Cure for Cabin Fever
What is perhaps most remarkable, then, about the mountain winter,is the fact that so many wild animals actually breed at this time ofyear. For some, it is a time of courtship; for others, incredibly,the moment of birth.
Rolling across the hollows and valleys, the insistent hoots of greathorned owls are a fixture of winter nights, as the pairs reinforce oldbonds and mark their territories with sound. By February the owls willhave usurped an old hawk or crow nest and laid their clutch of eggs;by March the chicks have hatched, usually into weather conditions thatwould kill them in moments if they were exposed to it. But the adultscarefully shield them from the elements for weeks, feeding them as theygrow through the dregs of winter.
Negotiations and Love Songs
The night woods ring with the songs of procreation in winter, especiallyafter the season pivots on the solstice and begins its long climb backtoward summer. On still, moonlit nights, coyotes howl and yip with abandon usually not the clichid, Hollywoodesque ow-ow-oooooo!, but a muchstranger wail, much weirder, much wilder. Many people do not even realizethey are listening to a coyote or to a red fox when it yowls fora mate on a frigid February night.
Wait 'Til Spring
Wild canines mate in late winter, then bear their young about twomonths later. Other mammals take a different approach, relegatingthe business of mating to fall, when they are in better physical conditionfor the trials of pursuit and courtship battles. These include themustelids, or weasels, including long-tailed weasels, martens, andriver otters. The fisher, one of the largest weasels, mates withindays of her litter's birth, but the new embryos, rather than growing,stop developing almost immediately. They remain in a state of suspensionas minute clusters of cells for the next ten months, only finallyimplanting on the uterus wall about thirty days before birth, which is usually in March or April.
Known as delayed implantation, this reproductive techniqueis rather common among northern mammals, and it offers a number of advantages.As noted, courtship can occur during the easy time of the year, when movementisn't hampered by snow and cold; this way, too, a female gets a jump onthe spring, bearing her young early so they are growing up in a seasonwhen the world is awash in young and unwary prey animals. This isespecially important with predators, like mustelids, whose young havea long development period. Baby fishers do not even open their eyes untilthey are nearly seven weeks old, and are not fully weaned until they reachfour months of age.
Getting a Good Night's Sleep
One northern animal takes delayed implantation to perhaps its greatestextreme. The black bear mates in midsummer, not long after the femalehas booted her previous litter of cubs (now a year and a half old) outon their own. Here again the embryos stop developing after a few celldivisions and become quiescent. But unlike weasels, which remain activeall winter, female bears den up in early winter perhaps choosing a rockden, a hollow tree, or a blowdown. Bears are not true hibernators likebats or woodchucks, but their metabolic rate does slow by about half,and they become sleepy and lethargic.
In early winter, the embryos attach themselves to the uterine wall andbegin to develop. About six or eight weeks later usually sometime in lateJanuary or February, depending on latitude the somnolent female givesbirth, scarcely aware of the act. The newborn cubs, covered with a thinsheen of black fur and looking like tailless rats, weigh less than twelveounces and are, in proportion to the size of their mother, among the smallestmammalian babies. They find their way to the female's nipples despitebeing blind, deaf, and unable to smell. Research has shown that they reactonly to warmth and the nipples are the warmest part of the mother'sbody.
Through the remainder of the winter, the cubs nurse on high-fat milk andgrow with only the periodic, drowsy attentions of their mother. When shefinally rouses and the family emerges from the den two months later, thecubs weigh about five pounds bright-eyed, active furballs that bear almostno resemblance to the tiny infants they were just eight weeks before, with a head starton the season of growth that lies ahead of them.
Details mentioned in this article were accurate at the time of publication