Sunday, January 10, 2010

Death and Destruction in Shangri-la Pond

That I call it Shangri-la Pond has nothing to do with beavers, and perhaps the death of one beaver

and catastrophic failure of the dam there

has nothing to do with the history of the fur trade. Shangri-la is or was a mythical valley in the foothills of the Himalayas where people were ageless and nature guileless. My wife and I discovered our Shangri-la in the late 1970s when we veered off a trail in Wellesley Island State Park and tried to walk up a small creek flowing down between two granite cliffs. The creek watered a valley that was choked with a variety of plants that we didn't think could exist outside of a rain forest. We gave up trying to walk up the creek and climbed up the cliff where hemlocks precariously hung. During the late 70s the island was well watered. Our feet were always getting wet no matter where we went. My wife blames porcupines and I blame the droughts of the 80s for killing the hemlocks.

The slow progression of beavers up a creek that drains into South Bay eventually required the damming of the little creek that drained our Shangri-la. So Shangri-la Pond was born. I remember one warm fall day when we sat high up on the granite ridge and watched two large beavers sunning themselves on their new lodge on the south side of the now widening creek. Of the many shrubs that choked Shangri-la, the beavers left only a few button bushes. They had trees enough to eventually make three lodges in the pond.

The pond struck me as a hard one for beavers to live in. The valley ran east-west, angled so that it got only a few hours of sun each day in the winter.

The pond ice froze thick. In January 2000 the beavers chewed through six inches of ice to make a hole next to their lodge

so that they could walk west

to where the granite walls ended so they could climb up slopes where they could find maples and oaks. That spring as they made their dam higher they began to flood a boardwalk trail that cut across the open area north of the pond proper. The park authorities put a pipe through the dam to lower the water level. I wasn't surprised when the beavers left, returning to the East Trail Pond, their last home. It supported them for several more years.

The East Trail Pond was much larger than Shangri-la Pond. They eventually had five lodges allowing them to easily adjust to different water levels and, what I assume are, different times to best eat certain vegetation. For example, they seemed to relish a certain fern flourishing up pond during the spring. I really thought they would never leave because there was always a good flow of water into the pond. In the winter of 2003 the otters put a hole in the dam that drained most of the water out, but the beavers seemed to have no trouble repairing the dam and restoring the pond in the spring. Then in the winter of 2005, another otter hole drained the pond,

And the beavers left by May, for good, leaving a green meadow and a small pool of frogbit encrusted water.

They didn't even check the viability of Shangri-la Pond with its three empty lodges and no beavers. I don't know where they went. Meanwhile another beaver family had been moving back and forth between two small ponds to the west of Shangri-la. The names I gave to the series of three ponds they used were Shortcut Trail Pond, Meander Pond and Thicket Pond. I first noticed this family when it wintered in Shortcut Trail Pond in 1999-2000, then it wintered in Meander Pond, then it moved back to Shortcut Trail Pond, then it moved up to winter in Thicket Pond, then back to Meander Pond, then back to Thicket Pond, then I was sure the family would move to Shangri-la Pond or the East Trail Pond, both larger than Meander and Thicket ponds combined, but they didn't. I theorized that beavers would not violate the territory of other beavers even years after they had left that territory.

Life in Meander and Thicket Ponds was not easy. Meander Pond was nothing more than a long meandering channel with a series of canals dug off it.

Over the years the beavers managed to build two lodges, about ten yards apart, and dig two burrows, one close to the lodges and the other near the dam. During a drought in the late summer of 2001 they survived by dredging,

making a deeper channel between their lodge and the burrow close to it.

In late September they went downstream fashioning a lodge in the dam of Short-cut Trail pond. But in the Spring of 2002 they moved back to Meander Pond, and then in the Spring of 2003 moved to Thicket Pond where they had one lodge, that was very hard to see,

and one small burrow. They flourished because they dug deep channels around and throughout a thicket of buttonbushes.

