Kingdom: Animalia (Animals)
The number of recognized cetacean species has changed in recent years, with recent research revealing that certain populations are not one species as previously thought, but in fact two or more separate and distinct species.
Currently, the order Cetacea includes approximately 87-88 species in twelve families grouped under two sub-orders, Baleen whales (Mysticeti) and Toothed whales (Odontoceti).
Baleen whales are named for the long plates of baleen which hang in a row (like the teeth of a comb) from their upper jaws. Baleen plates are strong and flexible; they are made of a protein similar to human fingernails. Baleen plates are broad at the base (gumline) and taper into a fringe which forms a curtain or mat inside the whale's mouth. Baleen whales strain huge volumes of ocean water through their baleen plates to capture food: tons of krill, other zooplankton, crustaceans, and small fish.
Tragically, one cetacean, the Chinese river dolphin (Baiji), has not been sighted since 2002 despite extensive searches of its limited habitat, and is now believed to be extinct. The Gulf of California harbor porpoise (Vaquita) is critically endangered and the most endangered species of cetacean in the world (~567 individuals estimated in 1997). The North Atlantic right whale is also critically endangered and the most endangered large whale in the world (approximately 300 to 350 individuals in 2001).
Size comparison of all known extant cetacean species. Note the human diver at lower right for scale. Source: Chris Huh
- Dale W.Rice. 1998. Marine mammals of the world: systematics and distribution. Society of Marine Mammalogy Special Publication Number 4: 231 pp.
- “Committee on Taxonomy. 2009. List of marine mammal species and subspecies. Society for Marine Mammalogy, www.marinemammalscience.org, consulted on May 27, 2011.”
- Smith, B.D., Zhou, K., Wang, D., Reeves, R.R., Barlow, J., Taylor, B.L. & Pitman, R. 2008. Lipotes vexillifer. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4.
- Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N. 2008. Eubalaena glacialis. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4.
- Rojas-Bracho, L., Reeves, R.R., Jaramillo-Legorreta, A. & Taylor, B.L. 2008. Phocoena sinus. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4.