Fin whales are the second largest mammals, after Balaenoptera musculus. They grow to 20 meters in length and weigh approximately 70,000 kilograms. Size varies geographically: southern hemisphere whales are roughly 20 meters long, while northern and Arctic fin whales reach up to 25 meters in length. Sexual dimorphism in fin whales is limited, with males and females reaching roughly the same size and weight as adults. It is generally easy to distinguish fin whales by their long, lean bodies, their brown-grey dorsal surface, and deep white undersides. Fin whales can be distinguished from other whales by the medium-sized white patch on their lower, right jaw. The base of the tail is raised, causing their back to have a distinctive ridge. The white underside wraps around to their midsection laterally. The dorsal fin is 50 cm in height, curved, and found relatively far back on the body. The head is quite flat and represents about 1/5 of total body length. These whales have two blowholes and a single, longitudinal ridge extends from the tip of the snout to the beginning of the blowholes. Fin whales are able to expand their mouths and throats during feeding because of the roughly 100 pleats that run from the bottom of their bodies to their mouths. These pleats allow the mouth cavity to engulf water during feeding. Fin whales are filter feeders, with between 350 and 400 baleen plates that are used to catch very small to medium-sized aquatic life suspended in the water. ("Balaenoptera physalus", 2008; Croll et al., 2002; Reeves et al., 2002)
Other Physical Features: Endothermic; Homoiothermic; Bilateral symmetry
Sexual Dimorphism: Sexes alike
- Reeves, R., B. Stewart, P. Clapham, J. Powell. 2002. Sea Mammals of the World. London: A&C Black.