Defense behavior occurs when an individual perceives a threat in a group. It involves devoting energy to defending oneself while still paying some attention to the common task. For example, cows will lower their heads, charge, and use their horns to protect calves from predators. Living in a herd helps overcome this problem through cooperation. Sheep also band together for safety and rely on humans for protection when separated from their group. Defensively aggressive dogs and cats may initially charge fearfully at a perceived threat, while whales find protection in their large size and social pods.