The orca, or killer whale, is the largest member of the oceanic dolphin family. These apex predators possess a robust physique, allowing them to thrive in oceans across the globe. Mature orcas often exceed 12,000 pounds and span lengths greater than 26 feet.
Defining the Maximum Size
The size of an adult orca varies significantly based on sex and population ecotype. A typical mature male measures between 20 and 26 feet (6 to 8 meters) long and weighs 12,000 pounds (5,400 kilograms) or more. Females are smaller, usually 18 to 22 feet (6 to 7 meters) in length and weighing 8,000 to 11,000 pounds (3,500 to 5,000 kilograms). The largest individuals belong to the Antarctic Type A ecotype.
The absolute maximum size recorded for orcas far exceeds these averages. The largest male ever reliably measured was 32 feet (9.8 meters) long, with an estimated weight over 22,000 pounds (10,000 kilograms). The largest female on record was 28 feet (8.5 meters) long, weighing approximately 16,500 pounds (7,500 kilograms).
Sexual Dimorphism in Orcas
Sexual dimorphism is noticeable between mature male and female orcas. Males are significantly larger and more robust than females, often weighing nearly twice as much as adult females. Their overall body girth is also considerably broader.
This size difference is most visible in the dorsal fin, which serves as a clear indicator of sex. The dorsal fin of a mature male is tall and triangular, standing straight up to six feet (1.8 meters), making it the largest dorsal fin of any cetacean. In contrast, the female’s dorsal fin is much smaller, generally less than four feet tall, and is moderately curved or falcate in shape.
Growth Rate and Development
The timeline for an orca to reach its full adult size begins with a large newborn calf. At birth, a calf is typically seven to eight feet (2 to 3 meters) long and weighs approximately 400 pounds (180 kilograms). Rapid initial growth is fueled by the mother’s rich milk. Calves typically nurse for one to two years, though they begin incorporating solid food into their diet around the age of one.
During the first year, a calf can quickly gain hundreds of pounds, sometimes doubling its birth weight. Females reach sexual maturity around 12 to 15 years of age, continuing to grow until they are physically mature. Males take longer to develop, reaching sexual maturity around age 15, but they may not achieve their maximum size until around 18 years of age or later.