Breeding box turtles in captivity is not difficult as long as you have healthy turtles and a proper environment. Hibernation is also an important factor for the reproductive cycles of both sexes. During this time, hormones are produced and reproductive organs go through changes. After coming out of hibernation, it is suggested to keep the males and females separate until they are eating well and are active.
As previously mentioned, males have a concavity to their plastrons while females have a flatness to theirs. This concavity aids the males in mounting the females during breeding. The flat or sometimes convex plastron of the female allows for slightly larger body cavity for developing eggs. Male box turtles have a thicker tail, with the cloaca (a vent in the tail) closer to the end as compared to the females thinner tail with the cloaca closer to the shell. It is also said that males have red eyes. That is true, but I also have seen red-eyed females. Most females have brown eyes.
Below are photos to show the difference of a male and female box turtle.
Male Eastern Box Female Eastern Box brown eyes Female Eastern Box red eyes
It is important to not mix subspecies of box turtles in order to prevent mixed subspecies hatchlings. Above is a photo of a hybrid box turtle: an ornate and a 3-toed.
While soaking, often times, a male will extend his penis out of his cloaca. This is normal behavior but alarming when a box turtle owner observes this for the first time.
The peak time of mating season is in the spring. Males will mate with more than one female, therefore when having a breeding colony it is best to have more females than males. Courtship may last a few hours, with the male circling, biting, and pushing the female. Not too romantic, in my opinion. The female keeps her head in, but keeps watching the male. There are times when he actually tips her over. He will mount her and hook his back toes in between her top and bottom shell, usually while biting the front edge of her top shell.
The male will then lean back, as you can see in the photo, and be in a vertical position. This can last for a couple of hours. Female box turtles are able to store sperm for several years, so after mating, eggs may not be laid in that year.
You can see the concavity of the plastron of the male in the above photo.
Click on the video link below to see box turtles nesting.
There are several ways I determine if any of my females are gravid. I weigh them regularly and note when there is a gain in weight. Also, I palpate for eggs in front of the back legs behind the bridge of the shell. To see photos of this procedure, click on the link from the box at the top of the page. A female will be more active when it is time for her to lay her eggs. Sometimes, she will make practice nests before she deposits her eggs. The entire process of nesting and laying can take hours. She will use her back legs to excavate the dirt out. Her back feet also pack the inside of the nest to make the walls very dense and compact. After the eggs are laid, she will then use her back legs to scoop the dirt back into the hole and over the eggs. Two clutches per year with the number of eggs averaging 4 to 5 is the norm. When the egg-laying is completed, it is very difficult to even locate the nest.
Once laid, it is best to remove the eggs and incubate them properly. You can leave them in the ground but the nest area should be protected from other turtles and native animals that may come into the area. Some aquatic turtles will lay eggs in the water. Usually, these are not fertile, but if you can remove them, it is worth trying to incubating them. You must be very careful when opening a nest. I use a paint brush and slowly brush the dirt away. This is a very time consuming process because the dirt is packed very tightly. When removing eggs, do not jostle or rotate them. The eggs should be placed in an incubator, purchased or home made. I use a plastic bowl, placing damp sphagnum moss or vermiculite at least 2 inches deep. I then make an indentation for the egg to be placed in. A thin layer of moss is placed over the top of the eggs and a lid is loosely placed on the top. Humidity is very important for incubation. You do not want it to be soaking wet, but just lightly damp. The temperature should be around 80 degrees. I keep my temperature around 82 for my box turtle eggs. Also, higher temperatures produce female hatchlings. Do not be alarmed if some of the eggs sink in. This happens in clutches. It does not necessarily mean that they are not fertile. Unless they are very flat and/or split, I will continue to incubate them. The eggs typically hatch at around 70 days, but again, it depends on humidity and temperatures.