Welcome to The STEM Sessions Podcast. I am your host, Jarl Cody.
A couple of years ago, while working in my backyard, my peripheral vision caught something out of place on the sliding screen door. It was a lizard, approximately the length of a sharpie, with brown, yellow, and copper banded scales. I run across lots of lizards while hiking, but I had never seen one of this type before. I snapped a few photos with my phone, then returned to work.
After finishing the gardening, I grabbed a refreshing beverage, sat down with my laptop, and began researching the lizard I had seen. After a few minutes, it was clear I had seen an alligator lizard. Narrowing down the species and subspecies was the next step, and based on geography and appearance, I’m confident my resident alligator lizards are the Southern Alligator lizards, specifically the San Diego Alligator lizard.
Since then, I’ve seen several more. My backyard field journal has 13 alligator lizard sightings on my property since early 2019. That’s not to say I’ve seen 13 individuals. First, I don’t believe my yard is large enough for such a population, and second, I’m confident about half of those sightings are of the same lizard based on coloration and other identifying characteristics. That said, I think three or four individuals is a reasonable assumption.
And I sincerely apologize for the pronunciation of the scientific names…
This is The STEM Sessions Podcast – Episode 14. Backyard Ecology: The Alligator Lizard
With a wide, round body, short legs, and a broad head, alligator lizards do bear a vague resemblance to their namesake cousins. However, they were given their honorary name because their back and belly scales are reinforced by bone, as are those of alligators.
Alligators lizards are “new world” lizards, meaning they reside in the Americas, but not Europe, Asia, or Africa. Their 43 recognized species are found in the family Anguidae. Because I live in California, my research quickly narrowed the list to the species in the genus Elgaria, which live west of the Rocky Mountains in North America. These are commonly called the western alligator lizards.
Of the seven species within the genus Elgaria, three (E. cedrosensis, E. paucicarinata, and E. valezquezi) are exclusive to Mexico. One (E. kingii) is found in the deserts of the U.S Southwest and northwest Mexico. And three (E. multicarinata, E. coerulea, and E. panamintina) are found along the Pacific coast and adjacent inland areas. My research narrowed further, focusing on these three coastal species.
E. multicarinata or the Southern Alligator lizard is found along the Pacific Coast from Baja California in the south to Washington in the north. It has five recognized subspecies:
E. m. ignava – San Martin Alligator Lizard
E. m. multicarinata – the California alligator lizard
E. m. nana – Los Coronados Alligator Lizard
E. m. scincicauda – the Oregon alligator lizard
E. m. webbii – the San Diego alligator lizard
E. coerulea or the Northern Alligator lizard is found from central California in the south to British Columbia in the north. It also lives further inland, with populations in eastern Washington, Idaho, western Montana, and the Sierra Nevada range in California. There are four recognized subspecies of the Northern Alligator lizard:
E. c. coerulea – the San Francisco alligator lizard
E. c. palmeri – the Sierra alligator lizard
E. c. principis – the Northwestern alligator lizard
E. c. shastensis – the Shasta alligator lizard
E. panamintina or the Panamint Alligator lizard is found only in east central California; in the lands of and around Death Valley National Park. While the habitats of the northern and southern alligators overlap with each other, the habitat of the panamint alligator lizard is isolated from the other two. There are no recognized subspecies, and it is likely more closely related to E. kingii, the species residing in Arizona and New Mexico than the other two west coast species.
The three species have equivalent body sizes, with a snout to vent length ranging from three to seven inch range. Their tail can be twice as long as their body, allowing large adults to reach over a foot in total length. Some literature describes the tail of the alligator lizard as being nearly prehensile, which I’m assuming means the tail can be used to bluntly hold on to objects like grass or branches, yet is not capable of dexterously manipulating those objects.
The tail also holds the fabled lizard ability to be dropped in self-defense, hopefully tricking predators to pay attention to the wiggling tail while the lizard escapes. I’ve seen this happen to at least one of my backyard alligator lizards. While an admirable defense mechanism, droping and regenerating one’s tail does have disadvantages. It’s very energy intensive, for one. The lizard must consume significantly more calories, or other biological functions may be stunted. The regenerated tail is also not as good as the original.
Instead of a hard skeleton of vertebrae, the regenerated tail is supported by a long tube cartilage, and instead of short muscle fibers, long ones span the length. Both differences, suggest the new appendage lacks the flexibility and prehensile abilities of the original. It also often lacks the original pigment. In the case of my alligator lizards, instead of being multi-colored, the new tail is monochromatic, making it very easy to determine which lizards have dropped and regenerated their tails.
Speaking of pigment, coloration of the alligator lizard includes all shades of browns, greens, yellows, oranges, whites, greys, blacks, and even reds. While both the Southern and Northern alligator lizard have stripes of alternating colors, usually about one scale thick, the southern is often more flamboyantly colored than its Northern cousin. And the Panamint is quite different with its wider alternating stripes.
While Southern and Northern alligator lizards share overall colorations, they have distinct eye colors. The southern species has yellow or light-colored eyes, while the northern species has darker eyes. The coloration of the belly scales is also a tell, with the southern having dark marks or stripes running lengthwise down the belly in the center of the scales, and the northern having dark stripes between the scales.
Alligator lizards exhibit subtle sexual dimorphism or distinct physical differences between sexes. A classic example of sexual dimorphism is a male bird having bright, colorful plumage while the female of the species is colored in earth tones. In alligator lizards, you need to compare the heads. Males have larger, broader, somewhat triangular heads. Females have narrower, less tapered heads. Beyond that, without observing the sex organs, there really is no difference between the sexes.
The western alligator lizards are a long-lived animal relative to their size, with lifespans of 10-15 years not uncommon in the wild. Sexual maturity is reached at 18 months. The southern species mates in the spring with eggs hatching in late summer and early fall. The female can lay two clutches of eggs a year, and she guards them until they hatch. In warmer climates, they can breed year-round. The Northern alligator lizard also breeds in the spring months, but surprisingly, the females give birth to live young. Typical litters have four or fives babies, but litters with up to 15 babies have been observed. Juvenile alligator lizards look quite different from their parents. They are very thin and have smooth, shiny skin; more closely resembling skinks or salamanders.
Diets of alligator lizards are very similar from species to species. You have the typical lizard diet of insects, spiders, snails, and grubs, of course. But alligator lizards, especially the larger individuals, have been observed preying on other lizards, amphibians, bird eggs, and even small mammals. Attribution for their expanded diet goes to their larger body size and a unique aspect of their behavior – they’re active in cool weather.
In general, lizards are obligate thermo-regulators meaning they need warm air or the warmth of direct sunlight to maintain their body temperature. But alligator lizards, particularly the Southern species is often active in cool temperatures. One field study observed activity in temperatures as low as 52 F (11 C). This means alligator lizards are not only diurnal (active during the day), but have the ability to be crepuscular (active during dawn and dusk). This greatly expands the time and conditions available to them for hunting, and gives them a distinct advantage against cold-blooded prey.
The alligator lizard is an impressive little critter, and it was a fun taxonomical investigation discovering the species (Southern) and subspecies (San Diego) of my local population. I’m happy to share my property with them, and will do what I can to keep my yard attractive and hospitable to them.
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This episode was researched, written, and produced by me, Jarl Cody.
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Until the next one, stay curious.
“Identifying Alligator Lizards in California”
“Southern Alligator Lizard”
“Southern Alligator Lizard”
“Elgaria multicarinata (BLAINVILLE, 1835)”
Jennifer C. Ast
Arizona State University College of Liberal Arts and Sciences
“Regenerated lizard tails are different from originals, researchers discover.”