About us: We own a wild bird feeding supply nature shop in East Lansing, Michigan,
a store that provides a wide variety of supplies to help you enjoy the birdwatching hobby.

This blog was created to answer frequently asked questions & to share nature stories and photographs.
To contribute, email me at bloubird@gmail.com.

Sunday, January 6, 2019

Survival of the fittest

Mammalian adaptations to the stresses of winter generally take on three different strategies; migration, hibernation, or by developing mechanisms to minimize the impacts of both the stresses of the cold and lack of food sources.

Ground squirrels, woodchucks and, to a lesser extent, chipmunks hibernate. Although chipmunks wake periodically and eat stored food, while the ground squirrel and woodchuck use stored fat for maintenance energy during hibernation.

Tree squirrels like the Fox and Gray/Black Squirrels prepare for winter by bulking up and hiding food. The squirrels spend less time foraging when the temperatures drop and it is common for several squirrels to huddle together in a drey to keep warm. A drey is a type of nest, in the forks of trees that they build with dry leaves and twigs. They will also hole up in tree crevices and I have an owl nestbox that is a very popular winter hangout as well as nesting area for squirrels.

Red squirrels cache cones and nuts in "middens", a secret store house for their food treasures. And they hang fungi in trees for easy winter sustenance.

Voles and mice build communal nests and tunnels under the insulating blanket of snow and eat from a cache of seeds and nuts or eat bark and roots. They occasionally pop up from the tunnels for more food and become vulnerable to attacks from hawks, owls and other predators like foxes.

Red foxes stay warm by growing a long winter coat. An adult fox rarely retreats to a den during the winter, but will instead curl into a ball in the open, using its bushy tail to wrap around its nose and footpads. Many times, they can be found completely blanketed in snow.

White-tailed deer change from grazers to browsers in winter. Their gray-brown winter coat has hollow hair shafts and a dense, wool-like under fur, providing effective insulation and they have special muscles that can adjust the angle of their hair shafts to obtain maximum insulation. And some deer populations will migrate to lower elevation grounds and congregate for more protection from predators.

Rabbits are awake all year too. They venture out from wood and brush piles at dusk and dawn to find herbaceous and woody foods such as raspberry twigs, stems of wild rose and the bark of sumac.

Bats in Michigan usually move further south too and are capable of hibernation in winter. Hibernation is a successful winter survival strategy for many warm-blooded mammals in cooler climates. Hibernation is when an animal alternates between torpor (deep sleep) and arousal while holed up in a winter den. The state of torpor is defined as a coma-like state where body temperature, heart rate, and breathing are lowered drastically.

Skunks, raccoons, and opossums do not hibernate but can hole up in their burrow or under decks for weeks at a time if the weather is not good for foraging. One extensive burrow system documented in Michigan was even occupied simultaneously by an opossums, woodchucks, raccoons, rabbits and striped skunks.

Related Articles:
- When do bats hibernate? http://goo.gl/IES4Bt
- Do Voles Hibernate? http://bit.ly/rTcbQI
- When do Chipmunks hibernate? http://bit.ly/uGhBOB
- Do opossums hibernate during winter? http://bit.ly/u4ORP6
- Migration vs. Hibernation http://bit.ly/sixWTH
- Feb. 2nd groundhogs end their hibernation http://bit.ly/vPHVtx
- Do skunks hibernate? http://bit.ly/xVKDXP

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