A closer look into the world of fishers and martens

Fishers and martens with Liz Bradley 12-15-2020

Raise your hand if you have ever seen a marten in the wild. OK, how about a fisher?

Not many of us have, and there are many reasons they are so elusive. Most people don’t know they live here.

Our monthly visit with Liz Bradley, FWP Biologist for Region 2, sheds some light on what they are, what they eat and why they are difficult buggers to monitor.

1. What exactly are fishers and martens?

Fishers and martens are both members of the mustelid, or weasel family which also include mink, wolverine, ferrets, weasels, otters, and badgers. Fishers can be distinguished from martens by their larger body size and darker brown fur. Marten have ears that are larger in proportion to their body than fishers.

Recent genetic research has uncovered there are actually two subspecies of marten living in Montana, the Pacific marten and the American marten. The Clark Fork Valley (through Plains) is suggested as a dividing line with the Pacific marten found to the south including Mineral County. Marten have a distinct bib on their neck that ranges in color from pale yellow to a vivid orange.

2. Where in Mineral County do they live? Meaning, what elevation and habitat helps them to thrive?

Although there is some elevational overlap between fishers and martens, fishers generally live at lower elevations than martens. Fishers, with their larger, heavier body size have a more difficult time traveling in deep snow. Martens, on the other hand, being smaller and more agile, are well adapted to snow and will travel and hunt under the snowpack.

Both fishers and martens live in mesic (or wet), conifer dominated forests with lots of physical structure and debris on the ground. Fishers prefer living in mature, dense forests and especially like Western Red Cedar stands found in drainage bottoms in Mineral County because they provide cavities for resting, as well as denning sites for females.

3. How common are they in Mineral County?

In Montana, martens are much more common than fishers, although both are shy and difficult to spot in the wild. In Mineral County both species are found more commonly on the south side of Interstate 90.

Mineral County provides excellent habitat for martens but less adequate habitat for fishers, which thrive just over the hill in Idaho where there are larger contiguous stands of Western Red Cedar.

4. Are they considered species of concern? Or endangered?

Martens are common and are not a species of concern. Fishers, are state listed as a species of concern, and have been petitioned, but denied for listing, under the federal Endangered Species Act.

5. What are their primary predators and are they affected by climate change?

Predators of fishers include bobcats, coyotes, and mountain lions. Martens are more subject to predation than fishers and their predators include bobcats, coyotes, foxes, mountain lions, and raptors. Fishers also will compete with and kill marten.

6. How large will they become and how old can they live?

A female fisher can weigh up to 8 pounds and a male up to 15 pounds. Martens are more in the 2-3 pound range. Fishers can live up to 10 years in the wild and marten can live up to 15 years.

7. When is their breeding season and how big, and often, do females have litters?

Both female marten and fisher exhibit what’s called “delayed implantation.” Female fishers start breeding at about one year of age and it is a year-long event. The breeding season occurs in late March/early April, but the embryo is not actually implanted until 10 months later in February when pregnancy begins. One to four kits are born 50 days later around late March/early April and then female will go into estrus 7-10 days later and the reproductive cycle starts again. Female martens start breeding at 1-2 years of age. Breeding season occurs in July or August but like fishers, also implant and start pregnancy in late winter with 1-5 kits born in late March/early April.

8. What does their diet consist of and are they primarily nocturnal?

Fishers and martens are both nocturnal and diurnal, and both are omnivores. Both eat small mammals such as squirrels, snowshoe hares, mice, voles, as well as birds, and will supplement their diet with insects, fruit, and other vegetation in the summer.

Snowshoe hares are an especially important prey item in Montana, especially for fishers. Both will scavenge on carrion, if available. Fishers generally do not eat fish, as the name might suggest. However, fishers are one of the few animals that have learned how to successfully prey on porcupine.

9. Can they climb trees?

Yes, both fishers and martens are accomplished tree climbers and will often rest on tree limbs or in hollowed out snags. Females will use hollowed out trees and cavities for denning.

10. I’d heard one of them can rotate their back feet almost 180 degrees. If this is true, which one is it and what it this used for?

Martens have the ability to rotate their hind limbs in order to descend trees headfirst.

11. What is the history of trapping and would you know the approximate value of their pelts?

The fur trade for marten, beaver, fisher, mink, otter, and other furbearers began in America in the early 1500s. Furs were and are still valued for their use in clothing. In the early years of the fur trade, furs were traded with Europe for goods like tea, knives, and guns. Today’s furs are largely purchased by Russia and China. A marten pelt today is worth approximately $20-30 and a fisher pelt may sell for approximately $40 (according to Trapping Today website).

Trapping opportunities are limited for fisher in western Montana and only allowed in the Bitterroot Zone which includes the Bitterroot Valley and Mineral County. There is total quota of five fisher allowed with a sub quota of one female (which means that the whole season closes if one female is harvested). Marten trapping is allowed throughout western Montana and there are no quotas in Mineral County.