This book is a practical, portable guide to all of the Arctic's natural history—sky, atmosphere, terrain, ice, the sea, plants, birds, mammals, fish, and insects—for those who will experience the Arctic firsthand and for armchair travelers who would just as soon read about its splendors and surprises. It is packed with answers to naturalists' questions and with questions—some of them answered—that naturalists may not even have thought of. Whether planning an arctic journey, doing one, or enjoying memories of one, this book is indispensable. Designed as a compact source of information for those who must limit their load--hikers, kayakers, canoeists, rafters, photographers, and naturalists of all kinds--this guide will ensure that naturalists in the Arctic miss nothing. E. C. Pielou , a former professor of mathematical ecology and Killam Professor at Dalhousie University, has been a naturalist all her life. She is the author of many books, most recently Fresh Water , A Naturalist’s Guide to the Arctic , and After the Ice Age ,all published by the University of Chicago Press. A Naturalist's Guide to the Arctic By E. C. Pielou The University of Chicago Press Copyright © 1994 The University of Chicago All right reserved. ISBN: 978-0-226-66814-7 Contents Preface......................................xiIntroduction.................................xiii1 Sky........................................12 Climate and Atmosphere.....................153 Terrain....................................274 Seas.......................................625 Plant Life.................................766 Birds......................................1917 Mammals....................................2548 Fish.......................................2999 Insects....................................307Index........................................321 Chapter One Sky 1.1 The Land of the Midnight Sun "The Arctic" means different things to different people. To those who pay more attention to the sky than to the ground (which includes astronomers, of course), it means all that part of the earth, centered on the North Pole, where, at least once in the year, the sun remains above the horizon for a full 24 hours without setting so that (if it isn't cloudy) the sun shines at midnight on at least one day of the year. An understanding of why there are days in summer when the sun doesn't set (and days in winter when it doesn't rise) cannot be gained without concentrating closely on astronomical matters, specifically on the way the earth rotates around a tilted axis as it makes its yearly journey round the sun. Readers not in the mood for heavy thinking on these topics should skip to section 1.3. The lowest latitude at which the midnight sun is ever seen is the Arctic Circle, at 66 ½° N (or at 23 ½° from the Pole; the two angles add up to a right angle). The reason for this can be understood from the diagram (fig. 1.1) showing how the axis on which the earth spins (joining the north and south poles) is tilted at an angle of 66 ½° to the earth's orbit round the sun. The day of the year on which the tilted axis points most nearly toward the sun is known as the summer solstice; it comes on June 21. On that day, as the diagram shows, every point within the Arctic Circle is in sunlight for the whole of the earth's rotation, that is, the whole day long. At the other end of the year is the winter solstice (December 22) when, at every point within the Arctic Circle, the sun is below the horizon the whole day long. Contemplation of figure 1.1 shows that the times of sunrise and sunset must change with the seasons. The exact times, taken from the Nautical Almanac, were used to draw figure 1.2. The four diagrams show how the number of days during which the sun never sets varies from zero at 60° N (below the Arctic Circle) to over 2 months at 70° N, nearly 4 months at 80° N, and finally 6 months (half the year) at the pole itself. These periods of continuous sunlight begin and end at the dates shown, respectively, on the left and right sides of each diagram, where it is crossed by the "sunrise line" (the line separating the white part from the rest of the diagram). The diagrams also show the duration of two kinds of twilight: Civil twilight , which begins when the sun sets and continues until it is 6° below the horizon; during this period "operations requiring daylight" can be carried on, as the legal description puts it. And nautical twilight , which begins when civil twilight ends and lasts until the sun is 12° below the horizon, by which time all the stars used for celestial navigation have "come out." In the morning, of course, the order is reversed: first comes nautical twilight and then civil twilight, which ends at sunrise. There is a third level of twilight, so dim it is treated as darkness in the diagrams. It prevails while the sun is between 12° and 18° below the horizon, and is called astronomical twilight . Dur