Pygmy Killer Whale
About the Species
Despite its common name, the pygmy killer whale is a small member of the oceanic dolphin family. They are often confused with false killer whales and melon-headed whales. This species is found primarily in deep waters throughout tropical and subtropical areas of the world. Until a live animal was discovered in 1954, pygmy killer whales were known only from two fossil skulls for over a century. Not much is known about them, and they are considered naturally rare.
Although they face threats from entanglement in fishing gear, pygmy killer whales in the United States are not endangered or threatened. Like all marine mammals, they are protected under the Marine Mammal Protection Act.
NOAA Fisheries estimates population size for each stock of pygmy killer whale in its stock assessment reports. A stock is a group of animals that occupy the same area and interbreed. There are three recognized stocks in the United States: Hawaii, northern Gulf of Mexico, and western North Atlantic.
CITES Appendix II
- Throughout Its Range
- Throughout Its Range
Pygmy killer whales can reach a length of 8.5 feet and weigh up to 496 pounds. They are about 2.6 feet long as newborns and reach adulthood at 6.5 feet. They have a small head with a rounded melon (or forehead) that extends in front of the mouth, and they have no discernable rostrum. Their dorsal fin is relatively large and tall and is located behind the mid-back. They have relatively long, pointed, tapering flippers (pectoral fins), and their body is dark gray to black. Their most distinctive features are some small white areas on the lips and belly. They have a fairly prominent, narrow cape that dips only slightly below the dorsal fin and a light gray ventral band.
Pygmy killer whales are easily confused with melon-headed whales because of their similar appearance. The best ways to distinguish between the two species are the pygmy killer whale’s frequent paired white tooth rakes, and the clear demarcation between the pygmy killer whale’s darker cape and lighter lateral pigmentation.
Behavior and Diet
Pygmy killer whales usually occur in groups of 12 to 50 individuals but have been seen in groups up to several hundred individuals. Both sexes may remain in their birth groups throughout their lives. They are generally less active than other oceanic dolphins and are frequently seen "logging"—resting in groups at the surface with all animals oriented the same way.
Pygmy killer whales are very aggressive when kept in captivity. They feed primarily on squids and fish.
Where They Live
Pygmy killer whales prefer deeper areas of warmer tropical and subtropical waters where their prey is concentrated. They have a circumglobal range from 40º North to 35º South. They may occasionally occur relatively close to shore around oceanic islands. In the United States, they can be found in Hawaii, the northern Gulf of Mexico, and the western North Atlantic. In Hawaiߵi, there are resident populations off Oߵahu, Penguin Bank, and Hawaiߵi Island.
Lifespan & Reproduction
Reproductive biology is poorly known in this species. Its estimated lifespan is unknown.
Pygmy killer whales can become entangled or captured in commercial fishing gear, such as gillnets, though there is no reported bycatch from U.S. fisheries.
Underwater noise pollution can interrupt the normal behavior of pygmy killer whales, which rely on sound to communicate. As ocean noise increases from human sources, communication space decreases—the whales cannot hear each other, or discern other signals in their environment as they do in an undisturbed ocean.
Sound can disturb important activities, such as feeding, migrating, and socializing. Scientific research has documented that ocean noise also causes marine mammals to change the frequency or amplitude of their calls, decrease foraging behavior, become displaced from preferred habitat, or increase the level of stress hormones in their bodies. If loud enough, noise can cause temporary or permanent hearing loss.
In the Spotlight
Like all marine mammals, the pygmy killer whale is protected under the Marine Mammal Protection Act. NOAA Fisheries is working to conserve this species to ensure populations remain stable.
Reducing Interactions with Fishing Gear
Pygmy killer whales can be entangled or caught as bycatch in fishing gear, such as gillnets. NOAA Fisheries is committed to minimizing bycatch in U.S. fisheries to ensure they remain sustainable and to protect species such as the pygmy killer whale.
Overseeing Marine Mammal Health and Stranding Response
We work with volunteer networks in all coastal states to respond to marine mammal strandings including all whales. When stranded animals are found alive, NOAA Fisheries and our partners assess the animal’s health and determine the best course of action. When stranded animals are found dead, our scientists work to understand and investigate the cause of death. Although the cause often remains unknown, scientists can sometimes attribute strandings to disease, harmful algal blooms, vessel strikes, fishing gear entanglements, pollution exposure, and underwater noise. Some strandings can serve as indicators of ocean health, giving insight into larger environmental issues that may also have implications for human health and welfare.
Marine Mammal Unusual Mortality Events
Pygmy killer whales have never been part of a declared unusual mortality event. Under the Marine Mammal Protection Act, an unusual mortality event is defined as "a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response." To understand the health of marine mammal populations, scientists study unusual mortality events.
Addressing Ocean Noise
Increasing evidence suggests that exposure to intense underwater sound in some settings may cause some cetaceans to strand and ultimately die. NOAA Fisheries is investigating all aspects of acoustic communication and hearing in marine animals, as well as the effects of sound on behavior and hearing. In 2016, we issued marine mammal acoustic technical guidance for assessing the effects of anthropogenic sound on marine mammal hearing.
Pygmy killer whales are protected under the MMPA.
Key Actions and Documents
NOAA Fisheries conducts a variety of research on the biology, behavior, and ecology of pygmy killer whales. The results of this research are used to inform management decisions and enhance protection efforts for this species.
Determining the size of pygmy killer whale populations helps resource managers gauge the success of NOAA Fisheries’ conservation measures. Our scientists collect and present these data in annual stock assessment reports.
NOAA Fisheries conducts research cruises to collect information on pygmy killer whale stocks, such as habitat preferences and feeding ecology. For example, the NOAA Pacific Islands Fisheries Science Center conducted a Hawaiian Islands Cetacean and Ecosystem Assessment Survey in 2017 and recorded sightings of pygmy killer whales and other cetaceans in the area. These studies help us estimate the abundance of these animals and can be used in management actions to protect them.
Our research also focuses on acoustics—the physics of the properties of sound. We study the basic acoustic behavior of cetaceans and fish, mapping the acoustic environment, and finding better ways to locate cetaceans using acoustic technologies. Our acoustic research also assesses the degree to which human-caused activities are changing the underwater soundscape, how these changes may potentially affect marine animals, and what measures can be taken to mitigate these potential effects.