Earless lizard

Earless lizard

Earless lizards are two genera of small lizards native to the semi-arid and grassland habitats of the southwestern United States and Mexico. The genus Cophosaurus and the genus Holbrookia are both characterized by having no external ear openings, presumably to prevent sand from entering the body as they dig.

Distinctive features

An average size earless lizard vary from three to seven inches long. Male tend to be larger than females. In identification, the male contains two heavy black strips ahead of its hind legs. Females differ in that they have a black stripe behind each thigh. An indication of pregnancy consists of pink throat and flanks.^[1] The earless lizard has two throat folds and with large eyes and twenty-seven or fewer femoral pores. They are also described as having shorter forelegs compared to their hind legs and also rather long toes. ^[2] Although they are called earless lizards, they are still completely capable of hearing, however; their ears do not have an external opening. This feature is useful when they burrow underground without dirtying their ears. ^[3]

Behavior

In terms of its wildlife range, earless lizards are most active during daylight. Hibernates during the winter and fall. When approached by a predator it uses its defense mechanism by raising and wagging its tail. To claim its territory, a combination of lateral body compression, head bobbing, and push-ups are done. Earless lizards are capable of homeostasis to a certain extent. As a feedback to temperature change, it undergoes mechanisms of conduction, convection, and radiation. In cooler temps it responds to raise its body temperature by turning its body broadside to the sun for the radiation.^[4] It can also align its body to the sun to receive reduced rays to maintain its core body temperature. In warmer temperatures, it decreases its body temperature by conduction, such as going in the shade under a tree or even on the tree to avoid elevated heat temperature from the ground. ^[5]

Diet

The diet of earless lizards consists of arthropods such as: butterflies, moths, beetles, grasshoppers, insects, and spiders. ^[6]

Defense mechanism

Earless lizards have a peculiar defense mechanism which is coupled to their cold-blooded life style. They have a small opening on the top of their head called a 'blood sinus' which helps the lizard to gain heat quickly during the daytime. However, the blood can also be channelized to the eyes of the lizard when a predator looms close by, efficiently spitting ^[7] the blood onto the predator giving it enough time to escape.

Reproduction

Mating takes place in spring. Earless lizards lay their eggs between March and August, from there it takes about fifty days in order for them to hatch. They tend to lay 1-3 clutches of eggs. Clutch sizes range from 1-10 eggs. When hatched, the lizard in length are two inches long.

Threats

There is no major threat that have been identified in the US or Mexico. However, habitat loss and degradation would result in an agricultural decline in the species.^[8]

Geographic range

Earless lizards are found from the southwestern and central United States, in the states of Texas, Arizona, New Mexico, Utah, Colorado, Kansas, Oklahoma, and as far north as Nebraska, South Dakota, and Wyoming. They are also found in Mexico, in the states of Sonora, Chihuahua, Coahuila, Sinaloa, Durango, Zacatecas, San Luis Potosí, Nuevo León, Tamaulipas and Veracruz.

Gallery

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  Greater earless lizard
• 
  Earless Lizard in the White Sands National Monument
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  Lesser earless lizard
• 
  Greater earless lizard

References

External links

• Genus Holbrookia at The Reptile Database
• Genus Cophosaurus at The Reptile Database
• Yahooligans! Animals: Greater Earless Lizard & Lesser Earless Lizard