By Jennifer Smith

The Rough-footed mud turtle (Kinosternon hirtipes), also called the Chihuahuan Desert mud turtle or Big Bend mud turtle, lives in a very remote area of the Chihuahuan Desert in far west Texas in Presidio County. This is the only known place in the United States that they reside. They are extremely rare, but they haven’t always been rare. They were at one time abundant in both Texas and Mexico, where the residents called them pestitos or “little stinkers.” They get this nickname because they put out a musky odor when they are threatened, much like a skunk will use their smell to run off predators. They may also use their scent to communicate or locate other turtles. We really don’t know yet, but they are definitely stinky!

Very little was known about these turtles until a few years ago when we started to study them intensely. This is also when we realized that they are very rare with fewer than 160 individuals left in the United States. We also didn’t know what they ate, where they went during the summer or winter, how fast they grew and how they spend their days.  I’m here to share with you a little bit about what we have learned. I have so much information to share that I am going to break this into several topics such as their habitat, what they do during the summer and winter, where they spend their time and how I, the researcher, did my work to study them. These stories are focused on the next generation of researchers, our youth, but some adults may find it interesting as well.

When a person studies reptiles, they are called herpetologists. That’s a very specific form of a wildlife biologist. I did this study as part of my dissertation for a PhD or doctorate degree. It’s a ton of work but if you study something really interesting, then it’s also a lot of fun. I picked these turtles to study, because I love the Chihuahuan Desert and we knew very little about the turtles, so it was like solving a mystery.

Mud turtle habitat

Their habitat is in the Chihuahuan Desert, where they spend most of their day in water found in “tanks” or ponds that are man-made. They share their pond water with livestock, herons, Roadrunners, bob cats, Elf Owls and other desert animals in need of the scarce water resource in a hot and dry environment. The water is typically provided by Artesian wells that bubble up from the ground naturally without the help of a pump. Some of this water is even hot! Because water in the desert is so rare, these locations typically have evidence of historic populations including Native Americans and Spanish Conquistadors that either stopped to rest by the water or made it their home. I have seen metates or grinding stones near these locations where Native Americans probably turned mesquite beans into a sweet flour for food. One of the landowners showed me some silver spoons he found. They were tied together with a worn leather strap. He said the Spanish Conquistadors tied these to the horn of their saddles, allowing them to dangle as they rode horseback, making a clinking sound, supposedly to scare off evil spirits on their long journeys. In the mostly dry creek beds that lead to the Rio Grande, you can see long trenches made from the wagon wheels long ago as travelers made their way into the area often looking for gold or silver. The turtles have also made this area their home. Over time, with less rainfall and changes of land use, many of these areas have dried up, with just a few remaining locations that are suitable for them to thrive. We are talking to the El Paso Zoo about creating a captive breeding population. If we can get some of them to lay their eggs  then hatch at the zoo, we can release them back into the wild at some new locations and bring their numbers back to where they once were in Texas and maybe even Mexico.

A summer day in the life of the mud turtle

Mud turtles spend their day swimming and peeking their heads out of the water and foraging for food such as algae and insects. When I trap the turtles to measure them, they would put out their stinky musk smell and they would typically defecate, which may be another defense mechanism. That’s when I would see exoskeletons of insects they had eaten, which were mostly dragonflies.  Dense algae grows on their shells or carapace during the summer months, giving them excellent camouflage from predators. I have even seen one stretch her long neck out of her shell which was about as long as her shell, to grab an algae “snack” off and munch it. I was sitting on a bank watching and saw one that seemed to be playing by swimming and bobbing his head in and out of the water over and over for no other reason, it seemed, except it was fun.

Tracking turtles

I trap the turtles in a minnow trap that is open on one end. I would put a can of sardines in the trap, hold onto the line attached and throw it in the pond. The turtles would smell those yummy sardines, climb into the trap and feast until I pulled the trap out of the water. Turtles can stay under water for hours, but I didn’t want them to escape or drown so I checked the traps every 30 minutes. Then I would measure them with a special instrument called calipers. These are really fancy rulers with a gauge at the end that I would open and close to measure the length, width and depth of the carapace. Then I would cut the end of the toenail off, a lot like trimming a dog’s nail, and preserve it for DNA analysis. I glued trackers on them one summer, which are these little battery powered transmitters that send out a radio signal. Each signal had a different number that my receiver, a big heavy box that I carried over my shoulder all summer, would pick up and tell me that the turtle was nearby. I wore head phones and carried a giant Yagi antenna to pick up the signals. I would listen for a “beep” in the head phones, look at my receiver to see which turtle was nearby, and walk toward to beep until it got louder and louder. Once I was near the turtle with a deafening beep, I would  mark the location of that specific turtle with my GPS as well as write it down in my field notebook, and keep going. I did this all summer, walking, listening for beeps, marking their different locations. We did this so we could learn more about the movement of the turtles so we could help them in the long run by providing what they need in their habitats. Most of the summer, they stayed in the pond. Interestingly, there were certain cohorts or friend groups that almost always were together. Two of the males, numbers 080 and 082, were always together no matter where they traveled. I found them once outside of the pond, which was pretty unusual, together, deep in the mud. I had my headphones on and was a little confused because they were not in the pond, so I followed the beeps to a muddy stream by the pond, until the beeps were at their maximum loudness, stuck my arm into the mud up to my elbow, and felt them both there, just hanging out together in the mud. They stayed there for two days, then returned to the pond. There was also an area in the deepest part of the pond that had a group of males that stayed there most of the time, including 080 and 082. This area was at the base of a huge old cottonwood that must have been there over 200 years. This cottonwood was halfway in the water with the base partly eroded away, providing a nice little shelter for the turtles. This is also where I felt hot water coming out of the ground. I figured the turtles like this little hot spring for the warmth, since they are cold-blooded and need a little help regulating their body temperature, especially since the area was entirely shaded with little chance for sun bathing. In this nice deep spot with a hot spring, only males were found. I called it the turtle man-cave. No females were ever spotted here. In the more shallow part of the pond, there were females and only a few males. There were just a few males that ventured to the girls’ area, so we learned that not all the males mated, so there were just a few breeder males. These breeder males were not necessarily the oldest or biggest, either. They were not the youngest either. They were pretty average in size, so we aren’t really sure what makes them the breeders, but they would venture to the female’s area then return to the turtle man-cave. I rarely saw any turtles out of the water. I caught one on a log with my game camera. One of the landowners said she left her chair halfway in the water while sunbathing and when she returned some were sitting on her chair, so it could be that we didn’t see them out of the water much because there’s just not much for them to sit on near the water at these ponds like a log or big rocks. Sometimes we would see them on the banks, but not often.

A winter day in the life of the mud turtle

During the winter, they go into a light sleep or “torpor” along the banks of their ponds in little burrows they have dug out with their strong claws. Typically these wintering sites are at the base of thick bunches of grass called Big Alkali Sacaton  (Sporobolus wrightii). They have also been known to over-winter in crevices at the base of huge old cottonwood trees or dig out a hole in the mud along the banks. Wherever they decide to spend the winter, it is always in a moist area. The mud turtles dry out quickly and need moisture to survive apparently even when they are in torpor. In fact, they dry out faster than any other mud turtles in their genera. Some of these burrows housed more than one turtle. They looked like little duplex houses in the grass and were quite neat with very little excrement, if any.