Pygmy killer whales account for less than 1% of odontocete sightings (McSweeney et al, 2008). Although pygmy killer whales are rarely seen in the wild, they have been recorded as far north as the Bay of Biscay near France (Williams et al., 2002) and as far south as the African cape (Perrin, 2010). They have been found at numerous locations worldwide, between 45˚ north and 35˚ south latitude; unfortunately, this species has not been reliably found in any one area (McSweeney et al., 2008). They are typically found in deep (Ward, Moscrop, and Carlson, 2001), warm temperate, sub-tropical and tropical waters all over the globe (Williams et al., 2002). They have been recorded most frequently in the temperate waters of the Pacific and south Atlantic Oceans, near the Hawaiian Islands (McSweeney et al, 2008), in the Gulf of Mexico, near Japan, in the Indian Ocean and in tropical western Africa (MarineBio, 1998). ("Feresa attenuata, Pygmy Killer Whale", 1998; McSweeney, et al., 2008; Perrin, 2010; Ward, et al., 2001; Williams, et al., 2002)
The following locations have been documented for pygmy killer whale sightings: the Venezuelan Caribbean, Puerto Rico, British Virgin Islands, Trellis Bay (Ward, Moscrop, and Carlson, 2001), Florida (Montie, Manire, and Mann, 2011), Brazil, Argentina, South Africa (Zerbini and de Oliveira Santos, 1997), Central English Channel, Bay of Biscay (Williams, Williams, Brereton, 2002), Maldivian archipelago, south of Sri Lanka (Madsen, Kerr, and Payne, 2004), West Indian area, South Atlantic, Pacific Ocean, Indian Ocean, Peru, Gulf of Mexico, western Africa (MarineBio, 1998), and the Hawaiian Islands (McSweeney et al, 2008). ("Feresa attenuata, Pygmy Killer Whale", 1998; Madsen, et al., 2004; McSweeney, et al., 2008; Ward, et al., 2001; Williams, et al., 2002; Zerbini and de Oliveira Santos, 1997)
Pygmy killer whales depend on their hearing for communication, hunting, and interacting with the marine world around them (Montie, 2011). Rarely kept captive, they have only been studied during the few chance observations in the wild (IUCN Red List of Threatened Species, 2009). While normally occupying warm, deep waters, pygmy killer whales have been spotted near shallower oceanic islands as well (Ward, Moscrop, and Carlson, 2001). A 21 year study in the Hawaiian Islands focused on whales at depths up to 500 meters; little is known about pygmy killer whales at depths greater than 500 meters, although they have been recorded at depths greater than 2500 meters (McSweeney et al, 2008). ("IUCN Red List of Threatened Species", 2009; McSweeney, et al., 2008; Montie, 2011; Ward, et al., 2001)
Pygmy killer whales were first documented in 1827 by J. Gray, using a skull. Gray gave them an alternate name. Pygmy killer whales were subsequently documented again in 1874 by Gray, at which time he called them Feresa attenuata. From 1960 to the present the name Feresa attenuata has been the recognized name (Zerbini and de Oliveira Santos, 1997).
On average, pygmy killer whales weigh 150 kg and are 2.3 meters in length (Madsen, Kerr, and Payne, 2004; Williams et al., 2002; MarineBio, 1998; IUCN Red List of Threatened Species, 2009). Pygmy killer whales are easily misidentified as either juvenile false killer whales or melon-headed whales (McSweeney et al, 2008). Some of the distinguishable features of Feresa attenuata include: a dark gray-black stout body, significantly lighter underbelly, blunt head without a beak, and an under slung jaw which usually contains a whitish color set of lips. The dorsal fin is nearly centered on the body and the flippers have rounded tips and are of moderate length. The dorsal fin itself is one of the best ways to distinguish this mammal from other cetaceans; it reaches high off the dorsal back, lacks rigidity, points slightly backward, and has a sub-triangular shape. Another physical characteristic is an extending groove on the pygmy killer whale's skin, from just ahead of the umbilicus to the anus. This feature holds the genitals, anus, and umbilicus in both sexes (Encyclopedia of Life, 2003); however the presence of a ventral, post-anal keel could be a definite distinction between males and females (McSweeney et al, 2008).
