Kogia sima (Owen, 1866)
English: Dwarf sperm whale
German: Kleiner Pottwal
Spanish: Cachalote enano
French: Cachalot nain
Kogia sima © Würtz-Artescienza (see "links")
Kogia spp. are superficially porpoise-like in body shape,
and robust, with a distinctive underslung jaw, not unlike sharks.
They have the shortest rostrum among cetaceans and the skull is
markedly asymmetrical. Dwarf sperm whales are smaller than pygmy
sperm whales and reach a maximum size of only about 2.7m total length
and a body mass of 272 kg. Colouration in adults is dark bluish
grey to blackish brown on the back with a light venter. On the side
of the head, between the eye and the flipper, there is often a crescent-shaped,
light-coloured mark referred to as a "false gill". The
teeth (up to three pairs of vestigial teeth are also found in the
upper jaw) are very sharp and thin, lacking enamel (McAlpine, 2002).
Baird (2005) found that photographs of several individual dwarf
sperm whales showed distinctive marks on the dorsal fins, demonstrating
that individual photo-identification is possible with this species.
Chivers et al. (2005) found that the results of comparisons of
mitochondrial DNA and morphological differences are consistent with
species- level differences between two K. sima clades,
one in the Atlantic and one in the Indo-Pacific: The combined gene
sequence haplotypes have accumulated 44 fixed base pair differences
between these two clades compared to 20 fixed base pair differences
between the recognized sister species K. sima and K. breviceps.
However, recognition of a third Kogia species awaits supporting
evidence that these two apparently allopatric clades represent reproductively
isolated groups of animals.
Kogia spp. are not easy to positively distinguish at sea
(Caldwell and Caldwell, 1989), as a consequence, most reliable records
of either species are based on stranded individuals or occasionally
on ones taken in fisheries.
Rice (1998) summarises that K. sima lives mainly over the
continental shelf and slope off tropical and temperate coasts of
all oceans. Range includes the western Atlantic from Virginia south
to Rio Grande do Sul in Brazil, including the Antilles; the eastern
Atlantic from the Mediterranean Sea south to Cape Province; The
Indian Ocean from Cape Province north to Oman, east at least as
far as Lomblen in Indonesia, and south to South Australia; the western
Pacific from Chiba prefecture on the east coast of Honshu, and the
Mariana Islands, south to Hauraki Gulf in New Zealand; and the eastern
Pacific from Vancouver Island south to Valpa-raiso in Chile (Rice,
1998). Mcalpine (2009) summarizes that K. sima prefers warmer seas
than K. breviceps.
Distribution of Kogia sima: deep temperate, subtropical,
and tropical waters of the northern and
southern hemispheres (Taylor et al. 2008b; © IUCN; click
here for large map).
Recent strandings have been reported from Sable Island,
Nova Scotia (Lucas and Hooker, 2000), the Gulf of Mexico (Delgado
et al. 1998), British Columbia, Canada (Willis and Baird, 1998),
the Azores (Goncalves et al. 1996), Ecuador (Felix et al. 1995),
the Antilles (Debrot and Barros, 1992), the coast of France (Duguy,
1990) and Japan (Sylvestre, 1988), supporting the notion of a wide
distribution in temperate zones of the world oceans.
3. Population size
Because of the lack of sightings at sea, which may be more because
of its inconspicuous behaviour than true abundance, and the fact
that Kogia spp. are only rarely encountered in commercial fisheries
where such records may be kept, there are no real estimates of abundance
for either Kogia species (Caldwell and Caldwell, 1989, Mcalpine,
The best U.S. Atlantic abundance estimate for both Kogia spp., 395
(CV=0.40), stems from two 2004 surveys, where the estimate from
the northern U.S. Atlantic is 358 (CV=0.44), and from the southern
U.S. Atlantic is 37 (CV=0.75). This joint estimate is considered
the best because together these two surveys had the most complete
coverage of the species' habitat. A separate estimate of dwarf sperm
whale abundance could not be provided due to the uncertainty of
species identification at sea. Furthermore, the available information
was judged insufficient to evaluate trends in population size for
the western North Atlantic (Waring et al. 2007).
