Wood turtle (Glyptemys insculpta)

Synonyms: Clemmys insculpta, Emys speciosa, Testudo insculpta
  
French: Clemmyde Sculptée
KingdomAnimalia
PhylumChordata
ClassReptilia
OrderTestudines
FamilyEmydidae
GenusGlyptemys (1)
SizeMale carapace length: 16 – 25 cm (2)
Weight0.4 – 1.5 kg (3)

The wood turtle is classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix II of CITES (4).

The wood turtle probably derives both its Latin and common names from the deep concentric growth rings and grooves known as ‘annuli’ that mark the somewhat raised carapacial scutes, which give the shell a ‘sculpted’ appearance as if carved from wood (5) (6) (7). In immature specimens (up to the age of 15 or even up to 20), roughly one ring is produced per year so that the annuli count can give a rough estimate of age, usually accurate within a couple of years (2) (7). Once they approach adulthood, however, accuracy drops off quickly (2). The back edge of the carapace is serrated and a prominent keel runs down the centre, also adding to its sculpted appearance (6). The carapace is typically brown or greyish-brown, sometimes with ray-like yellow streaking (5). The upper head is usually black, and upperparts of the limbs and tail are grey to greyish-brown, or even black with yellow spots (2). By contrast, the vividly-coloured underparts range from yellow in specimens from western (Great Lakes) parts of the species’ range (8), to orangish-yellow or orange in the central part of its range, to orange-red or ‘salmon-red’ in the northeast (2). Hatchling turtles have flat, non-sculpted, almost circular carapaces, and lack any of the adult yellow, orange or red pigment (3) (8) (9). The yellow plastron is also distinctive, with its pattern of dark blotches along the outside edge of each scute (9) (10).

The wood turtle is found in Canada and the U.S., ranging from southern Nova Scotia south to northern Virginia in the east, and from southern Quebec and the Great Lakes region to eastern Minnesota and north-eastern Iowa in the west (9) (11). Within this range, populations are thought to be relatively patchily distributed and fragmented (8).

Wood turtles are semi-aquatic and live along forested rivers and streams (10), usually in cool, upland areas of deciduous woodland, red maple swamp, marshy meadow and farmland habitats (3) (11). Streams with sand or gravel bottoms are preferred (8), while logs or banks near water and sunny woodland openings are often utilized for basking (6).

Upon emerging from winter hibernation, which generally takes place at the bottom of shallow streams and rivers (8), this diurnal species spends much of its day basking in the sunshine (6) (11). Wood turtles are omnivorous, foraging for a variety of plants and animals both in and out the water, including leaves, flowers, berries, fungi, slugs, snails, worms and insects, as well as opportunistically scavenging the occasional dead animal (8). In some populations, this turtle practices an extraordinary technique of hunting earthworms in which it thumps the earth, either by stomping its forefeet or rapidly dropping its shell to the ground. Earthworms appear to react to the vibrations by emerging from their burrows, and are then quickly snatched up (6).

Males actively pursue females both in and out of the water, and courtship can be an aggressive matter (11). Mating can occur at any time but is probably most frequent in spring and autumn (8). Females seek out open, sunny nesting sites, preferably sandy river banks, from May through to July, depending on climate (8) (9). Anywhere from 3 to 18 eggs are carefully buried, after which the nest site is covered over and concealed, which marks the end of parental investment. Nest predation by racoons, skunks, shrews, foxes and other predators means that most eggs sadly never hatch. After 47 to 69 days incubation, survivors emerge from their nests in late August or September and head to the water (8). It may take between 14 and 20 years before individuals attain sexual maturity and begin to produce offspring of their own (6) (8). The oldest known captive specimen was 58 years of age, but the lifespan in the wild may well exceed this (8).

The numbers of wood turtles have declined at an alarming rate in recent years, largely as a result of human interference and collection for the pet trade (9). Egg predation by skunks, raccoons and opossums is becoming a serious problem due to an increase in the number of these scavengers since human settlement, with egg and hatchling mortality exceeding 80 percent in some areas (6) (10). In the last few decades, commercial poachers have mercilessly exploited this turtle for the pet trade range-wide, and remain the primary threat to the species in a number of areas (6) (8). Significant numbers are also lost from road mortality, shooting of basking turtles by vandals, and incidental collection by recreationists (8). Indeed, two wood turtle populations in areas of Connecticut previously closed to the public declined to virtual extinction within a decade of being exposed to human recreationists (3) (8). Because these turtles have a late onset of sexual maturity and a slow reproductive rate, but a long lifespan, they depend upon a long adult reproductive span to sustain population levels. Removal of just a few individuals thus has a dramatic impact and can easily lead to local extinction (3).

Wood turtles have also suffered greatly from habitat loss and degradation (8). Although the species appears to tolerate modest timber harvest and agricultural activity, intensive forestry, farming, or industrial or residential development has a greater impact by fragmenting, destroying and polluting important wood turtle habitat (3) (8). Water management strategies that remove sand banks as a form of ‘stabilisation’ also limit available nesting sites and reproductive opportunities (8).

The wood turtle is legally protected to varying degrees by all the states and provinces where it lives, and is totally protected from commercial collection and trade (5) (8). Like many endangered turtle species, captive breeding may be the solution to satisfying the commercial demand for the wood turtle. Unfortunately, this has led to many reptile breeders scrambling to obtain specimens while they still can (11). Thus, unless its habitat is protected and the animals themselves are left undisturbed by poachers and predators, the long-term future for this ornately sculpted turtle looks increasingly bleak (8).

For more information on the wood turtle see:

Animal Diversity Web:
http://animaldiversity.ummz.umich.edu/site/accounts/information/Clemmys_insculpta.html

Woodturtle.com:
http://www.woodturtle.com

Reviewed (13/07/2006) by James H. Harding, Instructor / Herpetology Specialist, Dept. of Zoology / MSU Museum, Michigan State University.

  1. IUCN Red List (June, 2011)
    http://www.iucnredlist.org
  2. Harding, J. (2006) Pers. comm.
  3. Wetland Connections: A Program Dedicated to the Interdisciplinary Study of the Science and Ecology of Wetlands by Maine students (June, 2006)
    http://www.umaine.edu/wetlands/FGwoodt.htm
  4. CITES (May, 2006)
    http://www.cites.org
  5. Harding, J. (2006) The Decline of a Wood Turtle (Glyptemys insculpta) Population in Michigan: A 36 Year Study. Chéloniens, 2: 30 - 39.
  6. Michigan Department of Natural Resources (June, 2006)
    http://www.michigan.gov/dnr/0,1607,7-153-10370_12145_12201-33033--,00.html
  7. Woodturtle.com (June, 2006)
    http://www.woodturtle.com
  8. Animal Diversity web (May, 2006)
    http://animaldiversity.ummz.umich.edu/site/accounts/information/Clemmys_insculpta.html
  9. Turtles of the World (CD-ROM), by Ernst, C.H., Altenburg, R.G.M. and Barbour, R.W. (June, 2006)
    http://nlbif.eti.uva.nl/bis/turtles.php?selected=beschrijving&menuentry=soorten&id=312
  10. Wisconsin Department of Natural Resources (June, 2006)
    http://www.dnr.state.wi.us/org/land/er/factsheets/herps/WTURTLE.HTM
  11. Salvatore Santelli (Herpetoculturist) (June, 2006)
    http://www.geocities.com/RainForest/Vines/8524/wood.html