The Uta Project's Journal

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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Looking for a roadtrip? Looking for things to keep an eye out for? Or just looking for ways to help contribute to scientific research? Then read on.

I am sometimes asked, 'how can I help?' This is an important, but difficult question to answer. Below are some project ideas that I have developed that attempt to harness the power of the iNaturalist observer community. Feel free to contribute observations that help our understanding of Side-Blotched Lizards using the ideas below.

A few caveats. As always, be sure you respect private property rights whereever you observer and do not catch or collect animals unless you have permission to do so. If you observe on private property it is probably best to obscure your coordinates and to seek permission before posting.

1) Seasonal activity of Side-Blotched Lizards. Uta are small generalist lizards that are often active on what I call the 'shoulders' of the season. That is, they are often active very early in the season or very late. As such, observations at times of the year that seem less optimal are sometimes hard to come by. This is because researchers at an academic institution might not be able to get out to observe these lizards early in the spring or later in the fall due to other commitments, such as teaching.

Any observations that you add from September through March each year, regardless of where they occur, are likely to be valuable additions to our understanding, especially as activity profiles of species are altered by ongoing climate change. Recently I have begun using remote camera traps on timelapse setting at crevices I know to be places where lizards overwinter to collect data on winter activity. Moreover, I had the opportunity to spend time in Big Bend National Park a few winters ago and found Uta active nearly every week of the year.

So, even if you think it's not good weather for lizards, as long as it is sunny and above 50 °F (10 °C) there are usually Side-Blotched Lizards out basking. Look for them along south-facing washes, at the base of boulder on the sunny side, or places that are going to get good exposure to the sun all winter long, especially if there is a known population in that area. Over time we should be able to amass a dataset of activity times and places in different seasons and times of day that will give us a good perspective on these little lizard.

2) Mating behavior. Squamate reptiles have paired penile organs (called hemipenes) they store in the base of their tails. This is one way to distinguish males from females (males have a bulge in the base of their tail while females have a more even split). I did a lab experiment once where I tried to determine if males have a 'handedness' for their use of left vs. right hemipene. However, I didn't have enough observations of that in the lab to detect any difference. Enter iNaturalist where people sometimes post pictures of copulating lizards. I am amassing a dataset of copulating Uta observations in hopes of one day having enough data to tell if hemipene preference is random or lateralized (is there a preference). So, any pictures you contribute of copulating Uta are part of my database and are most welcomed.

3) Sub-specific contact zones. There are a number of species and subspecies of Uta that are most easily described based on geographic range. That's because the genetics of these animals is still poorly understood. The last taxonomic revision of the genus was attempted back in the early 1970's and I've helped several colleagues collect tissues for DNA analyses over the years even though that's never been my main focus. However, recently this question has become more interesting and important as I've sampled some of the areas that are genetic contact zones between different subspecies of the main species of Uta (U. stansburiana). Part of what I've tried to do is collect good quality photographs of animals to go along with tissue samples so as to link the eventual genetic lineages with visual cues for distinguishing these lineages...no easy task I've discovered. Hence, any observations you make in those contact zones are especially valuable as additional information as to the visual differences between genetic lineages. So where are these contact zones? Based on past research and my own observations (most of which are already added to iNat) the main contact zones are described below.

Uta stansburiana elegans—U. s. nevadensis. Uta stansburiana elegans occurs throughout the Mojave Desert and gives way to Uta stansburiana nevadensis as that desert transitions into the Basin and Range to the north. This contact zone is best studied in the Owens Valley of California and seems to have a break point somewhere around Bishop, CA. Uta stansburiana elegans comes up the valley and Uta stansburiana nevadensis crosses Montgomery Pass in Nevada to come down the upper reaches of the valley. Between an area from Lone Pine, CA north to just north of Bishop, CA, I can't tell the two subspecies apart visually. Hence any observations in the Alabama Hills or in the vicinity of Independence, Big Pine, or Bishop are quite informative even if they are vague with respect to subspecific identity (I usually just call these Uta stansburiana on iNat). However, this zone of contact appears to repeat east of the White Mountains and again along the Extraterrestrial Highway from Crystal Springs to Tonopah. Visually, it looks like Uta stansburiana elegans reaches north as far as Stonewall Pass on Hwy 95 and also appears to cross the low pass between the Inyo and White Mountains into the valley around Silver Peak, but doesn't quite reach as far north as Tonopah, so any observations in these areas are likely in the contact zone.

Uta stansburiana elegans—U. s. uniformis. Uta stansburiana elegans appears to follow the Colorado River up as far as the Grand Canyon before giving way to Uta stansburiana uniformis up on the Colorado Plateau. Visually, the animals in Grand Canyon National Park all appear to be intermediate between these two subspecies making the park itself the contact zone. However, it could be that elegans penetrates along the low elevations with uniformis restricted to the higher elevations, so any observations between Hurricane, UT and Page, AZ are possibly in the contact zone.

Uta stansburiana elegans—U. s. stejnegeri. Two of the better clades of Uta stansburiana appear to be the western (elegans) and eastern stejnegeri forms. While the other contact zones may represent recent post-glacial expansion, this one seems to be an older, deeper genetic split with the Cochise Filter Barrier slowing gene flow between the subspecies. Uta stansburiana elegans more obviously occurs west of the Tucson area and anywhere SW of the Mogollon Rim, but east of the Mescal Mountains things start to get interesting visually. Along the Gila River east of the Needles Eye Wilderness to the AZ-NM border appears to be part of the contact zone between these two subspecies. Usually the barrier is somewhere around the Chiricahua Mountains, but recent work in this area makes me think that Uta stansburiana stejnegeri may actually extend down the Gila River as far as the Mescal Mountains. Hence, any observations in the eastern third of AZ are valuable. However, one way I'm using to tell these apart is the striping in front of and above the blotch. So, photos here that show the blotch clearly (especially the front and top edges) are the most valuable contributions.

