The Uta Project's Journal

Since the last observation of the week on May 5, there have been 683 observations added to The Uta Project. There were many notable observations including:

—this pretty female Uta stanburiana stejnegeri by @georgezimmer.

—this nice male-female pair by @zachary488. I've seen males do laps between attending and courting females. I've also see a single male just hang out with a single female for a while.

—this very gravid female by @scubabruin.

—this male whose colors show even more sitting in the shade like this by @daniel0910.

—even the northern side-blotched lizards have started laying eggs, like this female by @alexsowers6.

—there are continued mating attempts being observed, such as this one or this one by @raphaela_fb and @dustdevil.

—this example or this example by @robtea and @cellomaniac of interspecific basking between a Fence Lizard and Side-blotched Lizard. These two species are surprisingly tolerant of one another.

Despite all of these observations, I am choosing as observation of the week this observation of a hatchling Uta by @lagardilla. This is amongst the very first hatchlings of the year and will not be the last. These can be hard to ID, so it's nice to note the even dark-light-dark stripes behind the eye. These stripes can be one of the only ways to tell these since their blotch often doesn't show until they sexually mature at age 10 months. Right now, the southern latitude/low elevation females are probably working on their third clutches, mid-latitudes/elevations on their 2nd clutches, and the northern latitude/higher elevation populations working on their 1st clutches still. The breeding season will usually continue into July, rain permitting. However, the monsoons can induce late-season clutches in some locations.

As always, thank you to everyone who has observed a Side-blotched Lizards in the past few weeks. Your contributions are greatly appreciated.
—Pete Zani

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22 May, 2024

5 May, 2024

14 April, 2024

23 March, 2024

10 March, 2024

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It's been three weeks since the last review of the observed Uta, so I thought it a good time to consider the status of spring. During the past three weeks there were over 1300 observations of Uta, all of which were Uta stansburiana. These observations spanned the range of this species, but with a definite focus in the range of U.s.elegans in Southern California.

Males are in full breeding colors in all corners of Uta's distribution. Examples of colorful males include:

—this male by @erayner

—this male by @jmaughn

—this male by @tmessick

—this male by @sunbelt

There continue to be good observations of gravid females as the spring breeding season progresses. Many of which come from Southern California and some look about to pop which is good indicator of how close they are to laying their eggs. Examples of gravid females include:

—this female by @plascenciaivett

—this female by @jonrobson

—this female by @joseph92

—this female by @cjustus320

For observation of the week I have chose a pair of observations of Uta in the act of mating by @knight17 and @roadddog. Mating in Uta can be quick, lasting no more than a minute or so. Courtship involves circling behavior and lots of headbob displays by both male and female. The female will also use body postures like a raise as part of the courtship. Mating only occurs once females have ovulated and so will often reject courtship displays before or after that time in her cycle, which takes about 28 days early in the spring or as few as 16 days in the heat of summer. Once mating occurs, it can still take several weeks for the female to yolk and then shell the egg before laying, so mating is an important time point in the breeding season. Mating will continue from now until mid-to-late June with last clutches usually laid by mid-July most places.

As always, thank you to everyone who has observed a Side-blotched Lizards in the past few weeks. Your contributions are greatly appreciated.
—Pete Zani

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I have updated the range map for Uta stansburiana and the five continental subspecies based on some recent work in the field the past couple years. The map can be found as this observation. Some areas of these distributions are still poorly understood, such as much of the non-Baja distribution in Mexico (especially at the subspecific level) and where U.s.elegans, U.s.nevadensis, and U.s.stansburiana come together in the Great Basin Desert. Let me know if you have any questions.
—Pete Zani

On the iNaturalist forum, I recently came across an older 'feature request' to allow the iNat Computer Vision to suggest annotations, such as for males or females. As part of that discussion it was pointed out that the model would need observations already annotated for training purposes. Hence, in the past few months I have been making a concerted effort to add to the 'sex' annotation for Uta to make that possible when/if that happens (feel free to vote on this feature request if you like). However, it occurs to me that you, dear reader, might be interested in learning how to identify the sexes of Uta, some of which is knowledge applicable to other lizards as well.

Tail Bulge

The most reliable way to distinguish males from females is via morphology. Squamate reptiles (lizards and snakes) have what are called 'hemipenes,' which are paired penile organs that are stored in the base of the tail for use during copulation. Males fill one of these with blood during copulation, which causes the hemipene (left or right) be everted and inserted into the female for sperm transfer (see here for example). The presence of hemipenes in males, but not females, means the shape of the base of the tail is different between the sexes.

In males, the base of the tail is slightly wider where the hemipenes sit before quickly tapering to a more modest width that then gradually tapers the rest of the length of the tail. It's this rapid change in width just behind the hind legs that is diagnostic. Here's a nice close up of this feature as well example observations where this bulge should be readily apparent for each of the primary subspecies of Uta stansburiana (listed alphabetically): U.s.elegans, U.s.nevadensis, U.s.stansburiana, U.s.stejnegeri, U.s.uniformis .

In females, the base of the tail is slightly narrower, but more importantly, it has an even taper along the length of the tail. Here are example observations where this bulge should be readily apparent for each of the primary subspecies of Uta stansburiana (listed alphabetically): U.s.elegans, U.s.nevadensis, U.s.stansburiana, U.s.stejnegeri, U.s.uniformis .

