American Marten

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The American marten (Martes americana) is a North American  member of the family  Mustelidae, sometimes referred to as the pine marten. The name " pine marten " is derived from the common but distinct Eurasian species of  Martes . It differs from the fisher  (Martes pennanti) in that it is smaller in size. 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 treeline in arctic Alaska  and  Canada  to northern  New Mexico. From east to west its distribution extends from Newfoundland  to  California. In Canada and Alaska, American marten distribution is vast and continuous. In the western United States, American marten distribution is limited to mountain ranges that provide preferred habitat. 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.| [2]  The American marten has been reintroduced in several areas where  extinction  occurred.| [3] |   The marten lives in mature  coniferous  or  mixed forests  in  Alaska  and  Canada, the Pacific Northwest of the United States| [4]  and south into Northern  New England | [5]  | [6]  | [7]  and through the  Rocky Mountains  and  Sierra Nevada. Small groups of martens live in the Midwest  in  Minnesota  and  Wisconsin. Trapping and destruction of forest habitat have reduced its numbers, but it is still much more abundant than the larger fisher. The Newfoundland subspecies  of this animal (Martes americana atrata) is considered to be threatened.

edit ] Home range
Compared to other carnivores, American marten population density is low for their body size. One review reports population densities ranging from 0.4 to 2.5 individuals/km2.| [2] Population density may vary annually| [8]  or seasonally.| [9]  Low population densities have been associated with low abundance of prey species.| [2]

Home range size of the American marten is extremely variable, with differences attributable to sex,| [10] | [11]  | [12]  | [13]  year, geographic area,| [2]  prey availability,| [2]  <sup class="reference" id="cite_ref-r165_13-0">| [14]  cover type, quality or availability,<sup class="reference" id="cite_ref-r28_1-5">| [2]  <sup class="reference" id="cite_ref-r165_13-1">| [14]  habitat fragmentation,<sup class="reference" id="cite_ref-r80_14-0">| [15]  reproductive status, resident status, predation,<sup class="reference" id="cite_ref-r19_15-0">| [16]  and population density.<sup class="reference" id="cite_ref-r165_13-2">| [14]  Home range size does not appear to be related to body size for either sex.<sup class="reference" id="cite_ref-r156_9-1">| [10]  Home range size ranged from 0.04 sq mi (0.1 km2) in Maine to 6.1 sq mi (15.7 km2) in Minnesota for males, and 0.04 sq mi (0.1 km2) in Maine to 3.0 sq mi (7.7 km2) in Wisconsin for females.<sup class="reference" id="cite_ref-r165_13-3">| [14]

Males generally exhibit larger home ranges than females,<sup class="reference" id="cite_ref-r156_9-2">| [10] <sup class="reference" id="cite_ref-r129_10-1">| [11]  <sup class="reference" id="cite_ref-r29_11-1">| [12]  <sup class="reference" id="cite_ref-r132_12-1">| [13]  which some authors suggest is due to more specific habitat requirements of females (e.g., denning or prey requirements) that limit their ability to shift home range.<sup class="reference" id="cite_ref-r129_10-2">| [11]  However, unusually large home ranges were observed for 4 females in two studies (Alaska<sup class="reference" id="cite_ref-r150_16-0">| [17]  and Quebec<sup class="reference" id="cite_ref-r64_7-1">| [8]  ). Males and females in northeastern California appeared to have approximately equal home range size.<sup class="reference" id="cite_ref-r152_17-0">| [18]

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.<sup class="reference" id="cite_ref-r165_13-4">| [14] Home range overlap is generally minimal or nonexistent between adult males<sup class="reference" id="cite_ref-r3_8-1">| [9]  <sup class="reference" id="cite_ref-r29_11-2">| [12]  <sup class="reference" id="cite_ref-r76_18-0">| [19]  but may occur between males and females,<sup class="reference" id="cite_ref-r3_8-2">| [9]  <sup class="reference" id="cite_ref-r29_11-3">| [12]  adult males and juveniles,<sup class="reference" id="cite_ref-r29_11-4">| [12]  <sup class="reference" id="cite_ref-r148_19-0">| [20]  and between females.<sup class="reference" id="cite_ref-r177_20-0">| [21]

