By Meg Jones of the Journal Sentinel
Posted: March 21, 2010
Black River Falls - The sawdust and sand mixture floated up from the floor in the dimly lighted garage as researchers and volunteers worked quickly to unlock the secrets of the elusive bobcat.
Bobcats taken during last fall's hunting season were lined up on plastic tarps this month in the state Department of Natural Resources facility here. The work being done will help determine the health of Wisconsin's bobcat population.
At the DNR's once-a-year event, students and researchers collect tissue and teeth from the bewhiskered, stub-tailed animals that are so secretive they're rarely seen by Wisconsinites.
"We have lots of unanswered questions about bobcats," said DNR furbearer specialist John Olson.
Among the questions: How many bobcats live in Wisconsin? Where? And what are their reproduction rates? Also, how long do they live and are they genetically related to bobcats in other states?
All hunters and trappers who harvest a bobcat must turn over the skinned carcass to the DNR for population and genetics studies. Wisconsin is among only a few states doing such a comprehensive survey.
"Because we have these centrally collected pools of furbearer carcasses, it's very unique. Most states don't do this," Olson said. "We have research that we can share with many scientists."
On this day in Black River Falls, volunteers also took samples from fishers and river otters. One research project is investigating the effects of heavy metals on Wisconsin's river otter population. Between 300 and 400 carcasses were processed by three dozen volunteers, which included students from the University of Wisconsin-Stevens Point and a Black River Falls charter school.
Bobcat canine teeth will be sent to a lab in Montana, which can determine age by counting rings, similar to aging a tree.
Sean Strom, a DNR wildlife toxicologist, carefully took samples from river otters in an effort to figure out how mercury, PCBs and newly emerging contaminants affect the animals.
"It really is valuable. I don't know many other places that do this. For researchers, it's literally a gold mine," Strom said.
While fishers and river otters are handled every couple years for research, bobcats are collected by the DNR annually. With few bobcat hunting permits allotted each mid-October to late-December season, it's akin to winning the lottery. Many hunters wait five to 10 years before getting a permit. Most keep the spotted pelt, though some are sold, Olson said. Sometimes, hunters keep the skull for mounting.
Tracking state's bobcats
Wildlife biologists estimate the bobcat population at 2,800 to 3,000 in the area north of Wisconsin Highway 64, roughly the top third of Wisconsin, where hunting is permitted. Bobcats have been seen south of Highway 64, and there's interest from hunters and trappers to expand the hunting zone. But wildlife biologists first need to know if there's a sustainable bobcat population south of Highway 64.
"If we look at expanding any zones, we better have good data because we want to protect the resource. We don't want to jeopardize any new or expanding population," Olson said.
It is believed the bobcat population increased in Wisconsin a few years ago. Though wildlife biologists are not sure why, it could be related to mild winters - bobcats have relatively small feet which makes it more difficult to walk on deep snow. Another factor could be an abundance of prey including rabbits, mice and fawns.
Dawn Reding, an ecology and evolutionary biology doctoral candidate at Iowa State University, used samples from 80 Wisconsin bobcats two years ago for a genetics study looking at the animal's population patterns across the Midwest. She discovered significant changes in the DNA of bobcats from different areas and learned that bobcats captured in southwestern Wisconsin were linked to bobcats found in southern Iowa. That suggests that southwestern Wisconsin bobcats may be migrating northward from southern Iowa, rather than coming down from northern Wisconsin.
Reding used 1,500 tissue samples from 15 states for her study.
"There's no way I personally would have been able to go out and collect all those samples. Without the efforts of the state agencies and hunters and trappers, I wouldn't have been able to do the research," she said. "These carcasses are extremely valuable not only to my research but people doing disease research and a lot of other projects."
Finding the nocturnal bobcats known for the tiny black ear tufts is difficult, which makes it hard to make a population estimate, said Eric Anderson, a UW-Stevens Point wildlife ecology professor. He brought 13 undergraduate and graduate students to the bobcat event.
"You have to be really careful with furbearers; it's easy to exploit them. We don't have a good handle on the numbers," Anderson said. "In Wisconsin, we probably have a minimum of 6,000 to 7,000 bobcats and yet most people have never seen them. They're a mystery."
Learn more about big cats and Big Cat Rescue at http://www.bigcatrescue.org