Southeast Alaska’s largest order of mammal, the Rodentia, includes three large species and many smaller ones. In order of size, they are: beaver, porcupine and hoary marmot. As we wrote in The Nature of Southeast Alaska (Carstensen, Armstrong & O’Clair, 3rd ed, 2013)
“Sedentary habits, combined with formidable appetites, means that our three large rodents leave unmistakable imprints on their environment. Marmots ‘farm’ the subalpine meadows, as if tethered like horses to their burrow entries, clipping, plowing, trampling, and fertilizing. Porcupines are the dominant herbivores in many Juneau forests, grazing and browsing herbs and shrubs in summer, but targeting the trees themselves in winter, occasionally killing hemlocks by girdling. And beavers are creators and modifiers of wetlands, factors as significant to the pageant of succession as landslides or wave erosion.”
The upper Mendenhall Valley is excellent habitat for beavers, with numerous ponds, several creeks, and plenty of willows and cottonwoods to eat. Beaver families live all over this area, including the river and the lake. Juneau naturalists Bob Armstrong and Mary Willson have studied these animals and their habitat for many years. Here’s what Bob wrote about the challenges in photography:
“In the beginning I watched them through binoculars to get some sense of their habits. . . Then I would position myself close enough to obtain photos. . . they were initially upset at my presence and would swim back and forth in front of me slapping their tails. . . .Eventually, on subsequent days, they completely ignored me and would eat, gather wood, groom, and play sometimes within a few feet of where I was sitting. Once they became used to my presence slow movements and shutter noise did not seem to bother them.”
The above 60-page publication is a great introduction to one of our keystone species, in the fascinating setting of the recently deglaciated upper Mendenhall Valley. This delightfully illustrated, 60-page book has been available in local bookstores for several years. Now Bob and Mary have generously made it available for free as a digital download (6 megs):
Bob and Mary explained their motivation for creating this guide to beavers and their local ecology:
“The main spark that caused us to write this book was the help and encouragement of the many people that volunteered labor and/or money to purchase tools in order to alleviate some of the flooding and fish passage problems caused by beavers in the Mendenhall area.”
Check out more of Bob’s digital nature guides, available for download here.
In some Juneau watersheds (especially where deer are scarce), this unassuming rodent may exert more influence over habitat structure and species composition than any other vertebrate
As with beaver, Bob Armstrong has dedicated many hours to watching and photographing these amazing, social rodents. Check out his Whistlers on the Mountains, a children’s book with Marge Hermans, available in local bookstores, and described on his website here.