Several authors have reported that home range boundaries appear to coincide with topographical or geographical features. In northeastern California, movements and home range boundaries were influenced by cover, topography (forest-meadow edges, open ridgetop, lakeshores), and other American marten.<sup class="reference" id="cite_ref-r152_17-1">| [18] In south-central Alaska, home range boundaries included creeks and a major river.<sup class="reference" id="cite_ref-r29_11-5">| [12]  In an area burned 8 years previously in interior Alaska, home range boundaries coincided with transition areas between riparian and nonriparian habitats.<sup class="reference" id="cite_ref-r177_20-1">| [21]  In northwestern Montana, home range boundaries appeared to coincide with the edge of large open meadows and burned areas; the authors suggested that open areas represent a "psychological rather than physical barriers".<sup class="reference" id="cite_ref-r78_21-0">| [22]

edit ] Description
EnlargeSkullThe 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 the tail and legs are darker. American marten usually have a characteristic throat and chest bib ranging in color from pale straw to vivid orange.<sup class="reference" id="cite_ref-r38_2-1">| [3] Sexual dimorphism is pronounced, with males averaging about 15% larger than females in length and as much as 65% larger in body weight.<sup class="reference" id="cite_ref-r38_2-2">| [3]  Body length ranges from 1.5 to 2.2 feet (0.5–0.7 m). Adult weight ranges from 1.1 to 3.1 pounds (0.5–1.4 kg) and varies by age and location. Other than size, sexes are similar in appearance.<sup class="reference" id="cite_ref-r28_1-6">| [2] American marten have limited body-fat reserves, experience high mass-specific heat loss, and have a limited fasting endurance. In winter, individuals may go into shallow torpor  daily to reduce heat loss.<sup class="reference" id="cite_ref-r136_22-0">| [23]

edit ] Behavior
American marten activity patterns vary by region,<sup class="reference" id="cite_ref-r165_13-5">| [14] though in general, activity is greater in summer than in winter.<sup class="reference" id="cite_ref-r38_2-3">| [3]  <sup class="reference" id="cite_ref-r136_22-1">| [23]  American marten may be active as much as 60% of the day in summer but as little as 16% of the day in winter.<sup class="reference" id="cite_ref-r136_22-2">| [23]  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 (66% active) than in late winter and early spring (43% active).<sup class="reference" id="cite_ref-r29_11-6">| [12] In northeastern California, more time spent was spent traveling and hunting in summer than in winter, suggesting that reduced winter activity may be related to thermal and food stress or may be the result of larger prey consumption and consequent decrease in time spent foraging.<sup class="reference" id="cite_ref-r189_23-0">| [24]

American marten may be nocturnal or diurnal. Variability in daily activity patterns has been linked to activity of major prey species,<sup class="reference" id="cite_ref-r165_13-6">| [14] <sup class="reference" id="cite_ref-r189_23-1">| [24]  foraging efficiency,<sup class="reference" id="cite_ref-r29_11-7">| [12]  gender, reducing exposure to extreme temperatures,<sup class="reference" id="cite_ref-r29_11-8">| [12]  <sup class="reference" id="cite_ref-r165_13-7">| [14]  <sup class="reference" id="cite_ref-r177_20-2">| [21]  season,<sup class="reference" id="cite_ref-r76_18-1">| [19]  <sup class="reference" id="cite_ref-r136_22-3">| [23]  <sup class="reference" id="cite_ref-r189_23-2">| [24]  and timber harvest. In northeastern California, activity in the snow-free season (May–December) was diurnal, while winter activity was largely nocturnal.<sup class="reference" id="cite_ref-r189_23-3">| [24] 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.<sup class="reference" id="cite_ref-r29_11-9">| [12]

