Fooling Beavers

 

A beaver dam is a structure built by beavers using branches, twigs, mud, sticks, rocks, and grass. The dam's shape can vary based on the number of beavers and the amount of water in the area. Beaver dams are usually semicircular or crescent-shaped. 

It turns out these dam-building actions can help the environment. They recharge groundwater, filter out sediments, and create habitat for waterfowl, amphibians, fish, and aquatic invertebrates—all while providing ecological services including flood control, drought management, and carbon sequestration. Those are not why beavers build them. A dam stops the flow of water and creates ponds that are safe from predators like coyotes, wolves, and bears, and provide food during winter.

Beaver pairs mate for life and produce one or two pups a year. When pups reach maturity at around two years, they strike out on their own, traveling an average of 3.5 miles in search of new terrain. Over time, beaver populations began to rebound, returning to their historical habitat—much of which included cities. According to a Sierra Club article, park officials are seeing the return of these aquatic rodents as the source of some wrecked landscapes as they have toppled trees, flooded trails and roads, and damaged infrastructure. 

Solutions are to trap the pioneering beavers and remove their dam debris, but they are persistent. Then someone found a way to baffle the beavers into better behavior.

It turns out that beavers build dams instinctively in order to stop the sound of running water. It is an innate quirk of the species. Building a flow device (some are trademarked as Beaver Baffler, Castor Master, and Beaver Deceiver) tricks the beaver into thinking they’ve built the perfect dam by eliminating the noise and sensation of flowing water. They use a long perforated pipe to divert water from the center of a pond out through a hole in the dam and down into the stream. The pipe helps muffle the sound of running water until it’s past the dam, and exclusion fencing on each end of the pipe keeps the beaver from plugging the system. 

Beavers have been a part of the North American landscape for 24 million years, evolving from bear-size rodents into their current form. Indigenous communities coexisted with a population ranging from 60 to 400 million animals and used them for food fur, and castoreum, a sweet-smelling gland excretion used in traditional medicines and—eventually—vanilla ice cream. But it was their fur—with 75,000 to 150,000 hairs per square inch—that nearly led to their downfall. Demand for the warm, waterproof pelts drove much of European exploration and colonization of North America. By the time beaver hats fell out of fashion, only remote pockets of the animals remained.

What's That Creature in the Water? part 1

North American river otter swimming -Wikimedia

No, it is not the Creature from the Black Lagoon or the Loch Ness Monster but there are some odd aquatic and semi-aquatic mammals that you might spot in the fresh waters of New Jersey.

Mink and beaver are native New Jersey mammals found in and around freshwater that most citizens of the state rarely ever see. Other aquatic and semi-aquatic mammals – including otters, weasels, ermine, fishers, and muskrats – are also here but elusive. They are most active at dawn, dusk, and nighttime when people are less active.

“They are incredibly secretive,” said Dr. Emile DeVito, staff biologist for the New Jersey Conservation Foundation. “Nobody really studies them in New Jersey. They are an overlooked group of animals, except by trappers.”

They are not really endangered or threatened in NJ even though they seem rare. It is thought that these aquatic mammals are actually becoming more common. Why? The reasons are actually good news: cleaner waters, more forest cover, and less trapping. 

Here are three of these elusive mammals. Maybe if you're out today for a Thanksgiving walk in the woods to build up your appetite or burn off the big dinner, you might be lucky enough to spot one. (In part 2, I will cover four others.)

American mink - Wikimedia

Mink (Mustela vison) are known for their exceptionally beautiful and soft fur. The American mink is lanky with a long tail, short legs, and partially webbed toes, which make them excellent swimmers. They are solitary creatures and quite territorial. They like to feed on crayfish, frogs, fish, mice, reptiles, earthworms, and even waterfowl. Take note that like their skunk cousins, mink defend themselves by spraying a foul-smelling liquid.

American beaver

Beavers (Castor candensis) are like humans in that they reshape their environment to suit their needs. That's rare in any animals. They will damn a stream to create a pond, and then build a separate beaver lodge by piling up mud, rocks and sticks inside the lodge to form a “floor” above the water.

Unlike mink, beavers are communal and live in groups. They also differ from most of these other mammals in that they are not carnivorous. They stand apart from their fellow members of the rodent family as vegetarians whose favorite foods include water lily tubers, spatterdock, clover, algae, apples and the leaves and green bark from trees.

North American river otter - Wikimedia

If you have ever spotted some river otters (Lutra canadensis) you would know that they're the most aquatic members of the mustelid family and often appear quite playful - as when they are sliding down riverbanks into the water. 

They have long stiff whiskers that help them find prey. They have flaps that allow them to close off their nostrils and ears to remain underwater for up to eight minutes on one breath. They are very social and form family groups centered on a female and her young. They eat fish, reptiles, amphibians, crustaceans, mollusks, insects, and even small birds and mammals.

New Jersey Furbearers

American mink

Despite the title of an online article, "The American Mink, one of N.J.’s most common semi-aquatic carnivore," I myself (and I suspect many readers) have never seen a mink in my Jersey travels. The mink (Mustela vison) is native to the state, although it is thought that escapees from mink farms have interbred with wild mink.

