Crotaphytus insularisEastern Collared Lizard

Geographic Range

Black-collared lizards (Crotaphytus insularis) are native to the Nearctic region. They are currently endemic to one island in the Gulf of California called Isla Angel de la Guarda. This island is east of Baja California and west of the Mexican mainland. (Fox and Guillette, 1987; Frost, 2007; McGuire, 1994; McGuire, et al., 2007; Moehn, 1976a)


Black-collared lizards use several habitat types available on Isla Angel de la Guarda, but they are most commonly found on rocky surfaces or hills with arroyos (steep gulleys on narrow rivers). Occasionally, black-collared lizards can be found basking on cliff faces or perched on broken portions of cacti. Plant life is sparse across the island to which they are endemic. The elevation of the island ranges from 15 to 500 m above sea level. (Frost, 2007; Goldberg, 2020; McGuire, 1994; McGuire, et al., 2007; Moehn, 1976a)

  • Range elevation
    15 to 500 m
    49.21 to 1640.42 ft

Physical Description

Black-collared lizards, as their name suggests, have a single black stripe around their necks that resembles a collar. These collars can be incomplete on the posterior edge. Black-collared lizards also possess visible bars on their dorsal sides. Adult black-collared lizards have a base scale color that is deep brown on their dorsal sides. Adult males also have large, dark brown or black inguinal patches and their tails are compressed laterally. Black-collared lizards also have a single white dorsal stripe along their tails. Adult and subadult females have tails that are not vividly colored. The forelimbs of black-collared lizards are yellow or brown in color, with white square-shaped patterns that extend to their wrists. Their hindlimbs also are brown and possess similar white squares or spots from their thighs to their knees.

Female black-collared lizards can be more colorful during the breeding season, displaying vivid orange or reddish lateral bars when they are gravid. Black collared lizards also have slimmer nasal bones than other species in the genus Crotaphytus. Males reach a maximum snout-vent length (SVL) of 121 mm and females reach a maximum SVL of 104 mm. (Frost, 2007; McGuire, 1994; McGuire, et al., 2007; Moehn, 1976b; Moehn, 1976a)

  • Sexual Dimorphism
  • female more colorful
  • Range length
    121 (high) mm
    4.76 (high) in


There is little information on the development of black-collared lizards. However, their development may be similar to other species in the genus Crotaphytus. For example, eastern collared lizards (Crotaphytus collaris) generally reach sexual maturity at about 1 year of age. They lay eggs in one or more clutches, generally in warmer months (April to July). Male eastern collared lizards are considered reproductively active when their testes enlarge in April or May. Their testes regress in June, after the mating season ends. Eastern collared lizards may double in size in their first year. Lizards and most other reptiles exhibit indeterminate growth, meaning they grow in size throughout their life. However, growth rates typically decrease upon sexual maturity. (Ballinger and Hipp, 1985)


There is little information on the mating systems of black-collared lizards. In the case of a closely related species, eastern collared lizards (Crotaphytus collaris), females that are receptive to mating will leave chemical trails. Males follow these chemical trails to find reproductive females.

Female black-collared lizards exhibit brighter coloration in the mating season. They have red or orange dorsal patterns when they are reproductively active. The presence of red skin on a female black-collared lizard may also suggest that the individual is mating or that it has rejected a potential mate. (Frost, 2007; McGuire, 1994; McGuire, et al., 2007)

The exact breeding season for black-collared lizards are unknown, but juveniles were visible and active in late June. Females with eggs were noted during this same time period, so their breeding season likely extends into July. Breeding colors have been observed in black-collared lizards from June to early August, but the full range in the breeding season has not been reported. Females can develop vivid orange or reddish lateral bars while they are gravid.

Black-collared lizards likely mate once a year, based on the reproductive behaviors of other species in the genus Crotaphytus. There is little information regarding gestation period, incubation period, or average clutch size for black-collared lizards. Black-collared lizards lay eggs and are presumed to be iteroparous.

