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’.
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.