Skinks: Scincidae

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SKINKS: Scincidae

PREHENSILE-TAILED SKINK (Corucia zebrata): SPECIES ACCOUNTS
BROAD-HEADED SKINK (Eumeces laticeps):SPECIES ACCOUNTS
SANDFISH (Scincus scincus): SPECIES ACCOUNTS

PHYSICAL CHARACTERISTICS

With about 1,400 species, the skinks come in many different sizes, shapes, and colors, but they do share a few features. Members of this family have large head scales, body scales that have bony plates underneath them, and a roof of the mouth that is made of two, flat bony plates instead of one, as humans and other animals have. The bony plate is called a palate (PAL-iht).

The skinks are divided into four major groups or subfamilies. The seventeen species in two of the subfamilies are legless, while the hundreds of species in the other two subfamilies have legs. A few species, known as comb-eared skinks, have noticeable scales that stick out near the ear opening on the side of the head.

Skinks, most of which have smooth scales, may be either small or large. The smallest adults grow to just 0.9 inches (2.3 centimeters) long from the tip of the head to the vent, which is a slit-like opening on the belly side of the lizard. If the lizard has legs, the vent is located between them. The longest skink is 20 times larger than the smallest, reaching 19.3 inches (49 centimeters) from the snout to the vent.

Color varies among the skinks, but many have rather drab, brownish bodies. The males of numerous species, however, often develop colorful heads during the breeding season. In many species, juveniles have bright blue, red, or yellow tails, which are believed to help them escape attacks by predators (PREH-dih-ters), or animals that hunt them for food. The predator snaps at the colored tail, which the young skink drops before running away. Adults are also able to lose their tails and survive.

GEOGRAPHIC RANGE

They live on land almost around the world, except for many islands in the ocean and very cold places, such as Antarctica and high up in mountains.

HABITAT

Many skinks live mostly underground, hidden beneath logs, rocks, or among piles of leaves and twigs. Many of those that live underground dig their own burrows. The night skink builds a large tunnel system, which is marked by a large pile of sand near the most-used entrance. This lizard often has to share its tunnels with other animals that drop in day and night to sleep or to escape the weather or a predator. Some other species of skinks are good climbers and spend time on tree branches and tree trunks. While most of them live on land, some do not mind taking a dip in the water. Several species, like Gray's water skink and the eastern water skink, spend part of their time in ponds or streams.

DIET

Most species enjoy insects. Some are rather picky eaters and prefer to eat one kind of insect. Some of the underground-living, legless skinks, for example, eat mostly termites. A few species of skinks, including bobtails and sandfish, mix some flowers and grains into their insect diets, and others, such as the prehensile-tailed skink, are strictly vegetarian.

BEHAVIOR AND REPRODUCTION

Many of the skinks are active during the day, spending much of their days looking for food and sunbathing, or basking. Some species, such as the well-named night skink, only come out in the darkness. Most skinks are nervous animals that take cover if they feel even slightly threatened. For this reason, people often have only short glimpses of them before the lizards dart into a pile of brush or under a log. If an attacker is able to catch a skink before it can take cover, many of the species drop the tail, which continues to wiggle for several minutes. This draws the attention of the attacker and allows the lizard to escape. When the coast is clear, some skinks will return to whatever is left of the tail and eat it themselves. The tail grows back, but it is typically not as long as the original tail. The bobtail is unusual among skinks in that it does not immediately flee when a predator arrives. Instead, this slow-moving lizard stands its ground, opens wide its mouth, and flaps its bright blue tongue.

Skinks do not pant as other lizards do, and scientists think that their extra palate is the reason why. Other lizards pant to cool off. The air they draw in and breathe out when panting cools off the blood in blood vessels along the roof of the mouth. The extra palate in skinks, however, may cover up the blood vessels so much that the air cannot get close enough to cool the blood, making panting useless. Instead, these lizards beat the heat by resting in a shady spot or cool underground burrow.

During mating season, males of many species will fight, biting one another on the head, neck, and tail until one gives up and leaves. In some species, male-female pairs remain together from year to year. Females of some species lay eggs, but other females give birth to baby skinks. Strangely, two species of skinks from Australia— Bougainville's skink and the three-toed skink—do both. Among skinks, the number of young varies from species to species, with some females having only one or two eggs or young at a time, and others having up to sixty-seven. Although most females make their own individual nests, mothers in a few species lay their eggs together in one big nest. Whether they nest together or alone, parents of many species provide some care to their eggs and young.

SKINKS AND PEOPLE

Some people keep the larger species as pets, but this family's biggest contribution to people comes when they are left in the wild. Skinks eat many insects, including those considered to be pest species.

IN THE BLINK OF AN EYE

When a person blinks, the upper lid slides down over the eye. When a lizard blinks its eye, only the lower eyelid moves. Skinks have a number of different lower eyelids, including some see-through types. These look rather like contact lenses that slide up and cover the eye. In some skinks, their lower eyelids always stay shut. These eyelids have a clear area or are completely clear, so the skinks can see even though their eyes are always closed.

CONSERVATION STATUS

According to the World Conservation Union (IUCN), three species are Extinct, which means they are no longer in existence. Twenty-six others are listed as Critically Endangered, Endangered, or Vulnerable, which means they face an extremely high, very high, or high risk of extinction in the wild. Five are Near Threatened and are likely to qualify for a threatened category in the near future; and seven are Data Deficient, which means scientists need more information before they can make a judgment about the threat of extinction. The U.S. Fish and Wildlife Service lists three skinks as Threatened or likely to become endangered in the foreseeable future: the Round Island, bluetail mole, and sand skinks.

