Thanks to all who attempted my lizard identification quiz. It wasn’t easy. The correct answers were: 1) western fence lizard, 2) granite spiny lizard, 3) southern sagebrush lizard, 4) southern sagebrush lizard, and 5) common side-blotched lizard.

Many of you just missed one identification, but only one person got them all right: Sue Shigenaga (CalNat 2018). She also figured out that I named each image using an acronym for each species (SCOC = Sceloporus occidentalis = western fence lizard) and so was able to confirm that she correctly identified each one. Congratulations Sue for both acing the quiz and being clever about checking your answers!

It is mid-summer, so I will take advantage of any slight dip in the temperature to get outside. Today was such a day with the high temperature predicted to be a mere 105 F (rather than 112 F), so out I went (out and back before the temperature broke 90). I went out on the sand dunes just across the freeway from the UCR Palm Desert Center with the goal of testing a hypothesis. 

Ever since Francis Bacon defined it back in the 1600s, testing hypotheses has been the cornerstone of the scientific method. And yet not many of the “scientists” who were studying animals and plants during that age and for the next couple centuries followed that approach. It was the age of discovery and naming thousands of new species was an all-encompassing task. It was all very descriptive and essential, but not science in the strict sense of the word, at least not science that used the scientific method. In biology, it took Charles Darwin in the early to mid-1800s to revive the scientific method in his quest to understand the mechanism for the origin of species. Mechanisms are, in the scientific world, synonymous with hypotheses. I don’t remember Darwin’s exact quote, but he said something along the line that, without hypotheses science was just a collection of names and ideas; developing and testing hypotheses allows one to change those collections into knowledge. When those hypotheses or mechanisms are tested and repeatedly found to be correct, the hypothesis is elevated to a Theory. This term is the source of much confusion since most folks would equate a theory with a conjecture, an idea; however, in science it is a repeatedly proven hypothesis, as close to a fact as science can get. So, we have the Newton’s Theory of gravity and Darwin’s Theory of natural selection. 

My hypothesis for today was not anywhere near as monumental. If you can remember back to those days before the COVID-19 pandemic, we had a relatively wet winter and spring. For deserts that means flowers and insects and so the animals that eat those flowers (and their seeds) and those insects should thrive (aka lots of reproduction). There then was my mechanism and hypothesis, given that wet winter and spring, there should be lots of hatchling fringe-toed lizards.

One step on the sand dune and I was confronted with myriads of rodent tracks; desert kangaroo rats, desert pocket mice and Palm Springs pocket mice tracks, and burrows covered nearly every centimeter of the sand surface. The wet spring was clearly good for these rodents. These furry creatures are all nocturnal, and mixed in were the tracks of sidewinders, undoubtedly taking advantage of the smorgasbord of rodents. The fringe-toed lizards are diurnal, so their tracks were on top of the rodent tracks.  The lizard tracks were common though not abundant, but they were all big, made by adult lizards. Where were all the hatchlings? I did find a hatchling flat-tailed horned lizard – perhaps one of the most adorable babies in nature. After a full hour of searching I did find one very small fringe-toed hatching (freshly hatched) and three that were bigger and perhaps hatched a month or more ago. Not what I expected.

So why was I apparently wrong? I say apparently only because its possible that I am just looking too early; if I go out next month I may see my expected cornucopia of hatchlings materialize. If not, then what hypotheses might explain their absence? Since, two months ago every female fringe-toed lizard I saw was gravid, it wasn’t for lack of trying on their part. That then focuses the question on what happened to the eggs or to the hatchlings as they emerged? One possibility may be that it was due to the plethora of rodents. Rodents burrow into the sand and the female lizards lay their eggs in the sand. The dense networks of rodent tunnels may have disturbed and destroyed many or even most of the lizard egg clutches. Mark Fisher once told me that he and Al Muth found that the highest rate of mortality in a population of flat-tailed horned lizards they were studying came from squirrel predation; round-tailed ground squirrels were eating their lizards. It turns out rodents will happily eat animal protein if they can get their furry paws on it. In my case, maybe the rodents ate the lizard eggs? Or, maybe just by disturbing the clutches, they failed to hatch? I can test this hypothesis, even though I didn’t see the kangaroo rat eat the lizard eggs, by comparing recruitment of fringe-toed hatchlings across all the sites we survey – some of which will have lots of rodents and some much less. 

The beauty (or is it a curse?) in doing science is that there are always new questions and hypotheses to pursue. 

I'm attaching the picture of the hatchling flat-tailed horned lizard I saw today, along with what may have been its father, as he was only about a meter from the hatchling.