Tom Mathies in Guam Tom Mathies at work in the jungles of Guam. Courtesy Tom Mathies.


Snakes, lizards, and bugs. Not what the average person might want to devote their career to, but principal investigator Dr. Tom Mathies is far from average. An expert in herpetology and invasive species, Mathies retired in June 2023 after six years with the Center for Environmental Management of Military Lands.

His interest in the natural world began in childhood. Growing up in Seattle, Washington, he roamed local woods, streams, and lakes, fascinated with the plants, animals, and birds he saw. “I was always bringing home jars of frogs and grocery bags full of garter snakes,” Mathies recalled. His aunt fed that interest, giving him books by British naturalist Gerald Durrell—A Zoo in My Luggage, The Amateur Naturalist, and others. He dreamed of someday becoming a collector for a zoo, of going to the deepest, darkest Amazon jungles to bring back new species.

Not surprisingly, those dreams led him to a zoology degree from the University of Washington. Mathies then relocated to Blacksburg, Virginia, and got a Master of Science and a PhD in biology at Virginia Tech, studying evolutionary reproductive biology in lizards. His next move was to Fort Collins, where he took a post-doctoral position at Colorado State University, working with the USDA National Wildlife Research Center. There, he researched methods to control brown tree snakes, an invasive species wreaking havoc on Guam’s native birds. That experience left its mark, Mathies said. “I still have nightmares about those snakes. They’re all climbing out of their cages and biting me, and I’m stuffing them back in but they keep popping out.”

He also worked on controlling another invasive snake, Burmese pythons, which can grow up to 10 feet long and have killed off 90% of small mammals in the Florida Everglades. “You would pin those huge snakes down with a plexiglass riot shield and they’d whack against it, trying to bite you,” he recalled. One even wrapped itself around his head when he was working alone, but he luckily managed to dislodge the powerful constrictor.

Despite those experiences, said Mathies, “I like invasive species work; I like trying to solve environmental problems.” That yern led him to various field jobs for consulting companies, such as surveying native and endangered birds, studying mosquitoes for a malaria eradication project in Africa, conducting studies of prairie rattlesnakes and general herpetological surveys for Boulder County, and continuing work on lizard ecology in Arizona stemming from his graduate studies. Eventually, a position opened at CEMML as a project manager for a new biosecurity effort on Guam, and he got the job, thanks to his earlier experience on the island. Once again, he was working to control invasive species, including those brown tree snakes.

In 2018, he was promoted to principal investigator and began building the Guam biosecurity program to its current level of 15 staffers. The program’s impetus was a document from the U.S. Fish and Wildlife Service that described the potential environmental effects of the military buildup in the Mariana Islands and ways to prevent and mitigate damage. One of the Service’s major recommendations was to prevent more harmful non-native organisms from getting a toehold. CEMML biologists now inspect all cargo arriving on military installations on Guam and the neighboring island of Tinian for stowaway frogs, lizards, spiders, plants, soil, and so on. They also work to keep other destructive invaders in check, such as the coconut rhinoceros beetle and the little fire ant. CEMML biosecurity efforts in the Marianas have recently expanded to include maintaining fenced-in conservation areas meant to protect native species.

Now that Mathies is retiring, another CEMML principal investigator will take over this important work. For his part, Mathies plans to get back to his boyhood dream of exploring the wild. He and wife Laurie are headed to Wyoming’s remote Red Desert first, then to various islands, none of them Guam—Portugal’s Azores, the Galapagos off the coast of Ecuador. But he’s far from ready to give up working. He plans to continue helping CEMML with invasive species control as an hourly employee and is hoping to get funding to study natural predators of a non-native insect that’s wiping out Guam’s endemic cycad trees. More bugs, snakes, and lizards; just what Mathies needs to stay happy. Perhaps the brown tree snake nightmares will finally fade, though.