PREHENSILE-TAILED SKINK (Corucia zebrata): SPECIES ACCOUNTS

Physical characteristics: Large in size, the prehensile-tailed skink can grow to 30 inches (76 centimeters) in length from head to tail. A prehensile (pri-HEN-sihl) tail is one adapted for grasping like a monkey's tail. It has a muscular tail, a large head, and clawed legs on a thick grayish to brownish green body. Its underside is lighter green. The males usually are a bit thinner than the females and have a slightly bigger head.

Geographic range: They live east of New Guinea on the Solomon Islands.

Habitat: Prehensile-tailed skinks spend much of their days hidden among the leaves high up in trees, especially the strangler fig tree, or in holes in tree trunks or branches. They become active at night when they look for food.

Diet: Unlike the vast majority of other skinks, this species is a strict vegetarian and particularly likes leaves and flowers it finds in the trees.

Behavior and reproduction: Active at night, this skink usually spends its time slowly and calmly climbing on tree branches. When it feels threatened, it will hiss and even bite if necessary. Females usually give birth to just one baby at a time.

Prehensile-tailed skinks and people: Native people eat this skink. Other people often see them in zoos or other lizard exhibits, and some keep them as pets.

Conservation status: Although the prehensile-tailed skink is not listed as endangered or threatened, it faces a serious threat from overcollection by the pet trade. ∎

BROAD-HEADED SKINK (Eumeces laticeps):SPECIES ACCOUNTS

Physical characteristics: Also known as the greater five-lined skink, the broad-headed skink is a brown to brownish gray lizard with darker, although often faint, stripes running from its wide head to the tail. The head of males turns reddish during the mating season. Adults grow to 9.8 inches (25 centimeters) in length.

Geographic range: Broad-headed skinks live mainly in the southeastern quarter of the United States.

Habitat: An excellent climber, the broad-headed skink lives in a variety of areas, including swamps, forests, and even near people, in everything from farm buildings to trash-filled city lots.

Diet: They spend much of their time looking for insects and other invertebrates (in-VER-teh-brehts), which are animals without backbones, to eat.

Behavior and reproduction: When broad-headed skinks feel threatened, which is quite often for these shy lizards, they quickly dart away. During the breeding season, males jump at and bite each other on the head, neck, or tail. Before long, one of the two fighting lizards will surrender and leave, and the other is left to mate with a female. Females lay six to ten eggs at a time under leaves or in some other hiding spot and stay with them until they hatch.

Broad-headed skinks and people: Most people see these lizards from a distance as they climb along fences or walk along tree branches. They are very shy and run when approached, so people rarely get a close look.

Conservation status: This species is not considered endangered or threatened. ∎

SANDFISH (Scincus scincus): SPECIES ACCOUNTS

Physical characteristics: Sandfish are light brown lizards with slightly darker brown bands down the back. They have a pointed snout and thin legs ending in fringed toes that help them run on shifting sands. Adult sandfish usually reach about 8 inches (20.3 centimeters) in length, including the short tail.

Geographic range: Sandfish can be found in northern Africa, Iraq, Iran, Israel, and Jordan.

Habitat: Although they live in deserts, sandfish tend to live near a moister area, such as an oasis, which has loose sand and many plants.

Diet: Sandfish eat insects, scorpions, and other invertebrates, and an occasional small lizard. They move their arms and legs in a motion that allows them to "swim" through and just below the surface of the sand. From this position, they snatch unsuspecting insects walking on the ground above them. They also eat flowers and grains.

Behavior and reproduction: Active during the day, this lizard is best known for the way it escapes attackers. When it feels threatened, the sandfish dives headfirst into the sandy ground and swims below the surface of the sand. After a June breeding season, female sandfish lay about six eggs.

Sandfish and people: Native people hunt sandfish for their meat. At one time, people believed that dead dried sandfish could cure various diseases.

Conservation status: This species is not considered endangered or threatened. ∎

FOR MORE INFORMATION

Books

Badger, D. Lizards: A Natural History of Some Uncommon Creatures— Extraordinary Chameleons, Iguanas, Geckos, and More. Stillwater, MN: Voyageur Press, 2002.

Greer, Allen E. The Biology and Evolution of Australian Lizards. Chipping Norton, Australia: Surrey Beatty and Sons, 1989.

Hutchinson, M. N. "Family Scincidae." In Fauna of Australia. Vol. 2A, Amphibia and Reptilia, edited by C. J. Gasby, C. J. Ross, and P. L. Beesly. Canberra: Australian Biological and Environmental Survey, 1993.

Mattison, Chris. Lizards of the World. New York, NY: Facts on File, 1989.

Pianka, E. R. Ecology and Natural History of Desert Lizards: Analyses of the Ecological Niche and Community Structure. Princeton, NJ: Princeton University Press, 1986.

Pianka, E. R., and L. J. Vitt. Lizards: Windows to the Evolution of Diversity. Berkeley: University of California Press, 2003.

Storr, G. M., L. A. Smith, and R. E. Johnstone. Lizards of Western Australia. Vol. 1, Skinks. Perth: Western Australian Museum, 1999.

Periodicals

"Black Market Animals: The Stealing, Smuggling and Selling of Endangered Species as Pets is a $10 Billion Illegal Business Worldwide." Current Events, a Weekly Reader publication (April 14, 1997): 2A.

Geschickter, Jacqueline. "Say Ahhhh!" National Geographic World (November 2000): 31.

Thompson, Sharon. "Attention, Lizard Parents!" National Geographic World (May 2002): 6.