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Winter Survival

Deer Mice And The Rigors of Winter

2-5-15  deer mouse 022Even though Deer Mice are active year round, we don’t often see them, as they are active from dusk until dawn. During the winter, when it’s very cold, they commonly resort to short periods of torpor (4 to 9 hours) during the day to conserve energy. While torpid, their body temperature may fall to 55° F. from a normal temperature of 98°F.

When active, Deer Mice travel both under and on top of the snow. When travelling under the snow, they tunnel through it or use tunnels created by other small mammals. When travelling on top of the snow, their tracks, and often the drag mark from their tail, are evident. The pictured Deer Mouse was found curled up, frozen, at the end of a very lengthy trail of tracks and tunnels that ran over and through woods. Where the tracks began there was a slight depression in the snow (no tunnel, no tracks), indicating that the mouse might have fallen from the air after escaping from the talons of a bird of prey.

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A Bobcat’s White-tailed Deer Cache

1-21-15  bobcat2 cache by Otto Wurzburg 009 (3)Rabbits and hares comprise much of a Bobcat’s diet, but when prey is scarce or hard to capture, adult male or sometimes large adult female Bobcats will attack bedded, weak or injured adult White-tailed Deer. Bobcats often cache prey (such as a deer) that is too large to eat in one feeding, returning to feed on it for an extended period of time. They scrape up leaves, bark, twigs, soil. snow – whatever is available – and cover their prey. When feeding on a deer, Bobcats bite away the hair to avoid eating it, and this discarded hair is frequently mixed with the debris that the cat drags over the kill to cover it (see main photo – taken the day after the deer was cached), or is left windblown around the carcass. A characteristic sign of Bobcat feeding is the amount of hair strewn around the carcass and the lack of broken long bones (Bobcats don’t have the strength to break them with their teeth).

Typically a Bobcat rests near its cache to protect it, but it doesn’t take long for other animals to detect and take advantage of an easy meal. Within three days of this deer being cached, Coyotes and Common Ravens had discovered it, and both they and the Bobcat had eaten enough of it to expose the deer’s rib cage (see insert).

Other predators that occasionally cache and cover their kills include Mountain Lions, Black Bears and Fishers. Large caches found in the winter in the Northeast are likely to belong to a Bobcat or Fisher (Fishers typically cache and feed on deer that they find as carrion).

(Cache discovered by Lynn & Otto Wurzburg, who observed the Bobcat leaving after caching the deer; photograph by Lynn Wurzburg)

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Huddling to Keep Warm

flying squirrel3 IMG_8550Animals which remain active year round in northern New England use different strategies to survive the cold winter temperatures. Lowering metabolism through torpidity (on cold nights black-capped chickadees and other species reduce their body temperature as much as 22 degrees Fahrenheit from their daytime level in a process called regulated hypothermia), shivering, caching food in the fall, puffing out feathers to create insulating pockets of air, excavating tunnels under the snow, seeking protection in cavities – these are just a few of the life-saving techniques used by mammals and birds which neither migrate nor hibernate.

Another strategy which some of these animals use is to huddle together to conserve warmth. Huddling reduces the animal’s surface-area-to-volume ratio, since it turns many small animals into a single big animal. The larger the animal, the smaller the surface-area to volume ratio and the less relative area there is to lose heat.

Bluebirds and flying squirrels are two animals which huddle to keep warm. Eastern bluebirds may huddle together in a tree cavity or hollow log in groups of up to ten. Flying squirrels often huddle together in large communal nests, sometimes with populations numbering over two dozen squirrels, in an effort to keep warm. If this is not sufficient, the squirrels will enter a state of torpor until temperatures return to normal. (Thanks to Susan Parmenter for photo op.)

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Ruffed Grouse Nostril Feathers

12-16-14 ruffed grouse nostrils IMG_2376Ruffed Grouse have adapted to cold winter months in a number of ways, from growing “snowshoe” pectinations on their toes to having their legs covered with fine feathers. Equally effective are the feathers covering a grouse’s nostrils, which are thought to heat cold air as the bird breathes in. (Thanks to Sara and Warren Demont for photo op.)


Wild Turkeys’ Struggle for Food Begins

wild turkey in snow121Wild Turkeys do not migrate. During the winter they often separate into three distinct groups — adult males (toms), young males (jakes) and females (hens) of all ages — and spend their days seeking out plant (90 percent of diet) and animal (10 percent of diet) matter. In the summer, greens and insects make up much of their diet; in the winter, Wild Turkeys rely heavily on acorns, beechnuts, crabapples and hawthorn fruit, as well as agricultural grains such as corn, buckwheat, soybeans and oats.

The winter survival of Wild Turkeys depends much more on snow conditions that impact the procuring of food than on the temperature. While research has shown that turkeys can tolerate very cold temperatures, they need adequate food to keep from losing significant body weight and eventually starving to death. In parts of northern New England, the current Nor’easter has dumped a large amount of deep, loose fluffy snow, which turkeys can’t walk on or dig through in order to reach nutritious nuts. For this reason, turkeys frequently seek out agricultural fields that are windblown and provide relatively easy access to grains.

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Spiders Hibernating

11-24-14  spider 050Spiders that don’t lay eggs and die in the fall have developed several adaptations to survive the cold temperatures and lack of food that winter presents. They seek out microhabitats for protection, increase their resistance to cold and reduce their metabolic rate.

About 85% of spiders that overwinter do so in leaf litter, where they are well insulated against the cold. Most of these spiders assume a rigid position, with their legs drawn close to their body so that the amount of exposed body surface is kept to a minimum. Leaf litter protects spiders from extreme temperature fluctuations and from desiccation. A heavy snow cover ensures a fairly steady temperature of 32° F. regardless of the air temperature, even in weather as extreme as -40 ° F. below zero.

Many of the remaining overwintering spiders can be found under the loose bark of dead trees. Some have no further protection, others, such as the pictured Eastern Parson Spider, spin a silk case within which they spend the winter.

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Millipedes Migrating

11-11-14 millipede IMG_8982We don’t often see millipedes because of their preference for secluded, moist sites where they feed on decaying vegetation and other organic matter. Compost piles, heavily mulched shrub or flower beds, rotting logs, or the soil under logs and stones are likely spots to find these arthropods. Millipedes overwinter as adults, and have been seen migrating in the fall, presumably in search of overwintering sites that will provide them with some protection.

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