Alligator Lizard Size: How Big They Get

Alligator lizard size is described two ways. Snout vent length (SVL) measures the body from nose to vent and skips the tail. Total length adds the tail back in.

The tail on an intact alligator lizard runs close to twice the SVL. A small difference in body length can turn into a much larger difference in total length.

That matters for field identification. Two lizards with similar body size can look very different once the tail is counted.

Southern alligator lizard size

The southern alligator lizard is the larger and more visible of the two California species. Washington Department of Fish and Wildlife gives an adult SVL of about 5.6 inches (14 cm). The San Diego Zoo Wildlife Alliance fact sheet lists adults at 2.5 to 7 inches (6.4 to 17.8 cm) SVL.

The tail runs up to double the body length. A large adult with an intact tail can therefore reach 16 inches or more nose to tail tip.

The two sources differ on typical total length. The zoo fact sheet puts most animals at up to about 12 inches overall.

That reflects how many wild adults carry a shortened, regrown tail. Only a lizard that has never lost its tail reaches the top of the range.

That makes it a genuinely large lizard by North American standards. It runs longer than most anoles, fence lizards, or skinks sharing its range.

Adults weigh a little over an ounce. The AnAge longevity database records an adult mass of 31.5 grams. The San Diego Zoo Wildlife Alliance fact sheet gives adult weight as over 30 grams (1.1 oz).

Sexual maturity arrives at about 31 grams. Hatchlings weigh just 0.55 grams at 34 mm (1.3 in) SVL.

Body mass shifts with sex, season, and reproductive status. A gravid female carrying 5 to 20 eggs weighs noticeably more than a male of the same length. Treat the 30 gram figure as a typical adult, not a ceiling.

Northern alligator lizard size

The northern alligator lizard is smaller and more secretive than its southern relative. Adults measure 2.8 to 3.9 inches (7 to 10 cm) SVL. The Montana Field Guide gives a maximum total length of 7.9 inches (20 cm).

Newborns are 2 to 3 cm SVL and about 7.5 cm (3 in) overall. This species gives birth to live young rather than laying eggs, usually 3 to 6 per litter and up to 15. Females mature at 32 to 44 months, so growth to adult size is slow.

Its smaller size and duller coloring make it easy to overlook in leaf litter and under logs. That likely explains reports calling it “less common,” when it may simply be harder to spot.

Northern alligator lizards range further north and higher in elevation than southern alligator lizards. That includes cooler parts of the Pacific Northwest and interior mountain ranges.

Idaho Fish and Game lists the species as a native, regularly occurring resident. Its state rank is S3 (vulnerable) even though its global rank is G5 (stable). That reflects a smaller, edge of range population rather than a rare species overall.

Texas and Madrean alligator lizard size

The Texas alligator lizard (Gerrhonotus infernalis) is the largest of the group and the largest lizard native to Texas. Texas A&M Natural Resources Institute researchers put its maximum at about 2 feet in total length.

That is more than double the northern species. Readers wanting the wider picture can check our types of lizards guide.

It is also the most prolific. Females lay one or two clutches of 15 to 30 eggs a year. A large female carries considerable extra mass in spring.

The Madrean alligator lizard (Elgaria kingii) of Arizona and New Mexico gets far less research attention. Field guides describe it as intermediate in size between the northern and southern species. No wildlife agency, university, or museum source with a measured length was found for this guide.

The Arizona Game and Fish Department tracks it as a Tier 2 Species of Greatest Conservation Need without publishing size data. For a related pet trade species of similar build, see the Mexican alligator lizard.

Alligator lizard size table

Use this table as a starting point, not a final word. Body condition, sex, age, and season all shift where a given lizard falls in its species’ range.

Alligator lizard growth rate

Hatchling southern alligator lizards emerge at 34 mm (1.3 in) SVL and 0.55 grams. A broad tan, reddish, yellow, or gray stripe runs down the back, and it darkens and patterns more clearly as they mature.

They reach sexual maturity at about 18 months and roughly 31 grams. A hatchling multiplies its body weight more than 50 times in a year and a half.

Northern alligator lizards grow more slowly. Newborns are 2 to 3 cm SVL, and females take 32 to 44 months to mature.

No source publishes a month by month growth curve for either species. Treat any care sheet with an exact inches per month figure with caution.

