When they are fully developed, manatees weigh 800 to 1,200 pounds (360-545 kilograms) and access ten toes (3 meters) in length. The biggest of the species can grow to be up to 3,500 lbs . (1,590 kilograms) and thirteen ft (4 meters) in duration. Their tricky skin is wrinkled, and their sizing is no joke: They're about four to 4.5 feet (1.2 to 1.4 meters) long at delivery and regular 60-70 lbs . (27 to 32 kilograms). Friends die.