The bone structure of pygmy killer whales is fairly distinctive; not only is the mandible hollow, but the left side is larger and usually contains one more tooth than the right. This difference in size makes the skull asymmetrical, common in many odotocete whales. The lower jaw holds between 11 and 13 large, conical pairs of teeth while the upper usually holds 8 to 11. Off the Brazilian coast, scientists recorded measurements of a stranded female, noting that physical maturity in this species is most likely reached when the vertebral epiphyses and centra in all vertebrae are fused. Also useful in distinguishing mature pygmy killer whales from juveniles is that each tooth's pulp cavity is filled and that ossified cranial sutures occur in adults (Zerbini and de Oliveira Santos, 1997). The distance between the end of the tooth row and the ante-orbital notch is another distinctive characteristic used in identifying a pygmy killer whale that was stranded in the Delta of Parnaíba River, Brazil (De Magalhaes et al, 2007). ("Feresa attenuata Gray, 1874", 2003; "Feresa attenuata, Pygmy Killer Whale", 1998; "IUCN Red List of Threatened Species", 2009; De Magalhaes, et al., 2007; Madsen, et al., 2004; McSweeney, et al., 2008; Williams, et al., 2002; Zerbini and de Oliveira Santos, 1997)
Pygmy killer whale mating behaviors are not reported in the literature.
Although there is very little data on the mating system of the pygmy killer whale, scientists believe that at lengths greater than 2.16 meters, males become sexually mature, and at lengths greater than 2.21 meters females become sexually mature (MarineBio, 1998).
Unfortunately gestation period, mating habits, or parental care, are unknown for this species. Other delphinids of similar size birth in the summer months, usually producing one calf (MarineBio, 1998). Pygmy killer whale calves measure roughly 0.8 meters (32 inches) at birth (Ward et al., 2001). One calf is born with each pregnancy. ("Feresa attenuata, Pygmy Killer Whale", 1998; Ward, et al., 2001)
Although it is fairly easy to distinguish nursing, female Feresa attenuata from males and juveniles, there are no studies about parental investment in this species. Generally, in a pod of newly born calves, adults nearest to the calves are the mothers, while other adults without calves are most often males. Besides viewing the adult females near the calves, there is little research about how long the mothers care for their young, or if the males help at all. Like most whales, young pygmy killer whales are born able to swim on their own (McSweeney et al, 2008). (McSweeney, et al., 2008)
Little is known about longevity of pygmy killer whales. In a study in the Hawaiian Islands that lasted over 21 years, scientists identified at least one individual pygmy killer whale throughout the entire study (McSweeney et al, 2008). (McSweeney, et al., 2008)
This species is social, having been seen in pods ranging from 4 to 50 individuals. Occasional groups of up to several hundred individuals have been observed (Ward et al., 2001). They have been spotted beating their flukes and flippers on the top of the water, growling, and even snapping their jaws aggressively. Even in captivity these creatures have been known to show defensive reactions towards other cetaceans and their trainers (MarineBio, 1998).