Uta stansburiana elegans—U. s. stansburiana. This is one of the contact zones I am less certain about. As one drives along I-15 from St. George toward Cedar City one passes through a narrow area through which Ash Creek drains off part of the Bonneville Basin to the north. This area seems to be a barrier to gene flow that gave rise to Uta stansburiana stansburiana that occurs throughout the Bonneville Basin. However, along the north-south running valleys northwest of the Pine Valley Mountains are areas where the Mojave gives way to the Bonneville Basin. In there somewhere is a contact zone between these two subspecies, though I am not certain where or how extensive the contact zone is, so any observations along the UT-NV border from St. George to Ely are valuable additions. I hope to sample here in coming years, so I should be able to narrow down the zones of interest someday.

Uta stansburiana elegans—U. s. taylori. This is another of the contact zones I am very uncertain about. More specifically, I am not even sure that Uta stansburiana taylori is a thing based on my reading of the original description. Past researchers who did recognize this subspecies placed it as occurring on several of the islands in the Gulf of California (Isla Angel de la Guarda, Tiburón) as well as along the coast in Sonora, Mexico, but there is little understanding of where it might occur or come into contact with elegans to the north.

Some of the contact zone above are easy to get to and would make for great road trips through the deserts of the southwestern U.S. My personal strategy would be to sample every 20 km or so and to try to get good pictures of the dorsal and lateral patterns as these are going to have the most information visually. If you want additional suggestions about where to look, feel free to message me.
—Pete Zani

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As part of the The Uta project, each week I will summarize the observations from that past week and select an observation to highlight as observation of the week.

2024

22 May, 2024

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Click here for observations of the week 2024 archive

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As part of the The Uta project, each week I will summarize the observations from that past week and select an observation to highlight as observation of the week. This is the inaugural such post.

During the first full week of March, 2024, there were 211 observations of Uta added to iNaturalist that achieved research grade. Of these, 140 observations were made during this week. All 140 of these were of Uta stansburiana and came from three subspecies. Most observations were of Uta stansburiana elegans with a few from U. s. stejnegeri and U. s. uniformis. This abundance of the Western Side-bliotched Lizard subspecies is not a surprise as their range encompasses nearly all of California, western Arizona, and southern Nevada where urban centers of Los Angeles, San Diego, Phoenix, Tucson, and Las Vegas help inflate the number of observations for this species. One thing I'm noticing is that males are starting to get their more intense spring breeding coloration. For example, here, here and here are nicely colored males observed this week (shared by @acleverpearl, @laradrizd, and @bill-blauvelt, respectively). This involves more intense colors such as orange on the throat that males use for communicating with other lizards. Meanwhile, females are starting to show the characteristic morphology associated with being gravid. For example, here, here, and here are females (shared by @debaraj, @quandary, and @sphilbin, respectively) I would predict are with enlarged follicles of their first reproductive event of the year. The cycle in these lizards takes about 28 days this time of year and progresses from through follicle enlargement to yolking and eventual shelling prior to egg laying. The subtle curvature of the abdomen just in front of the hind legs as well as the height of the body (see this observation by @sphilbin), which expands as the follicles develop is what I use to gauge their stage in the cycle, but physical palpation is a much better way to assess this as each phase feels slightly different. Mating and fertilization usually takes place sometime during the late enlargement or yolking phase, but I have not yet see any observations of mating yet.

Rather, this week's observation of the week is of this colorful male shared by @little_swift. The male is in full breeding colors with the intense blue tail and dorsal color characteristic of this subspecies. What's more, it shows off one of the regional color variants of this species with the orange eyeshadow. The orange over the eye like this really only occurs in a region between about Joshua Tree National Park and San Diego. Not every lizard shows this look and I estimate it only occurs in maybe 5-10% of the population, but it sure is a pretty look for this species. Another reason I selected this observation for highlighting this week is the male is doing a nice display that includes gular extension in which the under side of the throat is extended and enlarged. Males will combine this with head bobs as part of their communication with other Side-blotched Lizards.

I would like to thank everyone who shared observations this past week; keep it up. If you would like to receive future notifications from this project, feel free to become a member of The Uta project.

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In the past two weeks there were nearly 500 observations of Uta. Most of those (~300) were from southern California, which is continuing to give insight into the timing of reproduction in this the Western Side-blotched Lizard (Uta stansburiana elegans in particular). But other sub-species are starting to show up such as Nevada Side-blotched Lizards (U.s.nevadensis) and Eastern Side-blotched Lizards (U.s.stejnegeri) and Plateau Side-blotched Lizards (U.s.uniformis).

Good candidates for lizard of the week were these two or three colorful males (by @somebees, @vlmanning, @naturaltwenty, @bill-blauvelt, and @tmills), or this observation (by @zeevng) of what appears to be a colorful male and two females under the same cover object, but instead I went with this copulating pair (by @naturephotosuze)....the first observation of the year of mating Side-blotched Lizards. Hopefully the first of many. This observation, or somewhere around it, were the 50,000th Uta added to iNaturalist, which is another reason to celebrate it.

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