Dogs were probably the first animals to be domesticated, perhaps to help with hunting. By domesticating goats, cattle, sheep, pigs and poultry, humans have been able to ensure that food is always available. Horses, mules and camels have been used to carry people and goods over long distances. Pets provide companionship but can also be very useful. Sheepdogs help farmers to round up their flocks. Guide dogs for the blind and hearing dogs for the deaf help their owners to lead full lives. Animals are also used to guard property, perform rescues and carry messages.