Information on the geographic range of this species is limited due to its rarity. Based on stranding and fishery by-catch records, dwarf sperm whales have a worldwide distribution. Although stranding records show that they occur in areas of cold waters, they are more frequently observed in temperate and tropical regions. In the Atlantic Ocean, dwarf sperm whales have been spotted offshore near Virginia, Spain, Brazil, and along the coasts of Africa. In the Indian Ocean, strandings have occurred along the southern coast of Australia, in the Persian Gulf, and in the Indonesian archipelago. In the western Pacific, strandings have occurred along the shores of the island of Honshu in Japan, the Marianas Islands, and New Zealand. In the eastern Pacific, they range from Vancouver Island, Canada to the central coast of Chile.

Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native ); mediterranean sea (Native )

Other Geographic Terms: cosmopolitan

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Transient

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Worldwide in temperate, subtropical, and tropical seas, though the degree of continuity of populations is unknown. Along eastern North America, known from Virginia south to the Lesser Antilles and throughout eastern and northern Gulf of Mexico. Along western North America, recorded from Vancouver Island and central California and Baja California. Also occurs off western Africa, South Africa, India, Sri Lanka, Japan, Hawaii, southern Australia, and in the southwestern Pacific.

Dwarf sperm whales are compact and streamlined, with the body gradually narrowing to the tail. Average body length ranges between 2.1 to 2.7 m but rarely exceeds 2.5 m. Average body weight ranges from 135 to 270 kg. Skin color varies from bluish gray, dark gray, and blackish brown, to completely black with a white or lighter gray venter; speckled pink or purple blotches may also be present. The flippers are broad with round edges and the tail fluke is sharply pointed, measuring 61 cm in width. The dorsal fin, located midway along the back, can be used to distinguish individual whales because the shape varies from falcate (sickle-shaped) to curved and pointed to triangular. The head is square, with a conical, pointed snout and a small, under-slung jaw. The head measures about 1/6 of the body's length, which is the shortest proportion of any cetacean. The blowhole is located on the left side of the melon, contributing to the marked asymmetry of the skull. A lightly colored crescent-shaped mark may be present on either side of the head between the eye and flipper. This mark is called a false gill due to its resemblance to the gill slits of a fish. The lower jaw of dwarf sperm whales holds 7 to 13 pairs of sharp, curved, homodont teeth, while the upper jaw bears 3 pairs of vestigial teeth which are sharp, thin, and lack enamel. The throat region is grooved with several short longitudinal creases.

Range mass: 135 to 270 kg.

Range length: 2.1 to 2.7 m.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

• Marine

Dwarf sperm whales are usually seen over the continental shelf and slope. However, dietary evidence suggests that these whales forage in deeper waters, diving to 300 m.

Range depth: 300 (high) m.

Habitat Regions: temperate ; tropical ; saltwater or marine

Aquatic Biomes: pelagic ; coastal

Habitat Type: Marine

Comments: Stomach contents from South Africa indicate that distribution may be centered along edge of continental shelf (Leatherwood and Reeves 1983). Adults may occupy deeper waters than do immatures. Dive to at least 300 meters (Birchler and Potter, in Wilson and Ruff 1999).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

The diet of dwarf sperm whales consists mainly of cephalopods, especially the squid species Ancistrocheirus lesueurii, Histioteuthis species, Chiroteuthis veranyi, and Octopoteuthis species, though fish and crustaceans also form part of the diet. Echolocation is probably used to locate prey since these whales forage in dimly lit zones of the ocean.

Dwarf sperm whales appear to employ a suction feeding strategy to capture prey.

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Molluscivore )

Comments: Diet mainly squid; also eats fishes and crustaceans, including pelagic crabs and shrimp. Apparently feeds at great depths.

As predators, dwarf sperm whales play an important role in the ocean ecosystem linking the midwater zone to the epipelagic zone. Spearfish remoras (Remora brachyptera) share a commensal relationship with K. sima individuals by attaching themselves to the whales with their modified dorsal fins. Furthermore, dwarf sperm whales host many types of endoparasites in their intestines.