While the bulge in the base of the tail works on many lizards species, not just Uta, the bulge can be very subtle in some taxa like skinks or gecko. There is a second morphological feature, enlarged post-anal scales, which allows the sexes to be distinguished. However, this trait is limited to Family Phrynosomatidae.

Enlarged Post-Anal Scales

On the under side of the tail just behind the cloaca (the term for the single opening for metabolic and nitrogenous waste) are two scales that are noticeably larger than the surrounding scales in males. In females, all the scales behind the cloaca are the same size. Interestingly, this feature is diagnosable at hatching meaning phrynosomatids of any age can be sexed. However, in hatchlings this feature is so tiny that usually a magnifying hand lens is necessary to see it. Here are examples of the enlarged post-anal scales in males (see picture #7) and females (see pictures #4 & 5).

The problem with post-anal scales is one needs a ventral view of the lizard. However, there are situations where post-anal scalation can be all one needs for identifying a lizard's sex. For example, this observation of a dead lizard lying on its back where one of the two enlarged post-anal scales is barely distinguishable.

Color/Pattern

Another feature that is often a useful indicator of anatomical sex is a lizard's color or pattern. However, this is more limited because a) breeding colors can be quite muted out of the breeding season and b) some subspecies, namely U.s.uniformis, are very similar in color and pattern. In fact, this is why they were named uniformis...the sexes are uniform. For the remaining subspecies of Uta stansburiana, there are differences described below and organized by subspecies.

Three of these subspecies (U.s.elegans, U.s.stansburiana, U.s.stejnegeri) are all similar in that males have blue flecks on the back (dorsum) and atop the tail. These flecks are usually composed of small groupings of 3-5 blue scales. Even when the blue is faint, these flecks are light colored on a dark ground color as in this observation. In some populations, such as in Grand Canyon, the blue tail can be a vibrant or electric blue, especially when agitated during courtship or stressed by handling. Females never have the blue as in males. Thus, the blue in undisturbed males can be quite muted, but still present, as in this observation. Check out the difference between undisturbed (picture #4) and handled (picture #5) blue color in this male (yes, that's the same animal).

The only subspecies really different (other than U.s.uniformis) is U.s.nevadensis where the blue on the dorsum is still present, but the tail is instead vibrant orange. Again, the blue becomes more vibrant during interactions with other lizards and during handling. In U.s.nevadensis, males more consistently have orange coloration along their flanks. One thing to note, as one approaches the southern limits for this subspecies in Nevada and California the orange tail and flanks can be much more difficult to distinguish, such as this male from near Hawthorne, NV.

While the pattern can be variable within and between the subspecies as mention above, the blue flecks are fairly consistent. Females on the other hand lack these blue flecks even in their most colorful. So it's really the presence of color that suggests a male, but the absence of much color, other than dark and light flecks on a gray/brown ground color, is more consistent with females. This is true regardless of the chevroned, striped, or mixed morphs present in females.

So there you have it. Three ways to recognize males from females. Keep in mind that Uta are highly variable in color and pattern, which is why I list it third and tried to focus on those hard morphological traits like tail shape that help me in identification of the anatomical sexes. Hopefully these notes help you as well.
—Pete Zani

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It has been a couple weeks, so I thought I would summarize the observations of Uta over the past few weeks. Since the start of April, there have been 643 observations of Side-blotched Lizards. As expected as spring develops, there continue to be a number of observations of females that appear to be gravid. While exact stage of gravidity is nearly impossible to tell visually (I rely on physical palpation to score gravidity), the expansion of the lower abdomen as follicles develop give females a characteristic bulge just in front of the hind limbs. Once females oviposit their abdomens are not nearly as distended, such as this or this female (by @todd-black and @tsirtalis, respectively). However, size is an important determinant of when females lay eggs for the first time each spring, so while the presence of the bulge is indicative of gravidity, the absence of the bulge cannot be interpreted without information on the body size of the female.

Females with the telltale bulge ranged from southern California, Texas/Mexico, Nevada, Utah, and Arizona (submitted by @zeevng, @joseph1008, @cesarponce17, @skylermckinnon, @chrisjensen1, and @nolinad, respectively). As of right now, these observations are limited to the more southern populations/subspecies (U.s.elegans and U.s.stejnegeri), but will expand northward as the spring continues. While copulations began back in late March, as observed by @naturephotosuze, it is this observation (by @festuca59) of a female that appears to be nesting that I have selected for observation of the week.

Like most lizards, female Side-blotched Lizards excavate their own burrows for egg laying and this particular female looks both gravid and like she's burrowing. I did a lab experiment years ago to see how deep females would dig given soil of unlimited depth and noted that they went about three body lengths down before laying eggs...so about 6" (15 cm). Burrow construction can take several days and oviposition often happens late in the heat of a nice sunny day. However, it can be really difficult to spot female burrowing because they often start the burrow next to a rock or other cover object, but they are usually out in the open and not under bushes. This behavior will continue as females oviposit at which time we should start seeing more females with the post-reproductive skinny look before they produce a second, third, and even fourth clutch of eggs. A study years ago near Las Vegas estimated that females there had enough time to lay perhaps seven (7!) clutches of eggs and in Oregon I have observed females producing at least four clutches. The breeding season is long and productive in good years and with all the recent rains, this appears to be a good year for many populations of Uta.

—Pete Zani

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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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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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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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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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