Wildlife of the Far North

© Copyright, Princeton University Press. No part of this book may be distributed, posted, or reproduced in any form by digital or mechanical means without prior written permission of the publisher. MAMMALS ALL MAMMALS, from humans to lemmings to muskoxen to whales, share certain physical features. All mammals possess modified sweat glands called mammary glands, which in a female can produce milk. All have body hair, at least at the beginning of their lives, and all have a four-chambered heart, single-boned lower jaw, and a middle ear composed of three bones. Arctic mammals are warm-blooded, or endo- To prevent excessive heat loss from bare or lengthy thermic, creatures. They are able to maintain body parts, pinnipeds, caribou, and beavers a constant body temperature despite changing maintain two internal temperatures—a high body climatic conditions. Their core body temperatures core temperature and a much cooler temperature range from 97.7°F to 105°F (36.5°C–40.5°C), this in the flippers, legs, or tail, respectively. This is despite the fact that marine species live in seawater known as regional heterothermy, which is made of 28°F (−2°C) and land mammals experience possible through heat exchangers that shunt winter temperatures averaging −33°F (−36°C). cooled blood to the extremities before returning Most of the northern mammals have it to be warmed in the countercurrent system. developed well-insulated, compact bodies Walruses have a similar heat-exchange with short appendages, which minimize heat mechanism that controls blood flow to the loss and conserve body heat. Mammals that skin capillaries. When a walrus is warm, heat spend most of their time in water usually have exchangers shunt blood to the skin, where it a thick layer of blubber—a subcutaneous sheet is air-cooled. The skin becomes flushed with of fat, collagen, and elastin—that sheathes the blood, and the walrus acquires a rosy-red color. vital organs, increases buoyancy, and acts as When a walrus is submerged in cold water, blood an energy reservoir during periods of fasting. flow to the epidermis is reduced, the capillaries Terrestrial mammals typically have a dense contract, the skin pales, and heat loss to the coat of fur. Many have fur on both the upper environment is minimized. and lower surfaces of the feet and have a double Mammals also alter their behavior in response coat of fur that becomes heavier in winter. Air to oncoming winter. Many marine mammals trapped between the dense inner coat and the migrate south of the ice pack, some to subtropical outer layer of coarse, long guard hairs provides waters, while others congregate around open areas excellent insulation. in the sea ice (polynyas) where food is available. Some marine mammals also have fur for Caribou and sheep move to lower elevations, insulation. Sea otters have the greatest hair density forested areas, or places with little snow cover of any mammal, ranging from 170,000 to more in a response to food availability. Many of the than 1 million hairs per sq in (26,000–165,000 smaller mammals such as lemmings and voles hairs per sq cm). The highest hair density occurs have adapted to living and sometimes breeding on the forearms, sides, and rump, the lowest under the winter snow where they are sheltered on the chest, legs, and feet. Polar bears have a from the cold and wind, and where food in the double coat of fur, which is backed by a 4.5 in form of seeds and shoots can be found. (11 cm) layer of fat. Surprisingly few of the arctic mammals Arctic mammals, particularly pinnipeds, have hibernate—a condition characterized by low a complex circulatory system called counter- body temperature, slow breathing and heart current heat exchange, which minimizes heat loss rate, and low metabolic rate. The only arctic to the surroundings and also prevents overheating. mammals to enter this form of deep winter sleep In this system, each artery carrying warm blood are arctic ground squirrels, marmots, chipmunks, from the body core is surrounded by a network American black bears, brown bears, and pregnant of veins. Warmth transferred from the arterial polar bears. Male and non-breeding female polar to the venous blood is carried back into the bears remain active in winter and “nap” now body rather than being dissipated into the air. and then in shallow pits they dig into the snow. 25 For general queries, contact [email protected] 3 Arctic MAMMALS.indd 25 3/5/16 4:34 PM © Copyright, Princeton University Press. No part of this book may be distributed, posted, or reproduced in any form by digital or mechanical 26 SORICIDAE means without prior written permission of the publisher. Soricomorpha: Insectivores Soricomorpha encompasses insect-eating mammals such as shrews, moles, and