American marten
The American marten, also known as the American pine marten, is a species of North American mammal, a member of the family Mustelidae. The species is sometimes referred to as simply the pine marten. The name "pine marten" is derived from the common name of the distinct Eurasian species, Martes martes. Martes americana is found throughout Canada, Alaska, and parts of the northern United States. It is a long, slender-bodied marten, with fur ranging from yellowish to brown to near black. It may be confused with the fisher, but the marten is lighter in color and smaller. Identification of the marten is further eased by a characteristic bib that is a distinctly different color than the body. Sexual dimorphism is pronounced, with males being much larger.
The diet is omnivorous and varies by season, but relies chiefly on small mammals like voles. They are solitary except during the mid-summer breeding season. Embryonic implantation is delayed until late winter, however, with a litter of 15 kits born the following spring. Young stay with the mother in a constructed den until the fall and reach sexual maturity by one year old.
Their sable-like fur made them a thoroughly trapped species during the height of the North American fur trade. Trapping peaked in 1820, and populations were depleted until after the turn of the century. Populations have rebounded since, with them being considered a species of least-concern by the IUCN; however, they remain extirpated from some areas of the Northeast, and of the seven subspecies, one is threatened.
Taxonomy
The Pacific marten was formerly thought to be conspecific, but genetic studies support it being a distinct species from M. americana. The Pacific marten has a more westerly distribution, hence its common name, ranging into the Pacific Northwest and south to Northern California. Additionally, the Pacific marten has a longer snout and broader cranium than the American marten, and slightly different variations in coat color.Seven regional subspecies have been recognized for M. americana, none of which are distinct morphologically; typically, subspecies taxonomy is only emphasized for work involving those regional groups of a species and their unique set of needs or threats.
- Martes americana abieticola
- M. a. abietinoides
- M. a. actuosa
- M. a. americana
- M. a. atrata
- M. a. brumalis
- M. a. kenaiensis
Distribution and habitat
The American marten is broadly distributed in northern North America. From north to south its range extends from the northern limit of the treeline in arctic Alaska and Canada south to New York. From east to west, its distribution extends from Newfoundland to western Alaska, and southwest to the Pacific coast of Canada. The American marten's distribution is vast and continuous in Canada and Alaska. In the northeastern and midwestern United States, American marten distribution is limited to mountain ranges that provide preferred habitats. Over time, the distribution of American marten has contracted and expanded regionally, with local extirpations and successful recolonizations occurring in the Great Lakes region and some parts of the Northeast. The American marten has been reintroduced in several areas where extinction occurred, although in some cases it has instead been introduced into the range of the Pacific marten. It is considered extirpated from Pennsylvania, Maryland, Massachusetts, West Virginia, Ohio, New Jersey, and Illinois.Martens were once thought to live only in old conifer forests but further study shows that martens live in both old and young deciduous and conifer forests as well as mixed forests, including in Alaska and Canada, and south into northern New England, and the Adirondacks in New York. Groups of martens also live in the Midwest, in the Upper Peninsula of Michigan, Wisconsin and much of Minnesota. Trapping and destruction of forest habitat have reduced its numbers, but it is still much more abundant than the larger fisher. The Newfoundland subspecies is considered to be threatened.
A broad, natural hybrid zone between the Pacific and American martens is known to exist in the Columbia Mountains, as well as Kupreanof and Kuiu Islands in Alaska. Several translocations of American marten have been made without regard to the Pacific marten, threatening the latter species. On Dall Island, American martens have been introduced and are hybridizing with the native Pacific marten population, which may put them at risk. On many islands throughout the Alexander Archipelago, American martens have been introduced and are present, with no sign of the Pacific martens; it is unknown whether the islands previously had no marten species until American martens were introduced, or whether the Pacific martens existed on those islands previously but were extirpated by the introduced American martens. In addition, genetic evidence of introgression with American martens is present in other parts of the Pacific marten's range, which is likely also a consequence of American marten introductions.
