By J M Mann Pro Staff Mountain Mann Outdoors.
You can scout for beavers most any time of year, typically the best time is in the early fall when they start to harvest trees and corn stocks for their winter feast. But first lets learn a bit of information about the beaver and it's ways.
The North American Beaver "Castor canadensis" is the largest rodent native to North America. They are semi-aquatic, but spend most of their time in the water. They are slow moving on land, and are easily scared and will run quite fast when alarmed. They are excellent swimmers, and their bodies are well adapted for water. Their tails are large, flat, and paddle-like, while their feet are webbed. The North American Beaver can stay under water for up to 15 minutes at a time.
Mature males weigh 40 to 60 pounds, but can weigh over 100 pounds. Beavers usually mate for life, only one litter of 4 to 6 kits is produced each year from April to June, following a 100 to 105 day gestation. At two years of age, beaver leave the home colony to search for winter quarters, which may take them up to 50 miles away.I took this picture in late September the day after a hard rain and close to dark. This is a juvenile beaver and weighs around 7 pounds.
The life span of beaver is 5 to 10 years, with some living up to 20 years. Because of their size, behavior and habitat, beaver have few enemies. Mortality is highest during the first year; coyotes, bears, bobcats, river otters and humans are the main predators and now with the reintroduction of Eagles to the area young beavers are easy prey.
Most of the beavers that live in central Pennsylvania are referred to as bank beavers now, because they burrow into the banks of streams and rivers instead of building large dams known as lodges, reason being is because of loss of wetlands due to human population, flood protection projects and the breading of sub species brought on by importation of beavers from other parts of North America. Beavers have adapted to this by taking over Muskrat holes and digging them bigger and deeper into the banks. Beaver will store food such as corn stocks, tree limbs, hay, cattails, water lilies summer aquatic plants.and most any vegetable grown on farms into these under water caverns.
Where suitable conditions occur in wet lands beaver will construct large dams if their is an abundance of trees and human pressure is minimal.
Beavers will dig many holes along the beds of waterways close to their food source and lodge. Look for holes under very large Maple trees, or most any other hard wood tree, but usually not pine, hard woods have large root sections that penetrate deep under ground and makes a natural support structure to help stop cave in's and can be cleaned out easily when flooding occurs
There are 25 subspecies of the American Beaver, but different subspecies have been reintroduced to areas with previously geographically isolated subspecies, following population decline or extirpation of the indigenous subspecies. This has led to very substantial mixing of the subspecies gene pools, and some subspecies may have disappeared entirely.
The most widespread subspecies in North America are C. c. acadicus, C. c. canadensis (Canadian beaver), C. c. carolinensis (Carolina beaver), and C. c. missouriensis (Missouri River beaver). The Canadian beaver originally inhabited almost all of the forested area of Canada, and because of its more valued fur, was often selected for reintroductions elsewhere. The Carolina beaver is found in the southeastern United States, the Missouri River beaver, as its name suggests, is found in the Missouri River and its tributaries, and C. c. acadicus is found throughout the New England area in the northeastern United States.
A scent gland near their genitals secretes an oily substance known as castoreum which is used to waterproof its fur. A thick layer of fat under its skin insulates the beaver from its cold water environment. The eyes are covered by a nictitating membrane which allows the beaver to see underwater. Their nostrils and ears are sealed while submerged. The flat, scaly tail is used to signal danger and also serves as a source of fat storage.Its fur has a range of many different colors but is usually seen as dark brown. The beaver coat comprises two types of hair. The outer section is coarse and long and covers an inner layer which is much finer.
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Beaver air hole - Note: Maple twigs shoved into hole.Some holes range in size from 12 inches to 4 feet across and can reach a depth of 10 to 20 feet and 10 to 25 yards from the stream bank.
They are also used to escape high water when in the den and to escape danger when present on land.
I have seen these holes used by not only beaver but coon and coyote for dens, snapping turtles will enter and exit the water ways by these tunnels as well.
Mink, weasels, squirrels and chip monks will also frequent these air holes.
This is a top view of a Bank Beaver's entrance to his food store or den, as you can see the entrance is almost blocked with corn stocks and tree limbs from the near by farmers fields and wood lots.Beavers will fill these caverns completely full with food to sustain them through the hard Pennsylvania winter.
You can clearly see the path or what I like to call it the slide from the top of the bank ( lower right) to the water and the food store entrance.
Heavily used trail from the water to the corn field.Beavers have been known to travel several hundred yards from water to collect food such as corn stocks and cut the whole stock down and drag it across land back to it's food store cave in the waters banks.
Beaver prefer to work under the cover of night but can be seen close to sun set and right after hard rains turn the water a dark brown color.
Crop damaged by a family of beavers along the West Branch Of The Susquehanna River.
Beaver tracks along the river bank Large over hang limbs are a good place to look 
for beaver caves and swimming at dusk Small beaver at dusk
Beaver are strict herbivores who do not hibernate. Most of the beaver's diet is made up of tree bark and cambium, the soft tissue that grow under the bark of a tree. They especially like the bark of willow, maple, birch, aspen, cottonwood, beech, poplar, and alder trees. Beavers also eat other vegetation like roots and buds and other water plants. The beaver has a specialized digestive system that helps it digest tree bark.
Because they are so thoroughly adapted to an aquatic lifestyle, they do not have the ability to climb trees. In order to get the food that is out of their reach, they chew around the base of the tree until it falls. They do not know which way the tree will drop and are sometimes injured or killed by larger trees.
The front teeth (incisors) of a beaver, or any other rodent, grow throughout the life of the animal. The front surface of the incisors is made of a very hard enamel that is dull orange in color. Since the back part of the tooth is not as hard, it wears off first, resulting in a chisel-like shape which, for a beaver, is perfect for the tasks of felling trees and stripping their bark. A beaver can drop a 2 inch thick tree in just a few minutes.
So the next time your out fishing or hiking along a waterway, keep your eye out for these signs and if you hear a loud slap of water you just may have startled a beaver and thats his warning to other beavers of your presence.
By J Michael Mann
http://mountain-mann.blogspot.com