Overview

Kogia sima – (Owen, 1866)

ANIMALIA – CHORDATA – MAMMALIA – ARTIODACTYLA – KOGIIDAE – Kogia – sima 

Common Names: Dwarf Sperm Whale, Owen’s Pygmy Sperm Whale (English), Miniatuurpotvis (Afrikaans), Cachalot nain (French), Cachalote enano (Spanish; Castilian)
Synonyms: Physeter simus Owen, 1866; Kogia simus Owen, 1866 

Taxonomic Note: 
The genus Kogia contains two species, the Dwarf Sperm Whale (Kogia sima) and Pygmy Sperm Whale (Kogia breviceps), with no subspecies recognised (Committee on Taxonomy 2021). The cryptic behaviour and similar external morphology of the two species mean that records are often not displayed at the species level and are instead combined into Kogia spp. It has been suggested that K. sima may consist of two parapatric species occupying the Atlantic and Indo-Pacific Oceans, based on evidence from the mitochondrial cytochrome b gene (Chivers et al. 2005). K. breviceps and K. sima are clearly distinguished genetically, but full recognition of a putative third Kogia spp. awaits further supporting evidence (Plön et al. 2023; Chivers et al. 2005). 

Red List Status: DD– Data Deficient 

Assessment Information

Assessors: Plön, S.¹ & da Silva, J.² 

Reviewers: Patel, T.³

Institutions: ¹University of Cape Town, ²South African National Biodiversity Institute, ³Endangered Wildlife Trust 

Previous Assessors & Reviewers: Plön, S. & Relton, C. 

Previous Contributors: Elwen, S., Findlay, K., Meÿer, M., Oosthuizen, H., Child, MF. & Taylor et al. (2008a, 2008b)  

Assessment Rationale 

K.sima is naturally uncommon and there are no regional estimates of population size or trends (Plön 2022). However, as they are a deep-diving species (up to 800 m), the effects of marine noise pollution should be monitored (although thus far no strandings have been linked to this threat), and we urge more research into the severity of this threat within South African waters. Additionally, plastic pollution should be recognised as an increasing emerging threat, as they are known to fatally ingest plastic bags mistaken for squid. While their offshore distributions do not overlap with many major threats in the assessment region, their natural scarcity and presumed low population numbers make them vulnerable to minor threats, which may be increasing in severity in the assessment region. Thus, in line with the global assessments, we list this species as Data Deficient and urge more systematic monitoring and analysis to determine population sizes and trends within the assessment 

Regional population effects: Dwarf Sperm Whales occur extensively across pelagic waters of tropical and temperate regions, and although their movement patterns are largely unknown, no barriers to dispersal have been recognised (Plön et al. 2023), thus rescue effects are considered possible. 

Reasons for Change 

Reason(s) for Change in Red List Category from the Previous Assessment: No change 

Red List Index 

Red List Index: No change 

Recommended citation: Plön S & da Silva JM. 2025. A conservation assessment of Kogia sima. In Patel T, Smith C, Roxburgh L, da Silva JM & Raimondo D, editors. The Red List of Mammals of South Africa, Eswatini and Lesotho. South African National Biodiversity Institute and Endangered Wildlife Trust, South Africa.

Regional Distribution and occurrence

Geographic Range

Dwarf Sperm Whales are widely distributed and inhabit deep tropical, subtropical and temperate waters throughout all oceans (Plön 2022; Plön and Baird 2022; McAlpine 2002). They seem to prefer warmer waters, compared to the Pygmy Sperm Whale (Plön 2022; Plön and Baird 2022; Caldwell & Caldwell 1989). The distributional ranges of Kogia spp. are poorly known, and most records originate from strandings or occasionally as individuals captured in small fisheries, rather than live sightings at sea (Plön 2022; Nagorsen 1985; Caldwell & Caldwell 1989; McAlpine 2002). This may, however, be attributed to their cryptic nature and affiliation for pelagic regions, rather than low population abundances, particularly since a number of recent studies report extensive observations of K. sima in the wild off Hawaii (Baird et al. 2022), Reunion (Dulau et al. 2024) and in the Eastern Caribbean (Kiszka et al. 2024). The Dwarf Sperm Whale is thought to predominantly reside in waters over the continental shelf edge and slope (Plön and Baird 2022; Ross 1979). Ballance & Pitman (1998) recorded a number of sightings of Dwarf Sperm Whales in extremely deep waters (over 3,000 m) in the western Indian equatorial zone.

