Alligator Lizard Male vs Female

Alligator lizard male vs female differences show up mainly in the head and the tail base. Adult males grow noticeably wider, more triangular jaws than females of the same body length. A close look at the tail base often reveals paired hemipenal bulges in males, a feature females lack.

Genus Elgaria covers the northern alligator lizard, Elgaria coerulea, and the southern alligator lizard, Elgaria multicarinata. Both are native to the West Coast.

Genus Gerrhonotus covers the Texas alligator lizard, Gerrhonotus infernalis. All three belong to family Anguidae.

The species overview at the alligator lizard page covers identification, range, and general biology. This guide goes deeper into male and female differences. It also covers the mating bite and how a gravid female behaves.

Quick Differences Between Male and Female Alligator Lizards

The table below lists the marks keepers and field herpers rely on most. None of these traits shows up on a hatchling or a young juvenile. They become reliable once a lizard reaches adult or near adult size.

Head Width and Jaw Size

Head width is the clearest sign in an adult alligator lizard. A study of the Texas alligator lizard measured 102 wild specimens. It found that male heads grow faster than the rest of the body as the animal matures.

Researchers call this pattern positive allometry.

Female heads, by contrast, keep growing in the same proportion as the body through life. Two lizards of identical total length can look very different around the jaw as a result. A mature male often has a jowly, almost bulldog profile.

A female of the same length keeps a narrower, more streamlined head. This gap is small in juveniles and widens with age. It works far better for sexing an adult than a lizard under a year old.

Hemipenal Bulges and Tail Base Shape

Like most lizards, male alligator lizards carry a pair of hemipenes, the paired copulatory organs. These sit tucked inside the base of the tail. This creates a visible widening just behind the vent, which keepers often describe as two small bulges side by side.

Females lack this structure entirely. Their tail base tapers smoothly and evenly away from the body, with no widening at all. To check this mark, hold the lizard gently and look at the tail just behind the cloaca.

The comparison works best with two lizards side by side. A single animal gives no baseline for what counts as wide or narrow on that individual. This method applies across many lizard families, not just alligator lizards.

Pair it with head width rather than using it alone. Wild alligator lizards also drop their tails readily as a defense. A regrown tail section can look shorter or oddly shaped, and that makes the bulge check less reliable near a regenerated tip.

Body Size and Weight Differences

Total adult size differs mainly by species, not by sex. The southern alligator lizard reaches a body length up to about 5.6 inches, not counting the tail. Its tail adds roughly twice that length again.

The northern alligator lizard runs smaller. Its body measures near 4 inches, with a tail adding about 6 more inches in a full grown adult. The Montana Field Guide gives adults 7 to 10 cm snout to vent and up to 20 cm in total length.

That same guide states the sex difference plainly: males have larger heads than females, with no other size dimorphism. Within a single species, males and females reach similar overall lengths.

Total size is therefore a poor way to guess sex on its own. The ratio of head width to body length matters more than raw length. That ratio, not raw length, is why the head width comparison above works better; full size ranges by species sit on the alligator lizard size page.

Mating Behavior and the Courtship Bite

Alligator lizards mate in spring. Courtship is rough compared to many other lizard species.

The male grips the female by the neck or the back of the head with his jaws. He holds on through copulation, sometimes for an extended period.

This grip can leave a visible scar or scab on the female afterward. A fresh neck wound on a female in spring is usually a mating mark, not an injury from a predator or a cage mate. The wound typically closes within a few weeks.

The peer reviewed study on the Texas alligator lizard found that males carry bite marks far more often than females. The authors tied this to agonistic behavior, meaning fighting between competing males. The courtship grip on the female is a separate, widely reported field observation rather than a finding of that study.

Bite based courtship is common across the Anguidae family. It should never be mistaken for aggression toward keepers. Wild alligator lizards should always be left alone during spring; disturbing a mating pair does not benefit either animal.

Signs of a Gravid Female

A female carrying eggs or developing young shows a swollen, rounded mid body compared to her normal slim taper. The southern alligator lizard lays eggs, and this swelling is most obvious from late spring into early summer. Egg laying itself follows in June or July.

Clutch size runs up to about 20 eggs. Those eggs hatch after roughly 55 days. The northern alligator lizard gives birth to live young instead of laying eggs, but shows the same body swelling through the warmer months first.

