The authors of "Maine Amphibians and Reptiles" (Malcolm Hunter, Aram Calhoun and Mark McCollough) call the painted turtle (Chrysemys picta) "the most attractive turtle in Maine."
I think this is a bit subjective as we have some truly beautiful turtles in Maine; Blandings' and spotted turtles have lovely yellow spots, and the box turtle has beautiful yellow to orange splashes of color on its domed carapace. The painted turtle, however, is certainly the most colorful.
Painted turtles are medium-sized. The carapace (the shell) is smooth and dark and can reach a little over 7 inches in length. The marginal scutes (the plates that are along the edge of the shell) have red markings and the plastron (the hard underside of the turtle) is pale yellow with occasional dark blotches. The head and neck have yellow and red stripes with two distinct yellow spots on the side of the head behind the eye.
Painted turtles are the most widespread turtle in North America, their range extending from British Columbia to Nova Scotia, south to Georgia, west to Louisiana, north to Oklahoma, and northwest to Oregon. There are even small populations in the Southwest. While many turtle species are in decline due to habitat loss and road traffic, painted turtles seem to be doing all right over most of their range.
The most common human use of painted turtles is as school laboratory specimens. I highly recommend finding out what animals your local schools use for dissections and urging them to only use captive-bred species. Turtles and frogs, which are often collected from the wild, are having enough problems dealing with our rapidly changing environment.
Ogden Nash, in the poem "The Turtle" writes: "The turtle lives 'twixt plated decks/Which practically conceal its sex. /I think it clever of the turtle /In such a fix to be so fertile."
While turtle sex sounds comically ungainly, it can be quite tender, even passionate, between painted turtles, at least as described in "Maine Amphibians and Reptiles": "Mating takes place in the spring and fall with the male courting the female in shallow water by moving in front of the female face to face. He strokes her face with the back of his enlarged front claws ...; when the female sinks to the bottom, the male mounts her by placing his plastron on top of her carapace, and copulation takes place."
When ready to lay her eggs, the female digs a shallow hole in the ground and deposits the eggs. Amazingly, the gender of the young is not determined by sex chromosomes as it is with humans but rather by incubation temperature. Males are produced by cooler temperatures and females arise from warmer temperatures. This is called environmental sex determination (vs. the genetic sex determination with which we are more familiar) and is fairly common in reptiles and some birds.
This isn't a black and white system with all-male or all-female offspring. Females tend to dominate at higher temperatures and males at lower temperatures with more equal ratios of the two genders at intermediate transitional temperatures. One worry is that increasing local temperatures due to climate change could dramatically skew male-female ratios. In fact, some scientists believe that the extinction of the dinosaurs was linked to rapid climate change and rapid increases in temperature.
The benefits of temperature-dependent sex determination are not well understood, but according to a recent article by J.E. Lovich (Developmental Biology, 2006), "Theoretical ecologists have speculated that such a system would be expected to evolve under conditions in which the fitness of offspring varies according to their sex. If female offspring grow faster and mature earlier under warmer conditions, then mothers of offspring in those environments would benefit by producing more females. Alternatively, if male offspring are more successful in cooler environmental conditions, then mothers of offspring in those environments would benefit from production of males. "
Whatever the reason for temperature-dependent sex determination, it is a nice reminder that we should always expect the unexpected in the natural world. That what we think is normal probably isn't.
Sue Pike of York has worked as a researcher and a teacher in biology, marine biology and environmental science for years. She teaches at York County Community College and St. Thomas Aquinas High School. She may be reached at email@example.com.