Science & Biology

Beaver breeding season is no spring picnic!

A spring beaver colony inflicts damage on a commercial apple orchard in southern New Hampshire. (Photo | Furbearer Conservation)

Spring is known as a time of rebirth. Flowers begin to bloom, birds begin to sing, and the last of New England’s snowy grip hastily melts away into the streams and rivers of Southern New Hampshire.

For the beaver (castor canadensis), spring announces the height of breeding season - when the cold nights give way to warmer days and courtship sounds the beginnings of a new baby beaver litter arriving by the month of June.

While established mated pairs of beavers are busy solidifying the “next generation”, the pair’s two-year-old offspring are also commencing in new beginnings - like a new place to live at the behest of mom and dad. After getting “the boot” from the breeding pair to make room for a new litter, two-year-olds are driven out of the colony in late spring to establish new territories of their own.

As this brings “new beginnings” for the beavers, it also inevitably brings new beginnings for mankind - in the form of heightened complaint calls for roaming beavers who’ve now inconveniently “set up shop” in the wrong parts of civilization.

Whether its crop or tree damage from gnawing teeth, new dams creating flooding issues, plugged highway culverts, or bank erosion from beaver den construction and slides; it isn’t long before the migration of young beavers are made known to society - and the wildlife damage control trapper.

There’s something to be said for wading through the stagnant waters of a beaver pool in early spring. It certainly feels different than pursuing beavers during colder times of the year, such as the late winter or fall - where the ebbing and drawback of nature’s landscape tends to be the optimal time for trappers seeking thick, rich beaver pelts for fur usage.

The author removing a spring nuisance beaver from a commercial property in New Hampshire. (Photo | Furbearer Conservation)

Castor’s Primal Wiring

I find spring beaver trapping to be far more fast-paced than that of the staggered fall season for one primary reason (other than the damage control aspect) - territorial defense.

Beavers may look cute and cuddly from a distance, but make no mistake, they are as territorial as critters come - and they put those razor sharp incisors to use in more ways than just gnawing down trees.

Adult beavers whose offspring don’t quite take the hint that its time to leave can get quite the wake-up call; as adults will nip and bite at offspring to speed up the eviction process.

Rival beavers will also battle each other over the same body of water - biting each other’s backs and tails. You can typically tell how far a beaver has traveled in its lifetime by the amount of chunks missing from its familiar flat tail.

And it doesn’t just stop with gnashed teeth at tail skin…

Patrick Tate, a biologist with NH Fish and Game elaborates during an interview about beavers with NHPR.

“I once removed a beaver that had a beaver-tooth in its back, and it didn’t grow its own tooth in its back, that was a tooth from another beaver that somehow broke off in the animal’s back,”

“As I’ve reduced numbers in the wetlands, and went back subsequent years to trap, the amount of scarring and bite-marks on the beaver decreases. So the individual animal’s health increases.” he adds, suggesting that regulated trapping of beavers can reduce competition for survival and in-fighting.

A beaver tail with a fresh bite wound from a rival beaver. (Photo | Furbearer Conservation)

Its a constant case of “trail and error” for transient beavers, as the only way to tell if a water body is occupied is to run into the local residents. Its why beavers leave muddy scent mounds throughout the banks of their territory, marked with a gland secretion called castor. The castoreum scent marker tells passing beaver that the area is already occupied.

Trappers are typically well aware of which beavers have been fighting during the fur handling process, as scars and bite wounds become apparent under the skin once the animal’s hide has been removed for pelting.

Its why spring trappers keep the scent glands from the beavers they trap, as it can be handy throughout the season. The scent glands of a “foreign” beaver in spring time is guaranteed to raise full attention from the resident population.

That scent gland is used for a myriad of human resources - as we’ve previously reported on.

Kinda like that scene from Gran Torino where Clint Eastwood tells the “neighborhood punks” to keep off his lawn with a loaded M1 carbine ready to blow, resident beavers don’t typically take no guff from an intruder - warning with a tail-slap on the water’s surface before a brawl breaks out.

Its yet another reason why “relocation” or “translocation” of problem beavers isn’t always the simplest (or most humane) answer - as the pond that looks like the perfect place to release your unwanted guests may already be home to an established beaver colony; making a rough go for the new “visitor” that’s been unknowingly forced into a life-or-death match with a new rival.

Running The Gauntlet

Spring is also peak time of year to catch a glimpse of a road-killed wayfaring beaver who wasn’t fast enough for the local traffic while taking part in the “great migration”.

Spring-time beaver movements typically prompt comments from my friends and family about the noticeable increase in dead beavers observed along New England roadways.

Of course, as if cars, property owners, and rival beavers aren’t enough to contend with, traveling beavers seeking to establish new territory must also run the gauntlet of predatory wildlife looking for a fat-content-rich meal from the large rodents. Coyotes and bobcats will almost certainly outrun a beaver on land traveling from water body to water body. Even River Otters have been known to prey on beavers - infiltrating active beaver lodges and killing all inhabitants in a single visit.

Once a battle-free area of water is found and established, a single “bachelor” beaver, or a newly joined breeding pair, will swiftly begin altering the area to suit their needs. This tends in include cutting down trees to build a bank-side den into a lodge, damming obvious flow points of water systems to increase water levels for safety from predators, and feeding on the cambium layer just under the bark of trees such as willow, maple, birch, aspen, cottonwood, beech, poplar, and alder.

The next time you find yourself with a new rodent guest in your property’s waterway and ask “why me?” - you now have a bit of insight.

In the case of castor canadensis, all work and no play doesn’t necessarily make this semi-aquatic rodent a “dull boy”.

A beaver swimming in Canada. (Photo | Louis Renaudineau)

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