Beavers don't eat buttonbushes and that shrub leafs out late but thickly and that shade all summer kept the water in their channels from evaporating. Their secrets to winter survival in both Meander and Thicket ponds were the channels they dug from their lodge to springs along the north shore of the ponds.

Thicket Pond was at the top of a small watershed and precious little of its water flowed into Meander Pond just below it. These beavers didn't need a creek flowing in, just springs and dirt to dig into so they could pond water.

Because of their skill at surviving in such small ponds, I counted this family as exceptional. As I learned more about the fur trade, I wondered if the example of this family was exceptional enough to be the rule. Yes, because beavers so obviously shaped the land, they were easy to find and kill. These beavers showed me survival with minimal impact on the terrain, though large oaks were cut down.

Then they moved out of the rut they had been in for almost ten years. In what proved to be their last winter in Thicket Pond, they built a new lodge right in the midst of the tangle of buttonbushes, the "thickets" of "Thicket Pond." Then in the spring they moved down to Shangri-la Pond, which at that time wasn't much of a pond, merely two rivulets meeting in a pool behind an old dam with a pipe through the middle draining out any water that got too uppity.

The built a lodge below the wall of the cliff south of the pond and they began doing what they'd done so well the last eight years I'd watched them. They dredged deeper channels.

Of course the beavers I had been seeing over those eight years were the matriarch and patriarch. Since they survived in such small ponds, I hoped that by focusing on them I could help prove a thesis floating around among beaver watchers that beaver couples adjusted the size of their families to suit available resources. But this pair -- beavers are monogamous -- did not stint on making kits. They seemed to have two or three most years. I have no idea where all their offspring went, but I did see how kits in this family became serious dredgers by the fall. Other beaver kits I had seen in September were generally goofing around with siblings or haphazardly imitating the foraging or dam building techniques of adults. The only time I saw five month old kits dredging was in Thicket Pond. And then in Shangri-la Pond. So attuned was this family to dredging that all the beavers in the colony seemed to swim in an up and down manner so that they were always raising mud thereby keeping it loose, and then they would frequently collect an armful and push it up on the edge of the channel. Yes, beavers survive by building dams and flooding valleys to get to more trees, but as these beavers taught me, they also survive by simply dredging channels deeper.

I won't digress here and describe the differing styles of kit-rearing that I've noticed in beavers, but in Shangri-la Pond discipline seemed the watch word. I once saw a kit so sternly chastised by an adult that it fled back to the lodge and whined almost to the pitch of human crying. And it was in Shangri-la Pond that I first noticed what I've now noticed with other beaver families: adults try to curb the enthusiasm of kits when there is a danger of falling trees. This must have been a difficult lesson to teach when the pond was essentially a nexus of deep channels. Kits must have seemed oblivious to falling trees as they swam between banks a few feet apart that rose two feet above the water level in the channel. The response of one adult beaver, at least, was to keep kits away from trees that might fall. In early December I watched an adult turn from its gnawing on bark to face down a kit that tried to climb out of the channel and approach its mother.

Three weeks later in the same area of half cut trees, I found an adult beaver lying under a fallen tree, evidently dead from the tree falling on it.

I've watched beavers cut trees, and when the tree shows signs of falling they quickly go back to the safety of the pond. They let the wind blow the tree down, and I am sure 99.99% of beaver cut trees fall with out hitting a beaver. In the past 30 years or so, to my knowledge, only two beavers in the 600 acres of prime beaver territory that I explore have been hit by a falling tree. Based on that previous observation of the vigilant adult and the rarity of trees falling on beavers, I have a hunch that the adult beaver that was killed, the mother, was stymied by being over protective of her kit and by her habit of staring down kits to keep them back in the channel. (In another family, I saw an adult speed through out the pond forcing kits to dive just prior to a large aspen falling some fifty yards from where the kits were.)

Since the beaver died early in the winter, except for a few days after a thaw, the snow cover around the pond allowed me to keep track of the comings and goings of the beavers remaining in the colony. They continued to feed off the tree that killed the beaver.

Then they cut down a huge red oak closer to their lodge.

