This lizard species lives only in Southern Texas and coastal northeastern Mexico, as far south as Guanajuato. You won't find these unique lizards anywhere else (Behler and King 1979).

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (20,000-200,000 square km (about 8000-80,000 square miles)) The range extends from southern Texas south along northeastern coastal Mexico to Veracruz; inland in southern Texas, this lizard occurs northward to the southern edge of the Edwards Plateau (Axtell 1983).

These are small lizards that have no external ear opening, and have a tail that is longer than their head and body. They range from 11-14.1cm (4 1/2 to 5 9/16 in.) in length. Maximum head and body length is 7 cm (2 3/8 in.), so the tail can be about as long as 7.6 cm (3 in.). However, these lizards often lose part of their tails to predators, and can grow a new one, so tail length is not a good characteristic for identification. Unlike the other species of earless lizards (all genus Holbrookia), they have tiny keels on their dorsal scales. Their scales are granular, meaning they do not over lap and very small. The males and females have different and unique markings that are useful in telling them apart. The males have large black bands on either side of their stomach. The females are lighter in color and lack the black bands. Most of the males and females have irregular patterns of brown and grey stripes and blotches that cover their back and head (Conant 1958; Behler and King 1979).

Length: 14 cm

• Terrestrial

Keeled earless lizards are endemic to barrier beaches and sand dumes. Some prefer to live closer to the coast than others, but all of them prefer to live in dry sandy places. There are unique adaptions that Keeled earless lizards have, that allows them to live on sandy habitats. For a small lizard, they have long legs and feet for getting around at relatively fast speeds on the sand. Their blotched coloring gives them the advantage of camouflage. Burrowing into sand to hide and regulate their temperature is made easier by the shape of their head. The sand dunes on Padre Island on the Texas coast is one place where there are many keeled earless lizards. (Behler and King 1979; Bechtel 1995)

Terrestrial Biomes: desert or dune

Comments: Habitats include coastal dunes, barrier islands, and other sandy areas (Axtell 1983). Although it occurs well inland, this species is most abundant on coastal dunes, were it seeks shelter in the burrows of small mammals or crabs (Bartlett and Bartlett 1999). Eggs are laid in soil/underground.

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.

Keeled earless lizards are insectivorous, which means that they hunt down and eat insects. It is unknown which insects these lizards prefer. They seem to eat whatever they can get ahold of. They are diurnal, so they are only active and forage for food during the day and not at night. It may get too cold for them at night, as they are cold blooded animals (Cochran and Goin 1970; Behler and King 1979).

Primary Diet: carnivore (Insectivore )

Comments: Eats insects and probably other small invertebrates.

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

Estimated Number of Occurrences: 81 - 300

Comments: The species is represented by more than 100 extant populations (R. Axtell, pers. comm., 1997). Dixon (2000) mapped the presence of this lizard in 28 counties in Texas. Axtell (1983) mapped 12 collection sites in Mexico.

10,000 - 1,000,000 individuals

Comments: Total adult population size is unknown but likely exceeds 10,000. These lizards can be common in suitable habitat (Bartlett and Bartlett 1999).

Keeled earless lizards have femoral pores on each hind leg. There are on average 14-15, but they can have as many as 20. The femoral glands open into the dermal follicles. It is not known what they do exactly, but it is agreed that they are used for reproduction. Since they are diurnal, they have fairly good vision. They rely on their vision for courtship. They have very noticable sexual dimorphism. The male and female coloring is very important. The female coloring is controlled by hormones. When they change colors, it is a signal to males that they are ready to mate. Like most lizards, Keeled earless lizards are oviparous. Females have unique coloring when they are carrying eggs. They tend to be orange or pink. The female digs a burrow in which to deposit her eggs. After hatching, their young on average are 3.8 cm (1 1/2") long and have the same blotchy coloring as the adults (Cochran and Goin 1970; Conant 1958; Bechtel 1995; Cogger and Zweifel 1998).

Lays clutches of 2-7 eggs, March-September (most May-August) (Judd and Ross 1978).

Keeled earless lizards are endemic to southern Texas and coastal Mexico, which means that they are found no where else. So if anything happens to their habitat they could become endangered or even worse, extinct.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N3 - Vulnerable

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Occurs in southern Texas and northeastern coastal Mexico, south to Veracruz; stable or perhaps slightly declining; no major threats; potential threats include modification and destruction of habitat for coastal development and conversion of habitat to sugar cane fields, but uses areas immediately surrounding hotels, and the amount of area being converted for sugar cane is very limited; habitat fragmentation due to road construction is a potential concern.

Intrinsic Vulnerability: Moderately vulnerable

Global Short Term Trend: Relatively stable to decline of 30%

Comments: Populations in coastal regions and inland appear to be relatively stable (R. Axtell, pers. comm., 1997). Texas populations are doing well, particularly on coastal islands and dune fields; population status in Mexico is unknown, but the species occurs on barrier islands south of the Rio Grande in the state of Tamaulipas (J. Karges, pers. comm., 1997).

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

Comments: Probably the species declined somewhat during the historical period (A. Price, pers. comm., 1997).

Degree of Threat: CD

Comments: No major threats are known to exist (R. Axtell, pers. comm., 1997). Potential threats include modification and destruction of habitat for coastal development and conversion of habitat to sugar cane fields. It is unclear how much of a threat is posed by development or conversion to sugar cane fields; these lizards have been observed utilizing areas immediately surrounding hotels, and the amount of area being converted for sugar cane is very limited. A great deal of pasture habitat is still available (A. Price, pers. comm., 1997). Threats may include the conversion of habitat for agriculture and exotic grasslands, and habitat fragmentation due to road construction (R. Savage, pers. comm., 1997). A potential threat is off-road vehicles or heavy beach traffic (J. Karges, pers. comm., 1997).

Biological Research Needs: Map available habitat and determine effects of development, habitat conversion, habitat fragmentation, and beach traffic.

Global Protection: Many to very many (13 to >40) occurrences appropriately protected and managed

Comments: Keeled earless lizards occur on most of the Lower Rio Grande National Wildlife Refuge, Padre Island National Seashore, Mustang Island State Park, Aransas National Wildlife Refuge, and Matagorda Island State Park (J. Karges, pers. comm., 1997).

Unknown

These lizards may benefit humans by helping control insect populations (Behler and King 1979).