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Defensive Behavior

The Australian spiny-tailed gecko (Diplodactylus williamsi) displays the most unique defense of all lizards. When this grey, inconspicuous gecko suddenly swings opens its jaws, it displays a vivid, dark purple mouth outlined in bright blue. It may also emit a high-pitched squeak and, if attacked, shoots a thick, gooey liquid from spiny knobs on its tail, covering its enemy with a sticky weblike substance.

Although geckos in general show aggressive displays such as arching the back, stiffening the limbs to increase their height, and wagging their tails, they are relatively nonaggressive, fighting among themselves only when defending a homesite or feeding territory from a determined invader. Although small geckos will attack a foe many times their size if threatened. The Australian barking gecko (Underwoodisaurus milii) barks and lunges even at humans. Very few species of gecko are strong enough to break the human skin, and none are poisonous.

See also Reptiles.



Bustard, Robert. Australian Lizards. Sydney: Collins, 1970.

Cogger, Harold G., David Kirshner, and Richard Zweifel. Encyclopedia of Reptiles and Amphibians. 2nd ed. San Diego, CA: Academic Press, 1998.

Conant, Roger, et al. A Field Guide to Reptiles & Amphibians of Eastern & Central North America (Peterson Field Guide Series). Boston: Houghton Mifflin, 1998


Petren, Kenneth, and Ted J. Case. "Gecko Power Play in the Pacific." Natural History (September 1994): 52-60.

Petren, Kenneth, Douglas T. Bolger, and Ted J. Case. "Mechanisms in the Competitive Success of an Invading Sexual Gecko over an Asexual Native." Science 259 (January 15 1993): 354-57.

Marie L. Thompson


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—Able to reproduce without male fertilization.


—Containing calcium carbonate.


—The cavity into which the intestinal, genital, and urinary tracts open in vertebrates such as fish, reptiles, birds, and some primitive mammals.


—Refers to animals that are mainly active in the daylight hours.


—Regulate and control body temperature.

Additional topics

Science EncyclopediaScience & Philosophy: Gastrula to Glow dischargeGeckos - Distribution And Habitat, Physiology And Reproduction, Defensive Behavior