Alaska Land Mammals
Natural History of Alaska
- Native Peoples of Alaska
- Alaska Land Mammals
- Alaska Birds
- Close Encounters with Wildlife
- Denali National Park and Preserve
- Geologic History of Denali National Park
- Alaska Geology
- Major Vegetation Types of Alaska
- Trees of Alaska
- National Petroleum Reserve
- Alaska Government
- Legislation that Shaped Alaska's History
Alaska is well known for the mammals that are found in the state. There are several endangered or threatened species in the continental United States that are still found in relative abundance within Alaska. The highlight of many people’s visit to Alaska is the opportunity to see large mammals such as whales, moose, caribou, bears and wolves.
Flesh-eaters: Carnivora
This order includes those land mammals that are primarily meat eaters. Many of them also eat nuts, berries, and fruits, but usually their main diet is meat. They vary greatly in size from the Least Weasel (wt. approx. 1/10 lb; 45 g) to the Alaskan Brown on the front foot, although some have the inner toe high on the foot so that it does not show in the tracks. On the rear foot, there may be 4 or 5 toes, depending upon the species. Every species in this order also have large canine teeth.
Bears: Ursidae
The members of the bear family walk on the entire foot (known as plantigrade) like humans do and they have 5 toes on the font and back feet. They have short tails that are almost covered over by their fur, and their ears are relatively small and rounded.
Black Bear, Ursus americanus
Black bears are the most abundant of the three species of bears found in North America, as they have been recorded in every state except Hawaii. Black bears range throughout most of the forested areas of Alaska, but they are not found on the Seward Peninsula, to the west of Lake Illiamna on the Alaska Peninsula, or north of the Brooks Range. They are also not found on the following islands: Kodiak, Montague, Hinchinbrook, Admiralty Baranof, Chichaof, and Kruzof. Black bears are most commonly found in the forest, but they can also be found from sea level to alpine areas.
Description: Black bears are the smallest of North America’s three bear species. Adults stand about 26 inches at the shoulder and measure about 60 inches from nose to tail, with the tail being about 2 inches long. Males are usually larger than females, with males weighing 180-200 lbs. in summer (they can be considerably lighter in the spring after winter dormancy) and up to 20% heavier in the fall when they are fat. Their size is often overestimated.
;The color of black bears ranges form jet black to white, but three colors are most commonly seen in Alaska; Black is by far the most common color, but brown or cinnamon bears are seen in south-central Alaska. A rare blue or glacier phase may be seen in the Yakutat area. Black bears are distinguished from brown/grizzly bears by their straight face profile and sharply curved claws that are usually no longer than one and half inches in length.
Life History: Black bears are generally solitary, except during the mating period or when sows have cubs. Mating occurs from June through July. The cubs are born in he den during February to March. The gestation period is about 7 months and the cub are blind and weigh only a few ounces at birth. When the cubs emerge from the den in May, they weigh about 5 pounds and have woolly hair. A female may have one to four cubs in each litter, but a litter of two is the most common. The cubs will remain with their mother through their first full winter following their birth. Female black bears breed yearly and become sexually mature at 3 to 4 years of age.
Black bears spend the winter months in a state of semi-hibernation. Their metabolic rate and body temperature drops and they sleep for long periods of time. They are not considered true hibernators because they do occasionally awaken and may even emerge from their dens. They may remain dormant for up to 7 to 8 months and females with cubs emerge later in the spring than lone bears. Dens are located anywhere form sea level to alpine areas.
Diet: Black bears are creatures of opportunity, they follow some general patterns during the year as to which foods they primarily pursue, but they will take advantage of carrion when they can. In the spring , they will feed upon the new young plants emerging, but will also feed on any carrion or winter kill that they find. If salmon are available, they will shift to salmon during the summer months. Berries are a prominent food source in late summer and fall.
