Cetacea, from Latin cetus (“whale, porpoise, dolphin”), in reference to the fact that all the members of this infraorder are whales, porpoises or dolphins.

Common names of members

Whales, porpoises and dolphins.

Distribution 

All oceans.

Size

Large animals, size range: 20–180,000kg in weight  and  1.2–30 m in length.

Morphology

Their forelimbs are flippers, and their body is streamlined. Nearly all of them have a dorsal fin on their backs, though the specific species will determine how this looks. The purpose of the fin and flipper is to steer and stabilize in the water. Blubber, a thick coating of fat, envelops the body. This gives cetaceans their sleek, streamlined bodies and acts as heat insulation. It can get as thick as half a meter in larger species.

Ecology & Habitat

Mostly marine, few in freshwater rivers.

Diet

Exclusively carnivorous (krill and plankton or fish, mollusks, seals, etc).

Reproduction 

Most cetacean species have one mating season per year and they are polygynous. Multiple males congregate around a single female and jostle for position to mate. The female may mate with several males. The number of young per female: 1. Interbirth intervals:1-6 years. The gestation period: 10 - 17 months. Female cetaceans nurse their calves about 6 months to over 2 years, male parental care is rare

Total species known

80

Species in the collection

3

Species in Hong Kong

1

References

Wurtz, M., Repetto, N. (1999). Whales and Dolphins: A Guide to the Biology and Behavior of Cetaceans. Thunder Bay Press.

Berta, A., Sumich, J. L., Kovacs, K. M. (2005). Marine Mammals: Evolutionary Biology. Academic Press.