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Something Wild: How do their feet not freeze off?

This Something Wild episode was first heard in January 2015 and was produced by Andrew Parrella.

Cold enough for ya?

Right now the northern hemisphere is tilted away from the sun. Light enters our atmosphere at a much shallower angle and for fewer hours each day. To put it simply, it's cold in New England.

And as sure as January's cold is the usual grumbling from residents about the plunging mercury. It isn’t surprising when you consider how poorly adapted we humans are for living in the cold. However, adaptations in other species in New Hampshire have allowed them to flourish.

How do their feet not freeze off?

Chickadees, for instance, somehow manage to hang out on snow-covered bird feeders without fear of their feet freezing off. Fact is, their feet are mostly bone and scales, there's very little flesh to develop frostbite or gangrene.

Sara Plourde/NHPR

They've also developed a couple of ways to keep the blood where it is needed most. They restrict the blood flow to their feet, which allows them to keep the warm stuff in their core and maintain body temperatures.

Shivering is another adaptation these birds have used to protect themselves during the cold winter months. When the sun goes down, they shiver, raise their metabolism, generate a little heat, and then they shut down and get cold. At a certain point, the shivering mechanism kicks on again to generate heat.

These adaptations give an advantage to chickadees and other birds that spend the winter in New Hampshire. They save themselves the rigors and dangers they would have had to endure migrating to points well south of here and back again.

Plus they get an early start on breeding and frequently can have multiple broods while their migrating cousins usually only have enough time for one.

Cold means salvation for others.

Cold means death for some species like the hemlock wooly adelgid, an insect that cannot survive long stretches of cold, which means it has mostly stayed out of New Hampshire.

And in turn, the cold is salvation for the hemlock the adelgid feeds on. The insect is killing hemlocks in milder parts of the country but here in New Hampshire hemlocks have a leg up.

The farther north you go the more light-barked trees you'll see

Sara Plourde/NHPR

Bark is an adaptation of trees to cope with the climate. There are trees with light colored bark and trees with dark colored bark.

While we warm blooded animals might wear dark clothes to absorb sunlight and stay warm, trees don’t get the same benefits. Dark bark absorbs sunlight, warming up the tree during the day, only to have temperatures plunge at night. This kind of warming and cooling prompts daily freeze/thaw cycles, resulting in cracks in the bark, which exposes trees to all kinds of injuries and infections.

In New Hampshire, we see a lot of birch trees, beech trees - trees with light bark. The further north you go the more of the light-barked trees you’ll see. Farmers apply this principal to apple trees by painting their trunks white, providing protection for the bark of the tree - and next year’s crop of apples!

Take some time to appreciate the amazing ways in which life adapts to the cold this winter. And remember warmer weather is sure to return soon. In the meantime keep your bark warm!

Something Wild is a joint production of NH Audubon, the Forest Society and NHPR.

Naturalist Dave Anderson is Senior Director of Education for The Society for the Protection of New Hampshire Forests, where he has worked for over 30 years. He is responsible for the design and delivery of conservation-related outreach education programs including field trips, tours and presentations to Forest Society members, conservation partners, and the general public.
Chris Martin has worked for New Hampshire Audubon for over 31 years as a Conservation Biologist, specializing in birds of prey such as Bald Eagles, Ospreys, and Peregrine Falcons.
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