Last week I visited a wetland in northern Idaho. I saw several western painted turtles (Chrysemys picta bellii) that were on the gravel road. I observed one of the turtles for a few minutes and noticed she was clearing gravel. Then she started digging a hole, right on the edge where the gravel meets the vegetation... she was going to lay her eggs! I observed the entire process which took almost exactly one hour. The digging is done with the hind legs, always alternating between the right and the left leg. I did notice the dirt was quite wet and that surprised me given the fact that the road surface seemed pretty dry. Now, after having read about the egg laying process, I think that she probably lubricated the area with her bladder water to ease the digging. I could not see every egg, but I estimate that she may have laid about 10 eggs which is close to the average clutch size (about 12) for the western painted turtle. Turtles may select nesting sites along roads because these sites are relatively high and less likely to flood, and they are also relatively warm. Since temperature influences the sex ratio of many turtle species, nesting along road sides may have an effect on the sex ratio of the hatchlings. Furthermore, nesting along roads brings direct mortality risks to both the adult females, the eggs and the hatchlings. Click here for other images of the turtle, including egg laying.
All content © 2012 Marcel Huijser