Friday, March 1, 2013

American Martens

The American marten (sometimes known as the pine marten) is the only mammal remaining on the Wisconsin’s state endangered species list. Even when they were more abundant, people rarely caught a glimpse of this shy, solitary, nocturnal weasel.

Until the 1920s, American martens were widely distributed throughout the dense conifer and hardwood woodlands of northern Wisconsin. Unregulated fur harvest and habitat loss caused their demise. In 1986, a marten recovery plan was developed with the goal of reestablishing two self-sustaining populations of martens in the Chequamegon-Nicolet National Forest. But even with cooperation between the Wisconsin DNR, the US Forest Service, and the Great Lakes Indian Fish and Wildlife Commission (GLIFWC), marten populations in the Chequamegon National Forest are not rebounding as well as wildlife managers and researchers hoped.

Over a period of 15 years, 300 martens were released in the Chequamegon-Nicolet National Forest with limited success. Marten populations in the northeast part of the release range on the Nicolet side have grown to about 220 animals, and appear to be holding their own. Unfortunately, the number of these mink-sized weasels in the Chequamegon side of the forest appears to be lower.

Phil, a wildlife researcher and PhD student at the UW-Madison, is studying martens in northwestern Wisconsin. Not long ago he was doing research out west and seeing wolverines (martens’ largest cousins) on mountains. Today, he’s gathering DNA samples from hair traps to determine if the local martens are breeding with reintroduced martens.

Phil and his research technician, Caroline, are staying at the Museum’s Jackson Burke House during their winter research period, so I tagged along on their weekly trap line check to learn more. We skied about 10k in a morning, skimming along groomed snowmobile trails north of Clam Lake. Using GPS units, we navigated to the traps. After getting close as possible on the snowmobile route, we removed our skis and slogged off-road through deep snow to the trap location.

At each site, Phil or Caroline dug the trap out from beneath a fallen log and checked to see if something had tripped it. The hair traps are homemade, and consist of a wire brush fixed inside a PVC pipe about 2 feet long and 5 inches in diameter. The trap is baited with a little wire ball of food and squirt of strawberry jam. When an animal (usually a marten or another small weasel) goes in, it must pass the wire brush to get the bait and again to exit. The researchers who designed the traps did not intend for them to capture live animals. Instead, a wire brush just catches some hair, and that provides the DNA that researchers need.
By comparing the DNA of the hairs they capture to the DNA on record from every released marten, Phil will be able to tell if there has been any romance between the old and the new. Along with habitat and tracking data, this may help researchers tease out the reasons that martens aren’t doing as well as we’d like.

With a slew of traits that prepare martens for survival in northwoods winters, you would think they would be doing great. Small bodies and relatively large feet allow American martens to travel easily over snow. When the snow gets really deep, martens tunnel through snow to reach prey and to den under/in downed logs. These adaptations give martens an advantage over their competitors — bobcats, fishers, and red foxes. Not only do they help martens catch food, it helps them keep from becoming food!

DNR Wildlife Biologist Jim Woodford explains, "Martens do better during years of high snowfalls in the north where they tunnel under snow in search of mice and other rodents. When there is less snowfall, as we have seen in the last few years, they are at a disadvantage."

Unfortunately for martens, most climate change scenarios for the next 45 years in Wisconsin predict reduced snow pack conditions. This would substantially decrease the advantage the big-footed/small-bodied martens have over other carnivores during winter, and likely decrease the number of martens. Aggression between martens, fishers, and other carnivores (like red foxes and bobcats) may increase as shallower snow allows the other animals to get around better in winter.

Whatever the challenges martens face, I’m rooting for them, and hoping to catch a glimpse of this rare and fascinating weasel.

For over 44 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M. The current exhibit, STAR POWER: Energy from the Sun, opened in May 2012 and will remain open until April, 2013.

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