Brown Bear, Ursus arctos
The brown bear occurs throughout Alaska except on the islands of Fredrick Sound in southeastern Alaska, the islands west of Unimak in the Aleutian Chain and the islands of the Bering Sea. Brown bears also occur in Europe, Asia, Canada, and the western united States. Once numerous in the Lower 48 (10,000 as recent as 1850), there are about 1,000 brown bears left in the continental U.S. (maybe as few as 600). Brown bear population in Alaska is estimated to be 31,000.
Description: Brown bears are grizzly bears and used to be considered separate species. Taxonomists now consider them to be the same species – Ursus arctos –since they can interbreed and produce fertile young. Many people differentiate “brown bears are those that live near the coast and have access to salmon, whereas the grizzly bears live in the interior of Alaska without access to salmon and are primarily vegetarian.
Brown bears may closely resemble black bears, but the brown bear is larger, has a large shoulder hump, and longer straighter claws. The coloration of brown bears can vary from being dark brown to blond. Just as in black bears, weights vary according to the time of year. During the late summer and fall, a mature male brown bear weighs between 400 and 900 pounds, with very large individuals weighing as much as 1,400 pounds (Kodiak Island). Females weigh one half to three quarters as much as the males.
Life History: Brown bears mate anytime from May through July. Sometimes a mated pair may remain together for up to a month but otherwise, they are generally solitary creatures. Male s will occupy a home range (sometimes up to 1,500 square miles) that encompasses several females home ranges so that they have more of a chance to mate each year. In areas of high bear density, a female may mate with more than one male. At the earliest, females reach sexual maturity at 4 years of age, but it may not happen until 5 to 6 years of age.
When a female brown bear becomes pregnant, the blastocyst (the fertilized egg which has reached a level of multicellular development) does not attach tot eh uterine lining as it does in other mammals. Instead, the blastocyst remains dormant and unattached inside the uterus. The blastocyst will not attach to uterine wall and resume its development until the brown bear begins its semi-hibernation. This process is known as delayed implantation. Since semi-hibernation may not begin until October or November and the cubs are born in January or February, the actual gestation is only 3 months long. If the female does not have enough fat reserves to support herself and her young, then the blastocyst apparently may not implant itself and become aborted.
The cubs are born in the den, blind, weighing only about a pound, and covered with fine gray hair. Litter size ranges form one to four cubs, with a litter size of two being most common. Upon leaving the den in the spring cubs will weigh about 15 pounds, upon denning in their first fall, thy weigh 60-70 pounds. The cubs will remain with their mother through the second year and sometimes even through their third year. Only after driving her cubs away, will a sow come into estrus again.
Denning provides a good way to spend the winter. Regnant females are the first to den and the last to re-appear. Adult males den last and re-appear first. On Kodiak Island where weather condition are good and food is in abundance almost year round, denning is only a short period, sometimes not more than a month. In the Arctic, where weather is severe and food supplies short, grizzlies den up to 8 months.
Diet: Brown bears are omnivorous, feeding on plants and young shoots, carrion. fish, and moose and caribou when it can capture them. It is most common for brown bears to take calves in the spring, but some bears are capable of taking an adult moose or caribou in the summer and fall. In areas of high food abundance, such as McNeil Falls, brown bears may congregate in large numbers and tolerate each other’s presence.
Brown bears may eat up to 80-90 pound per day to gain 3-6 pounds of fat. They must be at the right place at the right time to take advantage of the most abundant, highest energy sources. Therefore brown bears have a very predictable feeding pattern.
Otters, Weasels And Skunks: Mustelidae
The members of this family vary in size and color. Most of them have long slender bodies and short legs, small rounded ears, and anal cent glands. In many species of this family, the males are distinctly larger than the females.
Wolves And Foxes: Canidae
The members of this family are all dog-like in appearance. They have 5 toes on the front feet (one toes is high) and 4 on the back feet. All of the members of this family have a scent gland at the base of the tail on top.
