Moose are the largest deer in the world. The males, or bulls, can weigh almost a half ton. The males also have large flat antlers that can spread as much as 6 ft. (2m) across. Their heads are long and they have a flap of skin that hangs down from their lower jaw. In the summer, moose eat vegetation and they especially like to eat water plants. They often wade into ponds and lakes where these plants grow. In the winter, they eat bark and twigs. Adult moose live alone. Calves will stay with their mother for a year before going off on their own.