Herpetology class field trip to southeastern AZ

Students respectfully observing a rattlesnake we found

The next morning we headed over to Granite Gap to learn visual encounter surveys for lizards. This is a really neat area with fascinating herpetological diversity, large boulders for climbing around, and is near a hybrid zone between two species of whiptail lizards that roughly coincides with the transition between the Sonoran and Chihuahuan deserts. There we saw a bunch of cool lizards, including leopard lizards, desert spiny lizards, whiptails, earless lizards, and surprisingly enough even a Gila monster!

Checking out the boulders near Granite Gap

Discussions regarding the tradeoffs associated with being bitten by a lizard

In the afternoon the students got to spend time learning about the history of Herpetology and broader patterns of herpetological diversity in the southwestern U.S. and Mexico through the fascinating exhibits at the Chiricahua Desert Museum. We then spent some time honing their lizard lassoing skills with Yarrow’s spiny lizards in the canyons of the Chiricahua mountains. Thunderstorms Saturday evening generated even larger amounts of snake activity in the area, we saw 10 different species that night, with several students having conquered their fear of snakes by the end of it! Laura seemed to have a gift for calling out the next species we see (‘I really hope we get to find a gopher snake’, though apparently she is unable to summon a chupacabra 😂). The students also really enjoyed the excellent introduction we received to bat research from the University of Arizona mammalogy research team that was also in the Chiricahua’s this weekend.

Conversation on an afternoon walk in the canyon turns from lizard lassoing techniques to the acceptability of purchasing a hat with a bird on it from the museum during a herping trip (and the differences between herpetologists and ornithologists😜).

After rescuing the gopher snake from being hit on the road, Maria and snakes are no longer foes, but friends.

On Sunday morning, we focused on a research component of the trip. Work in my lab focuses on the fascinating whiptail lizard system in the southwestern U.S. and Mexico, which comprises the largest group of unisexual vertebrates (species that only have female individuals, though there are also lizard species with both sexes in this group). The unisexual species form through hybridization (interbreeding) between different sexual species of whiptail lizards! And different species have different numbers of chromosome sets based on how they have formed. The lizard species that hybridize with each other are really different from each other too, it’s totally wacky biology that we are still trying to understand. One question my lab is trying to learn more about is why the unisexual species sometimes form when lizards hybridize, and why certain hybrid combinations appear to be successful at reproducing in this unique way, whereas others are not. To do this, we need more information on all the combinations of unisexual species that occur in nature. For example, to this point, only unisexual species that have 2 or 3 sets of chromosomes are known from nature, but species with 4 sets have been produced in the laboratory through hybridization.

So, we want to visit areas where different species have overlapping distributions to document how often they hybridize and determine if previously unknown/undescribed unisexual species exist in nature that have been overlooked. We visited a site where the little striped whiptail (a species with both sexes) overlaps with the desert grassland whiptail (a unisexual species with 3 sets of chromosomes) to see if there are potentially stable populations of individuals with 4 sets of chromosomes that have ancestry similar to species that have been generated by crossing experiments in the lab, but are unknown in nature. Since it’s late in the year, adults were not active, though we saw many juveniles. Whiptails generally are difficult lizards to capture, even for experts since they are extremely fast, tend to be very wary and constantly moving, and lack ‘necks’ that help often prevent the lasso’s we use to catch lizards from slipping off. The juveniles are especially difficult, so this was a nice illustration to the students of how even the sampling part of scientific research can be extremely challenging. I was super impressed by the tenacity and enthusiasm of the students, even under tough conditions they kept at it, got hands on experience with the survival value of caudal autonomy to lizards (as demonstrated by Sabrina 🙃), and saw their hard work result in some success! The next part of the project is to determine the identity of the lizards we found. Although we can partially do this by examining their morphology, some lizards looks extremely similar despite being genetically quite different, so we can do this more definitely by measuring their relative cell sizes, which correlate strongly with the number of chromosome sets they have (this is interestingly true in many species). Students have started doing that in class this week! It’s super exciting to be making new discoveries about these lizards in real-time with the students! And a great introduction to the process of science for them.

Students measuring lizard red blood cell sizes under the microscope to determine ploidy levels of sampled individuals.

Generally, the trip was about as successful as I could hope for! And a lot of fun. I felt very lucky that my first Herpetology class at ASU is comprised of such an excellent group of enthusiastic, appreciative, and hard-working students, we all got a lot out of the trip. And the herping was great despite the drought we’ve experienced in some parts of AZ this year! Here’s to hoping it’s the first of many great field trips in ASU Herpetology.