Box Turtle Diet
North American Box Turtles are opportunists. In the wild a box turtle will eat a wide variety of food.
60% or more of the box turtle diet is composed of animal matter. Some of the "animal" matter they eat in the wild includes: slugs, snails, worms, grubs, caterpillars, beetles, pill bugs, sow bugs, centipedes, crickets, grasshoppers, spiders, flies, crawfish and carrion. Essentially, if a box turtle can catch it, it will eat it.
The rest of the box turtle's diet is composed plant matter. A large part of which is fungi (mushrooms etc). Moss, berries and grass are also eaten.
Box turtles also consume stones and sand. Recent literature suggests that this may help with digestion.
Recent literature also shows that the diet of adult males is the same as females. Also that box turtle hatchling diets are essentially the same as adults (previous work speculated that hatchlings were more carnivorous and became more interested in plant matter as they got older).
In captivity the best box turtle diet is a wide variety of plant and animal matter.
Dodd in his recent book "North American Box Turtles" recommends the following:
"Vegetables and fruit should be mixed and of high nutrient content. Excellent choices include tomatoes, bananas, cantaloupes and other melons, berries, prickly pear fruits, grapes, corn, yams, mustard greens, collards, endive, dandelions, and mushrooms.
.....It is readily apparent that box turtles have insectivorous and carnivorous dietary preferences. They love insects, earthworms, snails and slugs, and many other types of invertebrates."
From personal experience over the past 30+ years, I would have to agree. Also keep in mind that like with people, individual tastes vary.
Probably the most important aspect of the box turtle's diet is variety. The following is what I feed. All insects, that are store bought, are gut loaded with greens and veggies before offering them to the box turtles.