False Killer Whale

False killer whales are a species of small toothed whale widely distributed in warm waters around the world. Nine false killer whales are currently being reared at Okinawa Churaumi Aquarium.
Okinawa Churaumi Aquarium in collaboration with Mie University studied blood data from three female false killer whales from approximately 2006 to 2017. The study was undertaken to shed light on the reproductive physiology of false killer whales. The results showed fluctuations in the concentration of the hormone progesterone in the blood. It also showed that the length of the estrous cycle was 40.5 days, and that gestation lasted for 14 months. White blood cell counts were at their lowest during ovulation, but gradually elevated towards the luteal phase. White blood cell counts were significantly higher during gestation than pre-pregnancy, particularly during the early stages of gestation. This is the first discovery in the world of a relationship between pregnancy in cetaceans (whales and dolphins) and their white blood cell counts.