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Mammals

Raccoons Fattening Up

11-13-14  raccoon tracks IMG_0045In the Northeast, raccoons spend the fall fattening up, for little, if any, food is consumed during the winter. Acorns, hickory nuts, beechnuts and hazelnuts are favorite foods. For as long as insects are available, they form a large part of a raccoon’s diet – delicacies include larvae of dug-up yellow jacket and bumblebee nests, and honeybees as well as the honey the bees have stored for the winter. Birds and rabbits injured by hunters, mice, bats, wild grapes and an occasional crayfish provide raccoons with enough sustenance so that fat makes up almost 50% of their body weight as they head into winter.

While signs of their presence, such as tracks, are still visible, they soon will be scarce. On the coldest winter days, raccoons will seek shelter in hollow trees, sometimes holing up for as long as a month at a time. Communal denning sometimes occurs, with up to 23 raccoons having been found in the same den. Considered “deep sleepers,” raccoons do not lower their metabolism significantly, and therefore are not considered true hibernators.

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Sign of Beaver Activity

beaver scat 041Beavers are meticulous housekeepers, in that they almost always defecate in the water, not in their lodge, and rarely on land. Because of this, it is rare to see their scat, but fall is as good a time as any to look for it (should you wish to see it).

In preparation for winter, beavers are repairing their dams and lodges, and stock-piling a winter food supply pile of branches in the pond near their lodge. They spend a lot of time working in the water in one area, which means that signs of their presence, including scat, are plentiful in these areas. If you look in the water along a beaver dam at this time of year, it’s highly likely that you will find light-colored, kumquat-size pellets, which, as you might expect, are full of tiny bits of woody fiber. The pellets are essentially little balls of sawdust, and disintegrate easily. (Handling, for those tempted to do so, is discouraged due to giardia or “beaver fever.”)

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Woodchucks Heading for Winter Burrows

11-10-14 woodchuck 122Woodchucks are one of the few species of mammals that enter into true hibernation. When the temperatures dip into the 40’s, usually in October or November in the Northeast, most woodchucks leave their summer burrows and head for the woods, where they dig a tunnel that ends in a chamber that is well below the frost line (and therefore above freezing). Here they curl up in a ball and live off of the 30% additional body weight they put on in the fall. In order to survive until March or April, a woodchuck’s metabolism slows way down. Its heartbeat goes from 100 beats a minute to five, and its body temperature goes from 96 degrees F. down to to 47 degrees F.

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Big Brown Bats Entering Hibernation

11-7-14  big brown bat IMG_7011Big Brown Bats, one of the most widespread mammals of North America, are one of the last species of bat to be seen flying in the fall. A relatively hardy species, the Big Brown Bat can tolerate conditions that other bats can’t. However, once cold weather arrives in the late fall and the nighttime temperatures dip down into the 30’s, they go into hibernation.

Both the Big Brown Bat and the endangered Little Brown Bat are considered “house bats,” because they are the most common bats found in houses in both summer and winter. During October, November and December, Big Brown Bats seek out caves, buildings and mines in which to hibernate. Some may migrate short distances to find an appropriate location for hibernating, but many find hibernacula close to their summer residence. Individuals often become active for brief periods during the winter months, sometimes even changing hibernation sites. Big Brown Bats can live up to 18-20 years in the wild but, unfortunately, most Big Brown Bats die during their first winter because they did not store enough fat to survive through their entire hibernation period.

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Porcupines Entering Winter Dens

porcupine IMG_2597During the summer, porcupines are almost always found out in the open. At the end of October/beginning of November porcupines den up for the winter in the Northeast, with up to a dozen porcupines sharing the same den. While some adult males will spend days at a time in a conifer, most porcupines seek out rocky crevices in which to spend the day, with a smaller number finding shelter in hollow trees. Porcupines are hardy creatures – while dens do protect porcupines from heat loss, they contain no insulation, the entrances are open and the porcupines don’t huddle together for warmth. In addition, porcupines emerge from their dens to feed at night, when outside temperatures are lowest. (And yes, that is porcupine scat that is stuck in/on the porcupine’s quills.)

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A Variety of Beaver Lodge Designs

10-20-14 beaver bank den 080Beavers are hard at work refurbishing their mud and stick lodges in preparation for the coming winter, when their movements will be restricted and they will spend both days and nights inside their lodge. When we think of a beaver lodge, we picture it in the middle of a beaver pond. This was not always the case, however, and still isn’t today. The earliest and most primitive beaver lodges consisted of a burrow in the side of a high bank with the entrance under water (see exposed bank lodge entrance in photo insert). The next advance was the addition of sticks and mud piled over the top of the bank as added protection from predators (see photo). Eventually beavers started building a complete lodge on top of the bank which had an underwater entrance. The most advanced design is the lodge we most commonly associate with beavers — one that is built up from the bottom of the pond and is completely surrounded by water. It requires the greatest amount of work but offers the greatest amount of protection to the beaver.

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Muskrats Constructing Lodges

10-8-14 muskrat lodge3 012Muskrats, in addition to digging bank dens, also build lodges in which to live. Muskrat lodges resemble beaver lodges, but are usually much smaller (up to eight feet high, and four feet wide) and are made of vegetation, not sticks, like beaver lodges. Most lodge construction occurs in May and early June, and again in October. Typically they are built in no more than two feet of water. A single dry chamber (entrance below, chamber above the water line) houses a pair of muskrats, and often several litters of young (the mother adds a chamber for each litter). Even though the walls of a muskrat lodge are up to a foot thick, mink, foxes and coyotes often dig into them in the winter. Two or three smaller versions of a lodge, called “pushups,” serve as protected feeding platforms.

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