Critter Corner No. 33 – The Eastern Box Turtle by George Sly
Let me introduce to you a member of the Goose Pond FWA biota that I find fascinating in a variety of ways. It isn’t likely that the eastern box turtle would be the first animal you would think of as a Goose Pond resident. After all, it isn’t a marshland animal. Besides that, it is the birds that usually get top billing on this vast area. Yet, as I’ve noted in previous editions of Critter Corner, the diversity here runs far deeper than birds alone. The range of animal life found on the property is remarkably rich. And remember, not all of GPFWA is wetland. There are grasslands and woodlands here too. It is in the moderately dry forest habitat where one is most likely to find the eastern box turtle.
About the time I begin my annual search for morels, I also eagerly anticipate seeing my first box turtles. Both are sure signs that spring is finally here! On occasion, I find the turtles only partially above ground and covered in mud. Once the cold weather of October and November arrives, box turtles retreat into shallow burrows or other protected sites and become dormant. The mud-covered individuals I see are likely just waking up from a long winter nap.
Eastern box turtles are so-called because they can close themselves up within their shell – thus forming a box-like fortress for protection. This is not a universal ability among turtles. The ventral shell (the plastron) is hinged and can be moved upward to close against the upper shell (carapace). The carapace is composed of expanded rib bones, dermal bone, and incorporates their backbone or vertebral column. Although it offers strong protection, their shell is not impregnable. Large mammalian predators can, with persistence, penetrate this defense and prey upon them. And, of course, their shell offers no protection from one of their most deadly enemies – the automobile.
Eastern box turtle males usually have reddish-orange eye color, the females brown. Mating occurs soon after emergence in the spring (April-May) but some mating continues throughout the summer. Females lay several eggs (1-7) by digging a nest and covering it with soil. These hatch in twelve to sixteen weeks. However, egg predation by animals such as raccoons and skunks is typically high. Interestingly, female box turtles may store sperm and have been known to lay fertile eggs several years after their last mating.
As with other turtles, nest temperature is critical in determining the sex of hatchlings. Cooler temperatures (<82F) tend to yield males, warmer temperatures (>88F) females. Concern has been expressed that rising environmental temperatures may cause “gender skewing” in which an abnormally high number of females is produced. This preponderance of females could present a threat. It makes finding a mate more difficult thus reducing reproductive success. This, in turn, may cause a population to decline.
Eastern box turtles eat a variety of foods. The late Sherman Minton, Jr. notes, in his authoritative Amphibians and Reptiles of Indiana, that box turtles eat about equal parts of vegetation and animal matter. Fruits, berries, and fungi (including poisonous species) are consumed. Animal foods in the turtle’s diet include slugs, snails, insects, and carrion. Minton also observes that: Turtles living near farmhouses sometimes more or less attain the status of pets and may appear at definite times and places for food. Such is the case of the box turtle shown at the head of this essay. This one, for a period of about two years, showed up somewhat regularly in our flower garden, or on our deck, where it eagerly munched on the raspberries my wife provided.