Wolf, Canis lupus
The wolf occurs throughout on the mainland of Alaska in a wide variety of habitats, form the rain forest in the southeast to the arctic tundra in the far north of the state. Wolves are common throughout much of the state with densities that vary for about one wolf per 25 square miles in southeastern and the interior, to one wolf per 150 square miles or less in the coastal portions of western and northern Alaska.
Description: The color of wolves varies tremendously, the vary between whit and black with many variations of tan or gray. Adult males generally weigh between 85 and 115 pounds, but hey occasionally weigh up to 130 pounds. Females are typically 5 to 10 pounds lighter than males but rarely weigh more than 110 pounds.
Life History: Wolves are highly social animals and typically live in packs which include the parents and the ups of the year, yearlings, and other adults. A dominance hierarchy is established with separate rank orders between males and females. Pack size is usually 6 to 12, but sometimes it may be as high as 20 to 30 members. Each pack maintains a home range in which other packs are usually kept out, but there may be some overlap. The home range of a wolf pack in Alaska is generally between 200 and 600 square miles.
Breeding occurs in February and March and pups are born in May or early June. Litter size on average is 5 pups, but it can range form 2 to 10 pups. The female gives birth to the pus in an excavated den that may go back as much as 10 feet. Food is brought back to the den for the mother and the pups by other members of the pack. As the pups get older, other members of the pack will watch over the young while the mother hunts for herself. The pups are weaned by mid-summer and by early winter, they can travel with the pack throughout the home range.
Diet: Wolves are carnivorous and in most of Alaska, moose and caribou make up a large portion of their diet. Other important prey items include Dall sheep, mountain goats, Sitka lack-tailed deer, and small mammals (depending upon the availability). The very young, diseased, and very old prey animals are most commonly taken by wolves.
Red Fox, Vulpes vulpes
The red fox is found throughout Alaska except for some islands in the southeast, western Aleutians, and Prince William Sound. The red fox prefers areas with a variety of habitats as they generally utilize forest edge to forage in. Red foxes do inhabit the tundra, but not in the abundance that thy do in other areas.
Description: The red fox is 22 to 32 inches long, head to base of tail, with tail being an additional 14 to 16 inches long. It is well known for its reddish coat, but other color phases, such as the cross, silver, and black exist as well. The cross fox has a black or brown cross on the back and shoulders. The silver and black color phases are similar to each other, but the black does not have the silver-tipped guard hairs that the silver color phase has. All color phases, however, do have a white-tipped tail. An adult will weigh form 6 to 15 pounds and they generally appear to be heavier than they are. Male red foxes are usually heavier than the females.
Life History: The red fox breeds during February and March. The pups are born inside a den that the parents have made themselves or in an abandoned den that they have taken over. Inside the den, there is a grass-lined nest where the blind and well furred kits are born. The gestation period is 53 days. The kits weigh approximately 4 ounces at birth, and their eyes open 8-10 days later. Both parents care for the young and by 3 months of age, the young are learning how to hunt. The family stays together until fall, when they all disperse and each fox heads out alone.
Diet: The red fox is omnivorous. Prey items include muskrats, squirrels, hares, birds, eggs, insects, vegetation, carrion, an voles. Foxes cache food items when hunting is good and have been known to seek out caches that wolves leave behind as well.
Gnawing Mammals: Rodentia
The order Rodentia is characterized by having only 2 incisors (gnawing teeth) above and 2 below. There is a space between those teeth and the grinding or cheek teeth. Most, but to all members of this order have 4 toes on the front feet and 5 on the back.
Squirrels And Marmots: Sciuridae
This family includes a wide variety of mammals, including marmots, woodchucks, ground squirrels, tree squirrels, prairie dogs, and chipmunks. The members of this family have 4 toes on the front foot and 5 on the back. The tail is always covered with hair and is sometimes bushy. All members of this family are active during daylight hours, except for the flying squirrels, which are nocturnal.
Hoary Marmot, Marmota caligata
The hoary marmot is one of three species of marmots found in Alaska, and our trips see it most often in Denali National Park. Hoary marmots can be seen on mountain slopes of central, southeastern, and southwestern Alaska. In some coastal areas, it can be found down the sea level.