Daily distance traveled may vary by age,<sup class="reference" id="cite_ref-r150_16-1">| [17] gender, habitat quality, season,<sup class="reference" id="cite_ref-r76_18-2">| [19]  prey availability, traveling conditions, weather, and physiological condition of the individual. Year-round daily movements in Grand Teton National Park ranged from 0 to 2.83 miles (0–4.57 km), averaging 0.6 mile (0.9 km, observations of 88 individuals).<sup class="reference" id="cite_ref-r76_18-3">| [19] One marten in south-central Alaska repeatedly traveled 7 to 9 miles (11–14 km) overnight to move between 2 areas of home range focal activity.<sup class="reference" id="cite_ref-r29_11-10">| [12]  One individual in central Idaho moved as much as 9 miles (14 km) a day in winter, but movements were largely confined to a 1,280-acre (518 ha) area. Juvenile American marten in east-central Alaska traveled significantly farther each day than adults (1.4 miles (2.2 km) vs. 0.9 mile (1.4 km)).<sup class="reference" id="cite_ref-r150_16-2">| [17]

edit ] Weather factors
EnlargeWeather may impact American marten activity, resting site use, and prey availability. Individuals may become inactive during storms or extreme cold.<sup class="reference" id="cite_ref-r165_13-8">| [14] <sup class="reference" id="cite_ref-r74_24-0">| [25]  In interior Alaska, a decrease in above-the-snow activity occurred when ambient temperatures fell below −4 °F (−20 °C).<sup class="reference" id="cite_ref-r177_20-3">| [21]  In southeastern Wyoming, temperature influenced resting site location. Above-snow sites were used during the warmest weather, while subnivean sites were used during the coldest weather, particularly when temperatures were low and winds were high following storms. High mortality may occur if American marten become wet in cold weather, as when unusual winter rains occur during live trapping.<sup class="reference" id="cite_ref-r38_2-4">| [3] In southeastern Wyoming, temperature was linked to resting site use; above-snow sites were used during the warmest weather, while subnivean sites were used during the coldest weather. In Yosemite National Park, drought conditions increased the diversity of prey items; American marten consumed fish and small mammal species made more accessible by low snow conditions in a drought year.<sup class="reference" id="cite_ref-r74_24-1">| [25]

Snow is an important habitat feature in many parts of the range of the American marten, providing thermal protection<sup class="reference" id="cite_ref-r148_19-1">| [20] and opportunities for foraging and resting.<sup class="reference" id="cite_ref-r76_18-4">| [19]  American marten may travel extensively under the snowpack. Subnivean travel routes of >98 feet (30 m) were documented in northeastern Oregon,<sup class="reference" id="cite_ref-r168_25-0">| [26] >33 feet (10 m) on the Upper Peninsula of Michigan,<sup class="reference" id="cite_ref-r168_25-1">| [26]  and up to 66 feet (20 m) in Wyoming.<sup class="reference" id="cite_ref-r76_18-5">| [19]

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 (5 cm) into the snowpack. Snowfall pattern may affect distribution, with the presence of American marten linked to deep snow areas.<sup class="reference" id="cite_ref-r148_19-2">| [20]

Adaptations to deep snow are particularly important in areas where the American marten is sympatric with the fisher, which may compete with and/or prey on American marten. In California, American marten were closely associated with areas of deep snow (>9 inches (23 cm)/winter month), while fishers were more associated with shallow snow (<5 inches (13 cm)/winter month). Overlap zones were areas with intermediate snow levels. Age and recruitment ratios suggested that there were few reproductive American marten where snow was shallow and few reproductive fishers where snow was deep.<sup class="reference" id="cite_ref-r98_26-0">| [27]

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.<sup class="reference" id="cite_ref-27">| [28] While American marten select habitats with deep snow, they may concentrate activity in patches with relatively shallow snow. In north-central Idaho, American marten activity was highest in areas where snow depths were <12 inches (30 cm). This was attributed to easier burrowing for food and more shrub and log cover.<sup class="reference" id="cite_ref-r96_28-0">| [29]

edit ] Breeding
American marten reach sexual maturity by 1 year of age, but effective breeding may not occur before 2 years of age.<sup class="reference" id="cite_ref-r136_22-4">| [23] In captivity, 15-year-old females bred successfully.<sup class="reference" id="cite_ref-r38_2-5">| [3]  <sup class="reference" id="cite_ref-r166_29-0">| [30]  In the wild, 12-year-old females were reproductive.<sup class="reference" id="cite_ref-r166_29-1">| [30]

