Pandas are solitary animals and prefer to live alone. They are mostly active during dawn and dusk. The bamboo that they eat does not have much nutrition, so they have to eat a lot to get enough nutrition. Pandas will only eat the most nutritious parts of the bamboo plant and do not eat the rest of the plant. They spend most of the day looking for bamboo, eating and sleeping. Pandas are also good at climbing and swimming. They can climb trees or swim across rivers. Pandas communicate with sounds and scent marking. They bleat, honk, and growl. They also use their scent glands to mark their territory and attract mates. Pandas only mate for 2-3 days per year. After mating, the male panda leaves and the female raises the cub alone. Panda cubs are born at about 100 grams, which is much smaller than a fully grown panda. Young pandas are very playful and will roll around, slide, and wrestle with each other. Pandas do not hibernate, while most other species of bears do. Pandas are active year round and they will migrate to lower elevations in winter to look for food and to avoid the cold.