Description: The hoary marmot weigh 10 or more pounds (4.5 kg) and may exceed 24 inches (61 cm) in length. They attain their maximum weight in late summer, when they have accumulated layers of fat for hibernation. They are distinguished by short legs, a heavy-set body, and a short an broad head. Their coloration is grayish overall, with a black and white head and shoulders, and dark brown to black feet. They have claws on their front feet for digging.
Life History: Hoary marmots are social animals that live in colonies, with each individual utilizing a separate burrow. Each burrow has several entrances and/ or exits. They give off a shrill, loud whistle to warn other marmots of danger. Wolves, bears, foxes, and eagles all prey on hoary marmots. During the winter, these animals are true hibernators, which means they enter a state of torpor in which all body and metabolic functions are reduced. They utilize the same burrows year- round. In the winter plug the tunnel leading to their winter nest chamber with soil, vegetation, and feces mixture. Hoary marmots re-emerge fro their burrows and hibernation from April to May.
Hoary marmots mate in April or May. After a gestation period of about four weeks, two to six young are born hairless and blind. The young disperse at two months of age and reach sexual maturity at 2-3 years of age. Their average lifespan is about five years.
Diet: Hoary marmots feed on grasses, flowering plants, berries, roots, mosses, and lichens.
Beaver: Castoridae
There is only one living genus (Castor) in this family.
Beaver, Castor Canadensis
The beaver is North America’s largest rodent. It can be found throughout forested areas of Alaska and on Kodiak Island.
Description: Beavers can be up to 4 feet long, including the tail an on average, they weigh between 40 and 70 pounds. The beaver has large webbed feet and a broad black tail that can be used as a rubber when swimming and slapped on the water surface to warn other beavers of danger. The beaver has nose and ear valves that close while it is swimming under water. The lips are loose and can be drawn tight. Behind its front protruding teeth so that is can chew wood without getting water in its mouth. Their lifespan in the wild is about 10 years.
Life History: Beavers must have 2 to 3 feet of water year round, and the water serves as a refuge from predators and as a place to store food for the winter. If there is not sufficient water, beavers build dams to create the habitat they need. A beaver may work alone or with family members to create a dam. Logs, trees, branches, rocks, and mud are used to create the dam. The use of trees up to 150 tall and 5 feet in diameter have been recorded in beaver dams. Beavers actually gnaw on a tree until it falls and then run to avoid it falling (the must be a sight to behold!) Large trees are usually not moved, but the bark is stripped off and eaten.
The lodge is utilized as a home and a food cache. Some beavers will not even build a lodge and instead, make a den along the bank of a stream. At least one entrance to the lodge or den will be into deep water so that it will not freeze over in winter. The lodge or den is added to year after year and they an become quite large.
Mating occurs in January though February, and the female produces one litter of one to six kits in late April to June. Their eyes are open at birth and they are covered with fur, and they can swim immediately. The young stay with their parents for two years and then leave to find their own homes.
Diet: Beavers depend on the inner bark of trees, aquatic plants, roots, and grasses. Eventually, the beavers in a colony will exhaust all their nearby food resources, roam farther, and farther from their homes. If the food supply becomes exhausted, then the family will move to a new location. In Denali, beavers that live above tree line must move every few years.
Porcupine: Erethizontidae
The porcupine is the only North American representative in this family.
Porcupine, Erethizon dorsatum
This rodent is second largest rodent found in Alaska. The porcupine is found throughout most of Alaska, except in the far north, western Alaska, and unforested islands.
Description: The porcupine is 25 to 31 inches long and is covered with fur and quills of varying length. Only the nose, foot pads, and stomach are completely free of quills. The average weight of a porcupine is 15 to 18 pounds, but they can weigh as much as 25 pounds. The quills are actually modified hairs that are hollow and barbed. Quills from different parts of the body vary in length, color, flexibility, diameter, and scaliness.
