Bog Bean (Menyanthes trifoliata) is an important plant around the Big Pond. An exclosure, made by Kevin Jones when he was doing his PhD, shows how much more bog bean there is inside it, protected from the beavers, than lives outside, where it plays a part in the beavers' rations.
Open water, some of it a channel along which the beavers swim, makes up the foreground. Further away is a bank of sedge with a feeding station, on which stripped branches of birch and willow remain. Two thirds of the way up the right side of the photograph, below that leaning birch tree, you can make out a lodge.
Mare's Tail (Hippuris vulgaris) is plentiful along the edges of the pond. I have just learned from Wikipedia (http://en.wikipedia.org/wiki/Common_Mare's_Tail) that 'It has been said to absorb methane in large quantities and so to improve the air quality in the marshes where it is often found.'
I don't know how popular Mare's Tail is with beavers. It always seems to me that they are eating Horse Tail (Equisetum arvense). As beavers pull the slender asparagus like stems to their mouths, I wonder if the plants are edible to humans.
A quick look to Wikipedia (http://en.wikipedia.org/wiki/Equisetum_arvense) assures me that this is so.
Jean-Pierre Choisy has sent me an email to say that his first message was precipitate and contained some errors. He has asked me to post this corrected version of his email.