Home range
Compared to other carnivores, the American marten population density is low for their body size. One review reports population densities ranging from 0.4 to 2.5 individuals/km2. Population density may vary annually or seasonally. Low population densities have been associated with a low abundance of prey species.Home range size of the American marten is extremely variable, with differences attributable to sex, year, geographic area, prey availability, cover type, quality or availability, habitat fragmentation, reproductive status, resident status, predation, and population density. Home range size does not appear to be related to body size for either sex. Home range size ranged from 0.04 sq mi in Maine to 6.1 sq mi in Minnesota for males, and 0.04 sq mi in Maine to 3.0 sq mi in Wisconsin for females.
Males generally exhibit larger home ranges than females, which some authors suggest is due to more specific habitat requirements of females that limit their ability to shift home range. However, unusually large home ranges were observed for four females in two studies.
Home ranges are indicated by scent-marking. American marten male pelts often show signs of scarring on the head and shoulders, suggesting intrasexual aggression that may be related to home range maintenance. Home range overlap is generally minimal or nonexistent between adult males but may occur between males and females, adult males and juveniles, and between females.
Several authors have reported that home range boundaries appear to coincide with topographical or geographical features. In south-central Alaska, home range boundaries included creeks and a major river. In an area burned 8 years previously in interior Alaska, home range boundaries coincided with transition areas between riparian and nonriparian habitats.
Description
The American marten is a long, slender-bodied weasel about the size of a mink with relatively large, rounded ears, short limbs, and a bushy tail. American marten have a roughly triangular head and sharp nose. Their long, silky fur ranges in color from pale yellowish buff to tawny brown to almost black. Their head is usually lighter than the rest of their body, while their tail and legs are darker. American marten usually have a characteristic throat and chest bib ranging in color from pale straw to vivid orange. Sexual dimorphism is pronounced, with males averaging about 15% larger than females in length and as much as 65% larger in body weight.Total length ranges from 1.5 to 2.2 feet, with tail length of 5.4 to 6.4 inches, Adult weight ranges from 1.1 to 3.1 pounds and varies by age and location. Other than size, sexes are similar in appearance. American marten have limited body-fat reserves, experience high mass-specific heat loss, and have limited fasting endurance. In winter, individuals may go into shallow torpor daily to reduce heat loss.
Behavior
American marten activity patterns vary by region, though in general, activity is greater in summer than in winter. American marten may be active as much as 60% of the day in summer but as little as 16% of the day in winter In north-central Ontario individuals were active about 10 to 16 hours a day in all seasons except late winter when activity was reduced to about 5 hours a day. In south-central Alaska, American marten were more active in autumn than in late winter and early spring.American marten may be nocturnal or diurnal. Variability in daily activity patterns has been linked to activity of major prey species, foraging efficiency, sex, reducing exposure to extreme temperatures, season, and timber harvest. In south-central Alaska, American marten were nocturnal in autumn, with strong individual variability in diel activity in late winter. Activity occurred throughout the day in late winter and early spring.
Daily distance traveled may vary by age, sex, habitat quality, season, prey availability, traveling conditions, weather, and physiological condition of the individual. One marten in south-central Alaska repeatedly traveled 7 to 9 miles overnight to move between two areas of home range focal activity. One individual in central Idaho moved as much as 9 miles a day in winter, but movements were largely confined to a 1,280-acre area. Juvenile American marten in east-central Alaska traveled significantly farther each day than adults vs. 0.9-mile ).
Weather factors
The weather may impact American marten activity, resting site use, and prey availability. Individuals may become inactive during storms or extreme cold. In interior Alaska, a decrease in above-the-snow activity occurred when ambient temperatures fell below −4F.A snowy habitat in many parts of the range of the American marten provides thermal protection and opportunities for foraging and resting. American marten may travel extensively under the snowpack. Subnivean travel routes of >33 feet on the Upper Peninsula of Michigan.
American marten are well adapted to snow. On the Kenai Peninsula, individuals navigated through deep snow regardless of depth, with tracks rarely sinking >2 inches into the snowpack. Snowfall patterns may affect distribution, with the presence of American marten linked to deep snow areas.
Where deep snow accumulates, American marten prefer cover types that prevent snow from packing hard and have structures near the ground that provide access to subnivean sites. While American marten select habitats with deep snow, they may concentrate activity in patches with relatively shallow snow.