Adult American marten are generally solitary except during the breeding season.<sup class="reference" id="cite_ref-r38_2-6">| [3] They are polygamous, and females may have multiple periods of heat.<sup class="reference" id="cite_ref-r166_29-2">| [30]  Females enter  estrus  in July or August,<sup class="reference" id="cite_ref-r136_22-5">| [23]  with courtship lasting about 15 days.<sup class="reference" id="cite_ref-r38_2-7">| [3]  Embryonic implantation is delayed until late winter, with active gestation lasting approximately a month. Females give birth in late March or April to a litter ranging from 1 to 5 kits.<sup class="reference" id="cite_ref-r136_22-6">| [23] Annual reproductive output is low according to predictions based on body size. Fecundity varies by age and year and may be related to food abundance.<sup class="reference" id="cite_ref-r28_1-7">| [2]

edit ] Denning behavior
Females use dens to give birth and to shelter kits. Dens are classified as either natal dens, where parturition takes place, or maternal dens, where females move their kits after birth.<sup class="reference" id="cite_ref-r28_1-8">| [2] American marten females use a variety of structures for natal and maternal denning, including the branches, cavities or broken tops of live trees, snags,<sup class="reference" id="cite_ref-r76_18-6">| [19]  stumps, logs,<sup class="reference" id="cite_ref-r76_18-7">| [19]  woody debris piles, witch's brooms, rock piles, and red squirrel (Tamiasciurus hudsonicus) nests or middens. Females prepare a natal den by lining a cavity with grass, moss, and leaves.<sup class="reference" id="cite_ref-r165_13-9">| [14] They frequently move kits to new maternal dens once kits are 7–13 weeks old. Most females spend >50% of their time attending dens in both preweaning and weaning periods, with less time spent at dens as kits aged. Paternal care has not been documented.<sup class="reference" id="cite_ref-r28_1-9">| [2]

edit ] Development of young
EnlargeAmerican martenWeaning occurs at 42 days. Young emerge from dens at about 50 days but may be moved by their mother before this.<sup class="reference" id="cite_ref-r28_1-10">| [2] In northwestern Maine, kits were active but poorly coordinated at 7 to 8 weeks, gaining coordination by 12 to 15 weeks. Young reach adult body weight around 3 months.<sup class="reference" id="cite_ref-r136_22-7">| [23]

Kits generally stay in the company of their mother through the end of their first summer, and most disperse in the fall.<sup class="reference" id="cite_ref-r28_1-11">| [2] The timing of juvenile dispersal is not consistent throughout American marten's distribution, ranging from early August to October.<sup class="reference" id="cite_ref-r28_1-12">| [2]  In south-central Yukon, young-of-the-year dispersed from mid-July to mid-September, coinciding with the onset of female estrus.<sup class="reference" id="cite_ref-r3_8-3">| [9]  Observations from Oregon<sup class="reference" id="cite_ref-r19_15-1">| [16]  and Yukon<sup class="reference" id="cite_ref-r3_8-4">| [9]  suggest that juveniles may disperse in early spring. Of 9 juvenile American marten that dispersed in spring in northeastern Oregon, 3 dispersed a mean of 20.7 miles (33.3 km) (range: 17.4–26.8 miles (28.0–43.2 km)) and established home ranges outside of the study area. Three were killed after dispersing distances ranging from 5.3 to 14.6 miles (8.6–23.6 km), and 3 dispersed a mean of 5.0 miles (8.1 km) (range: 3.7–6.0 miles (6.0–9.6 km)) but returned and established home ranges in the area of their original capture. Spring dispersal ended between June and early August, after which individuals remained in the same area and established a home range.<sup class="reference" id="cite_ref-r19_15-2">| [16]

