Turtles include tortoises, which live on land, fresh-water terrapins and turtles that live in the sea. All of these animals possess shells made of bone into which they can retreat if attacked. Two species, the box turtle and the hinge-back turtle, have shells that close completely. Despite this protection, turtles fall prey to numerous animals. The hatchlings of turtles and unborn embryos in their eggs are also vulnerable to predators.
TL;DR (Too Long; Didn't Read)
Among the animals that prey on turtles are various species of birds, mammals, reptiles and fish. The predators usually have to find a way to break the shell before they can dine on turtle meat.
Bearded vultures seize turtles and fly high above the ground to release the reptile, typically over rocky ground or onto large rocks or boulders. These vultures will repeat the exercise if the shell of the turtle does not break after the first attempt. The bearded vulture then feeds on the flesh of the turtle, which is now easily accessible. Crows prey on the western swamp turtle from Australia, while other carnivorous birds, including ravens and herons, also prey on turtles. Sea gulls grab and eat hatchling turtles as they attempt to reach the relative safety of the ocean after having hatched on the beach.
Numerous mammals prey on turtles. Raccoons are capable predators and will normally carry a turtle to a safe area where they can eat it without being disturbed. Coyotes and foxes prey on turtles, as do some domestic dogs. In many cases, the individual dog is merely playing with the reptile, but if its teeth manage to puncture vital organs, the game becomes fatal. Domestic cats sometimes kill young turtles. Opossums, weasels, skunks and ferrets will all kill turtles if given the opportunity. In some instances, these animals bite at and chew any part that the turtle can not retract deeply enough into its shell.
Reptiles and Amphibians
Some mature frogs attempt to eat small freshwater turtles in the absence of more suitable prey. The Nile monitor eats turtle eggs and hatchlings, while crocodiles and alligators eat adult turtles. Mature alligators, which can weigh up to 500 pounds, are capable of easily killing mature turtles.
Great White Shark Food
The great white shark, which is capable of killing a person with one bite, often includes sea turtles in its diet of fish and marine mammals. This huge shark often charges its prey from underneath. The great white effectively ploughs into the turtle with its mouth open, and the marine reptile has no chance of escape.