Montana State University Billings students working on a short-horned-lizard study develop warm feelings for the cold-blooded critters.
Students affectionately began calling pregnant lizards they caught “Roz” because the females look like the gruff character in the “Monsters, Inc.” film, said Rebecca Riley, a biology major who has worked on the project.
Students also were amused by young male lizards’ feisty attitude. When confronted by humans, they flick their tails back and forth.
“It is really funny to watch because they are about the size of your thumb but they act like they are 10 feet tall,” Riley wrote in an email.
Riley, a MSU Billings senior, liked the lizard project so much that after accumulating enough hours to earn two research credits toward her degree, she continued to go out on lizard-hunting trips as a volunteer. During two summers, she’s caught more than 100 lizards.
Eight years ago, James Barron, MSU Billings associate professor of biology, started the project, which may be the longest-running, most in-depth study of horned lizards that range from Alberta, Canada, to Mexico.
He’s captured and released more than 1,000 lizards at two locations near Billings. More than an additional 1,000 baby lizards were released into the wild after being born on campus. Although commonly known as shorted-horned toads or horny toads, they are in fact lizards.
Short-horned lizards get their name from a low ridge of horns at the back of their head, said Barron, a field ecologist who teaches evolutionary biology and vertebrate zoology.
Learning about lizards
Although he hasn’t made any Earth-shattering discoveries about the lizards during the study, he’s observed interesting features, including differences between lizards at his research sites on Bureau of Land Management land near Warren and at Hailstone National Wildlife Refuge north of Molt.
When out in the field, Barron and several students walk through an area looking for lizards. Because the lizards are so small and their mottled, scaly bodies blend in with their surroundings, they are hard to spot unless they move.
On one trip in late July, three students and Barron caught five lizards over five hours.
When a lizard is caught, it is weighed and measured and its temperature taken. The GPS location of where it was caught also is recorded.
Barron implants a passive integrated transponder tag, about the size of a grain of rice, under the adult lizard’s skin. After sealing
a small hole in the lizard’s skin, the animal is let go.
If the lizard is captured in the future and has a PIT tag, Barron waves an electronic reader over the implanted tag to get the tag’s number. Comparing recent data with that collected from previous captures, Barron can see where the lizard has traveled and changes in body size and temperature.
He brings pregnant females back to campus, where they give birth.
On their own
Newborn short-horned lizards are tiny but they quickly can fend for themselves.
They have to. If they stick around their mother too long, she may eat them.
When Barron sprinkles tiny crickets into a narrow plastic box that serves as a labor, delivery room and nursery for a family of the lizards, one baby darts out and snaps up an insect in no time flat.
Another lizard, meeting its first meal face to face, backs off apprehensively as a cricket scampers toward it.
The babies and their mother don’t get room service for long. Within a day or so of their births after sex, weight and measurements are collected, Barron takes babies and mothers back to where they were captured.
If lizard mothers aren’t very maternal with their newborns, that may be because she has had to lug around nearly her own weight in developing embryos before giving birth.
A 10-gram (0.35-ounce) female can nearly double her weight when pregnant.
Octomoms are pikers in the lizard world. Lizards giving birth at MSU Billings average 11 babies, Barron said.
Of the 14 species of horned lizards, half lay eggs and half give birth to live babies.
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The live-baby lizards, including those in Montana, live in northern latitudes and higher elevations where the season would be too short to incubate a clutch of eggs.
Females giving birth to live babies can move into the sun when pregnant, so the solar warmth speeds up development of the fetuses and they can be born within the shorter summer.
Despite the blazing temperatures students endure on the trips looking for lizards, they enjoy the outings.
Anneke Johnson, a pre-veterinary student at MSU Billings, went out eight times this summer.
“It’s really, really fun,” to hike all day looking for lizards, she said, because students also see coiled rattlesnakes, burrowing owls, golden eagles, hawks, fossils and plants.
“I feel fortunate to be part of the study,” she said.
Johnson never would have thought lizards were cute and charming, but they are, she insists.
And although they’re small, the lizards are fascinating to study.
Barron has found that the lizards don’t roam too far during their lifetime, ranging in an approximate circle with a radius of about 33 feet.
Lizards eat ants, grasshoppers and beetles, and their predators are mostly birds like hawks, kestrels and ravens with an occasional coyote and badger eating a few.
Barron has found several differences between the lizards at Warren, a near desert landscape, and Hailstone, a prairie grassland.
Lizards hibernate in the winter because they can’t produce their own heat.
In winter, lizards at Warren burrow under a few centimeters of loose soil but don’t get under the frost line, so they produce an internal antifreeze to prevent their bodies from freezing.
At Hailstone, the lizards appear to hibernate in burrows of an abandoned prairie dog town.
There’s another link between the success of lizards at Hailstone and prairie dogs.
Prairie dogs eat prairie grass, clipping it close to the ground, making it easier for lizards to move around. Lizards have very short legs and travel right on the ground “like round tanks,” Barron said.
The Warren lizards don’t have that problem because the dry terrain has less grass.
Different colors of the two groups of lizards help them blend into the unique soil color of their homes.
Warren lizards are brown and their babies a light dusty rose. Hailstone adults and babies are an olive-green gray.
Barron has found that survival rates of lizards is low — just 25 percent of the lizards survive through a winter.
This year, Barron found fewer lizards than previous years, but doesn’t know why. It may have been the long winter, or cold, wet spring. Or there may have been a midwinter warm spell that drew lizards out of hibernation and then killed some when cold weather returned. The oldest lizard he’s found was one that was at least 6 years old.
One of the most endearing traits of the Warren lizards is how they sleep, Barron said.
A few years ago, Barron marked some lizards with orange florescent powder during the day. Turning on a black light, he followed the orange trail until he came upon sleeping lizards with their faces stuck into clumps of grass, their bodies protruding outward.
While short-horned lizards found near Billings have the physical makeup to shoot blood out of their eyes as a defense mechanism, Barron, who has handled a couple thousand lizards, has never seen one do it.
That may only happen when a lizard is under attack from a canine.
However, a student, who was gathering lizards when Barron was at a scientific conference, did see a blood-shooting lizard.