Sperm Whales (Family Physeteridae and Kogiidae)
Alan Baker, Suze Baird, and Taoho Patuawa
General Description
Sperm whales are in the suborder Odontoceti, the toothed whales, and are classified into two families: family Physeteridae, the large sperm whale; and family Kogiidae, the pygmy and dwarf sperm whales. All sperm whales are characterised by spermaceti, liquid wax stored in a special organ in the whale's head. The Physeteridae has a single genus, Physeter, with a single species, macrocephalus. This is the largest of the toothed whales, with large conical teeth in the lower jaw, a large head, up to 10 deep throat grooves, low rounded dorsal fin, short wide flippers, and triangular tail flukes. This whale can dive deeper and longer than any other whale. Typical dives by sperm whales off Kaikoura are to more than 1000 m for 40-45 minutes. Sperm whales may live for 60-70 years. The small whales of the family Kogiidae are classed as two species in a single genus Kogia. These whales have small, robust bodies that taper sharply from the dorsal fin, with small flippers positioned unusually forward. Unlike the other two sperm whales, the dwarf sperm whale has teeth in the upper jaw as well as the lower jaw.
Sperm whales are cosmopolitan and Southern Ocean males migrate south in summer and return north in winter. Sperm whales forage throughout the year and are believed to feed near or on the sea floor. Females feed primarily on medium to large squid, and males eat larger squid, octopus, rays, sharks, and bony fishes. The diet of the pygmy and dwarf sperm whales, largely based on beach-cast individuals, suggests that these species feed on deep-water cephalopods and, less often, deep-sea fishes and shrimps.
Sperm whales are sexually dimorphic, with adult females reaching 12 m in length and about 24 tonnes and adult males reaching 18 m and 57 tonnes. Sperm whales are polygynous and females form stable groups of about a dozen females and their offspring. A dominant bull joins the group in the mating season. At about 6 years, young males form bachelor groups until they start breeding, after which time males are largely solitary. Sperm whales mature at 7-20 years, with females maturing earlier than males. The peak of mating activity is in September-December and gestation is usually 14-16 months long. Mature females give birth every 4 to 6 years in subtropical or tropical waters in November-March. Calves are nursed for about 2 years.
Limited sightings at sea of pygmy sperm whales suggest they reside primarily on the seaward edge of the continental shelf, and in the New Zealand region, they are one of the most common cetacean single-stranders, most records being from south of East Cape on the North Island. Dwarf sperm whales are a tropical species and they occur rarely in northern New Zealand waters as vagrants.
There is limited knowledge of the breeding behaviour and social organisation of pygmy and dwarf sperm whales. Adult pygmy sperm whales are 2.7-3.3 m long, and dwarf sperm whales are slightly smaller, with adults reaching 2.3 m. Females breed every two years, with a gestation period of 9-11 months. Both species are usually observed alone or in small groups of less than five individuals. When startled, pygmy-and possibly dwarf-sperm whales expel a cloud of rust-coloured liquid into the water, which is thought to act as a decoy to predators.
All three known species of sperm whale have been recorded in New Zealand waters. Although the large sperm whale is primarily encountered in open ocean environments, in New Zealand, it is commonly encountered in the near-shore environment of the Kaikoura Canyon, which has served as a key area for both whale watching and scientific research on the species.
Status
Sperm whales were a major target species of the "yankee whaling" era during the nineteenth century in New Zealand waters and also of the twentieth-century factory-ship whaling. Strong demand for their body oil and spermaceti oil resulted in large reductions in the world populations, and their slow maturation and reproductive characteristics mean that recovery is slow. At present, there are no valid estimates for sperm whale populations. Pygmy and dwarf sperm whales have never been hunted commercially; however, small numbers are taken in coastal whaling operations in Japan and Indonesia. The IUCN status of all three sperm whales is "insufficiently known".
Key Locations
Sperm whales have a cosmopolitan distribution, and the migratory behaviour of males differs from that of females. Males feed in colder waters of higher latitudes and are distributed over a far wider latitudinal range than females and immatures. In New Zealand waters, a group of up to 20 young males exists for most of the year in the vicinity of the Kaikoura Canyon. Pygmy and dwarf sperm whales occur mainly in tropical and temperate latitudes, and dwarf sperm whales inhabit areas on the edge of the continental shelf.
