WDCS Species Guide

Closest living relative to a whale is a hippo? It appears it may be so!

The traditional understanding of cetacean (whales, dolphins and porpoises) evolution was that they were descended from hoofed land-mammals, but more recent molecular data suggests a close relationship to the ‘artiodactyls’, an order of even-toed ungulates which includes the giraffe, camel and hippopotamus. In time it may be that cetaceans will be considered a suborder of a more inclusive order Cetartiodactyla, but for the moment they remain classified as belonging to the order Cetacea.

The order Cetacea is further divided into two suborders: Mysticeti – the baleen whales (comprising 4 families, 6 genera and 14 species), and Odontoceti – the toothed whales (comprising 10 families, 33 genera and 71 species), representing a total of some 85 currently recognised species of whales, dolphins and porpoises.

Further along the taxonomic tree, cetacean genetics are still at an early stage for many taxa, with differing views on where one species begins or ends. In several cases, what are currently regarded as single species appear, in fact, to be two or more. For example, the two distinct populations of the species Sotalia fluviatilis are likely to be reclassified as two distinct species very soon - Sotalia fluviatilis, the “tucuxi” being the river population and Sotalia guianensis, the “costero”, the coastal marine or Guiana dolphin. There is also strong genetic evidence for the long held view, due to marked differences in behaviour, feeding preferences and physical appearance, that there are in fact several species in the Orcinus genera, currently classified together as Orcinus orca.

SUBORDER MYSTICETI

All modern mysticetes are large whales with baleen instead of teeth, though the exact means by which baleen is used differs among species (gulp-feeding with balaenopterids, skim-feeding with balaenids, and bottom-feeding with eschrichtiids). All have a double blowhole, a symmetrical skull and only one sternum bone.

Family Balaenidae

Four species of right and bowhead whales make up this family. These are the ‘tanks’ of the whale kingdom. Individuals can grow up to 20m and weigh as much as 90,000kg. With a robust and rotund body, no dorsal fin or ridge, and with a head that measures at least a third of its total body length, members of this whale family can look intimidating! They are, however, slow animals feeding passively by skim-feeding, aided by the longest baleen with the finest baleen sieves of all mysticetes. All species were once intensively whaled and, to date, have been slow to recover. Although two of the four species are listed as ‘Least Concern’, almost all the populations of all species in this family are listed as ‘Endangered’ or higher on the IUCN Red list. Subsistence whaling of bowhead whales is still practiced by Alaskan natives.

Balaena mysticetus (Bowhead whale)
Eubalaena australis (Southern right whale)
Eubalaena glacialis (North Atlantic right whale)
Eubalaena japonica (North Pacific right whale)

Family Balaenopteridae

Otherwise known as the ‘rorquals’, there are 8 species in this family, although the Bryde’s whale may soon be split into more than 1 species. If balaenids are the ‘tanks’, then balaenopterids are the ‘sports cars’ of the whale kingdom; sleek, slender and incredibly hydrodynamic, these whales slip effortlessly through the water despite their immense size. All members of the family reach lengths of over 7m with a dorsal fin of varying shape and size. They are lunge-feeders and have long pleats extending from the snout to the navel enabling massive distention of the throat when they take in huge quantities of water before sifting out their food. The balaenopterids (or rorquals) can be distinguished from one another by the varying length, width and number of baleen plates, as well as overall size and pigmentation.

Balaenoptera acutorostrata (Minke whale)
Balaenoptera bonaerensis (Antarctic minke whale)
Balaenoptera borealis (Sei whale)
Balaenoptera edeni (Bryde's whale)
Balaenoptera musculus (Blue whale)
Balaenoptera omurai (Omura's whale)
Balaenoptera physalus (Fin whale)
Megaptera novaeangliae (Humpback whale)

Family Eschrichtiidae

There is only one species in this family, the gray whale. A stocky animal with a slightly arched jaw, they are another relatively slow-moving species, preferring shallow and coastal waters. Gray whales have the shortest (and coarsest) baleen of all mysticetes, possibly due to their preference for bottom-ploughing for food. Only two populations of this species remain, an Atlantic population having been wiped out, perhaps partly due to early whaling (although the cause remain a mystery), by 1675 or possibly the early 18th century. The remaining populations are the ‘western North Pacific’ (or Asian) and ‘eastern North Pacific’. Both populations undergo annual migrations; the eastern population travels from the cold, food-rich North Pacific waters to the warmer breeding grounds of the lagoons of Baja California, Mexico, but little is known of the Asian populations’ route and winter breeding grounds.

FACT – Gray whales only have 4 digits in their flipper (all others have 5) …!

Eschrichtius robustus (Gray whale)

Family Neobalaenidae

This is another family with only one species; the pygmy right whale. As the name suggests, this is a relatively small whale, reaching 6.5m in length and a weight of 3,400kg. There is very little known of this species, with only a few living animals having been found on southern hemisphere shores.

Caperea marginata (Pygmy right whale)

SUBORDER ODONTOCETI

These are the toothed whales, and all except the sperm whale are small to medium-sized cetaceans. The teeth of the odontocetes come in all shapes and sizes; not all are used for feeding and some stay buried in the gums or jaw throughout the animals’ lifetime. Sexual dimorphism (body differences between the sexes) is the rule and in some species can be extreme. All have a single blowhole, an asymmetrical skull, three sternum bones and a fatty organ in the forehead called the ‘melon’ – used for echolocation as they target individual prey items.