Barlow (2006) estimates that a total of 17,519 dwarf sperm whales
are found in the outer EEZ of Hawaii. Dolar (1999) estimated the
population size in the eastern Sulu Sea at 650. Using corrections
for missed animals, Ferguson and Barlow (2001) re-estimated the
abundance as approximately 150,000 of both species in the eastern
Habitat: The dwarf sperm whale is an inconspicuous animal and
generally lives a long way from shore (Jefferson et al. 1993). Being
the smallest of the whales and even smaller than some dolphins, it
is rarely seen at sea, except in extremely calm conditions.
4. Biology and Behaviour
Mullin et al. (1994) sighted dwarf sperm whales in the Gulf of Mexico
over water depths between 400 and 600m. The species accounted only
for 1% of the cetaceans seen and occurred in 12% of the herds observed
during the aerial survey. These waters of the upper continental slope
were also characterised by high zooplankton biomass (Baumgartner et
Caldwell and Caldwell (1989) suggested that K. breviceps lives
in oceanic waters beyond the edge of the continental shelf while K.
sima lives over or near the edge of the shelf. Wang et al. (2002)
compared the diet of both Kogia spp. off coastal Taiwan and
conclude that pygmy sperm whales fed on much larger cephalopods such
as Taonius pavo compared to those ingested by dwarf sperm whales,
while dwarf sperm whales ingested more Histioteuthis miranda
than did pygmy sperm whales. These results support the view that pygmy
sperm whales live seaward of the continental shelf and that dwarf
sperm whales live more in coastal waters, i.e. the opposite of what
Caldwell and Caldwell (1989) suggested.
Photo: Robert L. Pitman
Behaviour: Rises to the surface slowly and deliberately
and, unlike most other small whales (which roll forward at the surface),
simply drops out of sight. Probably does not approach boats. May
occasionally breach; leaping vertically out of the water and falling
back tail-first or with a belly flop. Some records suggest that,
when resting at the surface, it floats lower in the water than the
pygmy sperm whale. Probably dives to depths of at least 300m (Carwardine,
One of the few reported behavioural observations at sea stems from
Scott and Cordado (1987) who report sighting a mother and calf after
a purse-seine set was deployed on yellowfin tuna, Thunnus albacares,
associated with a mixed school of spotted dolphins, Stenella
attenuata, and spinner dolphins, S.
longirostris. The dwarf sperm whales were accidentally encircled.
While inside the net, the female released into the water a cloud
of reddish material, presumably faeces, 6-8 times during the course
of the set. The mother released the faeces whenever a dolphin approached
the calf; she then appeared to hide herself and the calf in the
middle of the opaque cloud.
In Hawaiian waters Kogia sp. were sighted most frequently
in deeper portions of the study area (mean depth, 1,425 m) and in
calm sea conditions (mean Beaufort sea state < 1). One group
of six dwarf sperm whales containing two mother-infant pairs did
not dive for more than a few minutes at a time (Baird, 2005).
Schooling: Group sizes tend to be small, most often less
than 5 individuals, although groups of up to 10 have been recorded
(Jefferson et al. 1993; Mcalpine, 2009).
Reproduction: In at least one area, there appears to be
a calving peak in summer (Jefferson et al. 1993).
Food: Dwarf sperm whales appear to feed primarily on deep-water
cephalopods (Jefferson et al. 1993) as well as on fish and crustaceans
(Caldwell and Caldwell, 1989).
Duguy (1994) suggests that the species does not migrate extensively,
since it can be observed year-round off African coasts.
Direct catch: Some small scale catches of dwarf sperm whales
have been reported (Caldwell and Caldwell, 1989 and refs. therein).
K. sima was encountered in a small harpoon fishery for pilot whales
at St. Vincent in the Lesser Antilles, in Japan and occasionally
in an aboriginal industry on Lomblen Island in Indonesia, and has
been reported from fish markets in Sri Lanka.
