Counting invisible beavers

In December, in deep snow, I stood on a bridge crossing the Quinsam River, and took photos of beaver tracks. I decided I would go back in the summer to look for a beaver lodge. Well, summer's still a way off, but I'm glad I went back now, while the trees and understory are just bare twigs.

I found a small mound that will be hidden again once the salmonberries that top it leaf out, right where the tracks had entered a hole beside the bank. Is it a lodge?

A small lodge. Or is it that the water's high?

As seen in December. With beaver tracks.

I walked to the far end of the bridge and looked down. Yes, the beavers have been here, and have been busy. No wonder the water looked high!

Dam loaded with fresh sticks.

The road skirts Echo Lake and a couple of smaller lakes, then finds and crosses the Quinsam River, veers off southeast while the river twists and turns, snaking (a very curvy snake) its way north to join the Campbell River. I followed the road, looking for skunk cabbages. On either side much of the forest, where the land is flat, was underwater. Trees stand with their feet in the water; many have died and stand, shedding crumbling bark. Looks like beaver country, with every little creek dammed.

I started wondering; how many beavers live in an area like this? How many does it support? Back home, I looked it up. A beaver lodge, with its 2 to 10 beavers, claims one to three kms. of creek or shore.  (Beaver: BC gov. publication)This area, (the road crossing it covers 11 km.) with many creeks, all tied in knots, probably can house several colonies.

Beaver country. From the second bridge, crossing a creek, not the Quinsam River.

Another BC government document, this one from 1979, estimates the number of beavers on Vancouver Island at 12 to 18 thousand, which would work out at 1.7 beavers per square km. of the island or one average colony per 3 sq. kms. (The island covers 31,285 sq. km.). 

That was a while ago, and much of the island has been logged off since then, so the numbers will be less. Or maybe not; what's gone is the evergreen cover, and the alders, prime beaver food, have spread out. A NatureServeExplorer page gives an estimate of a short-term increase rate at >10%.

And I still haven't seen even one beaver!

~~~~~~~~~~~~~~

En diciembre del año pasado, cuando la nieve cubría todo, me detuve en un puente que cruza el rio Quinsam, sacando fotos de huellas de castor. Decidí regresar en el verano para buscar la madriguera. Por suerte, fui ahora, cuando los arbustos y árboles desnudos no la esconden.

Encontré un montecito, abierto a la vista ahora, lo que no va a estar una vez que los arbustos de salmonberry se cubran de hojas.

Foto: El montecito, bajo un tronco, visto desde el puente. ¿Será la madriguera?

Foto #2: Lo que vi en diciembre. El mismo sitio, con huellas de castor.

Foto #3: Crucé al otro lado del puente y miré para abajo. Hay una presa, cubierta de palos nuevos. Sí, los castores han estado aquí y bastante activos, además. Con razón el rio me parecía más ancho.

El camino bordea el lago Echo y un par de lagunas, luego cruza el rio Quinsam, y se dobla hacia el sudeste mientras que el rio se retuerce y se enrosca, llegando últimamente a verterse en el rio Campbell. Yo seguí por el camino, buscando linternas de pantano. De ambos lados del camino, donde el terreno es plano, mucho del bosque estaba inundado. Los árboles tienen las raices en el agua; muchos han muerto y se quedan parados, mientras su corteza se desbarata lentamente. Parece terreno favorito de castores, con cada pequeño riachuelo bloqueado por sus presas.

Me puse a pensar: ¿Cuántos castores viven en un area como esta? ¿Cuántos puede sostener? Ya en casa, busqué la respuesta. Una madriguera, con sus habitantes, de 2 a 10, se consideran dueños de 1 a 3 kilómetros cuadrados de margen del rio o laguna. (Según este documento del gobierno de BC) Esta area, — el camino que la cruza mide 11 km. — con muchos riachuelos, todos enmarañados, probablemente puede sostener varias colonias.

Foto #4: Terreno ideal para castores. Desde el puente que cruza otro riachuelo.

Otro documento del gobierno, este fechado en 1979, calcula el número de castores en la isla de Vancouver en de 12 a 18 mil, lo que resultaría en 1.7 castores por cada km², o una colonia promedio en cada 3 km². (La isla cubre 321.285 km².)

Eso hace algún tiempo, y desde entonces han talado muchos de nuestros bosques, así que los números podrían ser menos. O tal vez no: lo que se ha perdido son los árboles de hoja perenne, y los alisos, que son buena comida para los castores, han multiplicado. Una página de NatureServeExplorer calcula el aumento en plazo corto de más de 10%.

¡Y sigo sin ver ni un solo castorcito!

Windfall

I never pass the beaver pond and lodge these days without stopping to look at it. Maybe I'll see a beaver one day. No, not this time, either. But I was glad I had stopped, anyhow.

I park down the road a ways, so the first thing I saw, before I came in sight of the water, was a number of downed trees.Not chopped down; there were no axe or saw marks, just splintered ends and shattered wood. One had obviously fallen into the road and had been removed; still no saw marks. And there were lichen-covered branches everywhere.

Next find: the little mud patch where I have seen beaver tracks (no beavers) was now a little pond. A creek ran into it. On a bit, following this creek, and I came to the dam.

New workings

This has always been the outlet for the lagoon, always barely a trickle, down there at the bottom of the ditch. Now, it has been built up with all those newly-donated, licheny branches, and the creek runs and chatters to itself.

Now, I'd come to the lagoon. And the water was higher than I've ever seen it.

Smooth water. See the lodge?

Usually the back half of this lagoon is covered with lily pads; it's only a couple of feet deep. Now the lily pads and the hardhack around the edges are well underwater. The beavers have been busy. And their lodge, built on the shore beside the pond, is now an island. Smaller than before, to the eye; half submerged now.

The lodge has new timber on top, too.

Now, the question arises: did the sudden abundance of building materials inspire the beavers to go on a dam-making spree? Or was it just an extra convenience, having all that extra wood to work with, without having to chew down any more alders? I didn't see any beavers, so I couldn't ask them.

Lichen on a floating log, ready to be added to the dam.

Poking about, some little ways down the highway, looking for mushrooms, I passed another downed tree.

The white splotches are mainly lichens.

And coming back to the highway, I saw, barely visible in this photo, a live, healthy, green tree, broken off halfway up, exposing fresh new wood. The top of the tree lay on the ground beneath. Now that I was noticing, I saw several others broken this way. That must have been a strong wind!