Within the assessment region, stranding records of Dwarf Sperm Whales suggest that this species occurs from 22°42’S on the west coast of southern Africa (Elwen et al. 2013) to 29°51’S on the east coast (Plön et al. 2023). Prior to 1977, Ross (1979) documented strandings of 42 Dwarf Sperm Whales along South Africa’s coastline from Saldanha Bay to East London. There appears to be no seasonal variation in the occurrence of either Dwarf or Pygmy Sperm Whales within the assessment region (Skinner & Chimimba 2005), and their movement patterns are largely unknown. 

Elevation / Depth / Depth Zones 

Elevation Lower Limit (in metres above sea level): (Not specified) 

Elevation Upper Limit (in metres above sea level): (Not specified) 

Depth Lower Limit (in metres below sea level): (Not specified) 

Depth Upper Limit (in metres below sea level): (Not specified) 

Depth Zone: (Not specified) 

Map

Figure 1. Distribution records for Dwarf Sperm Whale (Kogia sima) within the assessment region (South Africa, Eswatini and Lesotho). Note that distribution data is obtained from multiple sources and records have not all been individually verified.

Biogeographic Realms 

Biogeographic Realm: Afrotropical, Australasian, Indomalayan, Nearctic, Neotropical, Oceanian, Palearctic 

