Wood Turtle (Clemmys insculpta)

Habitat: The wood turtle has long been considered one of the most terrestrial of northeastern turtles; however, recent evidence may suggest other-wise (Remley 1997). Because the aquatic and riparian areas they inhabit are difficult to access, most sightings of wood turtles occur in upland habitats. Although wood turtles may spend some time in uplands, they are almost always closely associated with rivers and streams.

In Maine, wood turtles usually enter into hibernation in November, and emerge in April. Undercut banks and root masses along slow moving rivers, streams, or small ponds are usually used for hibernation sites. Several turtles may congregate and overwinter in the same area. Wood turtles tend to delay emergence in the spring until water and air temperatures are sufficiently high for animals to maintain a warm body temperature. Thus, open riparian areas that receive ample sunlight are used once wood turtles emerge. Wood turtles also use vernal pools throughout the spring, taking advantage of the abundant food that is available in these areas. Females make a yearly movement during June to nesting areas. Nesting areas are bare, sandy gravel, close to water, and receive plenty of solar radiation. Nesting areas close to water are very important as females use the water as a travel corridor and they rest in the water between successive nesting attempts.

Throughout the mid- and late summer, wood turtles continue to use aquatic habitats and areas of emergent and scrub-shrub vegetation. During this period, turtles may engage in long daily movements through both upland and wetland areas, which has led to the belief that they assume a terrestrial existence at this time of year. In early fall, wood turtles will return to aquatic habitats to avoid cool evening temperatures and to engage in reproductive activity.

Reproduction: Wood turtles do not reach sexual maturity until their carapace is around 18.5 cm (7.3") in length, or about 11-12 years of age, at northern latitudes (Brooks et al. 1992). Mating occurs throughout the year, but peaks in the fall when temperatures are warm and individuals are congregating in aquatic habitats prior to hibernation. Dominance hierarchies are established among males through aggressive behavior, and males may actually court females before copulation occurs (Kaufmann 1992). Copulation occurs in the water, with the male mounting the female's carapace, although plastron to plastron copulation can also occur. Copulation among individual turtles may occur infrequently, as females can store sperm from different males for several years.

Females nest in sandy-gravel areas throughout the month of June and into mid-July, on warm or sunny days. Nesting may occur throughout the day, but is concentrated in the evening and may last well into the night. Females dig using their front claws, and will dig false nests in different locations until a site suitable for egg deposition is found. Nests are 10-18 cm (4-7") deep, and are pocket-like in formation. Females exhibit incredible dexterity by carefully positioning each egg within the nest. Between 5 and 12 eggs are eventually deposited and the nest is carefully covered when laying is complete. Eggs are off-white, elliptical, and 3-4 cm (1.2-1.6") in length.

Incubation is variable, depending on summer temperatures and the amount of solar radiation that is received by the nest. Incubation typically lasts 60-70 days, but may last up to 130 days during a cool summer (Harding and Bloomer 1979; Remley 1997). Eggs may not hatch for a variety of reasons. Nest predation by mammalian predators is a major factor in nest mortality in some localities and may approach 100% in some years (Brooks et al. 1992). Because of the proximity of nests to water, nests may become flooded during the incubation period, and eggs may rot in the nest. Also, cool summer temperatures will slow development to such an extent that eggs may not hatch until late fall. Wood turtle eggs are not known to overwinter in the nest. Combined effects of all mortality factors may be quite high, and a low percentage of wood turtle nests may hatch in any given year.

Little is known about young wood turtles after emergence from the nest, although they are believed to use aquatic habitats. Because of their rarity, small size, and cryptic coloration, young turtles are seldom seen in the wild; however, mortality is thought to be high for juveniles. Delayed sexual maturity, together with low nest success and poor juvenile survival, means that wood turtle populations depend on long-lived females to nest over successive years to sustain population levels.

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