Summary of Threats
The slow recovery of sperm whale numbers to their pre-whaling abundance is less likely to be due to to present-day threats, and more likely to be due to the very large number of males harvested relative to females, and the slow maturation of these whales. Entanglements in fishing gear and collisions with ships have been reported for individuals. The growing whale watching tourism industry may pose a minor threat to the foraging and movement of some animals. Deaths of pygmy and dwarf sperm whales have occurred recently in gillnet fisheries in the Indian Ocean. The ingestion of plastics may pose a threat to some pygmy and dwarf sperm whales, especially in northern hemisphere waters.
Other human-induced threats include effects from climate change that may affect the location and abundance of food sources and habitat, exposure to marine pollutants, and overfishing of prey species. Natural threats include parasitic infestation and predation by sharks, killer whales, and false killer whales.
Typical Habitats
Typical habitats for sperm whales are in ice-free waters, particularly areas on the seaward edge of the continental shelf or in the vicinity of deep canyons where depths may reach 3000 m. The groups of females and offspring prefer waters warmer than 15°C and are rarely seen south of latitude 45° S or close to land.
State of Information
Although the general knowledge of sperm whales is good, the understanding of the ecology of pygmy and dwarf sperm whales is relatively poor.
Significance for Maori
In Maori cosmology, all whales descended from Tangaroa. Maori described whales as "chiefly fish". In the migration legends, whales were used to guide ancestral canoes and represented guardian spirits for Maori at sea. The presence of a whale near or stranded on land was a symbol of rich food and abundance and thus indicated a good place to settle. Strandings of sperm whales (paraoa) represented chiefs fallen in battle. Whangaparaoa means "bay of the sperm whales".
Stylised whale shapes on barge boards of storage houses represented the bounty within and ensured an abundance of treasures. Sperm whales were particularly prized for their teeth, and several Maori proverbs refer to the strength of the teeth. Rei puta, pendants carved from the teeth of sperm whales, were highly valued.
Maori did not traditionally hunt whales, but once whalers from the northern hemisphere nations began exploiting whales in the southern hemisphere in the 1790s, Maori joined in the hunt and ran several whaling stations. The bones from these whales were buried for 12 months until they were white, and were then used for walking sticks, battle axes, spears, and meremere.
Key References
Anon. 2005. The Conservation of Whales in the 21st Century. Department of Conservation, Wellington, New Zealand. 32pp.
Evans, P G H. 1987. The Natural History of Whales and Dolphins. Christopher Helm, London. 343pp.
Folkens, P A, Reeves, R R, Stewart, B S, Clapham, P J and J A Powell. 2002. Guide to Marine Mammals of the World. National Audubon Society. Alfred A. Knopf Inc. 528pp.
Gaskin, D E. 1972. Whales dolphins and seals with special reference to the New Zealand region. Heinemann Educational Books Ltd. 200pp.
Hoelzel, A R (ed). 2002. Marine Mammal Biology: An evolutionary approach. Blackwell Science Ltd, Oxford. 432pp.
Orbell, M. 1985. The Natural World of the Maori. William Collins Publishers, New Zealand. 230pp.
Perrin, W F, Würsig, B and J G M Thewissen (eds). 2002. Encyclopedia of Marine Mammals. San Diego: Academic Press. 1414pp.
Poata, T. 1989. The Maori as a fisherman and his methods. Southern Reprints. 27 pp.
Shirihai, H. 2002. The Complete Guide to Antarctic Wildlife: Birds and marine mammals of the Antarctic Continent and the Southern Ocean. Princeton University Press, Princeton, New Jersey. 510pp.
Table 9: Sperm Whales (Family Physeteridae and Kogiidae) in New Zealand
| Taxon | Common name | Status in New Zealand region | IUCN status | DoC status |
|---|---|---|---|---|
| Family Physeteridae | ||||
| Physeter macrocephalus | Sperm whale | Migrant | Vulnerable | Migrant |
| 1 | ||||
| Family Kogiidae | ||||
| Kogia breviceps | Pygmy sperm whale | Breeder | Unlisted | Data deficient |
| Kogia simus | Dwarf sperm whale | Vagrant | Unlisted | Vagrant |
| 2 | ||||
| Total | 3 |