A lot of new turtle keepers don't realize this, but female turtles produce eggs even if there are no males around. The eggs will be infertile and will not hatch, but all healthy adult female turtles produce eggs.
When a turtle is carrying eggs, she is said to be gravid, not pregnant. I used the word "pregnant" in the title tag only because that's what most new turtle keepers search for when looking for information about this topic. It's really not the right term. So from now on we'll use "gravid."
And unlike many amphibians, most species of turtles and other reptiles can't reabsorb unfertilized eggs into their bodies. When they have eggs, they have to expel them. If they don't, they can get "egg bound," which is also known as suffering from egg retention or dystocia. Dystocia isn't just painful for the turtle. She can die from it.
There are many reasons why turtles can get egg bound, but the most common reasons in the case of captive turtles are:
The most common reason for egg binding in gravid captive turtles, however, is lack of a suitable place for the turtle to lay her eggs. In nature, aquatic turtles lay their eggs on land in a particular kind of soil or mud, depending on the specie, when the season is right. Keepers of captive turtles need to provide as close as possible to a natural oviposition site as their turtles would seek in nature.
There are many signs that a turtle is gravid and needs to lay her eggs, and not all turtles will show all of these signs. Some things to look for include:
The advice here is general in nature. Every specie of aquatic turtle has their own breeding and egg-laying habits, so I suggest that you look up your specie of turtle in the Care Sheets on Austin's Turtle Page for more detailed instructions. But here are some general instructions.
Captive turtles who live indoors may need to lay eggs at unusual times of the year because they often lose track of what season it is. Wild turtles are believed to use factors such as the temperature, the angle of the sun and moon, the length of days, and possibly the appearance of various stages of vegetation to know what time of year it is. These cues are missing in most indoor turtle habitat. As a result, captive turtles may need to lay eggs during times of the year when it's impossible to provide an oviposition site outdoors, which is usually the easiest way to do it.
This leaves you, the keeper with several options. One is to try to provide a suitable oviposition site indoors. This is not as difficult as it sounds. You can either purchase a turtle nesting box, or you can use any plastic bin large enough to hold enough soil so that the depth of the soil is deeper than the turtle is long. The blue bin on the right cost me about ten dollars at my local dollar store.
The procedure is pretty simple. First fill the container with an adequate amount of the right kind of soil for your turtle (usually a mixture of potting soil and sand, although it varies by specie), lightly spray the top of the soil with a clean spray bottle of tap water, place the turtle in the box, and cover the top about two-thirds closed with the lid or a piece of cardboard. Then leave her alone for a few hours in a warm room.
Once you think she's done (or after two or three hours at most even if you don't think she's done), put her back in her regular habitat and check the soil for eggs. If you find any (they would be underground for most turtles), throw them away if they are unfertilized (which, of course, they will be if she doesn't have a male in her habitat).
If she does have a mate and you want to raise the eggs, that's something I plan to cover in a future page. For the time being, the Care Sheets at Austin's Turtle Page have good instructions for incubating the eggs of most aquatic turtle species. Read them before you touch your turtle's eggs.
A second option is to place the turtle in a small tub of warm water, about 10° F (18° C) warmer than the water in her usual tank, and leave her alone in there, in a room that's also warm, for a half hour or so. Sometimes that will cause her to expel her eggs.
If that doesn't work, then you'll need to find a veterinarian who is knowledgable in treating reptiles (often called a "herp vet"), who probably will want to inject her with oxytocin, which is the same way doctors induce labor in pregnant women when they need to. If the oxytocin doesn't cause the turtle to lay her eggs, then probably the vet will need to surgically remove them.
What's most important is not to ignore your turtle's signs that she is gravid and needs to lay eggs. If you do, your turtle will probably die. So try the instructions above, and if they don't work, call a veterinarian who treats reptiles for expert help.