Life History: Breeding occurs in November, and one male usually mates with only one female. The gestation takes four months and only one offspring is born. At the time of birth a porcupine weighs 1 to 2 pounds and is 10 inches long. Within hours, the drying quills will provide protection to the young. The offspring can also follow its mother in trees within hours of its birth. Porcupines becomes sexually mature at three years of age.
Flesh-eaters: Carnivora
This order includes those land mammals that are primarily meat eaters. Many of them also eat nuts, berries, and fruits, but usually their main diet is meat. They vary greatly in size from the Least Weasel (wt. approx. 1/10 lb; 45 g) to the Alaskan Brown on the front foot, although some have the inner toe high on the foot so that it does not show in the tracks. On the rear foot, there may be 4 or 5 toes, depending upon the species. Every species in this order also have large canine teeth.
Bears: Ursidae
The members of the bear family walk on the entire foot (known as plantigrade) like humans do and they have 5 toes on the font and back feet. They have short tails that are almost covered over by their fur, and their ears are relatively small and rounded.
Black Bear, Ursus americanus
Black bears are the most abundant of the three species of bears found in North America, as they have been recorded in every state except Hawaii. Black bears range throughout most of the forested areas of Alaska, but they are not found on the Seward Peninsula, to the west of Lake Illiamna on the Alaska Peninsula, or north of the Brooks Range. They are also not found on the following islands: Kodiak, Montague, Hinchinbrook, Admiralty Baranof, Chichaof, and Kruzof. Black bears are most commonly found in the forest, but they can also be found from sea level to alpine areas.
Description: Black bears are the smallest of North America’s three bear species. Adults stand about 26 inches at the shoulder and measure about 60 inches from nose to tail, with the tail being about 2 inches long. Males are usually larger than females, with males weighing 180-200 lbs. in summer (they can be considerably lighter in the spring after winter dormancy) and up to 20% heavier in the fall when they are fat. Their size is often overestimated.
;The color of black bears ranges form jet black to white, but three colors are most commonly seen in Alaska; Black is by far the most common color, but brown or cinnamon bears are seen in south-central Alaska. A rare blue or glacier phase may be seen in the Yakutat area. Black bears are distinguished from brown/grizzly bears by their straight face profile and sharply curved claws that are usually no longer than one and half inches in length.
Life History: Black bears are generally solitary, except during the mating period or when sows have cubs. Mating occurs from June through July. The cubs are born in he den during February to March. The gestation period is about 7 months and the cub are blind and weigh only a few ounces at birth. When the cubs emerge from the den in May, they weigh about 5 pounds and have woolly hair. A female may have one to four cubs in each litter, but a litter of two is the most common. The cubs will remain with their mother through their first full winter following their birth. Female black bears breed yearly and become sexually mature at 3 to 4 years of age.
Black bears spend the winter months in a state of semi-hibernation. Their metabolic rate and body temperature drops and they sleep for long periods of time. They are not considered true hibernators because they do occasionally awaken and may even emerge from their dens. They may remain dormant for up to 7 to 8 months and females with cubs emerge later in the spring than lone bears. Dens are located anywhere form sea level to alpine areas.
Diet: Black bears are creatures of opportunity, they follow some general patterns during the year as to which foods they primarily pursue, but they will take advantage of carrion when they can. In the spring , they will feed upon the new young plants emerging, but will also feed on any carrion or winter kill that they find. If salmon are available, they will shift to salmon during the summer months. Berries are a prominent food source in late summer and fall.
Brown Bear, Ursus arctos
The brown bear occurs throughout Alaska except on the islands of Fredrick Sound in southeastern Alaska, the islands west of Unimak in the Aleutian Chain and the islands of the Bering Sea. Brown bears also occur in Europe, Asia, Canada, and the western united States. Once numerous in the Lower 48 (10,000 as recent as 1850), there are about 1,000 brown bears left in the continental U.S. (maybe as few as 600). Brown bear population in Alaska is estimated to be 31,000.