One thing is well documented across lizards in general. Growth slows sharply once sexual maturity is reached. Alligator lizards, like most temperate reptiles, grow faster in warm months and largely stop growing during winter dormancy.

Longevity data offers an indirect clue to growth pace. The AnAge database records a captive southern alligator lizard at 9.8 years, while the San Diego Zoo Wildlife Alliance fact sheet estimates 10 to 15 years. More on the topic is on our lizard lifespan guide.

A lizard that lives a decade or more is not reaching full adult length in its first year. Maturity at 18 months marks the point where growth slows. The largest 7 inch SVL adults are several years old.

Tail regeneration and size

Like many lizards, alligator lizards can drop their tail when a predator grabs it. The defense is covered further on our alligator lizard bite and defense page.

This defense is called autotomy. The detached tail keeps twitching after separation, which distracts the predator while the lizard escapes.

A regrown tail rarely matches the original in length, shape, or color. It is usually shorter and stubbier than the tail it replaced.

The tail makes up as much as two thirds of a southern alligator lizard’s total length. In the northern species it is about half. Tail loss and regrowth can swing total length a lot, with no change in body condition or age.

That is one reason wildlife agencies favor SVL over total length when comparing lizards. SVL is unaffected by tail history, while total length is not.

Law and welfare: alligator lizards are wild animals

Alligator lizards are native wildlife, not a species bred for the pet trade. Collecting and keeping rules vary by state. In California, taking any native reptile, including both alligator lizard species, requires a current California Sport Fishing License.

Both species carry a daily bag and possession limit of two animals, under California Code of Regulations, Title 14, Section 5.60. Reptiles may not be taken from ecological reserves, state parks, or national parks and monuments. Breaking apart rocks, logs, or other natural shelter to find reptiles is prohibited under the same regulation.

In Idaho, the northern alligator lizard is classified as Protected Nongame wildlife under the Idaho Administrative Procedures Act. That status signals conservation concern, not a free pass to collect. Anyone considering keeping one should check current Idaho Fish and Game rules first.

Arizona gives the Madrean alligator lizard no special legal protection but ranks it a Tier 2 Species of Greatest Conservation Need. Reptile collection there falls under state hunting license rules.

Texas sets no species specific bag limit for the Texas alligator lizard, and Texas A&M researchers worry about pet trade collection. Confirm current rules with Texas Parks and Wildlife directly rather than a general guide.

There is also a welfare case for leaving wild alligator lizards where they are. They are not an established captive husbandry species the way leopard geckos or bearded dragons are. Far less published guidance exists on their temperature, humidity, and dietary needs in a tank.

A wild caught alligator lizard also carries a higher parasite risk than a captive bred lizard. The topic comes up in our alligator lizard diet guide.

Removing breeding age adults from a local population can affect that population more than it would for a widespread, abundant species. If you find one in your yard, watch it and leave it alone. At most, gently move it away from a driveway or a pet’s reach.

Frequently Asked Questions

How big do alligator lizards get?

Southern alligator lizards reach 5.6 to 7 inches snout to vent and 12 to 16 inches or more overall with a full tail. Northern alligator lizards stay under 3.9 inches snout to vent and 7.9 inches overall. The Texas alligator lizard can approach 2 feet.

What is an alligator lizard full grown size compared to a garter snake?

A full grown southern alligator lizard’s total length overlaps with a small to medium garter snake. The lizard has four legs, external ear openings, and a stiff, armored body from bony scales called osteoderms. The two are easy to tell apart despite the similar length.

How much does an alligator lizard weigh?

An adult southern alligator lizard weighs a little over an ounce, about 30 to 32 grams. Hatchlings weigh about half a gram. Weight climbs in gravid females and drops after a long winter dormancy.

Do alligator lizards keep growing their whole life?

Growth slows sharply after sexual maturity. The southern species matures at about 18 months and the northern species at 32 to 44 months. Adults add length slowly for a few more years, and no source publishes a precise growth curve for wild animals.

Can I legally catch and keep a wild alligator lizard?

Rules vary by state. California allows limited collection with a sport fishing license and a daily bag and possession limit of two. Idaho lists the northern alligator lizard as Protected Nongame wildlife, so check your state wildlife agency before collecting one.

Does tail loss change an alligator lizard’s size?

Yes, in terms of total length. The tail can make up two thirds of a southern alligator lizard’s total length. A dropped tail regrows shorter and often differently shaped, so snout vent length is the more reliable measurement for comparing individuals.