The mink is not threatened in the state and has a stable population. Not threatened, unless you consider that The New Jersey Hunting and Trapping Digest lists raccoon, skunk, opossum, weasel, mink, muskrat, red and gray fox, coyote, beaver, otter and nutria as species that have open seasons for trapping in the State of New Jersey. (In New Jersey, a Trapper Education course must be passed and a trapping license obtained to trap in the state - see http://www.state.nj.us/dep/fgw/trapping_info.htm)

Several of these species were not here historically or disappeared and have only returned through re-introductions.

Native to NJ are the river otter (Lontra canadensis), long-tailed (Mustela frenata) and short-tailed ermine (Mustela ermine). Also native are the striped skunk (Mephitis mephitis), raccoon (Procyon lotor) or gray fox (Urocyon cinereorgenteus).

Coyotes, which are now being reported with more frequency in the state, were never present in New Jersey until the past fifty or so years. Their appearance is due to many factors including habitat loss in their previous area of habitation. The current theory is that overall movement (based on DNA sampling) in the last century by the western coyote to the midwest, Great Lake states and through Lower Canada led to some western coyotes mating with gray wolves. Their offspring moved further eastward through Lower Canada and down through the New England states and into the Mid-Atlantic States.

NJ had gray wolves in the state until about the mid-1850s. Today, there are no wolves in New Jersey outside of zoos and preserves. But the eastern coyote appears to be here to stay.

Some of our other furbearing creatures past and present include:

• Marten (Martes americana) historically present but extirpated since the mid-1800s
• The fisher (Martes pennanti) also extirpated but again present in Sussex and Warren counties although few in number. Probably due to re-introduction by New York and Pennsylvania in the last decade
• Beaver (Castor canadensis) had almost disappeared from here by the early 1800s. It is believed that some escapees from the Rutherford-Stuyvesant game preserve in Allamuchy, Warren County established a breeding population. Restocking enabled the beaver to re-establish itself by the mid-20th century. 
• Most common to us is the raccoon which is, was and has always been a native of New Jersey and was a species that the British explorers to this new land reported, since they did not exist in Britain.
• Opossum (Didelphis virginiana) was thought to be numerous in the central and southern part of the state in the late 1860s, but in the last hundred years the range of both opossum and raccoons has extended much further north including into Canada where they historically never existed.

opossum

Busy New Jersey Beavers

USFWS.gov photo

The beaver is the second largest rodent in the world. Even children are familiar for its wide, flat tail, trre-gnawing and for building dams.

Those tails are useful for slapping the surface of the water to warn other beavers of approaching danger. Although these critters are rather awkward on land, they can navigate quickly under water and can stay submerged if necessary for up to 20 minutes.

Trees (bark and leaves) are their favorite winter food, but in summer other vegetation, especially aquatic plants like water lilies, make up their diet.

Beavers are known for their engineering of dams on rivers and streams. Their intent is to build their lodges (homes) in their preferred pond setting. They ingeniously place vertical poles, and then fill in the spaces between the poles with horizontally placed branches. Then, they further fill in the gaps with a combination of weeds and mud to hold back the water around their lodge. They have even been known to create "canals" in order to float larger tree materials they need rather than dragging them over land.

Their powerful front teeth are cartoonish but they are effective for cutting trees and plants for building and for food.

Though beavers are found throughout New Jersey, it is likely that many residents have never actually encountered one in the wild. Children and adults might mistake a groundhog for a beaver.

NJ's beaver population is strong because they generally coexist well with humans and they have few natural predators. 

Not all cases of beaver building have been met with amazement by humans. There have been reports over the years of busy beavers encroaching on human activities.  In Camden County, beavers on Kirkwood Lake created dams that made the water rise so that homes that normally had about 100 feet of land between them and the lake wound up with only a few feet of land.

In Middlesex County, a beaver blocked a culvert on a road in the Jamesburg Park Conservation Area and built a dam between two cranberry bogs. The town wanted to avoid flooding that had occurred in previous years. In that case, the town got a permit to trap the beaver out of season. They snared a 31.5-pound, 40-inch-long female beaver in an underwater trap.

This past year, in Princeton Township, human intervention with beavers also made the news.
A pair of busy beavers killed by a local animal control officer activated animal lovers who wondered why the beavers were not relocated rather than killed.

The beaver pair were contributing to flooding at the Pettoranello Gardens section of Community Park North, which has a pond and several streams. Workers tried to dismantle the dams, but the beavers got busy and rebuilt.

It didn't help that the state Division of Fish and Wildlife said the Princeton animal control department had not gotten the proper permit prior to killing the beavers. It seems odd but, according to a spokesman for the department, beavers trapped either in conibear traps, which kill them, or in live traps, still must be euthanized and may not be relocated.

As said earlier, our state beaver population is healthy. The state regularly surveys the 30 hunting and trapping zones in the state. Permits obtained from the Division of Fish and Wildlife are required to trap beaver and/or otter.

During the 2009-2010 season, more than 600 beavers were trapped and killed. The beaver season runs from the end of December to early February. (The duration of the trapping season for beaver on 23 Wildlife Management Areas is January 1 through February 9, 2012, but if the anticipated harvest of beaver and/or otter has not been accomplished during this season, up to 14 additional days may be authorized by the Director.)


More on "Beavers as Master Builders of Wildlife Habitats"

North American beaver (Castor canadensis)