Wood Turtle | New Brunswick Cooperative Fish and Wildlife Research Unit

Wood Turtle (Glyptemys insculpta)

Photo by G. Forbes

Figure 1. Adult Wood Turtle

Photo by D. Mullin

Figure 2. Hatchling Wood Turtle

The Wood Turtle (Glyptemys insculpta) is one of North America’s most striking turtles; the skin is generally brown but the legs and neck often have a yellow, orange or reddish colour. As its name suggests, the Wood Turtle is one of the most likely turtle species to be seen on land because they often search for food on land, sometimes as much as several hundred meters from the water.

This movement onto land exposes Wood Turtles to a variety of threats such as roadkill, heavy equipment, and predators which have contributed to the species being listed as Threatened in Canada and New Brunswick. A status of Threatened means that the species could go to a status to Endangered, a point at which the species could easily be extirpated (locally extinct).

This webpage is meant for the public and landowners as an information source on Wood Turtles in New Brunswick. We present an overview of the turtle’s ecology and biology, with references included, in case further reading is desired. We also provide recommendations on how you can help protect this species in New Brunswick. This webpage is divided into 2 sections, (1) Wood Turtle Biology and (2) Wood Turtle Threats.

Section 1. Wood Turtle Biology

1.1 Description

An adult Wood Turtle weighs approximately 1 kg (2.2 lbs), with the carapace (upper shell) ranging in length of 16-25 cm (6-10’’), and varying in colour from grey to brown (Litzgus and Brooks 1996, Smith 2002). Each scute on the carapace has pyramidal concentric ridges, giving the carapace a sculptured appearance. These ridges normally indicate a year’s growth and can help age a turtle, at least for the first 15 years or so. The plastron (bottom shell) is yellow with black splotches on the outer corner of each scute (Babcock 1971, Litzgus and Brooks 1996). The plastron is flat in females and juveniles, and in males becomes concave as they reach maturity; the concave shape helps with mating. Males are slightly larger than females and have a broader head (Foscarini 1994).

The Wood Turtle is very easy to tell apart from the other two turtle species found in New Brunswick, the Common Snapping Turtle (Chelydra serpentina, left) and Eastern Painted Turtle (Chrysemys picta picta, middle).

Fig 3. Common Snapping Turtle

Fig 4. Eastern Painted Turtle

Fig 5. Wood Turtle

The Snapping Turtle is one of Canada’s largest freshwater turtles (Ernst and Lovich 2009). The carapace is brown, black, or olive. It has a large head with a hooked upper jaw, a long neck, and a tail that tends to be longer than the body (Harding 1997). This characteristic gives it a dinosaur-like appearance.

The Eastern Painted Turtle has a smooth, gently rounded carapace that is dark green to black in color, with red markings on the sides. The plastron is tan to yellow, with some dark spots in the center. The head and limbs are black to green with yellow and red stripes (Ultsch et. al 1999).

More information about these species can be found on Constance Brown's (Research Associate, New Brunswick Museum) website or the Canadian Herpetological Society's website.

1.2 Distribution

Wood Turtles are distributed in northeastern North America from Nova Scotia west through New Brunswick, southern Quebec, Ontario to Minnesota, south to Virginia, and Maryland (Flanagan et al. 2013; Fig. 6). Canada is home to approximately 30% of the global distribution (Ernst et al. 1994, Conant and Collins 1998). Their distribution though is rather patchy; they often are found in small and isolated populations. In New Brunswick, Wood Turtle have been recorded in many watersheds but the exact locations of Wood Turtle are not advertised because of concerns from illegal collecting for the pet trade.

Figure 6. Global Wood Turtle Distribution (Amato 2006)

1.3 General Biology

Wood Turtles generally mate in the water, most often in spring and fall. Females lay eggs (normally 8 eggs) between May to early July in sand or gravel areas that receive a moderate to high amount of sunlight (Hunter et al. 2006). Eggs hatch in late August to early October (Farrell and Graham 1991). Young turtles (including eggs) are vulnerable to predation, mainly from raccoon, coyote, and fox (Saumure and Bider 1998, Cameron et al. 2002). Sexual maturity is reached at 11-22 years of age. Wood Turtles can live upwards of 80 years old. Adult Wood Turtles have high survival (over 95% yearly survival rate), and this high survival is critical to maintain healthy, sustainable populations (Mullin et al. 2020).

Figure 7. Dead Wood Turtle near Raccoon prints

Photo by D. Mullin

Wood Turtle eat a wide range of food items. They will scavenge dead fish in the river. Much of their food seems to be whatever is soft and available. Raspberries and field strawberries are available in many stream side areas. Slugs and earthworms also are easily obtained in fields, and alder swales. In the fall, Wood Turtle will move further into forests in search of mushrooms (Harding and Bloomer 1979, Ernst et al. 1994).

