Sperm whale of the Society for Marine Mammalogy, the largest international association of marine mammal scientists in the world, officially uses "Physeter macrocephalus" when publishing their definitive list of marine mammal species. The sperm whale is the largest toothed whale, with adult males measuring up to long and weighing up to . By contrast, the second largest toothed whale (Baird's Beaked Whale) measures and weighs up to . The Nantucket Whaling Museum has a -long jawbone. The museum claims that this individual was long; the whale that sank the "Essex" (one of the incidents behind "Moby-Dick") was claimed to be . A
Right whale single female, suggesting that sperm competition is an important factor in mating behavior. Although the blue whale is the largest animal on the planet, the testes of the right whale are actually ten times larger than those of the blue whale – with each weighing up to , they are by far the largest of any animal on Earth. Gestation tends to last a year, and calves are born at in weight and in length. Weaning occurs after eight months. Right whales were a preferred target for whalers because of their docile nature, their slow surface-skimming feeding behaviors, their tendency