Feresa attenuata

Geographic Range

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).

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).

• Biogeographic Regions
• indian ocean
  • native native
• atlantic ocean atlantic ocean
  • native native
• pacific ocean pacific ocean
  • native native

• Other Geographic Terms
• cosmopolitan cosmopolitan

Habitat

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).

• Habitat Regions
• temperate temperate
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• pelagic pelagic
• coastal coastal

Physical Description

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).

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Reproduction

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, and 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.

• Key Reproductive Features
• iteroparous iteroparous
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

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).

• Parental Investment
• precocial precocial
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

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).

Behavior

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) .

• Key Behaviors
• natatorial natatorial
• nocturnal nocturnal
• motile motile
• nomadic nomadic
• sedentary sedentary
• social social
• colonial colonial

Home Range

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).

Communication and Perception

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).

• Communication Channels
• tactile tactile
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

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).

• Primary Diet
• carnivore carnivore
  • piscivore piscivore
  • molluscivore molluscivore

• Animal Foods
• mammals
• fish
• mollusks
• aquatic crustaceans
• other marine invertebrates

Predation

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).

Ecosystem Roles

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)

Economic Importance for Humans: Positive

There are no known positive impacts of pygmy killer whales on humans.

Economic Importance for Humans: Negative

Pgymy killer whales have no negative impact on humans.

Conservation Status

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 sizes of pygmy killer whales are 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).

Additional Links

Encyclopedia of Life

Contributors

Tabitha Starjnski (author), University of Wisconsin-Stevens Point, Christopher Yahnke (editor), University of Wisconsin-Stevens Point, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

De Magalhaes, F., R. Garri, C. Tosi, S. Siciliano, S. Chellappa, F. De Llima Silva. 2007. First confirmed record of Feresa attenuata (Delphinidae) for the Northern Brazilian Coast. Biota Neotropica , 7(2): 313-318. Accessed August 25, 2011 at http://www.biotaneotropica.org.br/v7n2/en/fullpaper?bn03507022007+en .

Kiszka, J., K. Macleod, O. Van Canneyt, D. Walker, V. Ridoux. 2007. Distribution, encounter rates, and habitat characteristics of toothed cetaceans in the Bay of Biscay and adjacent water from platform-of-opportunity data. ICES Journal of Marine Science , 64(5): 1033-10433. Accessed August 23, 2011 at http://icesjms.oxfordjournals.org/content/64/5/1033.full .

Madsen, P., I. Kerr, R. Payne. 2004. Source parameter estimates of echolocation clicks from wild pygmy killer whales ( Feresa attenuata ) (L). Acoustical Society of America , 116(4): 1909-1912. Accessed August 12, 2011 at http://marinebioacoustics.com/files/2004/Madsen_et_al_2004a.pdf .

McSweeney, D., R. Baird, S. Mahaffy, D. Webster, G. Schorr. 2008. Site fidelity and association patterns of a rare species: Pygmy killer whales ( Feresa attenuata ) in the main Hawaiian Islands. Marine Mammal Science , 25(3): 557-572. Accessed August 12, 2011 at http://onlinelibrary.wiley.com.ezproxy.uwsp.edu/doi/10.1111/j.1748-7692.2008.00267.x/full .

Montie, E., C. Manire, D. Mann. 2011. Live CT imaging of sound reception anatomy and hearing measurements in the pygmy killer whale, Feresa attenuata . The Journal of Experimental Biology , 214: 945-955.

Montie, E. 2011. How pygmy killer whales hear. The Journal of Experimental Biology , 214.i: 1-3. Accessed August 17, 2011 at http://jeb.biologists.org/content/214/6/i.1.full.pdf+html .

Perrin, W. 2010. " Feresa attenuata Gray, 1874" (On-line). World Register of Marine Species. Accessed August 21, 2011 at http://www.marinespecies.org/aphia.php?p=taxdetails&id=137095 .

Ward, D., A. Moscrop, D. Carlson. 2001. Elements for the development of a marine mammal action plan for the wider Caribbean: a review of marine mammal distribution. First Meeting of the Contracting Parties (COP) to the Protocol Concerning Specially Protected Areas and Wildlife (SPAW) in the Wider Caribbean Region: 1-77. Accessed August 13, 2011 at http://www.cep.unep.org/pubs/meetingreports/SPAW%20COP/English%20Docs/IG20-inf3en.doc .

Williams, A., R. Williams, T. Brereton. 2002. The sighting of pygmy killer whales ( Feresa attenuata ) in the southern Bay of Biscay and their association with cetacean calves. Journal of the Marine Biological Association of the United Kingdom , 82(3): 509-511. Accessed August 12, 2011 at http://www.marine-life.org.uk/media/24585/williams_2002_pygmy%20killer%20whale_jmba.pdf .

Zerbini, A., M. de Oliveira Santos. 1997. First record of the pygmy killer whale Feresa attenuata (Gray, 1874) for the Brazilian coast. Aquatic Mammals , 23.2: 105-109. Accessed August 15, 2011 at http://www.aquaticmammalsjournal.org/share/AquaticMammalsIssueArchives/1997/AquaticMammals_23-02/23-02_Zerbini.pdf .

2003. " Feresa attenuata Gray, 1874" (On-line). Encyclopedia of Life. Accessed August 20, 2011 at http://www.eol.org/pages/328531 .

1998. " Feresa attenuata , Pygmy Killer Whale" (On-line). MarineBio. Accessed August 15, 2011 at http://marinebio.org/species.asp?id=356 .

2009. "IUCN Red List of Threatened Species" (On-line). International Union for Conservation of Nature and Natural Resources (IUCN). Accessed August 19, 2011 at http://www.iucnredlist.org/apps/redlist/details/8551/0 .