MANHATTAN, Mont. – With the microscopic image projected onto a screen, Carolyn Nistler quickly counted age rings resembling the contoured elevation lines of a topographic map, arriving at the age of 14 for this northern European lynx .
“If they all looked like this, our jobs would be so much easier,” she said. “It’s just magnificent growth, you couldn’t ask for a better example.”
Nistler owns Matson’s lab in Manhattan, which specializes in analyzing the cementum age of wild animal teeth. As a tooth grows, a tissue called cementum forms on the outer layer of the root. Much like growth rings on a tree, environmental stressors cause dark layers of cementum, forming rings called annuli. Under a microscope and using the body of knowledge about the growth of regional animal species or populations and when certain teeth “erupt” from the gumline, Matson’s cementum age analysis provides data used to track wild animal populations or learn more about individual animals.
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In 1969, Gary Matson opened Matson’s lab in Milltown, developing many techniques still used today. Nistler, who has a master’s degree from Montana State University, was running a wildlife consulting business when she met Matson at an aviation conference in 2013 — they’re both pilots.
From that meeting, Nistler would learn Matson’s techniques and purchase the lab in 2015, moving it to Manhattan, just off Interstate 90. There, she cultivated an atmosphere that feels more like a storefront than a lab – staff don’t wear lab coats and the leisurely beat of 90s hip-hop thumps through the speakers – but here some of the fundamental work of wildlife management and research takes place.
“We want people to come, we want to share what we’re doing with them, because it’s so important to wildlife in our state and wildlife everywhere,” Nistler said. “We really believe in what we do and why data matters.”
Most of Matson’s teeth come from wildlife managers or research projects. Biologists use age data to monitor or study wildlife populations, by removing a tooth from sedated animals or harvests from hunters. The information can be used to justify hunting seasons, adjust quotas, or learn more about age structure or reproduction.
The teeth arrive at the lab in husks — beluga whales from Canada, brown bears from Croatia, white-tailed deer and black bears from across the United States — where technicians begin the weeks-long process. Teeth are sorted, cleaned and decalcified in a partially proprietary process, emerging in a rubbery state that allows very thin cross-sections to be cut. These cross sections are placed on slides, stained and covered with a coverslip before passing under expert eyes for ageing.
“It’s very specialized, but it’s very cool because – even though it’s so specific and particular – it gives us a chance to be involved in wildlife research and conservation around the world here since our little lab in Manhattan,” Nistler said.
The laboratory processes around 400 teeth a day and 110,000 every year. Matson’s is also closing in on a milestone of 3 million teeth since Gary Matson opened the lab, which is expected to be eclipsed this year.
Matson’s continued to improve its process and create species profiles to aid aging. This includes technology updates, usually in the form of automating certain steps in the process, such as placing covers on slides.
“(The technology) has been helpful, but one of the things we’ve learned that’s really important is that there’s a lot of things that machines can’t do,” Nistler said. “You still need a human to check because each species takes the task a little differently.”
Nistler removed the blade from the 14-year-old lynx and replaced it with a new blade. Unlike the first cat, this specimen was much more ambiguous and took most of its knowledge of the species to arrive at an age range of 2-3 years. Where an exact age is not definitive, Matson’s assigns an age range as the best determination.
“Sometimes we can tell in a split second,” she said. “And sometimes I spend five or 10 minutes on a sample trying to assign the correct age because that’s just the nuance.”
Nistler counts river otters and cougars among the most difficult teeth to analyze. Knowing not only the typical characteristics of a species, but also the differences in distribution, is a major element in arriving at a precise age. In Texas white-tailed deer, for example, the annuli are less distinguishable, while deer living in harsh northern latitude winters display paler growth rings.
The sexes can also vary, and females can show differences in the years they produce young. Nistler suspects that hormones or the mother’s dwindling resources account for these distinctions.
Most teeth come from national wildlife agencies, but Matson’s has seen an increase in the number of teeth provided by individual hunters in recent years who simply want to know more about the animals they’re hunting. Matson’s offers step-by-step instructions on how to remove a tooth and subject it to aging and charges $75 for up to five animals.
“We are hunters, we believe in hunting as a conservation tool,” Nistler said. “Hunters definitely want to be better informed about the role they play, and age is one of them.”
Shannon Bell is an avid hunter of Helena and a client of Matson. He recalled shooting an older mule deer in Montana and a huge bull moose in Alaska which made him wonder about the age – Matson put the male at 7 and the moose at 12 years old. Hunters often look at physical characteristics of animals like body size to estimate age, but checking those assumptions helps them better understand what they see in the field.
“Just like a hunter, it’s very interesting to learn more about your career,” he said. “You think about the number of winters he’s been through…and I think that just educates the hunter. We’re the stewards of the animals and to be honest it’s also super cool and it was really fun.
While cementum aging is Matson’s primary work, Nistler also offers several other services, including ovary analysis, which can estimate litter size and timing of pregnancy, and screening for tetracycline biomarkers. used in rabies vaccine testing for raccoons and mark-recapture studies for black. bear.
The lab also provides a skeletochronology preparation, primarily for amphibians, whose toe bone cross-sections have been shown to have growth rings. Matson’s uses skeletochronology to analyze python and black bear ribs as well.
“Every living animal has a part of its body that is influenced by annual growth cycles, it’s just a matter of where it is,” Nistler said.
Tom Kuglin is an associate editor in the state bureau of Lee Newspapers. Its coverage focuses on the outdoors, recreation and natural resources.