Right whales don't have teeth or horns or claws to prevent the other males from mating with the female, so they have developed an interesting way to compete called "sperm competition."

Each male produces massive amounts of sperm in an attempt to dilute other sperm that might already be in the female. To do this, the whales need the appropriate plumbing, which explains why one southern right whale testicle weighs in at over 500 kg (1,100 lbs), making the right whale the animal with the biggest testicles. At 1% of the whale's total body weight, this size is very large even taking into account the size of the whale. Right whales can grow up to 18 m (60 feet) long and weigh up to 100 tons.

Even at that, breeding once is not enough for a right whale and they may need to mate multiple times to ensure being the father of a calf.

Females reach sexual maturity at 6–12 years and breed every 3–5 years. Both reproduction and calving take place during the winter months. Calves are approximately 1 ton in weight and 4–6 m (13-20 feet) in length at birth following a gestation period of 1 year.

The right whale grows rapidly in its first year, typically doubling in length. Weaning occurs after eight months to one year and the growth rate in later years is not well understood—it may be highly dependent on whether a calf stays with its mother for a second year. Right whales live in excess of 70 years.

They are called "right whales" because whalers thought the whales were the "right" ones to hunt, as they float when killed and often swim within sight of the shore.