Why Wood Turtles Need Clean Water



Splitting their time almost equally between land and water, Wood Turtles are unique compared to other North American turtle species, most of which are either chiefly aquatic or fully terrestrial. Aquatic species, such as Painted Turtles, rarely leave water except to bask and nest, and terrestrial species, including tortoises and Box Turtles, scarcely venture into water apart from briefly wading into the shallows and seeps. A few break from this trend, with Spotted, Bog, and Blanding’s Turtles being considered semi-terrestrial, but they all forage primarily in the water and use land mostly as a means to get from one wetland to another. Wood Turtles fall into the semi-terrestrial category too, but unlike the others, heavily favor spending time on land in the summer. They are also the only North American turtle that overwinters exclusively in streams, which is due, in part, to their need for well-oxygenated water through the winter.  

Although Wood Turtles spend considerable time on land, they overwinter in streams where clean, well-oxygenated water is important to their survival.

In regions where ice covers most standing water in the winter, small ponds and the bottoms of larger lakes are prone to oxygen depletion, a condition known as anoxia. Some turtles are remarkably tolerant of anoxic conditions, but Wood Turtles seem dependent on nearly continuous access to oxygen through the winter. The streams where Wood Turtles overwinter almost never entirely freeze over, and wherever ripples touch air, oxygen mixes into the water, which the turtles then absorb directly through the roof of their mouth and lining of their cloaca (informally known as “butt breathing”). But not every river is equal, and water quality issues caused by sediment and nutrient pollution can reduce oxygen availability in streams, as well as the turtle’s access to that oxygen. Clean water is key to the survival and management of Wood Turtle populations, but there are many other reasons apart from oxygen that clean water benefits Wood Turtles.

Here are just a few other ways in which clean water and features associated with healthy river systems help Wood Turtles:

  1. Clean water has less sediments that might settle on top of overwintering Wood Turtles and restrict their access to oxygen or force the turtles to move mid-winter.

  2. Clean water has a greater abundance and diversity of macroinvertebrates, which are important food sources to younger Wood Turtles (macroinvertebrates are even considered indicators of water quality).

  3. Streams with meandering (un-straightened) channels slow water during floods and can move over time, leaving behind oxbow wetlands where Wood Turtles forage, and creating sandbars where they nest.

  4. Heavily vegetated floodplains stabilize soils and capture nutrient runoff, but also slow water down during storm surges and spring floods, which protects Wood Turtles from being caught in strong currents and washed downstream (a major source of winter mortality to Wood Turtles).

  5. Exposed roots and log jams, which are more abundant in streams with forested streambanks, give turtles a place to hide in the winter, which protects them from predators. Roots and log jams also protect the turtles from strong river currents during floods.

  6. Rivers with forested streambanks are also more shaded, which lowers water temperatures (colder water holds more oxygen). The same rivers also have more leaf packs, which are another great place for turtles to hide from predators.
A Wood Turtle hiding deep within a logjam collected around the roots of a tipped over tree. Logjams and roots provide critical habitat to Wood Turtles, but are scarce in streams with unforested banks.

Protecting and restoring riparian buffers along streams helps facilitate every aspect of clean water and healthy rivers listed above. Simply put, a riparian buffer is a strip of land between water and human land use where trees and shrubs are planted, and where motorized vehicles and livestock are excluded. A typical riparian buffer might be in the realm of 50 to 100 feet wide and is meant to stabilize soils, reduce erosion, and to capture nutrient and chemical runoff from farms and urban areas. Where possible, buffers as large as 300 to 1000 feet are recommended to give Wood Turtles space to forage on land where they can’t be killed by cars and machinery. Buffers don’t just help Wood Turtles, but also improve habitat game fish such as trout, many species of wildlife, and they improve the quality of the water for recreational activities such as swimming and fishing. Everybody wins.

Riparian forest buffer in Queen Anne's County, Md.

An example of a forested riparian buffer recently expanded with the planting of additional shrubs to restore water quality. 

Setting land aside for riparian buffers comes at a cost to some landowners, however, because river valleys have incredibly rich soils that are important to agriculture. Thankfully, Farm Bill and some state programs provide financial incentives to reimburse farmers for setting land aside as riparian buffers and habitat along streams through purchasing conservation easements (permanent), short term buffer rentals, and other conservation programs. And while establishing a buffer may mean farming a little less land along streams, once established, buffers can prevent farm fields from greater losses over time through erosion, and can protect fields, roads, and other infrastructure from damage by intense floods. 

While any riparian buffer is better than no buffer, Wood Turtles need space to forage on land. Expanding buffers to 300-1000 feet, where possible, gives Wood Turtles the space they need so they don't spend as much time along the edges of and within farm fields where they are are high risk of being killed.

Recently, The Orianne Society partnered with the Connecticut River Conservancy in a landowner outreach initiative to help farmers restore Wood Turtle habitat through Farm Bill conservation programs (see the recent press release). This effort will result in cleaner water and more space for Wood Turtles to roam in key areas within the Connecticut River Watershed of Vermont, New Hampshire, and Massachusetts. If you own or manage working lands in river valleys within this area and want to learn more about Wood Turtle conservation, feel free to reach out to us by emailing Kiley at kbriggs@oriannesociety.orgAnd if you aren’t sure whether your land has good habitat for Wood Turtles, feel free to take a look at the second page of this brochure and this range map to learn a little more about where Wood Turtles live and what their habitat looks like, then reach out if you are still unsure.

Outside of our target area, you can learn more about conservation options for working lands through your local NRCS service center. NRCS staff are also knowledgeable about other conservation programs that may be a good match for your property, regardless of whether you have Wood Turtles in your area. Partnerships between farmers and conservation organizations are critical to protecting and restoring the clean water that Wood Turtles, other wildlife, and humans depend on. For us, it’s not just about protecting Wood Turtles, but restoring ecosystems. Enhancing agricultural sustainability is an added benefit, and a big one at that.