A female hippo will give birth to a single calf every two years. Calves are usually born in the rainy season and weigh about 93 pounds at birth. Calves will begin to eat grass at about 3 weeks old, however, it will continue to nurse from its mother for about a year. Serious grazing at night begins at around 5 months old. Calves stay close to their mothers for protection, not only from crocodiles and lions, but from male hippos who oddly enough do not bother with the calves on land but can attack young males in the water.