Slender Glass Lizard (Ophisaurus attenuatus)

Legal status in U.S.: None Legal Status in WI: Endangered Length: 18-36 inches

For information on Wisconsin's turtles and lizards including an identification key and more, order your copy of Turtles & Lizards of Wisconsin.

The descriptive name for this slender creature is appropriate. When caught this reptile will energetically twist and jump trying to escape, and in the process may shed its tail which can break into many pieces, hence the name slender glass lizard. Also called the glass snake or legless lizard, the slender glass lizard has a pointed snout, narrow head, and a long cylindrical body with no limbs. Because of its snake-like appearance the slender glass lizard is often mistaken for a snake. The slender glass lizard differs from a true snake in that it has eyelids and external ear openings, which snakes lack. In Wisconsin the average total length is 18-24 inches (45-61 cm), although an animal may reach up to 36 inches (91 cm), two-thirds of which may be tail.

The slender glass lizard's body is tan, brown or bronze. A dark brown to black stripe runs along the middle of the back from head to tail. Two additional dark brown to black stripes run immediately above the lateral groove and four narrow stripes run below the groove. The side of the  head and neck have scattered brown markings. The underside is white to light yellow.

Slender glass lizards reach sexual maturity in two or three years and usually mate in May. Females are oviparous, which means they lay eggs that will hatch outside the body. Eggs are laid in mid-June to early July, with a typical clutch size of six to seventeen eggs, twelve being the average. A variety of places are used for nest chambers, including abandoned mammal dens, hollow stumps, and spaces under rocks and logs.

The female does not provide protection for the eggs from predators, and may even eat them herself. However, she does stay with the clutch. The suspected advantage of this is the maintenance of higher humidity in the nest chamber to prevent the eggs from drying out, and turning of the eggs to aid in their development. The young hatch in August and are similar in appearance to the adults except for being smaller. Hatchlings will enter hibernation with a snout to vent length of 2-3 inches (5.5-7.6 cm). This is about the same size as when they came out of the egg.

Glass lizards in Wisconsin will reappear from hibernation in May and be active into September. During this time the slender glass lizard will eat just about anything that it can get into its mouth. The main source of food is beetles, but crickets, grasshoppers, snails, slugs, spiders, mice, worms, and eggs of reptiles and birds are alternate food sources. The search for food can take the glass lizard both above and below the ground. In sandy or loose soil the slender glass lizard is a good burrower. It apparently spends much time underground and is therefore seen less often than would be expected. However, predators do see and eat the glass lizard. Some of its predators include the broad-winged hawk, red-tailed hawk, raccoon, skunk and various snakes. Sometimes the glass lizard can escape predation by shedding its tail. The tail, once shed, will actively wiggle and writhe about. The predator is normally drawn to this portion due to the active movement. Hopefully the tail will distract the predator long enough for the lizard to escape. The glass lizard is only able to shed and regenerate the tail once in its lifetime. When the new tail grows back, it will be smaller than the original. Glass lizards can live to be about 8 or 9 years old.

Slender glass lizards are diurnal, which means they are most active during the day. They seem to prefer a temperature range between 68 and 80 degrees Fahrenheit and are extremely active on sunny days at temperatures around 74 to 77 degrees Fahrenheit. In summer, the insects that provide their main food source tend to be inactive during the heat of the day, so the glass lizards do most of their foraging between 3:00 and 7:30 p.m.

The slender glass lizard's mode of locomotion is somewhat unique. They use their sides to push against debris or vegetation in a side to side motion to propel themselves forward. Slender glass lizards are unable to move across smooth surfaces such as a black top or concrete road, because they cannot use their belly scales for locomotion. A snake can use its belly scales to help push itself forward, making locomotion on a flat surface possible. When a slender glass lizard comes to a smooth surface, usually a road, it may push itself onto the pavement until it cannot push any more. With nothing to push against, the animal is often stranded and caught in a very dangerous position. If it does not get off the pavement, a car may hit it, or a predator can easily see and capture it.

The fragmentation of habitat with roads contributes to mortality rates and limits the availability of habitat for glass lizards.

