The Pygmy sperm whale (scientific name: Kogia breviceps) is one of two species of cetaceans in the family Kogiidae, the other being the Dwarf sperm whale. As their names suggests they are small compared to their distant cousin the Sperm whale. Like Sperm whales, their mouth is on the underside of their body, but unlike Sperm whales their small teeth are few in number and are sharply pointed and curved. Like Sperm whales, they are suction feeders and chiefly consume squid. Knowledge about these species has been slow to accumulate, and in fact, the existence of the two species only became widely accepted in 1966.(Handley 1966)
|Pygmy Sperm Whale. Source: NOAA|
|Size comparison of an average human and a pygmy sperm whale (Kogia breviceps). Source: Chris Huh|
Kingdom: Anamalia (Animals)
Lesser sperm whale
Pigmy sperm whale
Short-headed sperm whale
Small sperm whale
The Pygmy sperm whale is a toothed whale and can be recognised as such by the single blowhole and the presence of teeth. It is an easily recognisable small whale with a stocky body reaching up to four meters in length. It has a large and distinctly square upper jaw which projects above the narrow lower jaw. The blowhole is positioned at the front of the head and directed forward obliquely. A small dorsal fin is present two-thirds down the body and the tail flukes are small. The flippers are almost spear-shaped. The body is blue-black to charcoal grey in colour, while the underside is white and the inside of the mouth and the lips are white. There is often a crescent-shaped, light mark between the eye and the flipper. Pygmy sperm whales are usually found either alone, or in small groups of up to five individuals. The blow is unique amongst whales by being obliquely forward directed.
Pygmy sperm whales are usually seen in small groups of six or fewer individuals, but there are few documented sightings. They tend to stay in deep water, beyond the continental shelf, and not much is known about their behavior. Calves are about 1.2 meters (m) long at birth (an adult's total length ranges from 2.7 to 3.4 m); gestation lasts nine to eleven months; and the calf nurses for about a year. Although strandings are relatively frequent in the southeastern United States, sometimes because the whales have swallowed plastic bags, these animals are sighted so infrequently that they are considered uncommon for conservation purposes. Pygmy sperm whales are believed to feed mostly on cephalopods, and may mistake floating plastic bags for squid.
The Pygmy sperm whale is a small whale averaging about three meters in length for both sexes. Calves are about 55 kilograms at birth. They have a swollen nose and head, which takes up about 15% of their body length. Their head is conical with a small underslung jaw that opens beneath the upper jaw in a shark-like manner. The flippers are short, broad, and far forward on the body. They have a small curved dorsal fin.
The Pygmy sperm whale is a steely grey color with a distinct pink tinge. In the water they often look purple. They are a paler grey on the belly. Between the eye and the flipper is a small white/pale grey bracket mark. This is often called a "false gill", further attributing to its resemblance to a shark. There is another similar pale spot in front of the eye. Scarring is rare. They have a short rostrum which makes their wide skull triangular.
Pygmy sperm whales have 12 to 16 teeth on each side and their blowhole is slightly displaced to the left. These two traits distinguish the Pygmy sperm whale, Kogia breviceps, from the Dwarf sperm whale, K. simus (Minasian et al. 1984, Watson 1981).
The tail flukes will often appear before a deep dive. Dive duration time is not clearly known (Kinze, 2002). It is often confused with the Dwarf sperm whale, Kogia sima, but the dwarf sperm whale does not occur in British and Irish waters (Jefferson et al., 1994). Length Range of the species is 2.7 to 3.4 meters, and body mass typically varies from 318 to 408 kilograms.
Though there are sightings of solitary individuals, most of the whales travel in small pods of three to six individuals Like the great Sperm whale, Physeter macrocephalus, the pygmy sperm whale breaches, landing in the water tail first. Also like the great sperm whale, pygmy sperm whales have spermaceti in their foreheads. This suggests that they have the ability to dive into very deep water and hover motionless at any depth to wait for prey. They have great speed and can stay under water for long periods of time, another reason to suspect very deep dives.
The Pygmy sperm whale is often found stranded. There seems to be a relation between strandings and motherhood, as most strandings are mothers with newborn calves. Kogia breviceps have been descibed as being very slow and deliberate swimmers while breathing and swimming near the surface.
Key reproductive features are: Iteroparous; Seasonal breeding; Gonochoric/gonochoristic/dioecious (sexes separate); Sexual; Viviparous. Mating usually takes place in the summer. Gestation lasts for about nine to eleven months and the calf is born in the spring. The calf remains with its mother and is nursed for about 12 months. Calves are about 1.2 meters long and about 55 kilograms at birth.
These mammals are known to be able to live at least 17 years in the wild (David Macdonald 1985)
Distribution and Movements
The IUCN Red List reports that "Pygmy sperm whales are known from deep waters (outer continental shelf and beyond) in tropical to warm temperate zones of all oceans (McAlpine 2002). This species appears to prefer somewhat more temperate waters than does the dwarf sperm whale. The range of Kogia breviceps is poorly known, though a lack of records of live animals may be more due to inconspicuous behaviour rather than rarity. Most information stems from strandings (especially females with calves), which may give an inaccurate picture of the actual distribution at sea (Culik 2004)."
