Orca – The Killer Whale

Killer Whales


Orcas, also known as killer whales, are toothed whales and the largest member of the dolphin family. They are apex predators found in all of the world’s oceans and can be identified by their unique physical features, similar to human fingerprints. The dorsal fin and saddle patch vary in size, shape, pigmentation, and scarring, making it possible for researchers to identify individual orcas.


Orcas are one of thirty-five species in the oceanic dolphin family, Delphinidae, and the most cosmopolitan of all marine mammals.  There are at least ten distinct ecotypes of orcas, with three ecotypes inhabiting Pacific Northwest waters: Resident, Bigg’s (Transient), and Offshore. An ecotype is a distinct population of a species that has adapted to a particular ecological niche or environment. In the case of marine mammals, different ecotypes can have distinct physical, behavioral, and vocal characteristics that are adapted to the specific environmental conditions of their habitat. For example, orcas have several different ecotypes, each with different feeding strategies and prey preferences. 




The Southern Resident orca community, designated as J, K, and L pods, has been identified through these unique physical features, with a population of 73. Researchers can accurately determine the annual population count by keeping track of every individual orca. The Northern Resident orca community, comprised of A, G, and R clans, has over 300 individuals in 34 matrilines.


Bigg’s (Transient) orcas have a population estimated at 350 individuals and are more fluid in their family structure than residents. They have a pointed, shark-like dorsal fin and primarily feed on marine mammals such as seals, sea lions, porpoises, and even other whales.


Offshore orcas were discovered in 1988 and are genetically distinct from Resident and Bigg’s orcas. They appear to be smaller and have a continuously rounded dorsal fin tip, and their saddle patch is usually solid.


Orcas are found in other parts of the world, such as the North Pacific, Antarctica, North Atlantic, Peninsula Valdez in Argentina, the Crozet Islands south of Madagascar, and New Zealand. They tend to congregate in certain areas, mostly in cold water.

Life Cycle

The life cycle of killer whales is similar to that of humans. Males begin to show signs of sexual maturity between twelve and fifteen years old, with their dorsal fin growing taller and straighter. They become fully physically mature around 25, but can sire offspring around age 20. The most recent estimate of the average male lifespan is 30 years (maximum 50-60 years). Females attain sexual maturity in their early teens and have an estimated average lifespan of 45 years with maximum ages between 80-90 years. Orca mating and calving take place year-round, with pregnancies lasting 18 months, one of the longest gestations of any mammal. Calves are born tail first with a collapsed dorsal fin, weighing approximately 400 lbs and typically nurse until their third year.

Southern Resident orcas have low reproductive output, with approximately 69% of pregnancies resulting in spontaneous abortion. The average SRKW female orca birthing rate is currently one viable calf per female every nine or ten years. Low reproductive output is attributed to reduced prey availability and toxins as the main threats to successful reproduction. Newborn calves have orange coloration on their underside and eyepatch and usually nurse into their third year. They gain strength, size, and weight during their first six months, shedding their skin and showing lots of exuberant and playful behavior.



How do you know?

Determining the sex of an orca is vital in gaining information about the breeding health of the population. Male killer whales have an elongated white pattern around their genital slit stretching toward the tail, while a female’s white pattern is more rounded with visible mammary slits.


Female orcas typically develop to an average length of 18-22 feet and a weight of 8,000-11,000 lb. The largest recorded female orca measured 28 feet and weighed more than 15,000 lb.

Males are larger than females, usually growing up to 30 feet in length and weighing 12,000 lb to 16,000 lbs. Adult males are sexually dimorphic, – the condition where sexes of the same species exhibit different morphological characteristics – with the increased size of their dorsal fin indicating sexual maturity. The largest male orca on record measured 32 feet (9.8 meters) and weighed over 20,000 lb. At birth, orca calves weigh about 400 lb and are 7-8 feet long.

 Looks are everything

The physical features of killer whales, or orcas, are quite distinctive. Orcas have a cylindrical shape, tapering at the head and flukes, and are characterized by their sharply contrasted black and white “tuxedo” coloring. Their black coloration is found on the head, rostrum, back, sides, pectoral fins, and flukes, while their throat, underside, and majority of the ventral side of their flukes are primarily white. This sharp contrast in coloration, along with their countershaded skin, allows orcas to blend with the ocean water and remain hidden from their prey when hunting.

An orca’s conical-shaped head has a small rostrum and a single blowhole used for breathing. Their eyes are located on the side of their head, just below and in front of their white eye patch, and behind and above the corner of their mouth. Orcas have excellent eyesight both above and below the ocean surface. They also have small ears with no external flap, but a highly developed sense of hearing, and use echolocation for hunting prey. Their mouth contains 10-13 conical teeth on each upper and lower jaw that tear into chunks of food.

Orcas have two large, roundish forelimbs called pectoral fins that are used for steering and stopping, working in conjunction with their flukes. Their dorsal fin is the largest of all marine mammals, reaching up to six feet tall in males, with a grayish-white saddle patch on each side and behind it. This saddle patch varies from individual to individual in shape, size, color, and scarring. Orcas also have two tail flukes, each half containing no bone or cartilage, just dense, fibrous connective tissue, and measure up to nine feet across in males. Their brain can weigh up to 15 pounds, and they have a 3“-4” layer of insulating blubber beneath their skin.