Description: Brown bears are grizzly bears and used to be considered separate species. Taxonomists now consider them to be the same species – Ursus arctos –since they can interbreed and produce fertile young. Many people differentiate “brown bears are those that live near the coast and have access to salmon, whereas the grizzly bears live in the interior of Alaska without access to salmon and are primarily vegetarian.
Brown bears may closely resemble black bears, but the brown bear is larger, has a large shoulder hump, and longer straighter claws. The coloration of brown bears can vary from being dark brown to blond. Just as in black bears, weights vary according to the time of year. During the late summer and fall, a mature male brown bear weighs between 400 and 900 pounds, with very large individuals weighing as much as 1,400 pounds (Kodiak Island). Females weigh one half to three quarters as much as the males.
Life History: Brown bears mate anytime from May through July. Sometimes a mated pair may remain together for up to a month but otherwise, they are generally solitary creatures. Male s will occupy a home range (sometimes up to 1,500 square miles) that encompasses several females home ranges so that they have more of a chance to mate each year. In areas of high bear density, a female may mate with more than one male. At the earliest, females reach sexual maturity at 4 years of age, but it may not happen until 5 to 6 years of age.
When a female brown bear becomes pregnant, the blastocyst (the fertilized egg which has reached a level of multicellular development) does not attach tot eh uterine lining as it does in other mammals. Instead, the blastocyst remains dormant and unattached inside the uterus. The blastocyst will not attach to uterine wall and resume its development until the brown bear begins its semi-hibernation. This process is known as delayed implantation. Since semi-hibernation may not begin until October or November and the cubs are born in January or February, the actual gestation is only 3 months long. If the female does not have enough fat reserves to support herself and her young, then the blastocyst apparently may not implant itself and become aborted.
The cubs are born in the den, blind, weighing only about a pound, and covered with fine gray hair. Litter size ranges form one to four cubs, with a litter size of two being most common. Upon leaving the den in the spring cubs will weigh about 15 pounds, upon denning in their first fall, thy weigh 60-70 pounds. The cubs will remain with their mother through the second year and sometimes even through their third year. Only after driving her cubs away, will a sow come into estrus again.
Denning provides a good way to spend the winter. Regnant females are the first to den and the last to re-appear. Adult males den last and re-appear first. On Kodiak Island where weather condition are good and food is in abundance almost year round, denning is only a short period, sometimes not more than a month. In the Arctic, where weather is severe and food supplies short, grizzlies den up to 8 months.
Diet: Brown bears are omnivorous, feeding on plants and young shoots, carrion. fish, and moose and caribou when it can capture them. It is most common for brown bears to take calves in the spring, but some bears are capable of taking an adult moose or caribou in the summer and fall. In areas of high food abundance, such as McNeil Falls, brown bears may congregate in large numbers and tolerate each other’s presence.
Brown bears may eat up to 80-90 pound per day to gain 3-6 pounds of fat. They must be at the right place at the right time to take advantage of the most abundant, highest energy sources. Therefore brown bears have a very predictable feeding pattern.
Otters, Weasels And Skunks: Mustelidae
The members of this family vary in size and color. Most of them have long slender bodies and short legs, small rounded ears, and anal cent glands. In many species of this family, the males are distinctly larger than the females.
Wolves And Foxes: Canidae
The members of this family are all dog-like in appearance. They have 5 toes on the front feet (one toes is high) and 4 on the back feet. All of the members of this family have a scent gland at the base of the tail on top.
Wolf, Canis lupus
The wolf occurs throughout on the mainland of Alaska in a wide variety of habitats, form the rain forest in the southeast to the arctic tundra in the far north of the state. Wolves are common throughout much of the state with densities that vary for about one wolf per 25 square miles in southeastern and the interior, to one wolf per 150 square miles or less in the coastal portions of western and northern Alaska.