Numbers for the northern species come from the Montana Field Guide. Mating runs April to May, gestation lasts about three months, and a single brood of 2 to 15 young, typically 3 to 6, is born in August or September. Females do not breed until 32 to 44 months old, so a swollen mid body on a small female is far more likely to be a full stomach than a brood.

A gravid female of either species tends to move less and bask more as she nears the end of the cycle. She also seeks out cover rather than open ground; full nesting and incubation detail sits on the alligator lizard breeding page.

Both sexes can look heavier after a good feeding season. Mid body swelling reads best as a sign in spring and early summer, when it lines up with the breeding calendar.

Live Birth in the North vs Egg Laying in the South

One striking fact about alligator lizards as a group is that reproduction mode splits by geography, not by sex. The northern alligator lizard ranges from southern British Columbia through northern Idaho, western Montana, and north to central California. It gives birth to live young in summer.

The southern alligator lizard ranges through Washington, Oregon, California, and Baja California. It lays eggs instead of bearing live young. This split is thought to track climate.

Live birth lets a female warm developing embryos by basking and moving. That is an advantage in the cooler, higher elevation parts of the northern range. Egg laying suits the milder, longer warm season found through more of the southern range, where buried eggs simply incubate in soil warmth.

The Texas alligator lizard belongs to a different genus, Gerrhonotus, and the Mexican alligator lizards belong to Abronia. Both are covered on their own pages, each with its own range and reproduction details.

Law and Welfare: Collecting and Keeping Wild Alligator Lizards

Alligator lizards are wild native animals. The rules for collecting or keeping one are set state by state, not by a single national law.

Anyone considering picking one up should check their own state wildlife agency first. A rule legal in one state can be illegal in the next.

California, home to most of the alligator lizard’s range, prohibits capturing, killing, injuring, possessing, or transporting any native reptile without department authorization. Even a legally possessed pregnant female collected from the wild has strings attached. Her offspring must transfer to another qualified person or institution within 45 days of birth or hatching.

The authorization itself is in Section 5.60 of the same code. It lists both the northern and southern alligator lizard as takeable under a sportfishing license, with a bag and possession limit of two. Take is by hand or hand tools only, never by breaking apart rocks or logs, and never inside state parks, national parks, or ecological reserves.

Washington is stricter. Its Department of Fish and Wildlife permits collection of the northern alligator lizard only under a Scientific Collection Permit for research or education. A lizard picked up in a Washington garden has no legal route to a home terrarium.

Rules like these protect wild populations that depend on animals staying where they are. They exist for conservation, not because alligator lizards make poor pets. The safest, most responsible move for anyone who finds a wild alligator lizard is to leave it exactly where it is.

Care information for a legally kept alligator lizard is covered on the alligator lizard care page.

General legal background for reptile keeping sits on the site’s main care hub. Nobody should try to work around a state’s collection limits or possession rules. When in doubt, the animal stays in the wild and the question goes straight to the state wildlife agency.

Frequently Asked Questions

How can you tell a male alligator lizard from a female without handling it?

Head width is the best mark from a distance. A mature male’s jaw looks visibly broader and more triangular than a female’s of the same body length, especially viewed from directly above.

Do female alligator lizards get bigger than males?

No consistent size gap between the sexes has been documented in alligator lizards. Total length tracks species and age far more than sex. Head shape remains the better guide.

What does a mating bite on an alligator lizard look like?

It usually appears as a scab or fresh wound on the female’s neck or the back of her head in spring, left by the male’s jaw grip during courtship. It typically heals within a few weeks and is not a sign of illness or a fight with a cage mate.

Can you tell alligator lizard sex from color or pattern?

Not reliably. Alligator lizard color and banding pattern varies mostly by species, age, and the individual animal, not by sex. Some other lizard species show sex based color, but alligator lizards do not follow that rule.

Is it legal to catch a wild alligator lizard and keep it as a pet?

It depends entirely on the state. California allows two alligator lizards per person under a sportfishing license, taken by hand outside parks and reserves, while Washington permits collection only for research or education. Check the state wildlife agency before assuming it is allowed.

How old does an alligator lizard need to be before you can sex it?

Head width and hemipenal bulges are unreliable in hatchlings and young juveniles. Wait until the lizard reaches adult or near adult size. The traits separating alligator lizard male vs female individuals grow more pronounced with age.