There are many species of wildlife that will help themselves to fruits or vegetables from your garden given the opportunity. Ground squirrels, woodchucks, rabbits, raccoons and deer are often the culprits in garden damage situations. Birds may cause damage too—blackbirds and robins sometimes peck at fruits such as strawberries and tomatoes.
If the animals are eating the foliage, try sprinkling the leaves with a crushed red pepper/cayenne powder mix. The leaves will be most vulnerable when they first come up, so monitor the plants closely. You will have to reapply the mix after rain or after you have watered the garden. If the vegetable or fruit is being eaten, installing a cage around the plant may work. If the damage is severe, you will have to fence the garden to keep wildlife out.
If you know which species is causing the damage, the links above will provide you with information about damage control methods. If you are not sure what type of animal is causing the damage, look for tracks or burrow holes to help identify the animal. The wildlife identification page has photos that can help in determining which species you are dealing with and strategies you can use to help prevent and control damage.