Snapping Turtle Egg Development

As hatchlings they enter the world weighing a quarter of an ounce and if lucky, will live over 50 years to become formidable 75-lb. scavengers. Common snapping turtles (Chelydra serpentina) are often feared and misunderstood, but if you can look past their rough exterior, you'll see many fascinating aspects to their biology. Not the least of which is the development of these future behemoths through the first few months of their lives, while at their most fragile existence.

  1. Time Frame

    • The ovaries of a female common snapping turtle contain all of the unfertilized eggs (termed follicles) that she will use in her lifetime. She will reach sexual maturity at five to 15 years of age and begin to annually release some of her follicles into the oviducts. Mating and fertilization take place from April through May, and the very young turtles are moved along into the uterus. Three to six weeks after fertilization, the female digs a nest, lays her eggs, covers them up and then abandons them. The nest temperature determines the duration of development in incubation. Hatching may take place in as little as 55 days in a warm climate to 125 days in a cool environment.

    Size

    • The ovarian follicles consist of one single cell and are microscopic. As the follicles are released into the oviducts, each is associated with yolk, enlarging them to 1 inch in diameter. Following fertilization, a shell forms around the developing egg. The shelled eggs are about the size and shape of Ping Pong ball and won't get any larger.

    Features

    • Eggs of the common snapping turtle are nearly perfectly round, and the shell is leathery and tough. Inside, the bulk of the egg is comprised of the yellow yolk, which feeds the developing embryo sitting atop it. Surrounding the yolk and embryo is the egg white or albumen. Its purpose is to aid in gas and water exchange between the inside and outside of the egg, while providing a buffer from physical injury.

    Considerations

    • DNA primarily determines a turtle's body structure. However, turtles are rare animals in that the environmental nest characteristics play a role in major aspects of their development. For example, the eggs on the edges of the nest produce the largest baby turtles due to their greater accessibility to moisture. Also, the temperature inside the nest determines the baby turtle's gender.

    Benefits

    • Female common snapping turtles will mate with many males and are capable of storing the sperm from these mating for up to a year. A single clutch of may contain the genetic contribution of several different males. From an evolutionary standpoint, the increased genetic variation enhances the survival of the population as a whole.

    Expert Insight

    • Chester L. Yntema, Ph. D., at the State University of New York was the first to demonstrate that nest temperature determines the gender of common snapping turtles. He found that eggs incubated below 68 degrees Fahrenheit or above 84 degrees produce all females, while eggs that remained between 69 and 83 degrees produce both males and females.