How to recognize Uta

As a research scientist using Uta (Side-Blotched Lizards) as my primary study species for over two decades, I have recorded data on well over 10,000 individual lizards in that time. As such, I have developed a decent eye at recognizing Uta. Add to that the fact that I have identified nearly every Uta on iNaturalist, and I think I can provide relevant insight into how to recognize and distinguish these lizards from other lizards. Below are my tips for recognizing Uta in order of ease of use and efficacy.

1) the blotch. As the common name suggests, members of the genus Uta have an irregularly bordered spot on their side, just behind the front legs. However, in juveniles, young females, and in some populations, the blotch may be hard to see or may be absent entirely. I estimate that 5-10% of some populations lack a blotch. Moreover, depending on the photo presented, the blotch may be obscured or hard to see, so additional traits are used to identify these lizards.

2) the eye stripes. The single best way to identify a Side-Blotched Lizard is by looking just behind the eye at the stripes. The stripes in Uta follow a pattern of dark-light-dark with the light stripe being centered behind the eye and progressing at least several eye widths along the head. This white stripe is about the same width (height from top to bottom) as the dark stripes above and below. In Sceloporus the white stripe is wider (taller) and expands as it runs down the head making the white look expansive. Moreover, in Sceloporus the lower dark stripe is often curved upwards slightly whereas in Uta this lower dark stripe is parallel to the white stripe above. In Urosaurus the white stripe is narrower and often appears pinched between the two dark stripes. However, there is some variation in the width of this white stripe in both Sceloporus and Urosaurus, but rarely is the width of these stripes anything other than even in Uta.

3) the upper lip. In Uta there are stripes on the throat that continue up onto the upper lip giving the upper lip a pattern of alternating dark-light spots along its length. In Sceloporus the upper lip is often more solid white, and in Urosaurus the upper lip is nearly always solid white with the white being a taller stripe along its length than in Uta

4) the top of the head. In Uta the top of the head lacks any obvious pattern and is usually a solid color that is slightly different from that of the body. I usually describe the head as the color of milk chocolate while the body can be more gray or dark chocolate. Thus, even blurry pictures from above can sometimes be identified based on the head color difference inUta. In Sceloporus and Urosaurus there is often a visible fine pattern of reticulations on the head.

5) the dorsal scales. On the back (dorsum) of Uta, in front of the tail, the scales are typically small, granular, and uniform. However, in hotter, drier areas the scales tend to be larger and more keeled. This is probably most noticeable in the area just south of the Salton Sea. Regardless, the dorsal scales in Uta differ in size and keeling on the back relative to the tail where the scales get larger and more strongly keeled, especially in males. In Sceloporus the dorsal scales are not nearly as granular and are nearly always noticeable pointed along their posterior (back) margin. This is more true in S. occidentalis than in S. graciosus where the scales are not nearly as large. Regardless, the scales on the backs of Sceloporus are more similar in size to the scales atop the tail than in Uta. In Urosaurus there are either one or two sets of mid-dorsal scales that are enlarged relative to the smaller granular scales on either size, so the heterogeneity of dorsal scale size is a good trait to recognize those. In addition, Urosaurus often has visible dorso-lateral folds that run along either side of the dorsum, but those can be hard to see.

6) the skin around the neck. Around the neck the skin in Uta is loose and creates folds, whereas in Sceloporus the skin along the sides of the neck is tighter and lacks the folded appearance, especially when they turn their heads. Urosaurus can have the loose skin around the neck like Uta, so this is really best for distinguishing Uta from Sceloporus.

7) the gular fold and throat color. If the underside of the throat is visible, both Uta and Urosaurus will have a fold across the back of the throat that goes continually across, whereas in Sceloporus the fold may occur at the corners of the throat, but is not continuous. However, I have on occasion seen pictures of Sceloporus where a fold of skin appear continuous, so this can be hard to distinguish, but in conjunction with the throat/lip striping (#3 above) these can be recognized from this angle along. Uta have a large color patch that covers nearly the entire throat while Urosaurus tend to have a small color patch in the center of the throat and not at the back of the throat as in Uta.

8) the shape of the head. This can be very subtle, but Uta have a different head shape than Sceloporus. Namely, the head and snout are slightly longer in Uta than in Sceloporus and the snout in Uta is slightly upturned whereas in Sceloporus the snout has a more flat appearance. Thus, it is possible to distinguish these from silhouette alone, but again this is very subtle.

9) ventral coloration. In Uta, females sometimes get an orange blush along the anterior portion of the belly, but this is never defined patches as in Sceloporus or Urosaurus. In those two genera, the belly often has elongate patches of color that stretch from forelimb to hindlimb on either side with a white area in-between. In Uta, this area is devoid of color.

10) the dorsal pattern. There are subtle differences in the pattern of Uta despite a wide range of dorsal patterns in nature. Any dorsal dark spots are slightly asymmetrical in Uta whereas they are more two rows of regular spots in Sceloporus. Moreover, the top of the base of the tail in Uta usually has a pattern of irregular light flecks. These are only really visible at the base of the tail and the asymmetric dominates otherwise, though tails can be unpatterned as well.

Notice what I did NOT use as recognition traits...general coloration or dorsal pattern (other than asymmetic nature of the dark spots), tail color, or limb proportions. These traits might be useful, but they are often regionally specific with vast differences in color and pattern between the subspecies and even among populations of the same species. For example, U. stansburiana elegans often have blue tails whereas U. s. nevadensis tend to have more orange tails, similar to Urosaurus. Uta, Sceloporus, and Urosaurus all can have very striped morphs or individuals in a population, so paying attention to scalation takes precedence.

Hopefully you find these tips helpful. —Pete Zani

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Posted on March 6, 2024 04:20 PM by petezani