Incidental catch: Caldwell and Caldwell (1989) suppose that
it is unlikely that Kogia spp. are significantly affected by humans.
When taken in commercial fisheries the numbers are so few that either
species is considered rare. This is confirmed by Waring et al. (2007):
Total annual estimated average fishery-related mortality and serious
injury to the North West Atlantic stock during 1999-2003 was zero.
However, Jefferson et al. (1993) believe that substantial numbers
are taken each year in gillnets in the Indian Ocean, and possibly
elsewhere. Zerbini and Kotas (2001) report on by-catch in the Brazilian
driftnet fishery. Because of their small size and habit of often
lying at the surface, apparently oblivious to approaching vessels,
a few Kogia are probably run down and injured or killed (Caldwell
and Caldwell, 1989).
Pollution: Both species have been reported with plastic bags
in their stomachs that may have prevented digestion of food and
ultimately brought death. Perhaps the textural or visual quality
of the plastic was similar to that of squid and thus enticed the
whales to devour it (Caldwell and Caldwell, 1989).
Range states (Taylor et al. 2008b):
American Samoa; Angola; Anguilla; Antigua and Barbuda; Argentina;
Aruba; Australia; Bahamas; Bangladesh; Barbados; Belize; Benin;
Bermuda; Brazil (Rio Grande do Sul); Brunei Darussalam; Cambodia;
Cameroon; Canada (British Columbia); Cape Verde; Cayman Islands;
Chile (Valparaíso); China; Colombia; Congo; Congo, The Democratic
Republic of the; Cook Islands; Costa Rica; Cuba; Côte d'Ivoire;
Djibouti; Dominica; Dominican Republic; Ecuador (Galápagos);
El Salvador; Equatorial Guinea; Fiji; France; French Guiana; French
Polynesia; Gabon; Gambia; Ghana; Gibraltar; Grenada; Guadeloupe;
Guam; Guatemala; Guinea; Guinea-Bissau; Guyana; Haiti; Honduras;
Hong Kong; India; Indonesia; Iran, Islamic Republic of; Jamaica;
Japan (Honshu); Kenya; Kiribati; Kuwait; Liberia; Madagascar; Malaysia;
Maldives; Marshall Islands; Martinique; Mauritania; Mexico; Micronesia,
Federated States of; Morocco; Mozambique; Myanmar; Namibia; Nauru;
Netherlands Antilles; New Caledonia; New Zealand (Kermadec Is.,
North Is.); Nicaragua; Nigeria; Niue; Northern Mariana Islands;
Oman; Pakistan; Palau; Panama; Papua New Guinea; Peru; Philippines;
Pitcairn; Portugal (Azores, Madeira); Puerto Rico; Qatar; Réunion;
Saint Helena; Saint Kitts and Nevis; Saint Lucia; Saint Pierre and
Miquelon; Saint Vincent and the Grenadines; Samoa; Sao Tomé
and Principe; Senegal; Sierra Leone; Singapore; Solomon Islands;
Somalia; South Africa; Sri Lanka; Sudan; Suriname; Taiwan, Province
of China; Tanzania, United Republic of; Thailand; Timor-Leste; Togo;
Tonga; Trinidad and Tobago; United Arab Emirates; United States
of America (Hawaiian Is.); Venezuela; Viet Nam; Virgin Islands,
British; Virgin Islands, U.S.; Wallis and Futuna; Western Sahara;
Classified as "Data Deficient" by the IUCN. Not listed
by CMS. The species is listed in Appendix II of CITES.
Both kogiid species also occur in southern South America. Recommendations
iterated by the scientific committee of CMS for small cetaceans
in that area (Hucke-Gaete, 2000) also apply (see Appendix
1). For recommendations on south-east Asian stocks, see Perrin
(1996) in Appendix 2.
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© Illustrations by Maurizio Würtz, Artescienza.
© Maps by IUCN.