White-tailed deer are the most common species of deer found in North America. They use their white tail as a flag to warn other deer when there is danger. They have antlers that they use to protect themselves. There are so many deer in the U.S. that they are causing problems. They run into roads and eat gardens. When there are too many deer in one place they run out of food and eat tree seedlings, then no trees grow there and there isnt enough food for years to come.