~~~~~~~~~~~~~~~~~~~~~~~~~~~

En estos dias siempre que paso por la laguna con la madriguera de los castores, me detengo para mirarla. Tal vez por fin logre ver un castor. Bueno, esta vez tampoco. Pero estaba contenta de haberme detenido de todas maneras.

En primer lugar, me estaciono a una poca distancia de la madriguera, y antes de llegar a la laguna, lo primero que vi era un gran número de árboles tumbados. No los habían cortado; no vi señales de hacha ni de cerrucho. La madera estaba rota, desbaratada. Uno de los árboles aparentemente había caído en la carretera, y los guardianes de caminos lo habían quitado. Ni en este había marcas de cerruchos. Y por dondequiera ramitas rotas cubiertas de líquenes cubrían el suelo.

En seguida llegué al sitio bajo lleno de lodo donde antes he visto las huellas de los castores. (Pero no los castores; nunca los castores.) Y ahora era todo una lagunita, donde entraba un riachuelo. Seguí adelante, al lado de este riachuelo, y llegué a la presa.

Foto #1: La presa, cubierta de esas ramitas caídas.

Esto siempre ha sido el lugar donde el agua de la laguna sale, despacito, apenas un chorrito, allá en el fondo de la zanja. Ahora a la salida hay esta presa, construida con las ramas recién caídas, cubiertas de líquenes, y el agua corre rápido, haciendo una música alegre mientras va bajando.

Y ahora llegué a la laguna. Y el agua estaba muy alta, más que nunca la he visto.

Foto #2: La laguna. ¿Ves la madriguera?

Siempre la mitad de la laguna, la de la orilla opuesta, está cubierta casi por completo de las hojas de los lirios de agua, ya que el agua solo tiene como medio metro de profundidad. Ahora no se ve ni una, ni los arbustos de hardhack; están bien bajo el agua. Los castores han trabajado con entusiasmo. Y ahora su madriguera, que antes estaba en la tierra a la orilla, es una isla; el agua la rodea completamente. Y se ve más chico, que no lo es, pero ya la mayor parte está sumergida.

Foto #3: También lleva madera nueva encima.

Ahora se me sugiere la pregunta: ¿Será que el regalo de tantas materias de construcción habrá inspirado a los castores a empezar esta obra? ¿O era nada más una buena suerte que, habiendo decidido aumentar su presa, la madre Naturaleza habrá contribuido para evitar que tumbaran nuevos alisos? No vi a ningún castor, así que no les pude preguntar.

