A Texas kangaroo rat found in Iowa Park, Texas, in 2016. Photo by John Stuhler.
By Samantha Stuhr
On a sunny and blistering hot day in July, a small group of researchers who dare to face the heat are getting packets of seeds (each weighing 3 grams exactly) out of a mud-ridden white Texas Tech Natural Resource Management truck with a dent on the side and pouring them into trays filled with sand. They will be up at 6 a.m. the next morning to tediously sift through the trays.
One may wonder what they could possibly be doing out there that’s so important. But that’s the thing — it may not look like they’re doing much, but they’re doing all of this for one very important reason. They’re searching for a certain species of rat that’s only been found in 13 northern Texas counties. And that particular rat is the Texas kangaroo rat, which scientists call Dipodomys elator.
What’s important about the Texas kangaroo rat is that it’s rare. It is listed as threatened in Texas and could potentially be listed under the Endangered Species Act as endangered. It’s so unique that it is only found in Texas. The people tirelessly working out in the field and in a lab for hours at a time are studying the species and seeking ways to conserve it.
“It wouldn’t be Texas without the Texas kangaroo rat,” said Richard Stevens, a Texas Tech Natural Resource Management professor. He was one of the first to study the Texas kangaroo rat under a project that started in 2015 with funding from the Texas Comptroller’s Office, which will give information to the U.S. Fish and Wildlife Service to decide whether to list the rat under the Endangered Species Act.
Listing a species as endangered is often “hastily done, in a hurry, with very little information,” Stevens said. So, the Comptroller’s mission is to send people like Stevens to study the Texas landscape, identify threatened and endangered species, and study them “so that good, solid decisions can be made.”
Many aspiring natural scientists are working on research projects in Stevens’s lab, and the project would be impossible without them.
“I have a soft place in my heart for young people who are trying to get this whole thing going—trying to do research, trying to do good research, and trying to do important research,” Stevens said. “It’s very rewarding to help them out with that. It’s also a lot of fun working with young people. I mean, you guys are cool, you guys keep me half hip, you guys are enthusiastic, you guys are fun.”
One of the graduate students in Stevens’ lab is John Stuhler, who earned his Bachelor’s and Master’s degrees at the University of Wisconsin—Madison. He was looking for a Ph.D. program when he saw a job posting from Stevens. The project was to study the Texas kangaroo rat — with funding. Stuhler was already interested in Stevens’s work, and he liked the conservation angle of the project.
“The chance to work with Texas kangaroo rats was really exciting to me because I think kangaroo rats in general are very intriguing animals,” Stuhler said.
Stevens, who has done research in the field for many years, is an expert primarily on bats and rodents. He defines the ultimate impact of research as “being able to create knowledge and information, and being able to do something novel and new that would shed more light on some sort of phenomena.”
One fascinating characteristic of Texas kangaroo rats and many others that live in desert climates is that they survive on little to no water. Their unique kidneys allow them to retain water for long periods of time. Instead of drinking water, kangaroo rats can get moisture from the seeds they eat.
“I have a fondness for arid-adapted species in general,” Stuhler said “As you would expect, living in arid environments is really challenging.”
Stuhler is most interested in the Texas kangaroo rat, but he also studies other types of rodents to understand how species diversity changes across different habitats. He has captured 15 different rodent species in the Wichita Falls area, including two species of kangaroo rats: Dipodomys elator (Texas kangaroo rat, which lives in a narrow geographic range and is hard to find) and Dipodomys ordi (Ord’s Kangaroo rat, which can be found from Mexico all the way up to Canada).
“I guess that’s another reason why I like kangaroo rats a lot — because there is a lot of interesting ecological variation among the species,” Stuhler said. “These two species that are very similar to each other have the same family, same genus, but have different habitat requirements or habitat associations. As a result, one has this massive distribution, is more common, and the other is much harder to find.”
Stuhler has handled a lot of kangaroo rats (there are about 20 species), but he’s seen a Texas kangaroo rat fewer than 100 times. He believes the species is rare, and consequently listed as threatened, because of its narrowing habitat.
“Many [kangaroo rats] are adapted to these arid environments with sandy habitats,” he explains. “But the Texas kangaroo rat is a little strange since it’s found in loamy soil—soil that is a little more compact, has more clay in it.”
The limited geographic area to which Texas kangaroo rats are adapted is complicated by the practice of converting land for agricultural purposes. This conversion limits species’ diversity.