Photo by G. Forbes

Figure 8. Wood Turtle eating a mushroom

1.4 Habitat

Wood Turtles are more terrestrial than most freshwater turtles but still spend most of the year in water (Wesley 2006). From October to May, they overwinter on the bottom of streams, rivers, and ponds, typically in deeper water that does not freeze to the bottom (Mitchell et al. 1997). As spring approaches, they emerge from their winter site and sometimes are pushed far down the river with the spring freshet. During summer, they may move up to 500 m perpendicular from the main river and travel several kilometres along the waterway (Daigle 1997). But, for most of the time they are within 100 m of the water.

Wood turtle most often are associated with small streams (as little as 1 m wide) to medium-sized rivers (up to 75 m wide) (Harding and Bloomer 1979). Riverbeds are usually made of sand, gravel, or cobble. A meandering stream with a year-round current is preferred (Quinn and Tate 1991). Nesting habitat consists of sand or gravel beaches, or the banks of streams. Anthropogenic sites, such as agricultural fields, gravel pits, and roads have also been documented as nesting sites.

Photo by G. Forbes

Figure 9. Typical Wood Turtle River

Section 2. Wood Turtle Threats

2.1 The Importance of Turtle Life-History

Most of the threats associated with Wood Turtles have to do with their unique biology. Some species, like mice can breed several times a year, produce large litters, which themselves can breed in just a few short months. Such a breeding strategy means mice can easily compensate for the loss of some members. Wood Turtles may not breed until they are over 12-18 years old, have a small number of young with low survival, and, in Canada, and may not breed every year. This breeding strategy only works because individuals can live for long periods, at least 50 years old, but could be upwards of 80 years old (COSEWIC 2007), and over their life span, they breed enough times to maintain the population.

Increased adult mortality can upset the entire strategy. For example, modeling of population parameters has indicated that in a population of 100 turtles, the death of only 2 adults every year would result in extirpation (local extinction) of that population within 80 years (Compton 1999). Take home message is that maintaining high adult survivorship is a key component for maintaining healthy turtle populations. Adult turtles face mortality from cars, farm and logging machinery, and predators, but also removal due to people taking animals for the pet or meat trade.

Photo by D. Mullin

Figure 10. Juvenile Wood Turtles showing colour variation

2.2 Specific Threats

We will be focusing on threats that are locally important for protecting Wood Turtles in New Brunswick. For an exhaustive list of threats please read the Committee on the Status of Endangered Wildlife in Canada (COSEWIC)'s status report and assessment of the Wood Turtle here.

2.2.1 Roads

Roads (including ATV trails) can be a major problem for turtles, but only because of the amount of traffic and exposure to people. Gravel and sandy shoulders are a good substrate for nesting but may be an ecological trap as females may be collected or hit. Nests laid on roads may be compacted and crushed by vehicles. Hatchlings that emerge from these nests may be at high risk from vehicle mortality. Roads running close and parallel to waterways increase the risk of contact. Turtles are relatively slow-moving and are unlikely to avoid traffic. Turtles found injured on roads should be brought to a licensed wildlife rehabilitator. Turtles heal remarkably well so there is always hope of saving injured turtles. If uninjured, please help turtles cross the road in the direction they're going.

by Ontario Turtle Conservation Centre

Figure 11. Blanding's Turtle (top) and Painted Turtle (bottom) rehabilitation success after being hit on the road

2.2.2 Forestry Practices

Forestry practices using heavy machinery can crush turtles. However, compared to agricultural practices, most forestry practices involve fewer site visits than agriculture (Crowley 2006) thereby reducing the likelihood of direct mortality from equipment. It is unclear if certain forestry practices improve, or degrade Wood Turtle habitat. This is currently being researched by Damien Mullin under the supervision of Dr. Graham Forbes (University of New Brunswick) and Dr. Chris Edge (Canadian Forest Service). Read more about this research on the Edge lab website.

2.2.3 Agriculture

Riparian and terrestrial habitats are not only essential for Wood Turtles, they are also important for agricultural practices. Wood Turtle populations that overlap with agricultural lands have shown unsustainable levels of mortality and mutilation caused by agricultural machinery (e.g. mowers; Saumure and Bider 1998). Besides collisions, there are reports of Wood Turtles being buried alive during ploughing periods (Saumure et al. 2007). The pursuit for food, like worms and berries and nesting sites, like sandy gravelly areas can encourage Wood Turtles into the agricultural areas. However, the increased food and nesting opportunities, may turn into an ecological trap for the turtles, as the risk of collision and nesting disruption is significant.

Shaylyn Wallace under the supervisor of Dr. Graham Forbes (University of New Brunswick) conducted a series of experiments in central New Brunswick farmland in 2017-2019 to evaluate the effects of these threats at a local level. Before presenting this work, they wish to thank the numerous landowners and farmers for their assistance. Financial assistance for the project came from the Environment and Climate Change Canada Habitat Stewardship Programme, NB Department of Natural Resources and Energy Development, and the University of New Brunswick.

Photo by G. Forbes

Figure 12. Adult Wood Turtle in a hayfield

Experiment 1) Is predation affecting Wood Turtles in agricultural landscapes?

Methods

Set up trail cameras in an agricultural and a forested site to measure the relative abundance of turtle predators. Recorded injury rates of Wood Turtles at each site.