Foto #4: Un tronco flotante, listo para añadir a la presa, lleva su liquen en alto.

Foto #5: Un poco más adelante, buscando hongos al lado de la carretera, vi otro árbol caído. Las manchas blancas son líquenes.

Regresando a la carretera, vi un árbol vivo, verde, totalmente sano, pero roto cerca de la altura donde sobresalía a los otros. Nuevamente roto: la madera expuesta se ve fresca. La otra mitad del árbol reposa en el suelo a sus pies. Y ahora que lo había visto, empecé a ver otros recién rotos. ¡Eso ha de haber sido un viento muy fuerte!

Housing project

The beavers have been hard at work in Cougar Creek. Making perches for mallards, as well as their own lodges.

Construction materials storage area.

And I think this is round 11 of the human/beaver war. Neither side is easily discouraged.

The Beaver Wars: round ten to the beavers

It's a long story, going back to 2008. (Previous posts: May, 2009; November, 2011; January, 2012; March, 2012; November, 2012.)

History to date:

We first saw signs of the Cougar Creek Park beavers in 2008. They were colonizing the newly-landscaped lagoons, and had dammed the lower creek outlet. The next year, they had dammed the inlet as well, creating a small pool on the upper level.

The city (Surrey) has objected; this was not in the official plans. So they've fenced and wired the trees, sometimes reinforcing them with wired-on chunks of wood. They've removed the dams, they've caught and killed a male, they've cleared trees off the banks, completely removing a shady stand of evergreens; the resulting erosion has turned the upper end of the original pond into a muddy slough.

The beavers shrugged off their losses and went back to work.

By November of 2012, the family had succeeded in damming the upper creek, filling in what had been a wasteland with a slow, muddy trickle down the centre. It made a pretty duck pond, striped with reflections from the alders around it, over patterns of green and gold animated by swimming, dabbling ducks.

Map of ponds, November 2011, with the dammed upper creek marked in blue. The pond now extends to the bridge at the far right.

In January, 2012, the dams and the new pond were gone. By that March, the three dams were back; the upper pond was filling again. Mallards, wigeons and mergansers were busy in the new feeding ground; as usual, a heron was hunting along the edges.

I took my grandson down to the park to show him the beaver dams in September of that year. We were disappointed; not only had the city removed all the dams, but they had gone into the wasteland with machinery and scraped off much of the vegetation, leaving an oozing, muddy mess, scattered with garbage. (So much for the much-advertised "Releafing Project".) A lonely pair of ducks patrolled the lower lagoon; nothing else, not even the heron.

We went back last November. (I calculated this as Round 8.) Now there were three good dams, and a lodge. The upper pond covered the machine scar nicely, and they'd built another dam at the top, making a new, third pond. The ducks were back.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

2013:

This spring, we found the upper pond area scoured clear again. By summer, there was a start on a new dam, near the bridge. It didn't last; the next time we visited, the creek was trickling over bare mud again. There was no sign of beaver activity anywhere. I wondered if they had finally given up.

The beaver is a stubborn animal.

I took a friend to the park last week to look at ducks. And found the beaver ponds expanded once more, swallowing up most of the space between the schoolyard and the fenced houses on the map above.

The ducks are happy with twice the water to dabble in.

The newest dam, raising the water level a couple of feet. Lots of good-sized lumber in there, probably incorporating trees the city had felled.

This latest project is quite ambitious; the beavers have cut down some large trees, red alder wood for construction, the juicy bark and cambium for food.

Two trees, the smaller one gone to the dam. The other will have to be cut in small chunks if they plan to use it for building.  If not, it has a whole season's worth of groceries under the bark.

Toothmarks in wood, cambium, and grey-green bark.

Part of the new pond.

In earlier episodes, the lodge was usually built in the lower lagoon. (The small, squarish one in the map above.) Here, it was highly visible to anyone walking on the paths, crossing the bridge, or in the back yards of the houses to the south. It never lasted long.

Someone, some beaver, has been thinking. The latest lodge is well hidden.

In the new pond, water has overflowed the previously established banks; much of the "bush" - salmonberry, elder, Indian plum, ferns and the inevitable blackberry canes - has its feet underwater. We walked around from the upper end, as far as we could go without wading. And hidden between trees and bush, we found the lodge.

It's a big lodge, high and long. This was as close as we could get. I think that's cattail growing on the far side; a new addition to the vegetation here.

And I still haven't seen the beavers themselves.