Occurrence 

Countries of Occurrence 

Country	Presence	Origin	Formerly Bred	Seasonality
American Samoa	Extant	Native	–	Resident
Angola	Extant	Native	–	Resident
Anguilla	Extant	Native	–	Resident
Antigua and Barbuda	Extant	Native	–	Resident
Argentina	Extant	Native	–	Resident
Aruba	Extant	Native	–	Resident
Australia	Extant	Native	–	Resident
Bahamas	Extant	Native	–	Resident
Bahrain	Extant	Native	–	Resident
Bangladesh	Extant	Native	–	Resident
Barbados	Extant	Native	–	Resident
Belize	Extant	Native	–	Resident
Benin	Extant	Native	–	Resident
Bermuda	Extant	Native	–	Resident
Bonaire, Sint Eustatius and Saba	Extant	Native	–	Resident
Brazil	Extant	Native	–	Resident
Brazil -> Rio Grande do Sul	Extant	Native	–	Resident
British Indian Ocean Territory	Extant	Native	–	Resident
Brunei Darussalam	Extant	Native	–	Resident
Cabo Verde	Extant	Native	–	Resident
Cambodia	Extant	Native	–	Resident
Cameroon	Extant	Native	–	Resident
Canada	Extant	Native	–	Resident
Canada -> British Columbia	Extant	Native	–	Resident
Cayman Islands	Extant	Native	–	Resident
Chile	Extant	Native	–	Resident
Chile -> Valparaíso	Extant	Native	–	Resident
China	Extant	Native	–	Resident
Christmas Island	Extant	Native	–	Resident
Cocos (Keeling) Islands	Extant	Native	–	Resident
Colombia	Extant	Native	–	Resident
Comoros	Extant	Native	–	Resident
Congo	Extant	Native	–	Resident
Congo, The Democratic Republic of the	Extant	Native	–	Resident
Cook Islands	Extant	Native	–	Resident
Costa Rica	Extant	Native	–	Resident
Cuba	Extant	Native	–	Resident
Curaçao	Extant	Native	–	Resident
Côte d’Ivoire	Extant	Native	–	Resident
Djibouti	Extant	Native	–	Resident
Dominica	Extant	Native	–	Resident
Dominican Republic	Extant	Native	–	Resident
Ecuador	Extant	Native	–	Resident
Ecuador -> Galápagos	Extant	Native	–	Resident
Egypt	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
El Salvador	Extant	Native	–	Resident
Equatorial Guinea	Extant	Native	–	Resident
Eritrea	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Fiji	Extant	Native	–	Resident
French Guiana	Extant	Native	–	Resident
French Polynesia	Extant	Native	–	Resident
Gabon	Extant	Native	–	Resident
Gambia	Extant	Native	–	Resident
Ghana	Extant	Native	–	Resident
Gibraltar	Extant	Native	–	Resident
Grenada	Extant	Native	–	Resident
Guadeloupe	Extant	Native	–	Resident
Guam	Extant	Native	–	Resident
Guatemala	Extant	Native	–	Resident
Guinea	Extant	Native	–	Resident
Guinea-Bissau	Extant	Native	–	Resident
Guyana	Extant	Native	–	Resident
Haiti	Extant	Native	–	Resident
Honduras	Extant	Native	–	Resident
Hong Kong	Extant	Native	–	Resident
India	Extant	Native	–	Resident
Indonesia	Extant	Native	–	Resident
Iran, Islamic Republic of	Extant	Native	–	Resident
Iraq	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Jamaica	Extant	Native	–	Resident
Japan	Extant	Native	–	Resident
Japan -> Honshu	Extant	Native	–	Resident
Kenya	Extant	Native	–	Resident
Kiribati	Extant	Native	–	Resident
Korea, Democratic People’s Republic of	Extant	Native	–	Resident
Korea, Republic of	Extant	Native	–	Resident
Kuwait	Extant	Native	–	Resident
Liberia	Extant	Native	–	Resident
Madagascar	Extant	Native	–	Resident
Malaysia	Extant	Native	–	Resident
Maldives	Extant	Native	–	Resident
Marshall Islands	Extant	Native	–	Resident
Martinique	Extant	Native	–	Resident
Mauritania	Extant	Native	–	Resident
Mauritius	Extant	Native	–	Resident
Mayotte	Extant	Native	–	Resident
Mexico	Extant	Native	–	Resident
Micronesia, Federated States of	Extant	Native	–	Resident
Montserrat	Extant	Native	–	Resident
Morocco	Extant	Native	–	Resident
Mozambique	Extant	Native	–	Resident
Myanmar	Extant	Native	–	Resident
Namibia	Extant	Native	–	Resident
Nauru	Extant	Native	–	Resident
New Caledonia	Extant	Native	–	Resident
New Zealand	Extant	Native	–	Resident
New Zealand -> Kermadec Is.	Extant	Native	–	Resident
New Zealand -> North Is.	Extant	Native	–	Resident
Nicaragua	Extant	Native	–	Resident
Nigeria	Extant	Native	–	Resident
Niue	Extant	Native	–	Resident
Norfolk Island	Extant	Native	–	Resident
Northern Mariana Islands	Extant	Native	–	Resident
Oman	Extant	Native	–	Resident
Pakistan	Extant	Native	–	Resident
Palau	Extant	Native	–	Resident
Panama	Extant	Native	–	Resident
Papua New Guinea	Extant	Native	–	Resident
Peru	Extant	Native	–	Resident
Philippines	Extant	Native	–	Resident
Pitcairn	Extant	Native	–	Resident
Portugal	Extant	Native	–	Resident
Portugal -> Azores	Extant	Native	–	Resident
Portugal -> Madeira	Extant	Native	–	Resident
Puerto Rico	Extant	Native	–	Resident
Qatar	Extant	Native	–	Resident
Réunion	Extant	Native	–	Resident
Saint Barthélemy	Extant	Native	–	Resident
Saint Helena, Ascension and Tristan da Cunha	Extant	Native	–	Resident
Saint Kitts and Nevis	Extant	Native	–	Resident
Saint Lucia	Extant	Native	–	Resident
Saint Martin (French part)	Extant	Native	–	Resident
Saint Vincent and the Grenadines	Extant	Native	–	Resident
Samoa	Extant	Native	–	Resident
Sao Tome and Principe	Extant	Native	–	Resident
Saudi Arabia	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Senegal	Extant	Native	–	Resident
Seychelles	Extant	Native	–	Resident
Sierra Leone	Extant	Native	–	Resident
Singapore	Extant	Native	–	Resident
Sint Maarten (Dutch part)	Extant	Native	–	Resident
Solomon Islands	Extant	Native	–	Resident
Somalia	Extant	Native	–	Resident
South Africa	Extant	Native	–	Resident
Spain	Extant	Native	–	Resident
Spain -> Canary Is.	Extant	Native	–	Resident
Sri Lanka	Extant	Native	–	Resident
Sudan	Presence Uncertain	Native	–	Seasonal Occurrence Uncertain
Suriname	Extant	Native	–	Resident
Taiwan, Province of China	Extant	Native	–	Resident
Tanzania, United Republic of	Extant	Native	–	Resident
Thailand	Extant	Native	–	Resident
Timor-Leste	Extant	Native	–	Resident
Togo	Extant	Native	–	Resident
Tokelau	Extant	Native	–	Resident
Tonga	Extant	Native	–	Resident
Trinidad and Tobago	Extant	Native	–	Resident
Turks and Caicos Islands	Extant	Native	–	Resident
Tuvalu	Extant	Native	–	Resident
United Arab Emirates	Extant	Native	–	Resident
United States of America	Extant	Native	–	Resident
United States of America -> Hawaiian Is.	Extant	Native	–	Resident
Uruguay	Extant	Native	–	Resident
Vanuatu	Extant	Native	–	Resident
Venezuela, Bolivarian Republic of	Extant	Native	–	Resident
Viet Nam	Extant	Native	–	Resident
Virgin Islands, British	Extant	Native	–	Resident
Virgin Islands, U.S.	Extant	Native	–	Resident
Wallis and Futuna	Extant	Native	–	Resident
Western Sahara	Extant	Native	–	Resident
Yemen	Extant	Native	–	Resident