As is typical for most lizard species, the lack of parental care following egg-laying means that black-collared lizards are immediately independent at hatching. Age of sexual maturity has not been reported for black-collared lizards. (Frost, 2007; McGuire, 1994; McGuire, et al., 2007)

  • Breeding interval
    Likely once a year
  • Breeding season
    Likely June - August
  • Average age at sexual or reproductive maturity (female)
    0 minutes

Parental investment has not been fully described in black-collared lizards. However, they are expected to behave similarly to other species in the genus Crotaphytus. For these species and many other reptiles, males provide no parental investment beyond the act of mating. Females provide no further parental investment beyond the act of digging a nest in which they lay their eggs. (Frost, 2007; Goldberg, 2020)

  • Parental Investment
  • no parental involvement
  • precocial


There is little information on the lifespan of black-collared lizards, but other members of the genus Crotaphytus have been reported to live an average of 2.7 years in the wild. Black-collared lizards are not kept in captivity, and thus there is no information on their lifespan in such conditions. There are no studies that have examined longevity for black-collared lizards, but predation may limit their lifespan in the wild. (Frost, 2007)


Based on the few reported observations in their native habitat, black-collared lizards are diurnal. Males and females are ectothermic, basking or seeking shelter to regulate their body temperature. Black-collared lizards spend time during the day basking on volcanic rocks or cacti. Juveniles have been reported to bask on talus slopes, which consist of smaller white stones. Black-collared lizards are thought to be fairly sedentary.

A 1976 study on black-collared lizards in captivity found that sunlight can change their behaviors, making them more aggressive in hotter weather. Furthermore, males were aggressive towards other males and, when housed together, males would fight for dominance. Captive females were less aggressive and did not challenge any of the males. Black-collared lizards walk or climb through their environment, and are capable of running on their hind legs if necessary. (Frost, 2007; McGuire, 1994; Moehn, 1976b; Moehn, 1976a)

Home Range

The home range of black-collared lizards has not been reported. Observations of black-collared lizards showed that they were spaced far apart, which may suggest territorial behavior. However, sparse vegetation throughout their natural habitat may also explain the spacing that was observed. (Frost, 2007; Goldberg, 2020; McGuire, 1994; McGuire, et al., 2007)

Communication and Perception

There is little information on communication in black-collared lizards, but such research has been conducted on other members of the genus Crotophytus. Many species communicate by visual or chemical means. When females are receptive to breeding, they leave pheromone trails that males follow. Males are more aggressive than females. When threatened or competing for mates, they will stand on their hind legs or puff up to make themselves appear larger.

The reddened, shiny skin of some female crotaphytids may indicate that they are brooding. Also, red colorful skin can signal maturation, mating, or even rejection of mate. Males and females use visual cues to communicate, both nodding their heads to recognize conspecifics. Most reptiles use similar courting behaviors to communicate with each other. Black-collared lizards and other crotaphytids also use tactile communication when they need to mate, catch food, or lay eggs. (Axtwell, 1972; Frost, 2007; Hendricks and Hendricks, 2002; Ingram III and Tanner, 1971; McGuire, 1994; McGuire, et al., 2007)

Food Habits

There is little information on the food habits of black-collared lizards. They typically eat insects such as grasshoppers (suborder Caelifera) and possibly other lizards that live on Isla Angel de la Guarda. Black-collared lizards may even eat some plant matter. (Frost, 2007; Goldberg, 2020; McGuire, 1994; McGuire, et al., 2007; Moehn, 1976a; Parker and Pianka, 1976)

  • Animal Foods
  • reptiles
  • insects
  • Plant Foods
  • leaves


Given that black-collared lizards are restricted in their geographic range to a single island, and that this island has not been well-studied, a list of potential or confirmed predators is unavailable.

