Box Turtle Observation Project

Eggs!

A number of readers have seen turtles laying eggs on their property and want to know what to do and when they will hatch. In general, box turtle nests have a high mortality rate due to predators such as skunks and raccoons. You probably want to protect the eggs in some way. Ideally, leave them in place. If you must move them (from your driveway, for instance), be careful to keep them right-side up - do not rotate them. Transfer them to a similar outside situation some distance away. I have never had any luck with eggs brought inside.

To protect a nest built outside, build a cage a few feet square around it. The cage can be made simply by driving 4 stakes into the ground, and stapling chicken wire, rabbit cage wire, or screening over it - don't forget the top. Be sure to bury the edges of the screen to discourage digging under it. If the cage is a few feet square it will help keep the smell of the buried eggs from the noses of any predators, and they will not be likely to dig. Some animal repellent, or flowers such as marigolds, will also discourage predation. If the screen mesh is small enough that the quarter-size babies will not be able to crawl out, be sure there are some leaves to hide under in one corner and check for hatching periodically. If you do have young to release, do so on a rainy night to give them the best chance to reach a place of safety by morning. If the mesh is large enough, the young will just crawl out on their own.   A very simple cage can be made out of 2 strips of gutter screening (see picture above).  These are about 3 feet long.  Simply curve one into a circle and tie it there using nylon cable ties.  Place the other one over the resulting circle, attach it to the circle with more cable ties, and cut it to fit the circle (it will cover about 1/2).  Use the remaining gutter screen to cover the other side, and close up any gaps with the cable ties.  The screen can be anchored to the ground with stakes (more cable ties) or weighted down with rocks.  Be sure the edges are buried in the soil a few inches.  The mesh of this cage is too small for the babies to get out, so check daily.

How long does it take? At least the summer. Probably about 3 months or so. Sometimes, however, the young will overwinter in the egg, so don't lose hope. Normally, 4-6 eggs are laid. To the right, you can see Riker hatching in 2003.  Picard's shell and a quarter are to the left.  Below (left), Riker as he came out of the egg.  The yolk sac was still attached, and Riker probably came out of the nest early.  In such cases I take the hatchling, wrap it in a moist tissue, and place it in a box in a darkened room for about a week for the yolk sac to be reabsorbed a bit. (Below, right)

 

 

What goes on in the nest?  The sex of box turtles is determined by the temperature of the egg at a critical point in development (which has not been pinned down as of fall, 2003).  In nature, the temperature in the nest cycles daily.  The graph shown here records temperatures from a sensor placed in an empty nest (the eggs were removed to incubate inside).  As you can see, there is considerable daily variation in temperature.

If you are trying to incubate eggs inside, your incubator should try to duplicate these temperature fluctuations.  This is one idea:

 Get a 10-gallon aquarium and fill it 1/2 full of water.  Purchase 2 submersible aquarium heaters of 50 watts each (the submersible types with thermostats that can be set to a specific temperature are the most convenient).  Submerge both thermostats at the bottom of the tank. Set one thermostat at about 70 degrees F, and the other one at 85- 90 degrees F.  Plug this second thermostat into a timer that is set to come on about noon and stay on for 5 hours or so.  Place the eggs in a plastic shoebox filled with potting soil.  Be careful not to rotate the eggs at any time.  The eggs should be almost completely buried.  Keep the potting soil moist but not wet.  You will probably need to place something in the water to hold the shoebox up off the bottom of the aquarium.  Adjust the water volume so that the water level in the aquarium is about 3/4 full and the water outside the shoebox comes about 1/2 the way up the side of the shoebox.  Cover the aquarium loosely to prevent excessive evaporation, but still allow for some air flow.  Keep the incubator out of direct sunlight.  This setup should maintain the eggs at normal soil temperatures and even simulate the normal warming and cooling of the soil during the day and night.  Be sure the soil stays moist but not wet, and remove any eggs that develop excessive fungus (a small amount of algae or mold on the outside of the egg is OK).  Do not handle the eggs.  It is much better to leave the eggs outside if at all possible.

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Right now, the data show that turtles in the south hatch out quicker - about 70 days, and in the north a bit slower - around 90-120 days, if they don't overwinter in the nest.

Click here to see what happened to the hatchlings pictured above.....

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Modified  6/25/97