The orca, or killer whale, is a globally distributed marine mammal recognized by its striking black-and-white coloration and imposing physical presence. As the ocean’s apex predator, it possesses a streamlined physique built for speed and power. Scientifically classified as Orcinus orca, the orca is the largest member of the oceanic dolphin family, Delphinidae. It dominates marine environments from the polar ice caps to the tropics.
Defining Adult Length and Weight
A distinct difference in size, known as sexual dimorphism, exists between male and female orcas. Adult males, or bulls, typically reach lengths between 20 and 26 feet, averaging 6 tons or more. The largest male recorded measured 32 feet long and weighed nearly 10 tons.
Female orcas, or cows, are noticeably smaller, generally reaching 16 to 23 feet in length. The average weight for an adult female falls within the range of 3 to 5 tons. This size difference is visually compounded by the male’s massive, upright dorsal fin, which can stand nearly six feet tall, while the female’s dorsal fin is shorter and more curved.
Growth From Birth to Maturity
Orca calves are large at birth, typically measuring seven to eight feet long and weighing 350 to 400 pounds. The gestation period lasts around 15 to 18 months, which contributes to the neonate’s size.
Growth continues rapidly, fueled by the mother’s milk. Females attain sexual maturity around age 15, and their physical growth slows significantly. Males mature much later, reaching sexual maturity closer to age 25. This prolonged development allows males to achieve their larger adult body size and characteristic immense dorsal fin.
Differences Among Orca Ecotypes
Orca measurements are not uniform globally because the species is divided into distinct populations, or ecotypes, adapted to specialized diets and environments. These ecotypes, such as Residents, Transients (or Bigg’s), and Offshores, display physical variations in body length and robustness linked to their primary food source and hunting strategies.
Transient orcas, which are mammal-eaters, tend to be physically larger than fish-eating Residents. This greater size is associated with a powerful build necessary for hunting and subduing large marine mammals. Conversely, Resident orcas, which specialize in fish, are typically slightly smaller and possess a less robust frame.
Size variation is even more pronounced among the Antarctic ecotypes, which are classified by different types (A, B1, B2, and C). The Type C, or Ross Sea orca, is generally considered the smallest ecotype, with males only reaching about 20 feet. In contrast, the Type A orcas, which primarily prey on minke whales, are among the largest. These size distinctions highlight how dietary specialization has led to measurable physical differences among global orca populations.
Contextualizing Orca Size
To contextualize the orca’s size, it is helpful to compare its dimensions to human objects and other marine giants. An adult male orca, up to 26 feet long and weighing 6 tons, is comparable in length and mass to a small school bus or a large moving van.
The orca easily outsizes the great white shark, which typically reaches 20 feet. However, the orca is not the largest cetacean in the ocean. Baleen whales dwarf the orca; humpback whales reach around 50 feet, and the colossal blue whale extends up to 100 feet in length. Even among toothed whales, the sperm whale can reach 60 feet, sometimes more than twice the size of an orca.