It sounds like what you have there is a baby box turtle Terrapene carolina sp. According to Conant and Collins Field Guide there are 3 subspecies of T Carolina that occur in Alabama. They are Eastern (T.c.carolina), Three-Toed (T.c.triunguis) and Gulf Coast (T.c.major). My guess is they all look similar when they are young because pictures are only showm of the Eastern.
Eastern occurs in the Northern half of AL. Gulf Coast occurs in the extreme southern regions of AL. Three-Toed occurs in the southern 1/2 of AL (has 3 toes on all legs..usually a good indicator, but not perfect). All three subspecies will intergrade.
It will eat crickets, earthworms, slugs, mealworms and maybe some fruit. I would suggest giving it plenty of calcium in its food. Use a supplement powder. At that age they grow a lot and plus they must use that calcium to thicken that shell. The shell is fairly thin compared to an adult. Also make sure it gets direct sunlight or a UV bulb. Have hides in the terrarium and a place where it can soak in water (a shallow waterbowl) away from the light if possible. Use soil, spaghnum moss or cypress mulch as substrate so that it may burrow. If possible put a potted plant in there (perhaps Pothos). Pothos tends to serve as a hiding place and an occasional snack for your turtle. You could always use plant some of the weeds from your garden in a pot and place them in there. Have fun with your turtle. I'd like to find a baby box one day. There may be more around your garden. How cool would that be?
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14 Leopard Geckos 5.9.0
2 Tokay Geckos 2.0.0
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1.0 Ambystoma tigrinum nebulosum
0.0.1 Leopard Gecko egg cookin...she looks good!