Going to the dredge islands

eagle bones, lichen gardens, and an octopus rescue

On a fine low tide in late April, I headed out to some of the dredge islands in Gastineau channel, along with two friends. Before we even got to the islands, we found several interesting things. In the middle of the dike trail lay the feathers and other remains of a dead bird. Grazing on the innards were at least twenty little brown slugs—officially known as reticulated tail-droppers. We often see them on bear scats filled with digested vegetation, and gardeners make war on them when they attack some treasured plants, but what were they getting from bird guts?

Just as we left the dike trail, our attention was drawn to a pinkish blob lying in sparse grass. A second look told us it was on octopus, stranded by a recent high tide. An octopus has no business being up in the grass, so after determining that it was still alive, we carefully put it in a plastic bag (from which it tried to crawl out, of course) and carried it with us until we reached some permanent salt water, where it was released and slowly crawled away. It may not have been in very good shape by then, and maybe some disability accounted for its being washed up into the grass, but at least it got a second chance.

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The octopus tries to escape its rescuers. Photo by  Katherine Hocker

One island of this chain of islands was a real island before the channel silted up; its core is a forested ridge of bedrock, now surrounded by uplifted land that supports a ring of small spruces and elder berry bushes. An exploration of this island turned up two bird skeletons, minus the skulls; a little forensic work later determined that the bones were very likely those of bald eagles. That made us suspect that they had been shot and left to rot. A sorry thing!

Under some of the trees we found burrows that looked like old otter dens, probably made back in the days before post-glacial uplift increased the distance to permanent water. A cast-up pellet of undigested bits, probably from a raven, held—of all things—the better part of the bowl of a plastic spoon. Overhead, a group of eagles and crows circled peaceably.

We flushed several snipe from the sloughs that cross the wetland. A female harrier coursed in and out of the trees on the smaller islands, probably on her way north (although harriers do nest here occasionally). And buttercups were starting to bloom along the edges of the spruce groves.

Best of all were the lichen gardens on the smaller islands, which are made of dredged sediment from the channel. Sometimes called lichen ‘barrens’, these gardens are barren only of trees and shrubs and tall herbs. They can be a wonderfully artistic spread of color and form. The lichens were very happy, owing to recent rains, so we spent some time admiring the natural art show. We also tried very hard to place our feet where they would do the least damage. Each of these gardens of miniatures was surrounded by a ring of young spruces, lending them a feeling of seclusion and privacy.

On the way back to the car, we spotted a little group of five snow geese, busily grazing—the last reward of a profitable excursion.

Middens

heaps of junk are a naturalist’s treasure

This interesting and useful word comes ultimately from an old Scandinavian term for a dunghill. The sense has been broadened to include heaps of all kinds of refuse and junk.

Archaeologists love human middens (except perhaps those that can sometimes accumulate in the bedrooms of certain young, or the backyards of not so young, persons…). These scientists mine around in ancient piles of shells and bones and debris, often finding such treasures as ceramic shards, broken and discarded tools, cordage and nets, lost ornaments of hard materials, charcoal, even plant and insect remains. It all gives them a good source of information for interpreting by-gone ways of life for humans. Sometimes it also yields information on changes in animal and plant communities over hundreds and thousands of years and, in coastal areas, information on locations of ancient shorelines. (Juneau has its very own large and ever-growing midden in the Lemon Creek area.)

Shell middens, up to several thousand years old, have been found in the Aleutians, on the north slope, and all over coastal Southeast, except where long sandy beaches are common. On Prince of Wales, middens composed mostly of barnacle and mussel shells have been estimated to be as much as five thousand five hundred years old. Many others are more recent.

Other animals regularly create middens too. Muskrats harvest cattails and other aquatic vegetation, typically eating only part of the plant. The leftovers pile up, as the muskrat returns again and again to the same lunch spot. The heap of vegetation then offers a dry place for future meals (but I don’t know if the muskrat cares about that).

Here in Southeast, bushy-tailed woodrats live on some of the nunataks in the coastal range of mountains. Woodrats are also known as packrats, for their habit of collecting and piling up all sorts of miscellaneous junk. Excavation of packrat middens in the deserts down south has provided important information about past climates and environments, as long ago as forty thousand years. However, I don’t think anyone has studied the woodrats in our regional populations.

Red squirrels are the well-known midden-makers. They have favorite spots for peeling the scales off cones to extract the edible seeds. The rejected scales and cone cores pile up, sometimes a foot or more deep. In some cases, a midden is spread out over a sizable area. I once found one near Atlin that was over eighteen yards in diameter; this one had been used a long time!

The accumulation of cone debris often blankets the squirrels’ burrows, probably providing some protection from cold and wet. Squirrels often cache their harvested cones in the burrows or between the roots of trees, to keep them from drying out and opening prematurely, letting the seeds fall out and get lost. And they sometimes dine near the entrances to the burrow, building up a midden. When a squirrel midden covers a cache of food, some sources conflate the terms, making cache and midden mean the same thing. But it is helpful to keep those words distinct: one for the rejects on the surface, the other for the still-useful cones in storage. The accompanying photograph shows a midden of cone debris with a pile of still-closed spruce cones on top. The squirrel that owns this pile will, presumably, move those cone below-ground to a cache, where the dampness will keep the cones from opening and shedding the seeds prematurely.

Here in Southeast, red squirrels commonly seem to live and nest in those burrows, but in the Interior I think they typically nest in collected bundles of leaves and other vegetation placed up in trees. (Also, next to my house, behind a pile of lumber, there is a beautiful round nest, which I am loath to disturb.) Those ball-shaped bundles are called ‘dreys’.

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Octopus den and midden. Photo by Annette Smith

Who else makes middens? Octopuses often pile up stones and shells in front of their dens. Marine biologists use the accumulation to locate the dens and analyze the shells to determine the diet of the den-dwellers. One kind of octopus favors snails for dinner, discarding the shells out in front of the den as usual. But in this case the shell pile often doesn’t grow, because hermit crabs appropriate the snail shells for their own use.