10 March, 2024

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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Posted on March 10, 2024 01:51 PM by petezani