Family Delphinidae

With 35 species, this family contains the most diverse members of the cetacean world. The delphinids are known as the ‘marine dolphins’ (although of course there are some exceptions to the rule, with the freshwater populations of Orcaella bucking the trend), have a noticeable beak (with Orcaella again the exception), a large falcate, dorsal fin mid-way along their back (but not Lissodelphis) and conical teeth. Large group sizes and a complex social structure is a theme within the delphinids.

Cephalorhynchus commersonii (Commerson's dolphin)
Cephalorhynchus eutropia (Chilean dolphin)
Cephalorhynchus heavisidii (Heaviside's dolphin)
Cephalorhynchus hectori (Hector's dolphin)
Delphinus capensis (Long-beaked common dolphin)
Delphinus delphis (Short-beaked common dolphin)
Feresa attenuata (Pygmy killer whale)
Globicephala macrorhynchus (Short finned pilot whale)
Globicephala melas (Long finned pilot whale)
Grampus griseus (Risso's dolphin)
Lagenodelphis hosei (Fraser's dolphin)
Lagenorhynchus acutus (Atlantic white-sided dolphin)
Lagenorhynchus albirostris (White-beaked dolphin)
Lagenorhynchus australis (Peale's dolphin)
Lagenorhynchus cruciger (Hourglass dolphin)
Lagenorhynchus obliquidens (Pacific white-sided dolphin)
Lagenorhynchus obscurus (Dusky dolphin)
Lissodelphis borealis (Northern right-whale dolphin)
Lissodelphis peronii (Southern right-whale dolphin)
Orcaella brevirostris (Irrawaddy dolphin)
Orcaella heinsohni (Australian snubfin dolphin)
Orcinus orca (Orca (Killer Whale))
Peponocephala electra (Melon-headed whale)
Pseudorca crassidens (False killer whale)
Sotalia fluviatilis (Tucuxi)
Sousa chinensis (Indo-Pacific humpback dolphin)
Sousa teuszii (Atlantic humpbacked dolphin)
Stenella attenuata (Pantropical spotted dolphin)
Stenella clymene (Clymene dolphin)
Stenella coeruleoalba (Striped dolphin)
Stenella frontalis (Atlantic Spotted dolphin)
Stenella longirostris (Spinner dolphin)
Steno bredanensis (Rough-toothed dolphin)
Tursiops aduncus (Indo-Pacific bottlenose dolphin)
Tursiops truncatus (Bottlenose dolphin)

Family Kogiidae

This family contains two species, the dwarf and pygmy sperm whales. Both occur off shore in deep water habitats and both are poorly known. They are far smaller than the sperm whale to which they only bear a slight resemblance.

Kogia breviceps (Pygmy sperm whale)
Kogia sima (Dwarf sperm whale)

Family Monodontidae

This family is known as the white whale group. It contains two species: the beluga and narwhal. Both are small and stocky with bulbous and blunt heads, rounded flippers and flukes and no dorsal fin. The single tooth of the narwhal, the so called tusk, is the longest of the odontocetes. Normally a male characteristic, the tusk is sometimes seen in females and sometimes there are two tusks erupting, with the second one typically shorter than the first. The cervical vertebrae of both species are not fused, allowing for a greater range of neck flexibility. Both species are restricted to the cold waters of the Arctic.

Delphinapterus leucas (Beluga)
Monodon monoceros (Narwhal)

Family Phocoenidae

This is the porpoise family, containing six species, each of which is small and stocky. Each species has flattened spade-shaped teeth, a small triangular dorsal fin, and either a short beak or no beak at all. The females of some species18can also be larger than the males.

Neophocaena phocaenoides (Finless porpoise)
Phocoena dioptrica (Spectacled porpoise)
Phocoena phocoena (Harbour porpoise)
Phocoena sinus (Vaquita)
Phocoena spinipinnis (Burmeister's porpoise)
Phocoenoides dalli (Dall's porpoise)

Family Physeteridae

This is a single species family containing the sperm whale or cachalot, the largest of the toothed whales and also the one that exhibits the highest degree of sexual dimorphism (the male grows up to 18 m long and has a huge head accounting for 2/5 of his body length; the female only grows to 12 m long. The teeth are only present on the narrow, underslung lower jaw and instead of a fin they have a low dorsal hump.

Physeter macrocephalus (Sperm whale (Cachalot))

Family Ziphiidae

This family comprises 21 species of beaked whales. All are medium to large-sized animals, with the females typically larger than the males. With 3 exceptions (the two Berardius species and Tasmacetus) it is only the males that have 1 or 2 pairs of functional teeth on their lower jaw. The Ziphiidae contains the ocean’s most mysterious whales; in some cases only remnants of skulls or partial skeletons exist as evidence of living species at sea. It is expected that future revisions of this family will occur as each and every sighting of these species increases our knowledge.

River Dolphins

The four species of River Dolphins are divided into four separate families; Family Platanistidae includes the Ganges and Indus River dolphin; the Family Pontoporiidae contains the franciscana; the Family Iniidae is the Amazon River dolphin; and the possibly extinct Family Lipotidae is the Yangtze River dolphin.

Lipotes vexillifer (Baiji)
Inia geoffrensis (Boto)
Pontoporia blainvillei (Franciscana)
Platanista gangetica (South Asian river dolphin)