Reverse Sexual Size Dimorphism

Our weekend of Whale Watching started out with a lot of surface activity. On Friday’s Breakfast with the Whales, guests saw 4 different Humpbacks. Two were in the distance, but the two closest to us were excited about something – we got to see tail lobs, pectoral slaps and even a breach! On Friday’s Whales and Cocktails, we saw 7 different whales but spent most of our time with a competitive pod of 4 that chose to come pretty close to us. We saw multiple tail lobs and peduncle throws, and at one point, one of the whales surfaced just 50 feet from us. Saturday and Sunday brought us more of the same great action. Highlights included seeing breaches, tail lobs, and pec slaps all from what our onboard naturalist Gary reports as a yearling (based on her size) just out of Anaeho’omalu Bay on Sunday’s Breakfast with the Whales. On Sunday’s 10:00 Whale Watch guests saw 5 different whales and lots of surface activity including multiple breaches, pec slaps and tail lobs.
Captain Claire’s Humpback Fact of the Day: Humpback Whales (and, in fact, all Baleen Whales) demonstrate something called “reverse sexual size dimorphism”. This means that an adult female Humpback is larger than an adult male (by about 5%). Though researchers are not sure of the exact reason for the difference in size, they theorize that the increased size allows the female to store more reserves to feed and care for her calf, and also to give birth to a bigger calf who might have a better chance of survival than a smaller one. Average length for a fully grown female Humpback is around 45 feet. At her heaviest, she weighs 35 – 40 tons.