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Coleonyx brevisTexas Banded Gecko

By Erin Sargent

Geographic Range

Texas banded geckos are found in Texas and from parts of Southern New Mexico, USA to Northeastern Mexico. In Texas, they are found mainly in the Trans-Pecos region in the southwest and also in western parts of the South Texas thorn scrub. (Hollister, 1998)

Habitat

Coleonyx brevis is found in dry, rocky areas. It inhabits burrows or dens, usually beneath flat rocks or in crevices. When active, C. brevis usually remains on the substrate, rarely climbing on rocks or branches. (Hollister, 1998)

Physical Description

Adults on average are 10.16-12.07 cm with a snout-vent length of 53.8 mm (Dial & Fitzpatrick 1981). Coleonyx brevis displays sexual dimorphism: females are larger than males. This gecko has a slender body with a tail of equal length. Its head is large and it has large eyes with vertical pupils and moveable eyelids. The toes are very slender and there are no pads. The dorsal side of C. brevis is covered with granular scales. The ventral side is slightly translucent. They are brownish in color and have alternating cross bands of brown and pale yellow. They can be recognized by the dark and light colored blotches and spots on their bodies, which become more prevalent with age (University of Texas 1998). (Dial and Fitzpatrick, 1981; University of Texas College of Natural Sciences and the Texas Memorial Museum, 1998)

  • Sexual Dimorphism
  • female larger
  • Range mass
    1.9 to 3.3 g
    0.07 to 0.12 oz
  • Average mass
    2.60 g
    0.09 oz
  • Range length
    10.1 to 12.1 cm
    3.98 to 4.76 in

Development

When the eggs hatch, the young C. brevis look like small adults. Soon after they are born, the young reach sexual maturity. (Dial and Fitzpatrick, 1981)

Reproduction

Texas banded geckos are oviparous, their reproductive season is from March-April. Average clutch size is two eggs, and approximately 2-3 clutches are produced each breeding season.

Fertilization is internal. Follicles appear as yellow masses in the oviducts, which change to white at ovulation. Yolk is deposited for 30-32 days after the initiation of vitellogenisis (the formation of the yolk of an egg). About ten days after the yolk is deposited, oviposition takes place. The female C. brevis lays her eggs in an underground burrow or den.

The eggs hatch about two months after being layed, and at this point the young C. brevis are similar in appearance to the adult C. brevis, only smaller in size. Soon after they are born, the young reach sexual maturity. (Dial and Fitzpatrick, 1981)

  • Breeding season
    March-April
  • Average gestation period
    42 days

Yolk is deposited for 30-32 days after the initiation of vitellogenisis (the formation of the yolk of an egg). About ten days after the yolk is deposited, oviposition takes place. The female C. brevis lays her eggs in an underground burrow or den.

During vitellogenisis, the female uses energy stored as lipids in carcass, fat body (corpora adiposa), and tail tissue. The utilization of lipid reserves allows the maximization of offspring size and quality by increasing mass and energy content of hatchlings. By the time oviposition takes place, all lipid reserves are depleted. (Dial and Fitzpatrick, 1981)

  • Parental Investment
  • pre-hatching/birth
    • provisioning
      • female

Behavior

When approached by a predator, Coleonyx brevis has a very interesting way of escape. When it realizes that it has become a target for a predator, C. brevis becomes very defensive. It stops and turns so that its head is away from and its tail is towards the approaching predator. It then remains motionless except for raising and lowering its tail at a 90 degree angle. At this point, the gecko will either flee when the predator is approximately 4 cm away, or it will distract the predator by detaching its tail. The predator attacks the autotomized tail while the gecko escapes. A new tail is regenerated in about 4-5 weeks. Females have significantly more regenerated tails and the frequency of regenerated tails increases with body size. This may be because larger individuals have a greater chance of being detected by predators, and in this case, female C. brevis are larger than male C. brevis.

Coleonyx brevis is generally not very aggressive. Males and females are often found under the same cover items, and they have low levels of aggression. When handled, C. brevis does not bite, but it does emit a squeak in order to signal territory or breeding.

