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| Ecology and Behavior |
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Habit:Oceanic
Group sizes tend to be small, most often less than five individuals (although groups of up to 10 have been recorded). This species, like the pygmy sperm whale, is shy and undemonstrative when observed at sea. They often drift motionless at the surface. When startled, dwarf sperm whales may leave a large rust-colored cloud of fecal material behind as they dive. In at least one area, there appears to be a calving peak in summer. |
| Feeding and Prey |
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Diet dominated by:Cephalopods
Dwarf sperm whales appear to feed primarily on deep-water cephalopods. This species is thought to feed in shallower water than does K. breviceps.
Feeding mode:Seizing
Known prey species:
Cephalopods:Semirossia tenera, Heteroteuthis dispar, Lycoteuthis lorigera, Abralia redfieldi, Octopoteuthis sp., Moroteuthis ingens, Moroteuthis robsoni, Histioteuthis spp., Illex argentinus, Ornithoteuthis antillarum, Chiroteuthis veranyi, Cranchiidae, Japetella diaphana |
| Threats and Status |
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Main threats:
Harvest
Fisheries bycatch
Plastic pollution
Conservation status:
The dwarf sperm whale is not listed as threatened or endangered by either the IUCN or the U.S. government. Dwarf sperm whales are sometimes killed in directed fisheries in the Caribbean and Indo-Pacific regions, and a few have been known to die incidentally in fisheries throughout the range. They have a habit of eating plastic discarded or lost at sea, and their tendency to lay quietly at the surface may make them vulnerable to vessel strikes.
The National Marine Fisheries Service considers animals in U.S. waters to be members of several distinct stocks, and assesses them separately. Delineations between stocks are often difficult to determine, therefore assessments should be considered ongoing processes. In the case of the dwarf sperm whale, concern that sightings may be confused with or for the cogener K. breviceps (the pygmy sperm whale) further complicates the estimation of abundance. Stocks are estimated as follows
All Kogia sp. (K. breviceps and K. sima) in the northern Gulf of Mexico 547 (CV=0.28) 1991-1994 shipboard surveys
All Kogia sp. in the western North Atlantic stock 536 (CV=0.45) 1998 shipboard and aerial surveys
For current information on the conservation status of this species, please consult the following websites.
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| References |
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Caldwell, D.K., and M.C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838) Dwarf sperm whale Kogia simus Owen, 1866. Pp. 234-260 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Vol. 4 River dolphins and the larger toothed whales. Academic Press.
Dos Santos, R.A. and M. Haimovici. Cephalopods in the diet of marine mammals stranded of incidentally caught along southeastern and southern Brazil (21-34° S). 2001. Fisheries Research 5299-112.
McAlpine, D.F. 2002. Pygmy and dwarf sperm whales Kogia breviceps and K. simus. Pp. 1007-1009 in W.F. Perrin, B. Würsig and J.G.M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.
Nagorsen, D. 1985. Kogia simus. Mammalian Species 239:6 pp.
Ross, G.J.B. 1979. Records of pygmy and dwarf sperm whales, genus Kogia, from southern Africa, with biological notes and some comparisons. Annals of the Cape Provincial Museums (Natural History) 15:259-327.
Willis, P.M., and R.W. Baird. 1998. Status of the dwarf sperm whale, Kogia simus, with special reference to Canada. Canadian Field-Naturalist 112:114-125.
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