Fish and their passage | Ecology of the river | Health of the river

At the river's edge, adjacent to the shallow marsh west of the Dealtry Pool in Watertown, painted turtles can often be seen sunning themselves on logs. Shallow marsh and shrub swamp habitat is found throughout the upper Reservation. Herons use the camouflage of rushes and sedges to forage on frogs and other prey.

Tall Silver Maple trees provide perch sites for birds such as cormorants, flycatchers, kingfishers and hawks which hunt along the river. The expansive tree canopy also provides roosting areas for colonies of black-crowned night heron.

Hawks, songbirds, foxes, squirrels and other small mammals inhabit the oak/pine forest habitat characteristic of the Lakes District in Waltham and Newton. Canada geese, mallards, black ducks, hooded mergansers, buffleheads and gulls can be seen all along the river corridor, especially in winter.