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Wildlife and Habitat

Approximately 70 percent of the refuge land is forested with white pine and mixed hardwoods dominating. Approximately 22 percent is considered wetland habitat, including remnant Atlantic white cedar swamp, 6 dwarf-shrub bogs, 2 minerotrophic peatland bogs, a collection of vernal pools and historical cranberry bogs, and grass and shrubland habitats in the remaining areas.

The primary purpose for which the refuge was created is its "...particular value in carrying out the national migratory bird management program". The refuge's interspersion of wetland, forested upland and old field habitats is ideally suited for this purpose. The refuge supports a diverse mix of migratory birds including waterfowl, wading birds, raptors, shorebirds, passerines, as well as resident mammals, reptiles, amphibians, fish and invertebrates. Assabet River NWR is included in the Sudbury-Assabet-Concord Inland River priority for protection Focus Area under the North American Waterfowl Management Plan (NAWMP). The refuge area is also included within the Emergency Wetlands Resources Act of 1986 and is included in the U.S. Environmental Protection Agency's Priority Wetlands of New England listing (1987). The refuge is identified as being High Biodiversity Focus Areas in the Sudbury-Assabet-Concord Watershed Biodiversity Protection and Stewardship Plan (Clark, 2000).

Blanding's Turtle Repatriation Project

Blanding's turtle Credit: Stephanie Koch/USFWS

The Blanding’s turtle (Emydoidea blandingii) is a medium-sized, semi-aquatic freshwater turtle that inhabits wetlands in parts of the upper Midwest and New England. The New England population is disjunct from the main portion of the range.  Blanding’s turtles are regarded as a species of conservation concern in every New England state in which they occur.  This species is listed as threatened in Massachusetts and the U.S. Fish and Wildlife Service is determining if federal listing under the Endangered Species Act is warranted. 

Blanding’s turtles require large landscapes, relative to many other turtle species. They require a variety of wetland habitats, make frequent seasonal overland movements between them, and therefore suffer mortality not only from direct wetland habitat loss, but from upland landscape fragmentation as well. Protection of individual wetland sites has been difficult enough, but large-scale landscape conservation is even more daunting, especially in the heavily-developed northeastern U.S. 

Two of the largest populations of Blanding’s turtles in the northeast exist at Oxbow NWR and Great Meadows NWR, and biologists are partnering with researchers to establish another population at Assabet River NWR, which is roughly equidistant between the other two populations. The project involves collecting Blanding’s turtle hatchlings from Oxbow NWR, individually marking them, and then either releasing them directly in wetlands at the donor site and new site, or raising them in captivity for their first year.  The year old “head-started” turtles are larger and more likely to survive into their second year when they are released into the wild.  To supplement the repatriation effort, biologists are also trapping and moving juvenile turtles from the source population at Oxbow NWR, marking and radio-tagging these juveniles, and tracking their movements and habitat choices at Assabet River NWR once they are released.