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Monday, November 5, 2012

Fishers and Martens: Weasels of the Trees

This is the fourth in a series of articles on the nine members of the weasel family that are found in Michigan.  More mustelids will be featured in future issues. 

The mustelids (weasel family) of Michigan include species that occupy a wide variety of habitats.  Some scurry across the land, one -- the badger -- is a digger, and otters and mink are at home in ponds and rivers.  Two species – the fisher (Martes pemmanti) and pine marten (Martes americana) – move through the trees with the greatest of ease.  They are capable of acrobatic catches of prey ranging from mice to birds to squirrels among the limbs of the tallest trees and can kill animals much larger than themselves on the ground.
Both species were listed as extirpated in Michigan by the early 1960’s.  But the smaller of the two – the pine marten – was written off before its time, and some naturalists suspect that the fisher also survived in small numbers.  Valued for its fur, the pine marten was declared by wildlife officials to be gone from Michigan by the 1950’s.  Even the authoritative 1983 book, Michigan Mammals by Rollin Baker, parroted statements from other biologists that intensive trapping and loss of habitat had eliminated martens from both the Upper and Lower Peninsulas.  After pine martens stopped showing up in trapping records and field reports of biologists, the species joined wolves, cougars, and other predators on the list of extirpated species.  Wildlife biologists assumed that a combination of land development, logging and wild fires in the late 1800’s and early 1900’s wiped out any martens that had not been trapped.  

Actually, there were small remnant populations of pine martens in Michigan that went undetected, according to a 2006 peer-reviewed paper, “Evaluation of a Marten Reintroduction,” by Dr. Brad Swanson and L. Robert Peters of Central Michigan University and Christopher Kyle of the Ontario Ministry of Natural Resources.  The authors noted that the Michigan pine marten population today is expanding and healthy from a genetic standpoint because of multiple reintroductions and follow-up relocations within the state.  They added, “The success was further aided by the presence of small remnant populations that remained in Michigan….”

In 1955-57, with the pine marten considered extirpated, the Michigan Department of Natural Resources (DNR) obtained 27 martens from Ontario and two from British Columbia and released them in the Porcupine Mountains Wilderness State Park in Ontonagon County in the western Upper Peninsula.  However, by 1962 there were no reliable reports of martens in the area and the planting was considered a failure.

In 1968, a new effort was launched with funding from the U.S. Forest Service as well as the DNR.  Between 1968 and 1970, another 99 martens from Ontario were released in Delta and Alger counties.  In 1978, the DNR, the Ontario Ministry of Natural Resources, and the U.S. Fish and Wildlife Service initiated the Michigan Marten Reintroduction Program.  The next year, a third planting of 148 Ontario martens was made in the Huron Mountains in Baraga and Marquette counties, and in western Iron County.  Finally, the DNR conducted several transfers in 1989-1992 that moved 20 martens from Iron to Chippewa, and 19 from the western U.P. to southern Keweenaw County.

In the Lower Peninsula, the DNR and U.S. Fish and Wildlife Service released 85 pine martens in 1985-1986 in the Huron-Manistee National Forest, the Pigeon River Country State Forest, and the Pere Marquette State Forest.  As in the Upper Peninsula, monitoring has since showed small, slowly expanding populations near the release areas. 

The evaluation by Swanson, Peters and Kyle found that Michigan’s pine martens are now a genetically-diverse group unlikely to have reproductive and survival problems that often plague new populations that come from small numbers of re-colonizing animals.  They found no evidence of such a “genetic bottleneck.” So, the population is not limited by in-breeding.  In addition, the researchers also detected unmistakable genetic markers only found in Michigan.  These genetic sequences are not seen in Chapleau or British Columbia pine martens.  That means that remnant populations of Michigan martens had survived.  How large the remnant populations were, and their exact locations, may never be determined. 

Since Michigan now has expanding populations of pine martens, many people would consider those questions somewhat moot.  The remnant martens may have been so low in numbers that the populations would never have bounced back on their own.  Many wildlife species slowly become extinct when they are geographically and genetically isolated.  So, the reintroduction of pine martens starting in the 1950’s by the DNR was probably a good idea, especially since most of the animals came from a nearby (Ontario) source that was adapted to climate and vegetation conditions similar to those found in Michigan.  Michigan’s martens were probably not genetically distinct enough to be of biological significance. 

