Reproductive Potential, Activity, and Cycles in the Painted Turtle, Chrysemys Picta

Abstract

Reproductive cycles, reproductive potential and activity were determined for populations of the painted turtle, Chrysemys picta. The male reproductive cycle is divisible into three phases. From late March to early May (the mating season) the testes are small but the sperm ducts are filled with sperm. Spermatogenesis occurs from July to October. This results in an increase in testis size. The winter phase is characterized by small testes. Most of the sperm are contained in the epididymis at this time. Transitional periods occur between each of these phases. Courtship behavior occurs in spring and fall, but effective mating probably does not occur in the fall. Ovarian follicles begin to increase in size in September. By March the largest follicles are around 16 mm in diameter. Immediately before ovulation these increases to about 18 mm in diameter. Ovulation occurs around the middle of May and enlarged follicles, as well as the oviducal eggs, are invariably present at this time. Presumably a second clutch is laid. The second ovulation probably occurs in middle June. Mean clutch size is about 6.5 eggs and the annual reproductive potential for an individual is around 13 eggs. Adults become active in early spring when water temperatures reach the minimum tolerance limits. Reproduction is believed to be the incentive for this early activity. Distances traveled by mature males are greatest in the spring. Travel is limited throughout the summer. Juveniles and mature males are found in the same general area in successive summers whereas mature females have often traveled long distances. This is attributed to females leaving the water in one area for nesting purposes and returning to the water in another area.