved 15 September 2008. 
  2. ^ Montgomery, C.E. & Mayer, G.C. (2010). "Sauromalus hispidus". IUCN Red List of Threatened Species. Version 2014.2. International Union for Conservation of Nature. Retrieved 18 February 2010. 
  3. ^ Schwenkmeyer, Dick. "Sauromalus ater Common Chuckwalla". Field Guide. San Diego Natural History Museum. Retrieved 17 September 2008. 
  4. ^ a b c d e Case, T. J. (1982). "Ecology and evolution of insular gigantic chuckwallas, Sauromalus hispidus and Sauromalus varius". Iguanas of the World (Park Ridge, New Jersey: Noyes Publications). pp. 184–212. ISBN 0-8155-0917-0. 
  5. ^ Hollingsworth, Bradford D. (2004). "The Evolution of Iguanas an Overview and a Checklist of Species". Iguanas: Biology and Conservation (University of California Press). pp. 43–44. ISBN 978-0-520-23854-1. 
  6. ^ Smits, A. W. (1985). "Behavioral and dietary responses to aridity in the chuckwalla, Sauromalus hispidus". Journal of Herpetology. 
  7. ^ a b c d e f g Stebbins, Robert C.,(2003) A Field Guide to Western Reptiles and Amphibians, 3rd Edition. Houghton Mifflin Company, ISBN 0-395-98272-3
  8. ^ Deban, S.M., J.C. O’Reilly, and T.C. Theimer 1994. Mechanism of defensive inflation in the chuckwalla, Sauromalus obesus. Journal of Experimental Zoology 270: 451-459.
  9. ^ Richard Felger and Mary B. Moser (1985) People of the desert and sea: ethnobotany of the Seri Indians Tucson: University of Arizona Press.
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