Whales are mammals and are nourished in the womb through an umbilical cord. Whales even have a belly button after birth (this is the place where the umbilical cord was attached to).
Whales are viviparous, they give birth to live young (unlike fish, most of which lay eggs). Like all mammals, whale calves are nourished with milk from their mothers. The nursing period is long (more than one year in many species), which is associated with a strong bond between mother whales and their young. In most whales, reproductive maturity occurs late, typically at 7 to 10 years.
Whales breed seasonally, usually in warm tropical waters and females usually have one calf every 1 – 3 years. The gestation period ranges from 9 – 18 months. Whale calves can swim soon after birth.
The genital organs of male whales are retracted into cavities of the body during swimming, so the whale is streamlined and to reduce drag. Most whales do not maintain fixed partnerships during mating, in many species the females have several mates each season.
At birth the newborn whale is delivered tail first, so the risk of drowning is minimized. Whale mothers nurse the young by actively squirting the fatty milk into their mouths. Whale milk is a bit like Cottage Cheese, very thick. It has to be textured like this to prevent disolving into the surrounding water.
The table below indicates the gestation times for different species and length and weights of calves:
Whale Type Whale Species Gestation Period Ballen Whales Blue Whale 11 – 12 months Calves are 25 feet long and weigh 6 – 8 tons Bowhead Whale 12 – 16 months Calves are 17 feet long and weigh 5 – 6 tons Grey Whale 13.5 months Calves are 15 feet long and weigh 1 – 1.5 tons Humpback Whale 11 – 12 months Calves are 14 feet long and weigh 2.5 tons Minke Whale 10 months Calves are 9 feet long and weigh 1,000 pounds Right Whale 12 months Calves are 16 – 19 feet long and weigh 6 – 7 tons Toothed Whales Baluga Whale 14 – 15 months Calves are 4-5ft long and 100-150 pounds Narwhal 10 – 16 months Calves are 5.25 feet and weigh 176 pounds Killer Whale (Orca) 16 – 17 months Calves are 6 – 8 feet long and weigh 600 pounds Sperm Whale 16 months Calves are 13 feet long and weigh 1 ton