Large Marine Ecosystems (LME) Occurrence 

Large Marine Ecosystems: (Not specified) 

FAO Area Occurrence 

	Presence	Origin	Formerly Bred	Seasonality
21. Atlantic – northwest	Extant	Native	–	Resident
27. Atlantic – northeast	Extant	Native	–	Resident
31. Atlantic – western central	Extant	Native	–	Resident
34. Atlantic – eastern central	Extant	Native	–	Resident
41. Atlantic – southwest	Extant	Native	–	Resident
47. Atlantic – southeast	Extant	Native	–	Resident
51. Indian Ocean – western	Extant	Native	–	Resident
57. Indian Ocean – eastern	Extant	Native	–	Resident
61. Pacific – northwest	Extant	Native	–	Resident
67. Pacific – northeast	Extant	Native	–	Resident
71. Pacific – western central	Extant	Native	–	Resident
77. Pacific – eastern central	Extant	Native	–	Resident
81. Pacific – southwest	Extant	Native	–	Resident
87. Pacific – southeast	Extant	Native	–	Resident

Climate change

The impact of global climate change, and the associated effects of increased water temperature and CO₂ concentration on Kogia spp. is largely unknown; however, it is likely to have cascading effects on the movements and feeding ecology of these species (Learmonth et al. 2006). 

Population information

Abundance estimates of this species are often underestimated due to their offshore habitats, long and deep-diving behaviour and inconspicuous nature at the surface (Barlow 1999). For example, they lie very low in the water when on the surface and can only be seen when wind speeds are between 0 and 2 on the Beaufort scale. Additionally, Pygmy and Dwarf Sperm Whales are often confused during sightings, which further complicates any population assessments. No global population size estimates are available for this species.

The 3-generation period of the species is calculated as 36 years (Taylor et al. 2007), and, globally, a 30% reduction over three generations cannot be ruled out (Taylor et al. 2008a, 2008b). 

Current population trend: Unknown 

Continuing decline in mature individuals? Unknown 

Extreme fluctuations in the number of subpopulations: (Not specified) 

Continuing decline in number of subpopulations: (Not specified) 

All individuals in one subpopulation: (Not specified) 

Number of mature individuals in population: Unknown 

Number of mature individuals in largest subpopulation: Unknown 

Number of Subpopulations: Unknown 

Severely fragmented: No 

Quantitative Analysis 

Probability of extinction in the wild within 3 generations or 10 years, whichever is longer, maximum 100 years: (Not specified) 

Probability of extinction in the wild within 5 generations or 20 years, whichever is longer, maximum 100 years: (Not specified) 

Probability of extinction in the wild within 100 years: (Not specified) 

Population genetics

Molecular evidence examining individuals across its range (South Africa, Australia, New Zealand, South America) have found extensive mixing (interbreeding) between locations, indicating individuals belong to a single metapopulation in the Southern Hemisphere (Plön et al. 2023). Given that no estimates of population size are available and no measure of effective population size (Ne) was conducted using the available genetic information, it is not possible to quantify the Ne 500 indicator.  

Habitats and ecology

Dwarf Sperm Whales inhabit deep waters over the continental shelf and slope (Plön and Baird 2022; Best 2007; Ross 1979). Although some studies document some division between K. breviceps and K. sima in their preference for water depth, largely based on the analysis of stomach contents (Plön 2004; Ross 1979), Mullin et al. (1994) using aerial observations noted that in the Gulf of Mexico, both species occurred in waters between 400–600 m deep. These depths constituted the upper regions of the continental slope, which exhibited high concentrations of zooplankton (Baumgartner et al. 2001). Both species appear to feed over the deeper continental shelf and slope (Plön 2022; Plön and Baird 2022; Ross 1979).

Ross (1979) reported that Dwarf Sperm Whales occur in socially structured schools of up to ten individuals and they lie very low in the water (Leatherwood & Reeves 1983).