Coyotes took the carcass of the dead beaver. I sometimes saw the beavers up on the ice of the pond.

I so no signs of any beavers leaving or entering the pond. There were no kits in the pond that spring and summer, and I think one beaver left the family in the spring. Three remained and I think that next winter the patriarch of the family mated with one of his two year old daughters. Just a hunch. I had no proof. I would have to wait until the late spring to see if some kits popped out of the lodge in Shangri-la Pond.

Then after a heavy spring shower, the pond's dam failed. The dam was about 40 feet long and five feet high. A 15 foot section of the dam was washed away, leaving only a two foot high remnant.

The pond disappeared.

The beavers repaired the dam. When I went out in the early evening I expected to see every beaver in the family hard at work, but I soon saw that's not how these beavers operate. Before repairing the main dam they built a smaller dam behind it, helping to keep the water level high around their lodge.

That small dam gave them some breathing room, and stemmed the flow of water out of the pond. So I'd see one beaver working on the main dam, another still putting mud on the back dam and another well up pond looking for greens to eat. The beaver working on the main dam would take generous breaks. I decided I wouldn't mind working with these beavers.

The restored pond was magnificent, larger than before.

And then a month after it was repaired, after another spring storm, the dam failed again. Here is a photo of the dam on May 1:

And here is how it looked on May 13:

This time an old tree trunk with a big stump was washed through the repaired end of the dam. This time 15 feet of the dam was washed away completely. I didn't discover the catastrophe until four days after it happened. By then, the beavers had abandoned the pond. I could see that they built a small back dam, but they didn't even make an effort to repair the main dam. I think the problem they faced was this: to build and repair the dam they dredged up a good bit of mud behind the dam. Usually there is an unending supply of mud behind a dam because silt always collects behind it. But twice in a month much of the accumulated silt in the pond had been washed away.

The death of the matriarch didn't dissolve this family of beavers. Now the dam had failed and the beavers had abandoned the pond. Would I ever see them again? Meanwhile, a year earlier, one beaver had moved into the East Trail Pond below Shangri-la Pond. Then for the winter it moved into Meander Pond, just one beaver and I often saw it. My hunch was that it was one a young beaver who left the Shangri-la Pond family. Two year old beavers generally leave the family. Then in the spring before the dam failures in nearby Shangri-la Pond that lone beaver moved up to Thicket Pond.

I expected the Shangri-la Pond beavers to move back to Thicket or Meander pond, too, especially if the Patriarch's new mate was pregnant. In slow chapters during the late spring and summer, the story unfolded. Another beaver appeared in Thicket Pond and the beaver that had been there didn't seem please. It slapped its tail at the intruder. Then I saw that interloping beaver respond by going down to Meander Pond just below. Then I stopped seeing fresh beaver cutting around Thicket Pond, just as a beaver started cutting large ironwoods on a rocky slope above Meander Pond. I often saw the beaver working. There was a burrow in a slight bank near the dam that beavers in the pond had used over the years. The beaver or beavers appeared to be staying there. Then I only saw muskrats coming out of the burrow. Then through the sprouting vegetation that all but obscures the main channel of Meander Pond, I saw a new lodge rising,

and a beaver packing logs up on it.

The beavers who had moved into the pond built a new lodge on top of a very old lodge that had just about shrunk away. Now I came out as many evenings as I could looking for one thing: a beaver kit.

When I saw it swimming gamely behind one of its parents, I knew the story had not ended, but I had story enough to amaze myself in the retelling. In two and a half years the beaver family had adapted to three major crises: the death of the matriarch, a dam failure, then another dam failure forcing them to abandon their pond. That lesson of survival, I think, pertains to the history I am trying to write. To reduce the fur trade to the killing of animals for their pelts is to miss the point of what really happened. In reality one beaver does not exist. Beavers find their existence in a family through which survival skills are taught. To be sure, the fur trade ravaged that nexus of skills. I have seen young beaver refugees from trapping season who seemed to be in shock, but how many Meander Ponds were there in North America where beaver families could find refuge?

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