Results

Raccoon occurrence was significantly higher at the agricultural site. Wood Turtles had a higher rate of limb injury at the agricultural site. Very few young turtles found at the agricultural site, compared to many young turtles found at the forested site.

Conclusion

Raccoons are a serious predator to Wood Turtles, and the turtles (and their nests) are especially at risk in agricultural sites. Further research is required to investigate management recommendations to mitigate this threat.

Figure 13. Adult Wood Turtle with front limb eaten,

with exposed bone.

Experiment 2) How often are Wood Turtles in farm fields?

Photo by D. Mullin

Methods

Radio-tracked 23 adult Wood Turtles (males and females) and monitored them for 2 years to see what habitats they used, and when.

Results

We had a total of 1,057 turtle relocations. Approximately 35% of our relocations were in hayfields. Females used the fields more often and for a longer period than did males. Over 80% of turtle relocations in June and July were within 30m of the hayfield edge.

Conclusion

Wood Turtles readily use farm fields. They're hard to see, but they do spend a good amount of time there.

Experiment 3) Can Wood Turtles escape haying machinery?

Methods

We expected most Wood Turtles to move and escape because turtles have excellent hearing, can feel vibrations through their shell, and can learn from past injuries (Tinklepaugh 1932; Saumure et al. 2007). We had 2 groups of turtles, one group was already in the field when the tractor arrived, the other group were turtles temporarily placed in the field and that had not moved for an hour before the tractor arrived. We watched how turtles responded as the tractor approached.

Results

A few moved, most did not move, and of the turtles that did move, they did not move fast enough to escape. If a turtle was in danger, we moved the animal to safety. Of interest, if a turtle did move, they invariably moved towards the safety of the river. In separate trials, we placed turtles in uncut and cut fields, sometimes as far as 180m from the river. Every turtle lifted its head and turned towards the river within a few meters of moving, regardless of whether they had been pointed in a different direction, if someone was standing between them and the river, and whether they could see the river or not.

Conclusion

Wood Turtles lack the mobility to escape haying machinery, and likely face mortality if they're in the field that is being harvested.

Follow up question) Is there benefit to mowing in a specific pattern?

This ability to detect the water made us optimistic that turtles will hear machinery approaching and move to safety. Can farmers harvest in a different pattern that allows the turtle to escape? Mitigation strategies in agricultural landscapes include directing machinery to mow from the inside of the field to the outside, instead of vice versa (the most common technique) in order to allow wood turtles a chance to escape (STRIDES 2016). From our research, if the pattern was changed from inside to the outside pattern, turtles that are far from the river would likely still be hit by agricultural machinery because they crossed large fields to get to water and do not successfully avoid the tractor. A better option would be a zigzag pattern that would start on the side of the field furthest from the main river because it may allow enough time for turtles to move towards the water and escape. It is recognized that this pattern might be difficult for farmers to implement because they would be taking sharp turns and likely miss cutting portions of the field.

Experiment 4) Does raising blade height help turtles?

Methods

The experiment tested the effect of two common mower types on proxy Wood Turtles. We used hard cantaloupes cut to the dimensions and weight of turtles as a proxy to avoid injuring real Wood Turtles.

Results

Rotary disc mowers caused more injuries compared to sickle cutter bar mowers. We found that raising the blade height to 17 cm on a rotary disc mower would reduce injury of adult wood turtles to 50%, and raising a sickle cutter bar mower to 4cm would reduce injury to 60%. Tires still pose a risk during harvest, with turtles have a 20% chance of being struck by a tire. If struck by a tire, there would be a high chance of mortality due to the heavy weight of the machinery.

Conclusion

Sickle cutter bar mowers caused less injuries than rotary disc mowers to proxy Wood Turtles. Raising blade heights could help turtles, but there is still a major risk of running them over with the tires.

Solutions: Wood Turtle buffer strips may be a good option

Wood Turtles stayed near to the edge of hayfields, thus implementing an un-mowed buffer strip within a field during the summer months (30-50 m, on river side), or at least until the end of July, would be ideal to save turtles during harvest. Strips would need to be cut at the end of the season, or every couple of years, to keep the field dominated by preferred grasses. If strips were left to grow, then it is likely that the wood turtles would stop using the buffer and move back into the field due to low canopy cover. The Wood Turtles at our site showed that a field buffer along the edges would be an ideal management strategy to reduce the amount of injury and mortality due to the hay harvest. Landowners may not be willing to implement a 10-50m buffer surrounding the edges of their fields but another option could be to leave a buffer strip along the field edge closest to the main river. If a 30m buffer was applied to the edge closest to the river in June and July, then more than 50% of turtles could be potentially safe from machinery and a 50m buffer would save over 75% of turtles.

Best Practices for Farmers

Harvest as late in the season as possible, preferably after July
Harvest in a zig-zag pattern to allow better chance of turtle escape
Leave a 30-50 m wide buffer of uncut hay in the field section adjacent to the river
Use a sickle mower, if possible, and raise blade height for sickelbar or rotary blades to at least 17 cm

Photo by G. Forbes

Thanks!!!

References

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