Fishers were also declared extirpated, and reintroduction efforts began in 1961.  About the size of a domestic cat, the species was, like the pine marten, highly valued for its fur.  They were certainly wiped out in some locations by the early 20th century.  The stocking program and trapping restrictions gradually led to increases in fisher numbers in the U.P.  But continued population monitoring showed a 70 percent drop in fisher numbers from 1996 to 2007.  That prompted the DNR to make changes in trapping rules to reduce the harvest of fishers beginning in 2011. 

There are some U.P. locales where it is now easy to find fisher tracks.  But there is a quiet controversy over the animal’s status in the Lower Peninsula.  The DNR says it has no verified reports of fishers in the Lower Peninsula.  However, some naturalists have reported fisher sightings and evidence such as tracks and scat from Emmet and Cheboygan Counties south as far as the Traverse City area.  Remnant fisher populations went undetected for many years in Montana until (as in the case of Michigan’s pine marten) genetic tests showed unique genes. 

One of the fisher’s claims to fame is its ability to kill porcupines.  The attacking fisher makes repeated bites to the face of the porcupine, eventually killing it.  When feeding, it avoids most quills, but ingests a few.  Thus, fisher scats often contain quills. 

Fishers also prey on snowshoe hares, showing great agility on snow.  They have oversized feet that help them stay on top of snow, but they struggle in powdery deep snow.  Their climbing prowess is linked to extremely flexible ankle joints; fishers can rotate their hind paws almost 180 degrees.  That lets them climb down head first – a great advantage when it is hunting in trees. 

A big male can weigh 18 pounds, yet fishers have been known to kill turkeys and are suspected of occasionally killing deer fawns.  One study in Maine found fishers responsible for at least four deaths of lynx.  It’s possible that fishers occasionally kill bobcats as well.  But, tales of their killing powers are probably exaggerated somewhat because they feed on carrion.  So, their stomachs and scats often contain evidence of animals they did not actually kill. 

Fishers and pine martens are now found in the same general areas, but most biologists think of the two species as separated ecologically by habitat type.  Fishers favor mature hardwoods, and martens do best in coniferous forests.  But recent studies suggest both fishers and martens can be found in second growth habitats.  Fishers will move to habitats with large pines in winter, following porcupines.  So, fishers and martens do occasionally occupy the same locales. 

Dr. Patrick Rusz
Director of Wildlife Programs


Facts About Martens

·         In Michigan, the marten is usually referred to as the “pine marten” or American sable.  It has a fairly broad distribution across the northern part of North America, and there is a related species, the beech or stone marten, in northern Eurasia. 

·         Martens are similar to mink in size, with a head and body length of 14 – 17 inches and a tail about one-third that length.  They typically weigh about two pounds; males are larger than females. 

·         The brown fur of martens has long been valued.  Hides of martens were the third most numerous, behind beaver and raccoon, in furs exported at Michilimackinac in 1767.  Almost 10,000 were shipped that year.  Between 1835 and 1839, the American Fur Company in the Upper Peninsula and Detroit handled nearly 23,000 marten pelts.

·         Martens are born and reared in a hollow tree, a hole in a fallen log or stump, or in a rock pile.  Home ranges are 4-8 square miles for males, and typically about 1-2 miles for females.  They are generally solitary animals that associate with each other only briefly during mating times.

·         Martens tend to be nocturnal and have excellent vision, hearing, and sense of smell.  Like most weasels, they are very quick and can kill prey larger than themselves.  Major predators of martens include fishers, coyotes, bobcats, wolves and great horned owls.
·         The pine marten does best in fairly dense stands of pines, hemlocks, or firs where there are lots of large woody tree limbs and fallen trees on the ground.  Pine martens are excellent climbers and feed on squirrels (especially red squirrels), birds, small mammals, insects, and occasionally fruits and nuts. 

Facts About Fishers

·         Fishers are larger than pine martens.  Males are 31-41 inches long and can weigh up to 18 pounds.  Females are much smaller, usually weighing four to six pounds.  
·         Fishers lack the orange throat patches that distinguish martens.
·         Female fishers can delay implantation of fertilized eggs as long as 10 – 11 months and give birth to as many as 6 young.
·         Like pine martens, fishers are mostly nocturnal, but also hunt in daylight.  Fishers will often enter water and typically have home ranges of 50 to 150 square miles.
·         Its name is a misnomer because the species seldom feeds on fish or any other aquatic animal.  But fishers feed on carrion, so almost any kind of animal matter and  prey parts can show up in fisher scat. 



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