The stomach contents of stranded Dwarf Sperm Whales contained the remains of deep-water cephalopods, suggesting that this species feeds at depths of up to 600 m, possibly even deeper, and is mostly found over the continental shelf (Plön and Baird 2022; Ross 1979The majority of the diet of Kogia spp. consists of cephalopods, but they may also consume other prey, for example deep-sea fishes and shrimps (McAlpine et al. 1997; dos Santos & Haimovici 2001; S. Plön pers. comm.). In South African waters, Pygmy and Dwarf Sperm Whales consumed at least 67 and 38 different prey species, respectively, and Pygmy Sperm Whales are likely to feed in deeper waters compared to Dwarf Sperm Whales (Plön 2004; Ross 1979).

Although little is known about the reproductive biology of Kogia spp., and no seasonality can be inferred, female and male K. sima from South Africa are estimated to reach sexual maturity at 2.15 m and 1.97 m, respectively (Plön 2004). Dwarf Sperm Whale calves are born at an approximate length of 1.03 m (Plön 2004).

Ecosystem and cultural services: Marine mammals integrate and reflect ecological variation across large spatial and long temporal scales, and therefore they are prime sentinels of marine ecosystem change (Moore 2008). 

IUCN Habitats Classification Scheme 

Habitat	Season	Suitability	Major Importance?
10.1. Marine Oceanic -> Marine Oceanic – Epipelagic (0-200m)	–	Suitable	Yes
10.2. Marine Oceanic -> Marine Oceanic – Mesopelagic (200-1000m)	–	Suitable	Yes
10.3. Marine Oceanic -> Marine Oceanic – Bathypelagic (1000-4000m)	–	Suitable	Yes

Life History 

Generation Length: (Not specified) 

Age at Maturity: Female or unspecified: 5 yrs (Plön 2004) 

Age at Maturity: Male: 2.6-3 yrs (Plön 2004) 

Size at Maturity (in cms): Female: 215 cm (Plön 2004) 

Size at Maturity (in cms): Male: 197 cm (Plön 2004) 

Longevity: 21.5 yrs for females, 17 yrs for males (Plön 2004) 

Average Reproductive Age: (Not specified) 

Maximum Size (in cms): 274.3cm in females, 260.4 cm in males (Plön 2004) 

Size at Birth (in cms): 103 cm (Plön 2004) 

Gestation Time: (Not specified) 

Reproductive Periodicity: (Not specified) 

Average Annual Fecundity or Litter Size: (Not specified) 

Natural Mortality: (Not specified) 

Does the species lay eggs? No 

Does the species give birth to live young: Yes 

Does the species exhibit parthenogenesis: (Not specified) 

Does the species have a free-living larval stage? (Not specified) 

Does the species require water for breeding? (Not specified) 

Movement Patterns 

Movement Patterns: (Not specified) 

Congregatory: (Not specified) 

Systems 

System: Marine 

General Use and Trade Information

Although this species is hunted at low levels in some parts of their range, there is no trade or use of the species within the assessment region. In other parts of the world, such as the Philippines, Kogia spp. are hunted for bait to be used in fisheries or meat for human consumption (Leatherwood et al. 1992; Anonymous 1996). Additionally, where they are caught accidentally in fisheries, such as gillnets, they may also be utilised for human consumption (Klinowska 1991; Muñoz-Hincapié et al. 1998). 

Subsistence:	Rationale:	Local Commercial:	Further detail including information on economic value if available:
Yes	–	–	–

National Commercial Value: Yes 

International Commercial Value: No 

End Use	Subsistence	National	International	Other (please specify)
1. Food – human	true	true	–	–

Is there harvest from captive/cultivated sources of this species? (Not specified) 

Harvest Trend Comments: (Not specified) 

Threats

Although no major threats have been recognised for Kogia spp. within the assessment region, and the threats listed below are not likely to cause drastic population reduction on their own, they may result in slow, significant declines in the future, especially if the threats synergise. 
 
Kogia spp. were not historically hunted commercially but are currently hunted on a small-scale in regions such as Japan, Taiwan, Sri Lanka, Indonesia and the Lesser Antilles (Jefferson et al. 1993). Dwarf Sperm Whales are occasionally caught as bycatch in many areas of their range (including southern Brazil; Zerbini & Kotas 1998). No direct or indirect catches of this species has been reported from South African waters. 
 
