Distribution of Elgaria Lizards in Reservoir park

Elgaria is a small genus of anguid lizards that are limited to the West Coast of North America. Commonly known as 'alligator lizard's they are characterized by their slender, snake like appearance with small, stubby legs and a tail that usually takes up half of their body. Alligator lizards normally inhabit coastal areas though some subspecies tend to tolerate higher elevations, especially in the Cascade and Sierra Ranges (https://californiaherps.com/lizards/pages/e.c.palmeri.html). There are two species recorded from the Bay Area: The southern alligator lizard (E. multicarinata) and the northern alligator lizard (E. coerulea). They often occupy similar habitats and are hard to distinguish in the field as juveniles.

I came across a small alligator lizard skittering under a rock near my house in Reservoir park in Jan 2025. I had not expected seeing an alligator lizard in that small patch of native habitat as the park was isolated from the main park (Glen Park) by O'Shaughnessy Blvd. The lizard was too fast for me to catch. Therefore I was not able to determine the species. I came back in May of 2025 and recorded a couple more alligator lizards from the same area. This time, they were all adults and easily identifiable as southerns (E. multicarinata).

A little later in July, I started exploring the opposite side of the park that was mostly characterized by long grass with scattered rock formation and sagebrush. This area received significantly more moisture as moisture loving banana slugs (Ariolimax) and California Slender Salamanders (Batrachoseps attenuatus) were frequently observed.

This map of the park illustrates the distribution of both E. multicarinata and E. coerulea. "Assumed zone of sympatry" suggests that the two species may coexist in the microhabitat but the frequency of reptiles occuring there is unknown.

I flipped a rock and a larger lizard skittered away. The patterning of the lizard was high in grey and black tones which may have indicated E. coerulea.

I came back in September and over the course of three weeks, I flipped four different Northern Alligator Lizards. The habitat (north-western facing slope) mostly consisted of grasses and mosses which aligns with my theory that northerns, who primarily favor those conditions will predominante this area. I have yet to find a southern alligator lizard in this location, although the climate already suggests against finding one. However   when I came back to this site several time between November - March I have found no lizards.

Trends: E. multicarinata tend to favor drier and rocky climates with ample access to scrub. E. coerulea tends to favor more shaded grasslands with sparse rocks and lichens. However it is difficult to guess if both species occur in a given area without considering other factors.

Photo of Reservoir Park (Southern side) taken during the summer . It shows the rocky, dry conditions that are usually correlated with high E. multicarinata density. This picture corresponds with the right side of the map above

Photo of Reservoir park (Northeastern) taken during the spring. It shows the grasslands that are preferred by E. coerulea and corresponds to the left side of the map above.

Drone view of Mount Davidson: a park where both species occur and are almost equally distributed. This photo, taken in Feb 2026, captures both the rocky conditions favored by E. multicarinata and the scrub-transition grassland preferred by E. coerulea