Coleonyx brevis is nocturnal, and generally remains under cover during daylight hours. Its nocturnal lifestyle is successful due to the adaptation of a eurythermic (adaptable to a wide range of temperatures) strategy. During the day, rock covers are responsible for a large portion of body heat. This thermoregulation helps to maximize the efficiency of digestion, which in turn regulates metabolic activity. Coleonyx brevis is capable of consistently maintaining body temperatures above 30 degrees celsius. Their tolerance for the wide range of air temperatures has enabled C. brevis to successfully exploit a nocturnal lifestyle.

In Western Texas and Northern Mexico, the coexistence of C. brevis and C. reticulatus is the only known area of sympatry of an atuberculate and a tuberculate Coleonyx. (1. Dial, 1978; 2. Dial, 1978)

Communication and Perception

Coleonyx brevis emits a squeak in order to signal territory or breeding. During foraging and feeding, C. brevis relies on visual cues, which can be reinforced by chemical cues before an attack occurs. This strategy is imortant because it prevents the attack of harmful organisms and also helps in finding more prey in a short foraging time. (1. Dial, 1978)

Food Habits

Coleonyx brevis is mainly insectivorous and has a very wide variety of prey. It is nocturnal, so has a relatively short foraging time. They begin feeding at sundown and end about 3-4 hours later, when temperatures become too low for foraging. For this reason, C. brevis does not have a very specialized diet. It tends to eat most prey encountered in order to get enough to survive. The main prey of C. brevis is termites and cicadellids, while they also feed on spiders, solpugids, crickets, and moths. The type of prey suggests that this species is an active forager. They search for prey in several microhabitats and also dig or turn items in order to find food.

When foraging, the body is in an elevated position and the tail is raised to the height of the body and is laterally curved. There are also frequent tongue flicks to the substrate and surrounding objects. When prey is detected, either from motion or chemoreception, C. brevis approaches it with a series of short runs. It then arks its head over the prey and strikes downward. After biting the prey, the gecko usually shakes it vigorously 3-4 times. (1. Dial, 1978)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods

Predation

Coleonyx brevis is preyed upon by many mammal and bird species, and also by many species of snakes that focus primarily on lizards, such as Hypsiglena torquata, Salvadora deserticola, and Masticophis flagellum. (1. Dial, 1978)

Ecosystem Roles

Texas banded geckos eat many invertebrates, and are prey to many vertebrates.

Economic Importance for Humans: Positive

Coleonyx brevis positively benifits humans by eating and controlling insect pests such as termites and cicadellids.

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

Coleonyx brevis do not have any significant adverse affect on humans.

Conservation Status

Contributors

Matthew Wund (editor), University of Michigan-Ann Arbor.

Erin Sargent (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Nearctic

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

acoustic

uses sound to communicate

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

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).

native range

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

nocturnal

active during the night

oviparous

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

seasonal breeding

breeding is confined to a particular season

sexual

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

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

visual

uses sight to communicate

References

1. Dial, B. 1978. Aspects of Behavioral Ecology of Two Chihuahuan Desert Geckos. Journal of Herpetology, 12: 209-216.

2. Dial, B. 1978. The Thermal Ecology of Two Sympatric Nocturnal Coleonyx. Herpetologica, 34: 194-201.

Dial, B., L. Fitzpatrick. 1981. The Energetic Costs of Tail Autotomy to Reproduction in the Lizard Coleonyx brevis. Oecologia, 51: 310-317.

Hollister, J. 1998. "Geckos of the Southwestern United States" (On-line). Accessed March 16, 2001 at http://www.kingsnake.com/gecko/c_brevis.html.

University of Texas College of Natural Sciences and the Texas Memorial Museum, 1998. "Herps of Texas-Lizards" (On-line). Accessed March 19, 2001 at http://www.zo.utexas.edu/research/txherps/lizards/coleonyx.brevis.html.

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