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Vail Daily column: Changing coats: A seasonal fashion statement?

Jeanine Junell
Curious Nature
Vail, CO Colorado

Winter is here! Aside from the official arrival that we celebrated on the solstice, it’s hard to miss the cold temperatures and the incredible snowfall that mark the change of seasons. Another sign of winter is our change of wardrobe, from sweatshirts to sweaters and down coats.

Animals also change their coats with the change of seasons. Since they don’t have the benefit of heated houses and cars, those animals that stick around and remain active for the winter must find a way to conserve energy and stay warm while dealing with the cold temperatures which we experience here.

Mammals have two distinct types of hair. The more visible, coarser hairs are called guard hairs which protect the finer hair underneath. The underhair serves mainly as an insulator. In the fall, as an animal prepares for winter, the number of hair follicles increase and more underhair grows to improve insulation. This hair is usually crimped or wavy in order to provide more space to trap warm air being produced by the animal’s body. The winter guard hairs may also be different in thickness and length, thereby providing better insulation. Most dog owners have experienced the shedding of this winter coat come spring, but may not notice the shedding that occurs in the fall as these warmer hairs replace the summer coat.



There are several examples of local residents whose twice-yearly change is more noticeable. Along with a change in shape and density of hairs, they also experience a color change. The snowshoe hare and the long-tailed and short-tailed weasels have a thinner brown coat in the summer and a thick, white coat in the winter. A local bird, the white-tailed ptarmigan (pronounced with a silent “p”) does the same with its feathers. Aside from the advantage that the color may have for camouflage purposes, the white feathers and fur also have a superior insulation advantage.

When we see colors in an animal’s coat, we are seeing the pigment that produces that color as it fills the shaft of the hair or feather. When the animal is white, we are seeing the absence of such color. Therefore the hair or feather shaft is actually hollow, filled with air instead of pigment. This is an advantage for warmth because the heat being lost by the animal’s skin on a continuous basis gets trapped in these structures and provides additional insulation to the animal. This allows these animals to remain active above the snow during our cold winter days and nights.



The ptarmigan goes one step further. In addition to the color change and longer and thicker feathers over its body during the winter, it also grows feathers over its feet. This reduces heat loss by the feet but also increases the surface area of the foot which allows this bird to walk more easily over the snow. This increase of four to five times in surface area is equivalent to our use of snowshoes or skis for over-snow travel.

To pet owners, the increase in pelt thickness and its subsequent shedding may be a nuisance, but to animals that live outside here in our mountainous home, that additional insulation is the answer to a life or death question. If you ever have the chance to touch and compare the pelts of winter and summer animals (and you can at the Nature Discovery Center on Vail Mountain), you will wonder at the amazing capabilities for survival of even some of the most common animals of our beautiful area.

Jeanine Junell is the Lead Naturalist for Walking Mountains Science Center (formerly Gore Range Natural Science School). She enjoys learning and sharing information about the natural world and can often be found watching and photographing birds or playing in the snow.


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