Bernd Heinrich's Winter World

From flying squirrels to grizzly bears, and from torpid turtles to insects with antifreeze, the animal kingdom relies on some staggering evolutionary innovations to survive winter. Unlike their human counterparts, who must alter the environment to accommodate physical limitations, animals are adaptable to an amazing range of conditions.

February's Book Club selection was Bernd Heinrich's Winter World. Heinrich is a physiological ecologist, and professor at the University of Vermont.

Winter World, illustrated with the author's drawings,  describes the winter survival strategies of many animals, including the success of the golden-crowned kinglet (Regulus satrapa), a small bird that remains active throughout the northern winter.  The kinglet, shows the "astounding and ingenious strategies that animals have evolved for coping in the winter world."

From ruffed grouse to voles to polar bears, digging into available snow offers insulated quarters for overnight protection and longer term housing. This strategy carries risks for smaller critters if a hard crust develops, creating an impenetrable barrier. 

For small birds, often a combination of strategies emerge, such as roosting together, lowering their heart rate, shivering, and gathering inside of small places such as bird boxes, hollowed out tree cavities and even old nests.  Some amphibians are able to survive below freezing point by utilizing chemical changes that alter their cell structures. Many overwintering insects employ a similar strategy.  

For those who do not hibernate, or have some form of reduced metabolism, the effort to find enough food to sustain energy needed for staying warm and alive, remains a constant. From scratching in leaf litter, prying bark from trees to find hiding invertebrates, to peeling and eating bark, scrounging for buds, and harvesting carcasses of the less fortunate, animals do what they must to survive the winter.