Rodents, Rodents, Rodents on the River

They are no one’s favorite animals but on any given day you might spot a furry critter scurrying, waddling, hunting along or swimming in the water. It is likely a rodent since our river embraces several species that are important contributors to a healthy river ecosystem and following are brief descriptions of our rodent friends.

The brown rat, aka: common rat, street rat, sewer rat, Hanover rat, Norway rat, Norwegian rat, or wharf rat is one of least loved but most common river rodents. It evolved in northern China but has now spread to all continents except Antarctica making it one of the most successfully disbursed mammals on the planet alongside humans.

Living in burrows, rats have course brown to grey fur with lighter bellies, a body up to 10 inches long with a similar length scaly tail and weighs 12 oz. or less. The brown rat is mostly nocturnal and is a good swimmer both on and under the water.

A more common swimming rodent is the muskrat found throughout Canada, the United States, and northern Mexico. Adult length is up to 28 inches, half of that is the tail and muskrats can weigh 4.5 lbs. That is about four times the weight of the brown rat although a muskrat is only slightly longer.

Muskrats are covered with short, thick fur, which is dark brown or black in color, with a lighter belly. They have long tails covered with scales rather than hair and to aid them in swimming their unique shaped body is slightly flattened.

Then there is the beaver, an animal we expect to live in a piled stick lodge in the center of a pond behind a stick dam but if a bottom of a deep pool insures adequate winter food storage and underwater access to the den secure from predators in winter, then it will live in a riverbank den, no dam needed thank you very much.

Beaver live to 24 years, their body measures 39 inches with an added 12 inches for their tail and weigh a hefty 60 lbs. Beavers defend territories by marking scent mounts made of mud, debris that they load with castoreum, a stinky urine based liquid excreted from castor sacs at the base of its tail. Once a beaver detects another beaver in its territory finding the intruder takes priority, even over food and any encounters are often violent.

On the smaller side are chipmunks that construct 10 foot burrows with hidden entrances and several refuse storage tunnels to keep their sleeping areas clean since they sleep an average of 15 hours a day. The eastern chipmunk hibernates in the winter and typically live about three years.

Eastern chipmunks produce two litters, spring and summer of four or five young. The young emerge from the burrow after about six weeks and strike out on their own only two weeks later.

The best known rodent is the mouse and the best known mouse is the house mouse; the one that invades our homes, cars, and outbuildings in fall but on the river, you could see woodland jumping mice that really can jump six to eight feet. Two other river mice are the white footed and deer mice, unfortunately they are reservoirs for the Lyme Disease causing bacteria.

Mice have a high breeding rate starting at 50 days of age and they breed year round with their average gestation period of 20 days. Isn’t that a delightful thought come October as they start their invasion into our space.

A more upland critter is the porcupine. They are black with white quill highlights with a stocky body, a small face, short legs, a short tail and weighing up to 39 lbs. making them one of the largest rodents, second only to the beaver. Their length is up to 3 ft. and they hold the record for being the longest lived rodent with one recorded living 27 years.

Solitary porcupines are born after a gestation period of 210 days with the young born fully developed with open eyes and they can climb trees within a few days.

Groundhogs aka as whistle pigs or woodchucks typically measure up to 26 inches with a 6 inch tail and weigh up to 9 lbs. In areas with few natural predators and lots of alfalfa, groundhogs can grow to 30 inches and up to 31 lbs. Groundhogs have short, powerful limbs with curved thick claws that aid in burrow building.

Groundhogs hibernate in "winter burrows” dug below the frost line that stay at a stable winter temperature. They as with bears are at their maximum weight just before hibernation. Breeding occurs March through April with litters of two to six blind and hairless young that by the end of August scatter to burrows of their own.

Common everywhere including on our river, the northeastern grey squirrel insulates their nest consisting of dry leaves and twigs with moss, thistledown, dried grass, or feathers. Males and females may share the same nest for short times during the breeding season and during winter since squirrels do not hibernate.

Squirrels will hoard and recover food in numerous small caches depending on the food supply in their territory using their accurate spatial memory of the locations and/or smell to retrieve the food. Squirrels will fake burying food to prevent other animals watching them from stealing real cached food.

Rodents provide several valuable ecosystems functions. Their harvesting and burying tree seeds play a role in seedling establishment and fungi eating rodents help spread the spores of fungi that tree roots need to take up nutrients and although you may not like them, rodents do serve as tasty prey for various predatory mammals and birds from otters, raccoons, and coyotes to eagles, hawks, and ospreys.

Submitted 1/7/18 by Representative David L. Deen (D) of Westminster. Deen is Chair of the Natural Resources, Fish and Wildlife Committee in the Vermont House and Board member of the Connecticut River Valley chapter of Trout Unlimited.

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