It is reported that Angel Island speckled rattlesnakes (Crotalus mitchelli) are endemic to the same island and would be likely predators. Common kingsnakes (Lampropeltis getula) also live on this island, and evidence of feral cats (Felis catus) have been noted by visual observations or indirect signs. It is likely that these predators would also eat black-collared lizards. Scat collected from a feral cat on a small southern island just off the coast of Isla Angel de la Guarda did contain 2 reptile mandibles; that individual was since lethally removed from the island. Norway rats (Rattus norvegicus) and house mice (Mus musculus) also have been introduced to Isla Angel de la Guarda and could possibly prey on the eggs of black-collared lizards. (Frost, 2007; Gottscho, et al., 2014; McGuire, 1994; McGuire, et al., 2007; Mellink, et al., 2002; Moehn, 1976a; Vázquez-Domínguez, et al., 2004)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Black-collared lizards likely eat insects, other lizards, and plants. There has not yet been any studies on the predators of black-collared lizards, but it is likely that snakes and feral cats (Felis catus) prey on them. No parasites have been reported for black-collared lizards. (Frost, 2007; Gottscho, et al., 2014; Mellink, et al., 2002; Moehn, 1976b)

Economic Importance for Humans: Positive

Black-collared lizards have no reported positive economic impacts on humans. (Frost, 2007)

Economic Importance for Humans: Negative

Black-collared lizards have no reported negative economic impacts on humans. (Frost, 2007)

Conservation Status

Black collared lizards are a species of “Least Concern” on the IUCN Red List and has no special status on the U.S. federal list, CITES, or State of Michigan list.

Black-collared lizards are endemic to one island in the Gulf of California, called Isla Angel de la Guarda. This island is uninhabited and thus there are no major threats to black-collared lizards from humans. However, introduced mammals including cats (Felis catus), Norway rats (Rattus norvegicus), and house mice (Mus musculus) may prey on black-collared lizards or their eggs. Isla Angel de la Guarda has apparently not been inhabited by human colonies since the 1970s. The terrain is deemed inhospitable for long-term human settlements.

A possible threat to black-collared lizards is the possibility that a natural or anthropogenic disaster decimates animal life on the island. The limited range of black-collared lizards inherently puts them at risk for extinction. Another conservation concern for black-collared lizards is lack of knowledge. Research on black-collared lizards is relatively sparse, and thus there is little information on diet, reproductive behaviors, food web dynamics, and other important aspects of their life history. Most existing literature regarding black-collared lizards is limited to physical descriptions.

Because of the limited range of black-collared lizards, conservation efforts cannot be enacted until more is known about their habitat preferences, behaviors, and other general aspects of their natural history. Black-collared lizards are protected because this island is currently uninhabited by humans. The island to which they are endemic is part of the Islas del Golfo de California Fauna and Flora Protection Area. This placement inherently affords black-collared lizards some level of protection. (Frost, 2007; Mellink, et al., 2002; Quammen, 1997)


Sergio Foster (author), Radford University, Sierra Felty (editor), Radford University, Bianca Plowman (editor), Radford University, Karen Powers (editor), Radford University, Victoria Raulerson (editor), Radford University, Christopher Wozniak (editor), Radford University, Galen Burrell (editor), Special Projects.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

  1. active during the day, 2. lasting for one day.

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.


An animal that eats mainly insects or spiders.

island endemic

animals that live only on an island or set of islands.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


having the capacity to move from one place to another.


This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


uses touch to communicate


Living on the ground.


uses sight to communicate

young precocial

young are relatively well-developed when born


Axtwell, R. 1972. Hybridization between western collared lizards with a proposed taxonomic rearrangement. Copeia, 1972/4: 707-727.

Ballinger, R., T. Hipp. 1985. Reproduction in the collared lizard, Crotaphytus collaris, in west central Texas. Copeia, 1985/4: 976-980.

Fox, S., L. Guillette. 1987. Luteal morphology, atresia, and plasma progesterone concentrations during the reproductive cycle of two oviparous lizards, Crotaphytus collaris and Eumeces obsoletus. American Journal of Anatomy, 179/4: 324-332.

Frost, D. 2007. "Crotaphytus insularis" (On-line). The IUCN Red List of Threatened Species 2007: e.T64010A12734833. Accessed February 01, 2022 at

Goldberg, S. 2020. Reproduction in the Baja California collared lizard, Crotaphytus vestigium (Squamata: Crotaphytidae). Bulletin of the Southern California Academy of Sciences, 109/3: 153-156.