TTU Natural Resource Management truck out in the field in Iowa Park, Texas, in 2022. Photo by Samantha Stuhr.
“Out in that region, there’s increasing shrub and grass cover now,” Stuhler said.
“The Texas kangaroo rat likes open, shortgrass habitats, where it’s easier to move around and forage and detect predators overhead due to their enlarged auditory bullae, which are these pockets in their skulls that allow them to hear well.”
A big obstacle to studying the Texas kangaroo rat is that 98% of Texas land is privately owned, and many landowners are not keen on letting researchers on their property, even though they do their best to clearly explain why the research is important.
“It’s hard enough to ask someone that doesn’t know you if you can go run around on their property to collect data,” Stuhler said. “But it gets even harder when you start mentioning the fact that you’re working with a species that’s threatened and potentially endangered. That understandably scares off some people.”
The current project is assessing how Texas kangaroo rats use what’s left of their habitat. The term for this research on foraging patterns is “GUD,” or “giving up density.”
Craig Wallace, an undergraduate research assistant working for Stuhler, explains “GUD” as a study of foraging behavior—specifically, how much energy the rodents are willing to give up to search for food. For the Texas kangaroo rat, collected food consists of seeds they put in their cheek pouches.
“If they’re foraging and not finding anything, how long should they stick around and forage more to find something?” Wallace said, to illustrate some of the questions researchers are asking. “Or, if they’re foraging and finding a lot, how long are they going to stay there?”
Trays with seeds mixed with sand are used to quantify how much the kangaroo rats forage at a particular spot. The researchers expect the rats to spend more time foraging for seeds in the open, where they can hop freely, like kangaroos (hence, their name) and less time in areas under shrub cover. But they don’t know the answer yet.
Spending the hot summer of 2021 in Iowa Park with Stuhler, Wallace worked as a research assistant, trapping rodents and designing the first part of the foraging portion of the project. He, Stuhler, and another assistant set traps in the evening; then woke up early to collect the traps. Though they were based in Iowa Park, they trapped rodents everywhere around North Texas before starting the “GUD” study.
Why would conserving this one particular rat species be so important? The researchers explain how each species fills a “niche” that could impact the survival of others.
“Different species play different roles,” Stuhler said. “When you take one away, that changes the relationships and interactions in the system, and that can have much bigger implications than just losing a species. For example, these guys live in burrows; they dig holes and go underground. A lot of different species—not just rodents, but a lot of insects and even snakes—will use these burrows for habitat and cover. Also, a lot of times animals that eat seeds will take them and move them somewhere else. That helps disperse the plant so it can grow in a different location.”
Although biodiversity is central to ecosystem stability, there is also a more sentimental reason to preserve the Texas kangaroo rat.
“It’s part of the state’s identity,” Stuhler said. “We can’t find this anywhere else, so it’s important we work hard to conserve the species because if we lose it in that region, it’s gone forever, and you can’t bring it in from anywhere else.”
When asked where he thinks the future of the species is headed, Stevens said he “honestly [doesn’t] know.”
“We have barely scratched the surface,” he said. “For every pattern that’s been described, someone else has described the opposite pattern. Sifting through the reality of it all has been a little challenging, but that’s also the fun aspect of it all.”
Stuhler emphasizes the objectivity of science. “We go out and collect our data, we interpret our data based on what the statistics and analysis tell us, and then our job is to pass that information along to the decision makers.”
Science is directionless, Wallace adds, but he likes conservation science for its inherent purpose: “It’s to benefit the world around you, and see what you can do, if you can do anything.”
So, what are Texas kangaroo rats actually like?
Different species behave differently “in terms of how they act in your hand,” Stuhler said, but Texas kangaroo rats tend to be docile: “A lot of times when you handle them, they just kind of sit there, resigned to whatever you’re doing, and then you let them go. They’re kind of a sweet species to work with.”
Wallace recalls how excited he was to hold a Texas kangaroo rat for the first time: “We didn’t see or get anything the entire summer, and John and I went on this one last trip to see if we could get one. We set traps, and the next morning when we went, John picked it up and said, ‘Craig, can you ID this?’ And I was like ‘maybe,’ and then I looked in there and was like ‘Oh my God!’” The team measured, sexed, and aged the rat, took pictures and released it.
Many more researchers continue to work on conserving the Texas kangaroo rat at Texas Tech and other universities.
“[It’s] a species that leaves constant reminders that there’s still so much to learn about it,” Stuhler concluded.
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