The ingestion of plastic bags (which the animals possibly mistake for squid) is common among squid-eating cetaceans and has been documented for both Kogia species (Plön 2022; Plön and Baird 2022) and is considered to be relatively common among these species. Plastic pollution in the stomachs of cetaceans frequently hinders natural digestion of food resources, leading to gut-blockage, starvation, strandings and death (Caldwell & Caldwell 1989; Laist et al. 1999; S. Plön pers. obs.).  
 
As deep-diving species (similar to beaked whales), Dwarf Sperm Whales are presumably vulnerable to anthropogenic noise pollution, for example those produced by seismic surveys and sonar generated during naval operations (Cox et al. 2006; Wang & Yang 2006; Yang et al. 2008). A number of stranding events, which included Kogia spp., have been documented in Taiwan (Wang & Yang 2006; Yang et al. 2008), the Gulf of Mexico and off the east coast of Florida (Waring et al. 2006). Although, anthropogenic noise pollution is a possible cause of these stranding incidents, due to spatial and temporal associations, this assumption has not been confirmed (Hohn et al. 2006; Wang & Yang 2006; Yang et al. 2008). Marine noise pollution is thought to be intensifying within South African waters (Koper & Plön 2012). 

Conservation

K. sima is listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). In the absence of further data, no specific conservation measures can be recommended for this species within the assessment region at present. Continued research is necessary into the impact of and interactions between threats, such as plastic and noise pollution, climate change and incidental bycatches in pelagic fisheries. Management plans should be developed as such data become available.

Recommendations for managers and practitioners: 

• The interaction between Kogia spp. and gillnet, purse seine and longline fisheries requires ongoing monitoring, and regular records of bycatch should be collected by fishing operations. 

Research priorities: 

• Population size, distribution and trends of these species in South African waters. 
• Investigations into threats to these species, such as the impacts and severity of marine pollution (both plastics and noise) on populations. 

Encouraged citizen actions: 

• Use information dispensed by the South African Sustainable Seafood Initiative to make good choices when buying fish in shops and restaurants, e.g. FishMS 0794998795. 
• Save electricity and fuel to mitigate CO₂ emissions and hence, the rate of climate change. 
• Sightings data from pelagic commercial tourism operators may be valuable. 
• Report any strandings to the relevant local authorities. 

Bibliography

Baird, R. W., Nelson, D., Lien, J. and Nagorsen, D. W. 1996. The status of the pygmy sperm whale, Kogia breviceps, in Canada. Canadian Field-Naturalist 110: 525-532. 

Baird, R. W., Mahaffy, S. D., & Lerma, J. K. 2022. Site fidelity, spatial use, and behavior of dwarf sperm whales in Hawaiian waters: using small-boat surveys, photo-identification, and unmanned aerial systems to study a difficult-to-study species. Marine Mammal Science, 38(1), 326-348. 

Ballance, L. T. and Pitman, R. L. 1998. Cetaceans of the western tropical Indian Ocean: distribution, relative abundance, and comparisons with cetacean communities of two other tropical ecosystems. Marine Mammal Science 14: 429-459. 

Barlow, J. 1999. Trackline detection probability for long-diving whales. In: G. W. Garner, S. C. Amstrup, J. L. Laake, B. J. F. Manley, L. L. McDonald and D. G. Robertson (eds), Marine mammal survey and assessment methods, pp. 209-221. Balkema Press, Netherlands. 

Barlow, J., Forney, K. A., Hill, K. A., Brownell Jr., R. L., Caretta, R. L., Demaster, D. P., Julian, D. P., Lowry, M. S., Ragen, M. S. and Reeves, R. R. 1997. U.S. Pacific marine mammal stock assessments: 1996. NOAA Technical Memorandum NMFS-SWFSC 248: 223 pp. 

Baumgartner, M. F., Mullin, K. D., May, L. N. and Leming, T. D. 2001. Cetacean habitats in the northern Gulf of Mexico. Fishery Bulletin 99: 219-239. 

Best, P. B. B. 2007. Whales and Dolphins of the Southern African Subregion. Cambridge University Press, Cape Town. 338pp. 

Caldwell, D. K. and Caldwell, M. C. 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): Dwarf sperm whale Kogia simus Owen, 1866. In: S. H. Ridgway and R. Harrison (eds), Handbook of marine mammals, Vol. 4: River dolphins and the larger toothed whales, pp. 234-260. Academic Press. 

Chivers, S.J., Leduc, A.E., Robertson, K.M., Barros, N.B. and Dizon, A.E. 2005. Genetic variation in Kogia spp., with preliminary evidence for two species of Kogia sima. Marine Mammal Science 21(4): 619-634. 

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