soledons. Th ese small animals are the descendants of the fi rst primitive placental mammals and are the predecessors of all other placental mammals. Th e earliest known fossils of shrews date back to 130 million years ago. FAMILY SORICIDAE SHREWS Th ese mouse-like insectivores originated in shredded vegetation, and are set in a burrow or Europe and later spread throughout Africa, rotted log. Gestation lasts 2–3 weeks. Th e young Asia, and the Americas. are nursed for about 3 weeks. Litter size is 4–9 Th e northern species are part of a group known young, with up to 4 litters produced annually. as red-toothed shrews, owing to the presence of reddish-brown teeth. Th e color comes from GENUS SOREX: Th e genus Sorex encompasses iron pigments in the diet, which are deposited the long-tailed shrews, which inhabit the boreal in the tooth enamel. Iron serves to harden the forests and, more rarely, the arctic tundra. Th e tips of the teeth, the parts most subject to wear. genus contains some of the world’s smallest Unlike rodents, which have gnawing incisors mammals. Most species weigh less than 1 oz (28 g) that grow throughout life, the teeth of shrews and measure less than are permanent and wear down throughout life. 5 in (13 cm) from nose to When the teeth are completely worn, a shrew tail tip. Th e skull is long, starves to death—a factor contributing to shrews’ narrow, and extremely lifespan of less than 2 years. small, as can be seen Shrews feed on insects, spiders, seeds, nuts, here by the skull of a worms, and carrion, and will also attack and eat Dusky Shrew juxtaposed next to a US penny. mice and frogs several times their own weight. Th e snout is long, pointed, and mobile. Th e Some species specialize in climbing trees, living small ears and beady eyes are almost hidden underground, living under snow, or even hunting by facial fur. Th e feet are plantigrade (i.e., the in water. Th ose that forage underground or in full length of the foot is placed on the ground) dark places rely on touch, smell, hearing, and and there are 5 toes on each foot. echolocation to fi nd their prey. Th ese insectivores have an extremely high Cinereus Shrew metabolic rate and need to consume at least 90 Sorex cinereus percent of their body weight each day in order to ALSO: American Masked survive. Th ey have to eat every 2–3 hours, day and Shrew, Amerikanische Mask- night, to achieve this goal. Th e digestive tract is enspitmaus, Musaraigne short, and food passes through it without being cendrée, Krattspissmus, Масковая бурозубка. completely processed. For this reason, shrews Formerly conspecifi c with the ST LAWRENCE ingest their feces to recover nutrients. IS SHREW, S. jacksoni, and BARREN-GROUND Most shrews are active year round. Th ey SHREW, S. ugyunak. SN means “ashy gray shrew.” do not hibernate, but are capable of entering RANGE: Found from Alaska to Labrador and torpor in winter, during which time they can Newfoundland, and south to 45° N, in dense leaf lose from 30 to 50 percent of their body weight, litter and around fallen logs in moist deciduous shrinking the size of bones, skull, and internal and evergreen forests. organs. Th ese small animals are solitary in nature ID: L 3.5–5 in (9–13 cm). WT 0.1–0.25 oz (3–7 g). and very territorial. If a shrew enters the home Dark brown to brownish gray on the back, with range of another, one will kill and eat the other. pale gray underparts. Bicolored tail. Th ey seem to tolerate another’s presence only HABITS: Active day and night, all year. Mostly when breeding. Nests are usually made of fi nely terrestrial, but can swim well. Feeds on conifer For general queries, contact [email protected] 3 Arctic MAMMALS.indd 26 3/5/16 4:34 PM © Copyright, Princeton University Press. No part of this book may be distributed, posted, or reproduced in any form by digital or mechanical means without prior written permission of the publisher. LONG-TAILED SHREWS 27 Eurasian Least Shrew Sorex minutissimus N Eurasia L 2–3 in (– cm) World’s second smallest mammal by weight American Pygmy Shrew Sorex hoyi N Amer L 3–3. in (–9 cm) Smallest mammal in N Amer Eurasian Shrew Sorex araneus N Eurasia L 2.–3. in (–9 cm) Arctic Shrew Tundra Shrew Sorex arcticus Sorex tundrensis Alaska, Canada N Eurasia, Alaska L – in (1–1 cm) L – in (1–1 cm) Laxmann’s Shrew Sorex caecutiens N Eurasia L 3– in (–1 cm) Moving the young Montane Shrew to another nest Cinereus Shrew Sorex monticolus Sorex cinereus W N Amer N Amer L – in (1–1 cm) L 3.– in (9–13 cm) seeds, salamanders, mice, and invertebrates, RANGE: Occurs in Canada and Alaska, south to including sawfl ies Pristiphora( erichsonii) whose Appalachia and Rocky Mtns, in boreal forests, larvae can defoliate a conifer.

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