Common Earless Lizard (Holbrookia maculata)

photo by Robert L. Bezy and Kathryn Bolles

Male Speckled Earless Lizard. Photo by Robert L. Bezy and Kathryn Bolles

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Description

The taxonomy of the Holbrokia maculata complex is still a tangled ball of twine in desperate need of teasing apart. Three articles appeared in the December 2010 issue of the Sonoran Herpetologist that summarize the problems in this confusing group of earless lizards (Bezy 2010, Jones 2010a&b).  Owing to his diligent work measuring characters and comparing lizards across southern Arizona, Bezy’s 2010 work paints the best picture we have of the distribution of the Elegant and Common Earless Lizards (H. elegans and maculata) in the 100-Mile Circle and Arizona.  That paper is reproduced as the Elegant Earless Lizard species account here in the 100-Mile Circle, and those further interested in the Common Earless Lizard should also consult that account.

Bezy’s Figure 1 is Ralph Axtell’s (2009) compilation of differences between the Elegant and Common Earless Lizards.  Based on that and examination of specimens, Bezy concluded that, in Arizona, the Common Earless Lizard occurs in two distinct regions (above and below the Mogollon Rim), which also form distinct morphological and genetic groups (also see Blaine 2008).   Below the Rim, the Common Earless Lizard “is confined largely to the grasslands of the southeastern part of the state: localities near Sonoita, Elgin, Fry, Tombstone, Willcox, and the western and eastern flanks of the Chiricahua and Dos Cabezas mountains, north to the southern bajada of the Winchester Mountains.”  Above the Rim, the species “occurs from the New Mexico border west to at least Seligman, Yavapai County” (Bezy 2010).   Earless Lizards from the Huachuca and Patagonia mountains were not always assignable to species, partially due to a patternless form that is fairly common in those areas.  Lizards from the Huachuca Mountains that could be assigned to species were identified as Common Earless Lizards, whereas in the Patagonia Mountains, identifiable lizards were always found to be Elegant Earless Lizards.  According to Rorabaugh and Lemos-Espinal (2016), a third form of Earless Lizard (H. approximans) occurs in the Sierra San Luis, Sonora, near the border with Arizona.  It has a short tail (like the Common Earless Lizard) but there is no orange spot on the throat.  This form may occur in the mountains of southeastern Arizona.

In the 100-Mile Circle, the Common Lesser Earless Lizard occurs primarily in semi-desert and Plains grasslands, but also ventures into oak savanna, and a record from “Tombstone” would place it in Chihuahuan desertscrub.  The natural history of this species is poorly studied in Arizona, and due to the taxonomic issues, extrapolating demographic information from other areas is probably unwise; however, Rosenblum et al. (2009) summarized what is known of the species throughout its presumed range, which as they define it includes portions of Arizona east to central Texas, south to Durango, and north to southern South Dakota and southeastern Wyoming.  The following is taken from that publication, as well as Degenhardt et al. (1996), Ballinger et al. (2010), and other sources as cited.

The Common Earless Lizard reaches lengths of about 60 mm SVL and 100 mm TL.  It is active from early March to late November and breeds mostly from May to July. Male and female Common Earless Lizards mature at 44 and 55 mm SVL, respectively. Females lay clutches of 2-7 eggs, and larger females produce larger clutches.  Hatchlings are about 25 mm SVL.  This is a sit-and-wait predator that feeds upon true bugs, grasshoppers, cicada larvae, beetles, butterflies, spiders, ants, and an occasional small lizard (Aspidoscelis and Sceloporus).  This lizard is primarily diurnal, with activity becoming bimodal (mornings and late afternoon) in the heat of summer.  However, some individuals have been found active after dark, as well.  The Common Earless Lizard often avoids extremes of weather and hides at night by retreating to burrows or shuffling into loose sand.  Maximum longevity in the wild is at least five years.  Maturation occurs at about one year of age.  At a study site 2 km west of the Arizona-New Mexico border along the Portal Road in Cochise County, mean home range of males and females were 958 (100-2393, n=19) and 653 (52-1315, n=12) m2, respectively, during 1977-78 (Hulse 1985).  Considerable overlap of male home ranges occurred, suggesting a lack of territoriality. Goldberg and Bursey (1992) examined gastrointestinal parasites of the Common Earless Lizard in Arizona.

This lizard is listed as a species of least concern on the 2017 IUCN Red List.  With a valid Arizona hunting license, 20 Common Earless Lizards can be taken per day or held in possession, alive or dead.  There is no reason to believe the species is declining in Arizona.  In Nebraska, after cattle were removed, grass cover increased substantially and the Common Earless Lizard population in the area declined to near zero (Ballinger et al. 2010).  The species apparently needs open spaces between shrubs and grass clumps, and increasing plant densities may result in declining populations in some circumstances.

Suggested Reading

Axtell, R.W. 2009. Elegant Earless Lizard, Holbrookia elegans Bocourt, 1874. Pages 150-153 in: L.L.C. Jones and R.E. Lovich (editors). Lizards of the American Southwest. Rio Nuevo Press, Tucson, Arizona.

Ballinger, R.E., J.D. Lynch, and G.R. Smith. 2010. Amphibians and Reptiles of Nebraska. Rusty Lizard Press, Oro Valley, Arizona.

Bezy, R.L. 2010. Herpetofauna of the 100-Mile Circle: Elegant Earless Lizard, Holbrookia elegans Bocourt,1874. Sonoran Herpetologist 23:177-180.

Blaine, R.A. 2008. Biogeography of the North American Southwest Sand Lizards. Ph.D. Dissertation. Washington University, Saint Louis, Missouri.

Brennan, T.C., and A.T. Holycross. 2006. A Field Guide to Amphibians and Reptiles in Arizona. Arizona Game and Fish Department, Phoenix.

Degenhardt, W. G., C. W. Painter, and A. H. Price. 1996. Amphibians and Reptiles of New Mexico. University of New Mexico Press.

Goldberg, S. R., and C. R. Bursey. 1992. Gastrointestinal parasites of the Southwestern Earless Lizard, Cophosaurus texanus scitulus, and the Speckled Earless Lizard, Holbrookia maculata approximans (Phrynosomatidae). Journal of the Helminthological Society of Washington 59:230-231.

Hulse, A.C. 1985. Home range size in Holbrookia maculata (Iguanidae) from southeastern Arizona. The Southwestern Naturalist 30:608-610.

Jones, L.L.C. 2010a. Taxonomic turbulence for Holbrookia in southeastern Arizona. Sonoran Herpetologist 23:170-174.

Jones, L.L.C. 2010b. Color patterns of Holbrookia elegans in southeastern Arizona. Sonoran Herpetologist 23:174-177.

Moll, E.O. 2007. Patronyms of the pioneer West XV. Holbrookia maculata Girard, 1851—Common Lesser Earless Lizard. Sonoran Herpetologist 20:26-30.

Rorabaugh, J.C., and J.A. Lemos Espinal. 2016. A Field Guide to the Amphibians and Reptiles of Sonora, Mexico. ECO Herpetological Publishing and Distribution, Rodeo, NM.

Rosenblum, E.B., D. Burkett, and R. Blaine. 2009. Common Earless Lizard, Holbrookia maculata Girard, 1851. Pages 154-157 in: L.L.C. Jones and R.E. Lovich (editors). Lizards of the American Southwest: A Photographic Field Guide. Rio Nuevo Publishers, Tucson, Arizona.

Author: Jim Rorabaugh

 

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