Description: The color of wolves varies tremendously, the vary between whit and black with many variations of tan or gray. Adult males generally weigh between 85 and 115 pounds, but hey occasionally weigh up to 130 pounds. Females are typically 5 to 10 pounds lighter than males but rarely weigh more than 110 pounds.
Life History: Wolves are highly social animals and typically live in packs which include the parents and the ups of the year, yearlings, and other adults. A dominance hierarchy is established with separate rank orders between males and females. Pack size is usually 6 to 12, but sometimes it may be as high as 20 to 30 members. Each pack maintains a home range in which other packs are usually kept out, but there may be some overlap. The home range of a wolf pack in Alaska is generally between 200 and 600 square miles.
Breeding occurs in February and March and pups are born in May or early June. Litter size on average is 5 pups, but it can range form 2 to 10 pups. The female gives birth to the pus in an excavated den that may go back as much as 10 feet. Food is brought back to the den for the mother and the pups by other members of the pack. As the pups get older, other members of the pack will watch over the young while the mother hunts for herself. The pups are weaned by mid-summer and by early winter, they can travel with the pack throughout the home range.
Diet: Wolves are carnivorous and in most of Alaska, moose and caribou make up a large portion of their diet. Other important prey items include Dall sheep, mountain goats, Sitka lack-tailed deer, and small mammals (depending upon the availability). The very young, diseased, and very old prey animals are most commonly taken by wolves.
Red Fox, Vulpes vulpes
The red fox is found throughout Alaska except for some islands in the southeast, western Aleutians, and Prince William Sound. The red fox prefers areas with a variety of habitats as they generally utilize forest edge to forage in. Red foxes do inhabit the tundra, but not in the abundance that thy do in other areas.
Description: The red fox is 22 to 32 inches long, head to base of tail, with tail being an additional 14 to 16 inches long. It is well known for its reddish coat, but other color phases, such as the cross, silver, and black exist as well. The cross fox has a black or brown cross on the back and shoulders. The silver and black color phases are similar to each other, but the black does not have the silver-tipped guard hairs that the silver color phase has. All color phases, however, do have a white-tipped tail. An adult will weigh form 6 to 15 pounds and they generally appear to be heavier than they are. Male red foxes are usually heavier than the females.
Life History: The red fox breeds during February and March. The pups are born inside a den that the parents have made themselves or in an abandoned den that they have taken over. Inside the den, there is a grass-lined nest where the blind and well furred kits are born. The gestation period is 53 days. The kits weigh approximately 4 ounces at birth, and their eyes open 8-10 days later. Both parents care for the young and by 3 months of age, the young are learning how to hunt. The family stays together until fall, when they all disperse and each fox heads out alone.
Diet: The red fox is omnivorous. Prey items include muskrats, squirrels, hares, birds, eggs, insects, vegetation, carrion, an voles. Foxes cache food items when hunting is good and have been known to seek out caches that wolves leave behind as well.
Gnawing Mammals: Rodentia
The order Rodentia is characterized by having only 2 incisors (gnawing teeth) above and 2 below. There is a space between those teeth and the grinding or cheek teeth. Most, but to all members of this order have 4 toes on the front feet and 5 on the back.
Squirrels And Marmots: Sciuridae
This family includes a wide variety of mammals, including marmots, woodchucks, ground squirrels, tree squirrels, prairie dogs, and chipmunks. The members of this family have 4 toes on the front foot and 5 on the back. The tail is always covered with hair and is sometimes bushy. All members of this family are active during daylight hours, except for the flying squirrels, which are nocturnal.
Hoary Marmot, Marmota caligata
The hoary marmot is one of three species of marmots found in Alaska, and our trips see it most often in Denali National Park. Hoary marmots can be seen on mountain slopes of central, southeastern, and southwestern Alaska. In some coastal areas, it can be found down the sea level.
Description: The hoary marmot weigh 10 or more pounds (4.5 kg) and may exceed 24 inches (61 cm) in length. They attain their maximum weight in late summer, when they have accumulated layers of fat for hibernation. They are distinguished by short legs, a heavy-set body, and a short an broad head. Their coloration is grayish overall, with a black and white head and shoulders, and dark brown to black feet. They have claws on their front feet for digging.
