Used to hike the trails of the C&O Canal near the potomac a lot.
Have seen all kinds of water snakes, snapping turtles, black snakes, toads, and frogs carp, shiners, feral goldfish.
Saw a muskrat once. Beavers are very conspicuous. You see how they have reengineered creeks. Once in a while you see beavers themselves. And theyve seen me: one warned its campanions of my presence and gave the danger signal: a tail slap on the water which sounded like a shot gun blast.
But of course birds are the most conspicuous:barn swallows, redwing black birds, peliated wood peckers, downy woodpeckers, bitterns, great blue herons, kingfishers, humming birds, grebes, migrating loons, Canada geese, red tail hawks, osprey, black headed vultures, turkey vultures, and even bald eagles.