Mutualist Species:

• spearfish remoras (Remora brachyptera)

Commensal/Parasitic Species:

• acanthocephalans (Bolbosoma vasculosum)
• acanthocephalan (Bolbosoma capitatum)
• nematodes (Anisakis species)
• nematodes (Crassicauda anthonyi)
• nematodes (Heterochaeilus tunicatus)
• nematodes (Pseudoterranova ceticola)
• cestodes (Monorygma grimaldi)
• cestodes (Phyllobothrium delphini)
• trematodes (Chiorchis groschafti)
• trematodes (Pulmonicola cochleotrema)
• trematodes (Monoligerum blairi)

While there are no direct observations of predation on K. sima, its small size would make it potential prey for larger carnivores such as killer whales (Orcinus orca) and great white sharks (Carcharodon carcharias). When threatened, dwarf sperm whales eject a concealing fluid as a decoy, much like a squid does. They excrete a dark reddish-brown liquid from a sac located in the lower portion of the intestine. It can eject over 12 liters of liquid to create a dense cloud which may frighten predators or distract them, allowing the whale to swim away. Their coloration also helps to camouflage them in ocean waters.

Anti-predator Adaptations: cryptic

Usually in groups of no more than 10; composition by age and sex is variable.

Information on communication and perception of dwarf sperm whales cannot be found. However, as members of the family Physeteridae, it seems reasonable to assume that they use echolocation (sonar) and vocal communication in similar ways to their cousins, sperm whales.

Communication Channels: acoustic

Perception Channels: visual ; acoustic ; ultrasound ; echolocation

The lifespan and longevity of this species is unknown in the wild, and only a few specimens have survived more than a year in captivity. Based on necropsies of stranded individuals, ingested plastic debris found within the stomach is a clear cause of morbidity and mortality. Furthermore, entanglement and drowning in gills nets is also a serious problem contributing to premature mortality.

Range lifespan

Status: captivity: 1 (high) years.

The mating system of dwarf sperm whales is not known.

Little information is known about reproduction in this species. The mating process is likely to be similar to other cetaceans: as both females and males align themselves belly to belly, the male inserts his penis into the female's genital canal, and fertilization occurs internally. The gestation period is 9 months and the duration of the calving season appears to last at least 5 or 6 months. There appears to be at least one calving peak during summer months. Frequent observations of pregnant females accompanied by unweaned calves suggest an annual reproductive cycle with one calve per year.

Breeding interval: Females may give birth annually.

Breeding season: Births seem to occur mainly in sumer, suggesting breeding in fall or winter of the previous year.

Range number of offspring: 1 (high) .

Average number of offspring: 1.

Range gestation period: 9 (high) months.

Range birth mass: 41 to 50 kg.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Specific information on parental care of young is lacking for dwarf sperm whales. It may be that they cares for their young in ways similar to more well-studied cetaceans, wherein females and their calves stay together in pods for months to years. Females nurse and protect their young, but it is not known if dwarf sperm whales employ extramaternal care by related females within the pod or by males. Their ability to excrete fecal matter to distract predators can be considered an additional means of protecting their offspring.

Parental Investment: precocial ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); extended period of juvenile learning

Calving season apparently long (at least 5-6 months). Gestation lasts about 9.5 months. Observations of pregnant females accompanied by unweaned calf suggest annual reproduction or prolonged lactation (Leatherwood and Reeves 1983, IUCN 1991). Sexually mature at about 2.1-2.2 m.

Population size in the waters around Hawaii has been estimated at about 19,000 individuals, but worldwide estimates are lacking.

US Federal List: no special status

CITES: appendix ii

State of Michigan List: no special status

IUCN Red List of Threatened Species: data deficient

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: NU - Unrankable

Rounded Global Status Rank: G4 - Apparently Secure

Comments: No known significant threats; rarely incurs incidental mortality associated with fisheries (IUCN 1991).

There are no known negative impacts on humans. Interactions with humans are rare due to their timid behavior and their tendency to avoid approaching ships and boats.

Dwarf sperm whales are not commercially exploited, though they may be an economically valuable commodity in aboriginal/artisanal fisheries.

Positive Impacts: food ; research and education

Comments: Sometimes taken by coastal fishermen off southern Japan, Indonesia, Lesser Antilles, and Sri Lanka (Leatherwood and Reeves 1983).

Comments: This species is placed in the Physeteridae by some authors (e.g., Mead and Brownell (in Wilson and Reeder 1993, 2005). However, Jones et al. (1992), Baker et al. (2003), and Rice (1998) regarded Kogiidae as a family distinct from Physeteridae. Kogia sima formerly was regarded as conspecific with K. breviceps. Because of the uncertainty of identification, literature on K. breviceps published prior to the revision by Handley (1966) could refer to either K. breviceps or Kogia sima.