edit ] Food habits
American marten are opportunistic predators, influenced by local and seasonal abundance and availability of potential prey.<sup class="reference" id="cite_ref-r136_22-8">| [23] They require about 80 kcal/day while at rest, the equivalent of about 3 voles ( Microtus ,  Myodes , and  Phenacomys  spp.).<sup class="reference" id="cite_ref-r165_13-10">| [14]  Voles dominate diets throughout the American marten's geographic range,<sup class="reference" id="cite_ref-r136_22-9">| [23]  though larger prey—particularly  snowshoe hares —may be important, particularly in winter.<sup class="reference" id="cite_ref-r148_19-3">| [20]   Red-backed voles  (Myodes spp.) are generally taken in proportion to their availability, while meadow voles (Microtus' spp.) are taken in excess of their availability in most areas. Deer mice (Peromyscus maniculatus) and shrews (Soricidae) are generally eaten less than expected, but may be important food items in areas lacking alternative prey species.<sup class="reference" id="cite_ref-r28_1-13">| [2]  Birds were the most important prey item in terms of frequency and volume on the Queen Charlotte Islands, British Columbia. Fish may be important in coastal areas.<sup class="reference" id="cite_ref-r118_30-0">| [31]

American marten diet may shift seasonally<sup class="reference" id="cite_ref-r29_11-11">| [12] <sup class="reference" id="cite_ref-r152_17-2">| [18]  <sup class="reference" id="cite_ref-r148_19-4">| [20]  <sup class="reference" id="cite_ref-r189_23-4">| [24]  <sup class="reference" id="cite_ref-r96_28-1">| [29]  or annually.<sup class="reference" id="cite_ref-r29_11-12">| [12]  <sup class="reference" id="cite_ref-r74_24-2">| [25]  In general, diet is more diverse in summer than winter, with summer diets containing more fruit, other vegetation, and insects. Diet is generally more diverse in the eastern and southern parts of American marten's distribution compared to the western part,<sup class="reference" id="cite_ref-r136_22-10">| [23] though there is high diversity in the Pacific states. American marten exhibit the least diet diversity in the subarctic, though diversity may also be low in areas where the diet is dominated by large prey species (e.g., snowshoe hares or red squirrels).<sup class="reference" id="cite_ref-r112_31-0">| [32]

American marten may be important seed dispersers; seeds generally pass through the animal intact, and seeds are likely germinable. One study from Chichagof Island, southeast Alaska, found that Alaska blueberry (Vaccinium alaskensis) and ovalleaf huckleberry (V. ovalifolium) seeds had higher germination rates after passing through the gut of American marten compared to seeds that dropped from the parent plant. Analyses of American marten movement and seed passage rates suggested that American marten could disperse seeds long distances: 54% of the distances analyzed were >0.3 mile (0.5 km).<sup class="reference" id="cite_ref-32">| [33]

edit ] Life span
American marten in captivity may live for 15 years. The oldest individual documented in a wild was 14.5 years old. Survival rates vary by geographic region, exposure to trapping, habitat quality, and age. In an unharvested population in northeastern Oregon, the probability of survival of American marten ≥9 months old was 0.55 for 1 year, 0.37 for 2 years, 0.22 for 3 years, and 0.15 for 4 years. The mean annual probability of survival was 0.63 for 4 years.<sup class="reference" id="cite_ref-r20_33-0">| [34] In a harvested population in east-central Alaska, annual adult survival rates ranged from 0.51 to 0.83 over 3 years of study. Juvenile survival rates were lower, ranging from 0.26 to 0.50.<sup class="reference" id="cite_ref-r150_16-3">| [17] In Newfoundland, annual adult survival was 0.83. Survival of juveniles from October to April was 0.76 in a protected population, but 0.51 in areas open to snaring and trapping.<sup class="reference" id="cite_ref-r80_14-1">| [15] In western Quebec, natural mortality rates were higher in clearcut areas than in unlogged areas.<sup class="reference" id="cite_ref-r135_34-0">| [35]

