Baby turtle diets vary from one species to the next. For example, painted turtle hatchlings consume small animals while they are young before switching to a diet heavy in plants upon maturation, according to the University of Michigan, Department of Zoology. Likewise, box turtles begin life by consuming animals and convert to a primarily plant-based diet as adults. Often, these young box turtles catch their prey in ponds and streams.
The University of Michigan, Department of Zoology explains that green turtles also exhibit an ontogenetic dietary shift. While these ocean-dwelling turtles consume animal-based diets while they are young, they begin eating vegetation as they mature. While young, their prey includes crabs, jellyfish, mollusks, sponges and worms. SeeTurtles.org explains that the other six species of sea turtles are carnivorous, and they consume pelagic crustaceans, mollusks, corals, jellyfish and fish eggs.
Other species are herbivorous throughout their lives. For example, the Tortoise Trust raises the Mediterranean tortoises that they hatch on a completely herbivore diet to mirror the diet of their wild counterparts. Such a diet is composed almost entirely of leaves, grasses, flowers and succulent vegetation. Such species do not grow properly on diets that contain high-protein foods, such as insects, worms or carrion.