Gottscho, A., S. Murray, H. Heinz, J. Lemos-Espinal. 2014. Crotalus angelensis (Isla Ángel de la Guarda rattlesnake) diet and predation. Herpetological Review, 45/3: 514.

Hendricks, P., L. Hendricks. 2002. Predatory attack by green-tailed towhee on sagebrush lizard. Northwestern Naturalist, 83/2: 57-59.

Ingram III, W., W. Tanner. 1971. A taxonomic study of Crotaphytus collaris between the Rio Grande and Colorado Rivers. Brigham Young University Science Bulletin, Biological Series, 13/2: Article 1.

Klauber, L. 1997. Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind (Second Edition). Berkeley, CA: University of California Press.

McGuire, J. 1994. A new species of collared lizard (Iguania: Crotaphytidae) from northeastern Baja California, México. Herpetologica, 50/4: 438-450.

McGuire, J., C. Linkem, M. Koo, D. Hutchison, K. Lappin, D. Orange, J. Lemos-Espinal, B. Riddle, J. Jaegar. 2007. Mitochondrial introgression and incomplete lineage sorting through space and time: Phylogenetics of crotaphyid lizards. Evolution, 61/12: 2879-2897.

Mellink, E., G. Ceballos,, J. Luévano. 2002. Population demise and extinction threat of the Angel de la Guarda deer mouse (Peromyscus guardia). Biological Conservation, 108: 107-111.

Moehn, L. 1976. The effect of sunlight on a despotism in the desert collared lizard, (Crotaphytus insularis). Journal of Herpetology, 10/3: 259-261.

Moehn, L. 1976. The effect of sunlight on a despotism in the desert collared lizard, Crotaphytus insularis (Reptilia, Lacertilia, Iguanidae). Journal of Herpetology, 10/3: 259-261.

Montanucci, R. 1974. Convergence, polymorphism or introgressive hybridization? An analysis of interaction between Crotaphytus collaris and C. reticulatus (Sauria: Iguanidae). Copeia, 1974/1: 87-101.

Montanucci, R. 1983. Natural hybridization between two species of collared lizards (Crotaphytus). Copeia, 1983/1: 1-11.

Montanucci, R., R. Axtell, H. Dessauer. 1975. Evolutionary divergence among collared lizards (Crotaphytus), with comments on the status of Gambelia. Herpetologica, 31/3: 336-347.

Palmer, W., A. Braswell. 1976. Communal egg laying and hatchlings of the rough green snake, Opheodrys aestivus (Linnaeus) (Reptilia, Serpentes, Colubridae). Journal of Herpetology, 10/3: 257-259.

Parker, W., E. Pianka. 1976. Ecological observations on the leopard lizard (Crotaphytus wislizeni) in different parts of its range. Herpetologica, 32/1: 95-114.

Quammen, D. 1997. The Song of the Dodo: Island Biogeography in an Age of Extinctions. New York, New York: Scribner.

Sanborn, S., R. Loomis. 1979. Systematics and behavior of collared lizards (Crotaphytus, Iguanidae) in southern California. Herpetologica, 35/2: 101-106.

Schwartz, A., T. Baird, D. Timanus. 2007. Influence of age and prior experience on territorial behavior and the costs of defense in male collared lizards. Ethology, 113/1: 9-17.

Smith, N., W. Tanner. 1974. A taxonomic study of the western collared lizards, Crotaphytus collaris and Crotaphytus insularis. Brigham Young University Science Bulletin, Biological Series, 19/4: Article 1.

Smith, N., W. Tanner. 1972. Two new subspecies of Crotaphytus (Sauria: Iguanidae). The Great Basin Naturalist, 31/1: 25-34.

Vázquez-Domínguez, E., G. Ceballos, J. Cruzado. 2004. Extirpation of an insular subspecies by a single introduced cat: The case of the endemic deer mouse, Peromyscus guardia on Estanque Island, Mexico. Oryx, 38/3: 347–350.

Weiner, N., H. Smith. 1965. Comparative osteology and classification of the crotaphytiform lizards. The American Midland Naturalist, 73/1: 170-187.