edit ] Predators
American marten are vulnerable to predation from raptors and other carnivores. The threat of predation may be an important factor shaping American marten habitat preferences, a hypothesis inferred from their avoidance of open areas and from behavioral observations of the Eurasian pine marten  (Martes martes).<sup class="reference" id="cite_ref-r28_1-14">| [2]  Specific predators vary by geographic region. In Newfoundland, red foxes  (Vulpes vulpes) were the most frequent predator, though coyote (Canis latrans) and other American marten were also responsible for some deaths.<sup class="reference" id="cite_ref-r80_14-2">| [15]  In deciduous forests in northeastern British Columbia, most predation was attributed to raptors.<sup class="reference" id="cite_ref-r132_12-2">| [13]  Of 18 American marten killed by predators in northeastern Oregon, 8 were killed by  bobcats  (Lynx rufus), 4 by raptors, 4 by other American marten, and 2 by coyotes. Throughout the distribution of American marten, other predators include the great horned owl (Bubo virginianus), bald eagle (Haliaeetus leucocephalus), golden eagle (Aquila chrysaetos), Canada lynx (L. canadensis), mountain lion (Puma concolor),<sup class="reference" id="cite_ref-r38_2-8">| [3] <sup class="reference" id="cite_ref-r166_29-3">| [30]  fisher (M. pennanti), wolverine (Gulo gulo), grizzly bear (Ursus arctos horribilis), American black bear (U. americanus), and gray wolf (C. lupus).<sup class="reference" id="cite_ref-r177_20-4">| [21]  In northeastern Oregon, most predation (67%) occurred between May and August, and no predation occurred between December and February.<sup class="reference" id="cite_ref-r20_33-1">| [34]

edit ] Hunting
The fur of the American marten is shiny and luxuriant, resembling that of the closely related sable. At the turn of the twentieth century, the American marten population was depleted due to the fur trade. The Hudson's Bay Company  traded in pelts from this species among others. Numerous protection measures and reintroduction efforts have allowed the population to increase, but deforestation  is still a problem for the marten in much of its habitat. American marten are trapped for their fur in all but a few states and provinces where they occur.<sup class="reference" id="cite_ref-r136_22-11">| [23] The highest annual trapping rate in North America was in 1820 (272,000).<sup class="reference" id="cite_ref-r165_13-11">| [14]

Harvest is a major source of American marten mortality in trapped populations<sup class="reference" id="cite_ref-r150_16-4">| [17] <sup class="reference" id="cite_ref-r135_34-1">| [35]  and may account for up to 90% of all deaths in some areas.<sup class="reference" id="cite_ref-r28_1-15">| [2]  Overharvesting has contributed to local extirpations.<sup class="reference" id="cite_ref-r10_35-0">| [36]  Trapping may impact population density, sex ratios and age structure.<sup class="reference" id="cite_ref-r28_1-16">| [2]  <sup class="reference" id="cite_ref-r165_13-12">| [14]  <sup class="reference" id="cite_ref-r136_22-12">| [23]  Juveniles are more vulnerable to trapping than adults,<sup class="reference" id="cite_ref-r80_14-3">| [15]  <sup class="reference" id="cite_ref-r10_35-1">| [36]  and males are more vulnerable than females.<sup class="reference" id="cite_ref-r28_1-17">| [2]  <sup class="reference" id="cite_ref-r80_14-4">| [15]  American marten are particularly vulnerable to trapping mortality in industrial forests.<sup class="reference" id="cite_ref-r136_22-13">| [23]

edit ] Other
Other sources of mortality include drowning,<sup class="reference" id="cite_ref-r168_25-2">| [26] starvation,<sup class="reference" id="cite_ref-r59_36-0">| [37]  exposure,<sup class="reference" id="cite_ref-r20_33-2">| [34]  choking, and infections associated with injury.<sup class="reference" id="cite_ref-r80_14-5">| [15]  During live trapping, high mortality may occur if individuals become wet in cold weather.<sup class="reference" id="cite_ref-r38_2-9">| [3]

American marten host several internal and external parasites, including helminths, fleas (Siphonaptera), and ticks (Ixodida).<sup class="reference" id="cite_ref-r165_13-13">| [14] American marten in central Ontario carried both toxoplasmosis and Aleutian disease, but neither affliction was suspected to cause significant mortality.<sup class="reference" id="cite_ref-r166_29-4">| [30]  High American marten mortality in Newfoundland was caused by encephalitis.<sup class="reference" id="cite_ref-r59_36-1">| [37]

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