Life History: Hoary marmots are social animals that live in colonies, with each individual utilizing a separate burrow. Each burrow has several entrances and/ or exits. They give off a shrill, loud whistle to warn other marmots of danger. Wolves, bears, foxes, and eagles all prey on hoary marmots. During the winter, these animals are true hibernators, which means they enter a state of torpor in which all body and metabolic functions are reduced. They utilize the same burrows year- round. In the winter plug the tunnel leading to their winter nest chamber with soil, vegetation, and feces mixture. Hoary marmots re-emerge fro their burrows and hibernation from April to May.
Hoary marmots mate in April or May. After a gestation period of about four weeks, two to six young are born hairless and blind. The young disperse at two months of age and reach sexual maturity at 2-3 years of age. Their average lifespan is about five years.
Diet: Hoary marmots feed on grasses, flowering plants, berries, roots, mosses, and lichens.
Beaver: Castoridae
There is only one living genus (Castor) in this family.
Beaver, Castor Canadensis
The beaver is North America’s largest rodent. It can be found throughout forested areas of Alaska and on Kodiak Island.
Description: Beavers can be up to 4 feet long, including the tail an on average, they weigh between 40 and 70 pounds. The beaver has large webbed feet and a broad black tail that can be used as a rubber when swimming and slapped on the water surface to warn other beavers of danger. The beaver has nose and ear valves that close while it is swimming under water. The lips are loose and can be drawn tight. Behind its front protruding teeth so that is can chew wood without getting water in its mouth. Their lifespan in the wild is about 10 years.
Life History: Beavers must have 2 to 3 feet of water year round, and the water serves as a refuge from predators and as a place to store food for the winter. If there is not sufficient water, beavers build dams to create the habitat they need. A beaver may work alone or with family members to create a dam. Logs, trees, branches, rocks, and mud are used to create the dam. The use of trees up to 150 tall and 5 feet in diameter have been recorded in beaver dams. Beavers actually gnaw on a tree until it falls and then run to avoid it falling (the must be a sight to behold!) Large trees are usually not moved, but the bark is stripped off and eaten.
The lodge is utilized as a home and a food cache. Some beavers will not even build a lodge and instead, make a den along the bank of a stream. At least one entrance to the lodge or den will be into deep water so that it will not freeze over in winter. The lodge or den is added to year after year and they an become quite large.
Mating occurs in January though February, and the female produces one litter of one to six kits in late April to June. Their eyes are open at birth and they are covered with fur, and they can swim immediately. The young stay with their parents for two years and then leave to find their own homes.
Diet: Beavers depend on the inner bark of trees, aquatic plants, roots, and grasses. Eventually, the beavers in a colony will exhaust all their nearby food resources, roam farther, and farther from their homes. If the food supply becomes exhausted, then the family will move to a new location. In Denali, beavers that live above tree line must move every few years.
Porcupine: Erethizontidae
The porcupine is the only North American representative in this family.
Porcupine, Erethizon dorsatum
This rodent is second largest rodent found in Alaska. The porcupine is found throughout most of Alaska, except in the far north, western Alaska, and unforested islands.
Description: The porcupine is 25 to 31 inches long and is covered with fur and quills of varying length. Only the nose, foot pads, and stomach are completely free of quills. The average weight of a porcupine is 15 to 18 pounds, but they can weigh as much as 25 pounds. The quills are actually modified hairs that are hollow and barbed. Quills from different parts of the body vary in length, color, flexibility, diameter, and scaliness.
Life History: Breeding occurs in November, and one male usually mates with only one female. The gestation takes four months and only one offspring is born. At the time of birth a porcupine weighs 1 to 2 pounds and is 10 inches long. Within hours, the drying quills will provide protection to the young. The offspring can also follow its mother in trees within hours of its birth. Porcupines becomes sexually mature at three years of age.
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