Slender glass lizards are found in oak savannas, sand prairies, old fields, and pine barrens in central Wisconsin. The western sub species occurs from western Indiana to southern Wisconsin and southern South Dakota; south to Louisiana and the southern tip of Texas.

History and Current Status in WISCONSIN

Historically, slender glass lizards were likely quite abundant on the vast open prairie that once dominated the Wisconsin sandcountry. Over time their range has been reduced by human inhabitation and land use practices such as urban and agricultural development, and Christmas tree and other pine tree plantations that have compromised presettlement habitats.

Pesticides may also contribute to the decline of this species. The accumulation of toxins from the insects that are eaten may affect reproduction and survival. A University of Wisconsin-Milwaukee study found the highest densities of lizards in areas that had not been sprayed with pesticides.

The slender glass lizard was placed on the Wisconsin Endangered and Threatened Species List in 1979 due to its reduced range and numbers. Since 1985, glass lizards have been found in Waushara, Marquette, Green Lake, Adams, Juneau, Monroe, Columbia, Sauk, and LaCrosse counties.

Slender glass lizards are encouraged by maintaining areas of sand prairie, savanna, and grass through the use of prescribed brush removal, fires and mowing. Maintenance of grassy roadside with these methods rather than chemical treatments is also a good way to provide habitat.

You can help the slender glass lizard by supporting the Bureau of Endangered Resources and other conservation organizations that purchase and manage land for the protection of rare habitats and their inhabitants. If we hope to keep this unique member of the reptile community in Wisconsin we must set aside and manage enough habitat so that the glass lizard can recover and persist.

In addition, you can help by letting us know where and when you see slender glass lizards and other reptiles and amphibians (known collectively as herptiles). The Wisconsin Herptile Atlas Project [exit DNR], run by the Milwaukee Museum [exit DNR] and supported by the Bureau of Endangered Resources, is attempting to document the presence of all herptiles state-wide to provide a current picture of species distribution and status. If you are interested in becoming involved, please write to one of the following addresses:

Wisconsin Department of Natural Resources
Bureau of Endangered Resources
P.O. Box 7921
Madison, Wisconsin 53707

or

The Milwaukee Museum [exit DNR]
800 W. Wells Street
Milwaukee, Wisconsin 53233

Excerpt from THE ENDANGERED AND THREATENED VERTEBRATE SPECIES OF WISCONSIN

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Status: State Endangered (1979).

Occurrence: Isolated meta-population found in central sands and into western Wisconsin.

Aid to ID: Long, limbless, snake-like lizard. Usually 18-28 inches (45-70cm) in length with pointed snout and narrow head. Tan, brown, or bronze back with dark brown to black stripe down the middle. Also two dark stripes above and four narrow stripes below the lateral groove. Brown markings on head and neck. Underside white to light yellow. Approximately 2/3's of total length is tail. May snap off tail if captured. Grows back shorter and darker.

Habitat: Oak savannas, open oak woods, dry prairies, and dry-mesic grasslands including old ag fields, all associated with sandy soil.

Food Habits: Carnivorous/insectivorous. Eat grasshoppers, crickets, beetles, spiders, small mice, snails, and the eggs of reptiles and ground-nesting birds. Forage above ground and underground in burrows.

Natural History:

Active: May to September, mostly diurnally. Prefer temperature of 68^o-80^oF. Rarely seen. Good burrowers. Fall activity primarily by hatchlings. Very active when restrained, and very rigid compared to a snake. Tail is extremely fragile.
Hibernation: September to May in burrows.
Reproduction: Oviparous. Mate in May. Four to 18 eggs laid in June to mid-July in burrows, hollow stumps, spaces under logs and rocks and under clumps of grass. Females stay with clutch until hatching in August. Sexually mature in 2-3 years. Females don't breed every year.

Management Considerations: Decline primarily due to habitat destruction either by natural succession to forests or by conversion to agricultural fields and pine plantations. Additional threats include highway mortality and accumulation of toxins due to insect spraying. Species encouraged by maintaining areas of sand prairie, savannas, and grasses with use of brush removal, fire, and mowing. Burning suggested during pre- and postseasonal activity. This species has a wide habitat range and structural diversity may be a key to its survival.

Information compiled from publications ER-526 92REV and ER-091.

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