Tracks on the Assabet ... a mink.

April 29.

When I examine a flat sandy shore on which the ripples now break, I find the tracks of many little animals that have lately passed along it close to the water's edge. Some, indeed, have come out of the water and gone into it again.  

Minks, squirrels, and birds; they it is that walk these inland strands. The moist sand and mud which the water has but just ceased to dash over retains the most delicate impressions. 

It is the same with all our rivers. I have noticed it on the sandy shore of the broad Merrimack. Many little inhabitants of the wood and of the water have walked there, though probably you will not see one. They make tracks for the geologists.

I now actually see one small-looking rusty or brown black mink scramble along the muddy shore and enter a hole in the bank.

H.D. Thoreau, Journal, April 29, 1860

One small-looking rusty or brown black mink. See April 15, 1858("Having stood quite still on the edge of the ditch close to the north edge of the maple swamp some time, and heard a slight rustling near me from time to time, I looked round and saw a mink under the bushes within a few feet. It was pure reddish-brown above, with a blackish and somewhat bushy tail, a blunt nose, and somewhat innocent-looking head. It crept along toward me and around me, within two feet, in a semicircle, snuffing the air, and pausing to look at me several times.”); March 13, 1859 ("I commonly saw two or three in a year. ")