Pygmy killer whales have been documented on several occasions as being slow swimming delphinids. Some sightings have noted that they are playful and acrobatic (Encyclopedia of Life, 2003) while others regard their movements as slow and non-acrobatic (Williams et al., 2002). Several categories have been used to classify behaviors of pygmy killer whales while moving in the water. During the 21 year study off the main Hawaiian Islands, McSweeney et al. (2008) described these group behaviors as travel, slow travel, milling, social, logging, and/or resting. Each was used depending on the speed of the animal, interaction with potential prey, direction of movement, or location within the water and other individuals. They may be mainly active at night, when they are thought to feed. They have been spotted on numerous occasions swimming slowly at a distance of at least 50 meters from ships (Williams et al., 2002) . ("Feresa attenuata Gray, 1874", 2003; "Feresa attenuata, Pygmy Killer Whale", 1998; Madsen, et al., 2004; McSweeney, et al., 2008; Ward, et al., 2001; Williams, et al., 2002)
This species is thought to be non-migratory based on year-round observations of individuals in areas such as the Lesser Antilles (Ward et al., 2001). ("Feresa attenuata Gray, 1874", 2003; McSweeney, et al., 2008; Ward, et al., 2001)
Pygmy killer whales make clicking and whistling sounds similar to bottlenose dolphins and can growl through their blowholes (Encyclopedia of Life, 2003). Like other dolphins, they use echolocation to navigate their environment. A study done in the Indian Ocean recorded a peak range between 45 and 117 kHz (kilohertz) made through these bimodal clicks; the clicks themselves were short, directional broadband signals with intensity levels ranging from 197 to 223 dB (decibels). Both frequency and intensity were higher than false killer whales.
Anatomical studies done on 2 stranded pygmy killer whales off a Florida beach in 2008 provided insight into sound perception. Acoustic vibrations travel through blubber in hollow jawbones. This blubber presses against the tympanoperiotic complex, transmitting the sound to the middle and inner ear. There are two regions of the brain, the medial geniculate body and inferior colliculus, as well as the auditory nerve, that recieve and interpret acoustic signals (Montie, 2011). Scientists were able to document that pygmy killer whales perceived frequencies at 40 kHz best. The lowest audible threshold was about 20 kHz whereas the highest was 120 kHz (Montie, 2011). ("Feresa attenuata Gray, 1874", 2003; Madsen, et al., 2004; Montie, 2011; Montie, et al., 2011)
Little is known about the diet of this species. However, based on stomach contents of several stranded specimens, pygmy killer whales have been known to consume cephalopods (Williams et al., 2002), large fish, octopus, squid, (MarineBio, 1998), and smaller cetaceans (Madsen et al., 2004). Scientists believe that these whales feed in deep waters at night (McSweeney et al, 2008). ("Feresa attenuata, Pygmy Killer Whale", 1998; Madsen, et al., 2004; McSweeney, et al., 2008; Williams, et al., 2002)
Pygmy killer whales are aggressive and don't have many natural predators. Some potential predators include orcas, large sharks, and humans (Encyclopedia of Life, 2003). ("Feresa attenuata Gray, 1874", 2003)
Pygmy killer whales prey on fish, mollusks, and small cetaceans. Little research has been done to determine the potential parasites or diseases of Feresa attenuata, although they are known to harbor nematode parasites, Anisakis simplex (Zerbini and de Oliveira Santos , 1997) (Madsen, et al., 2004; Zerbini and de Oliveira Santos, 1997)
There are no known positive impacts of pygmy killer whales on humans.
Pgymy killer whales have no negative impact on humans. (McSweeney, et al., 2008)
Some of the potential threats to this species include fishing and harvesting (intentionally killing for subsistence by humans or accidental mortality from bycatches), pollution, such as solid waste and garbage, noise pollution from sonar, and climate change that can alter habitat (IUCN Red List of Threatened Species, 2009). Although it is not known for certain, the thyroid system of the pygmy killer whale (much like other marine species) could be negatively affected by some man-made pollutants (Montie, 2011). Studies show that estimated population size of pygmy killer whales is 817 in Hawaiian waters, 408 in the northern Gulf of Mexico, and 38,900 in the tropical Pacific (IUCN Red List of Threatened Species, 2009). ("IUCN Red List of Threatened Species", 2009; Montie, 2011)
Tabitha Starjnski (author), University of Wisconsin-Stevens Point, Christopher Yahnke (editor), University of Wisconsin-Stevens Point, Tanya Dewey (editor), University of Michigan-Ann Arbor.
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.
having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
generally wanders from place to place, usually within a well-defined range.
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
an animal that mainly eats fish
mainly lives in oceans, seas, or other bodies of salt water.
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
young are relatively well-developed when born
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