The Pygmy sperm whale prefers warm tropical waters. They may migrate to more temperate waters in the summer months. They also stay in deep waters (Watson 1981).
The IUCN Red List adds:
Kogia breviceps is rarely seen at sea; it tends to live a long distance from shore and has inconspicuous habits. According to Caldwell and Caldwell (1989) 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. However, this separation was not apparent in the study by Mullin et al. (1994) who, by aerial observation, found both species over water depths of 400-600 m in the north-central Gulf of Mexico. These waters of the upper continental slope were also characterized by high zooplankton biomass (Baumgartner et al. 2001).
Studies of feeding habits, based on stomach contents of stranded animals, suggest that this species feeds in deep water, primarily on cephalopods and, less often, on deep-sea fishes and shrimps (dos Santos and Haimovici 2001; McAlpine et al. 1997). In South Africa, they take at least 67 different prey species and appear to feed in deeper waters than do dwarf sperm whales (Ross 1979).
Pygmy sperm whales eat mostly squid, shrimp, fish, and crabs with what seems to be a preference for deepwater foraging. (Watson 1981)
Economic Importance for Humans
There is little economic benefit with respect to harvesting of this species; however, the scientific and research benefits from preserving this species are very high. The species is relatively uncommon so few are taken by the Japanese, and only an occasinal individual is taken by Indonesians.
Threats and Conservation Status
Less is known about this species in comparison with many other cetaceans. The infrequency of sightings is often assumed as rareness. It is vulnerable to Hawaiian fisheries and gillnets, float lines and long lines.
The IUCN Red List reports that "there is considerable uncertainty about the status of this species, which may span a range from Least Concern to a Threatened category. There is no information on abundance or on trends in global abundance. As a relatively uncommon species it is potentially vulnerable to low-level threats and a 30% global reduction over three generations (36 years; Taylor et al. 2007) cannot be ruled out."
There are no estimates of global abundance. Abundance of this and similar whales is often underestimated using visual survey methods because they dive for long periods and are inconspicuous when they surface (Barlow 1999). The frequency with which they strand in some areas (such as Florida and South Africa) suggests that they may not always be as uncommon as sightings would suggest. Recent genetic studies suggest the there is some gene flow between the Atlantic and Indo-Pacific oceans (S. J. Chivers pers. comm.).
Delineations between stocks are often difficult to determine, therefore assessments should be considered ongoing processes. In the case of the Pygmy sperm whale, concern that sightings may be confused with the cogener K. sima (the Dwarf sperm whale) further complicates the estimation of abundance. There are estimated to be about 247 (CV = 106%) off California, Oregon, and Washington (Barlow 2003); 7,251 (CV=77%) off Hawaii (Barlow 2006); 742 of both species of Kogia (CV=29%) in the northern Gulf of Mexico (Mullin et al. 2004); and 395 of both species (CV=40/75%) in the western North Atlantic (Waring et al. 2006).
Although they have never been taken in large numbers and have never been hunted commercially, small numbers of the species have been taken in coastal whaling operations off Japan, Indonesia, Taiwan, the Lesser Antilles, and Sri Lanka (Jefferson et al. 1993).
A few have been killed in gillnet fisheries of Sri Lanka, Taiwan and California, and it is likely they are killed in gillnets elsewhere as well (Jefferson et al. 1993; Barlow et al. 1997). Perez et al. (2001) reported on occasional bycatch in fisheries in the northeast Atlantic (mostly gillnet and purse seine operations). However, although it is taken in small numbers both directly and incidentally in fisheries, Baird et al. (1996) found no serious threats to its status.
A young male Pygmy sperm whale stranded alive on Galveston Island, Texas, USA and died in a holding tank 11 days later. During necropsy, the first two stomach compartments (forestomach and fundic chamber) were found to be completely occluded by various plastic bags (Laist et al. 1999). Such ingestion of plastics, with associated gut-blockage, appears to be a common issue in this species.
This species, like beaked whales, is likely to be vulnerable to loud anthropogenic sounds, such as those generated by navy sonar and seismic exploration (Cox et al. 2006).
In 2005, a large series of unusual stranding events over about 3 weeks in and around Taiwan included several Kogia (Wang and Yang 2006; Yang et al. 2008) with at least two pygmy sperm whales (Yang et al. 2008). It is unknown if military, seismic or other loud noise-producing human activities resulted in these strandings.
There are high levels of unexplained strandings in the Gulf of Mexico and the Atlantic coast of Florida (Waring et al. 2006).
Possible impacts of climate change on the marine environment may affect Pygmy sperm whales, although the nature of impacts has not been demonstrated (Learmonth et al. 2006).
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