Orcas of the Atlantic Ocean

Orcas of the Atlantic Ocean

Two killer whales swimming together in the Atlantic Ocean.

The Orca (Orcinus orca) or “Killer Whale” is the largest member of the dolphin family. They are the most widely distributed mammal on Earth besides humans and rats. Orcas are found in all of the world’s oceans.

Why Are They Called Killer Whales?

The story in Newfoundland goes that the name “killer whale” dates back to early 20th-century Antarctic explorers. Many of these explorers employed crews and dog teams from Newfoundland and Labrador. A group of sailors was standing on an ice pan when a pod of orcas attempted to tip the pan, which almost caused the sailors to slide into the water. The men hung on and later commented that they thought the whales were trying to kill them, hence the name “killer whales”. Orcas use this technique of tilting ice pans as a method of capturing seals and penguins. Even though people today believe that the orcas mistook these early Antarctic explorers for penguins, the name “killer whale” has stuck.

A wild killer whale poking her head out of the water.

History and Evolution

The orca has been a subject of art and curiosity for thousands of years. Pliny the Elder wrote the earliest known scientific description of the species. Ancient coastal peoples captured the animal in bone and soapstone carving thousands of years before Pliny.

The orca entered the fossil record about 8 million years ago. Its arrival on earth appears to have coincided with the disappearance of the giant shark Megalodon. Megalodon is the famous cousin of the great white shark. Megalodons were 12 m (40 ft) in length or longer. They undoubtedly would have preyed on young dolphins, including orcas, just as sharks do today. Scientists speculate that Megalodons lost their place on top of the marine food chain to the smarter and swifter orca. Orcas likely would not have tolerated predation on their calves by this ancient nemesis. In fact, today many dolphin species lose up to half of their calves to shark predation; and both popular and scientific literature include accounts of orcas killing large predatory sharks.


Orcas are versatile predators; they eat fish, sea turtles, birds, seals, sea lions, penguins, squid, sharks, and even other species of whales. Some orcas are known to be specialists, eating a diet that appears to be exclusively small sharks off New Zealand or salmon off British Columbia. Most orcas choose a wider variety of prey items.

The average orca eats around 500 pounds of food per day. Orcas hunt together in pods, where they herd fish or chase down larger animals similar to how wolves hunt.


Killer whales typically live for 50 years in the wild although at least one wild individual in the Pacific was known to live for 80 years. Males appear to live shorter lives than females.

Females become sexually mature between the ages of 10 and 15. Males are fully mature at age 25, and typically will not mate before the age of 20. Females are reproductive until about age 40.

Physical Appearance

Orcas are noted for their striking color pattern. Since they have no real natural enemies, the protective coloration found in most ocean animals has been lost in the killer whale. Their bodies are black with a white underside and eye patches, and there is a white to gray area behind the dorsal fin called the saddle. They have approximately 48 cone-shaped teeth, each about 4 cm (1 1/2 in) long.

A killer whale breaching.


Killer whales may reach a length of 9 m (30 ft) and weigh up to 7,256 kg (16,000 lbs). The dorsal fin may reach a height of 2 m (6 ft) in the adult male. The average adult male is 6-7 m (21-23 ft) in length and weighs around 4,535 kg (10,000 lbs).

Females are usually about 0.5 m (2 ft) smaller and weigh about 3,628 kg (8,000 lbs). Although the female dorsal fin is shorter and therefore appears to be less prominent to our human eyes, orca society revolves around breeding females and their young including the larger sons who accompany mom throughout their life.

Atlantic Migration and Distribution

Orcas do not follow a fixed annual migration pattern. They travel freely around the oceans and between hemispheres. They have been observed following the availability of food and avoiding harsh ice formations.

Some killer whales are referred to as resident whales, which tend to be quite vocal and predictable in their movements within their home range. Resident whales stay in one area and feed off salmon and other marine resources. Some of the most abundant salmon populations in the Atlantic Ocean are located off the coasts of Greenland and Newfoundland / Labrador.

Two killer whales swimming together off the coast.

Other orcas, termed transients, follow a nomadic lifestyle. They quietly swim hundreds or thousands of miles in pursuit of fish, seals, small whales, and larger whales. Many orcas around the Atlantic follow the transient lifestyle.

The orcas of Norway in the eastern part of the North Atlantic follow a transient lifestyle. They move from the fjords of Norway to the coast of Iceland. There are times when the fjords are filled with herring or salmon and the transients can be reliably sighted.

>> Best Places to See Killer Whales <<

Courtship and Reproduction

Orcas have a courtship ritual. Family groups come together and the large males from one group approach the females in the other group. Courtship can be an active affair with animals sometimes seen leaping out of the water together. Orcas will sometimes have scars caused by the teeth of other orcas. Like many other dolphins (and humans and chimps), orcas are also known for “sex play” when not involved with actual mating.

A pod of orcas swimming in the Atlantic Ocean.

Observations from captive animals have supplemented our knowledge of orcas. The gestation period of the killer whale is approximately 17 months. The breeding season appears to last all year, so births can occur at any time throughout the year. Females give birth to a single calf with approximately 3-5 years between births. When an orca is ready to give birth, it will sometimes spiral under the water’s surface to work with the force of water and gravity to expel the calf.

Newborn Calves

Calves are usually born fluke first as opposed to land animals which are typically born head first. The birth of a dolphin/orca calf occurs rapidly. This is necessary because the young must surface for its first breath very soon after the umbilical cord breaks, to avoid suffocation.

A newborn calf weighs approximately 70 kg (150 lbs) and measures 2 m (6 feet) long. The mother quickly guides the newborn to its first breath of air and swims alongside her calf protecting it from intruders and danger. The mother and other members of the pod are extremely protective of the calf. Nursing begins shortly after birth and continues for about one year. After approximately 2-1/2 months, the nursing periods become shorter and the calf starts receiving solid food from its mother.

Wild Orcas in Captivity

While orcas are most often associated with the Pacific, most animals in captivity have been captured from Atlantic populations near Iceland. As it became less acceptable to capture and enclose these large, fast-moving, wide-ranging whales, marine theme parks began attempting wild captures in more obscure portions of their range such as northern Russia. The Western world has largely abandoned the practice of collecting and keeping wild orcas. Russia and China still actively participate in the capture and sale of wild orcas today.


Declining food sources, entanglement, environmental toxins, and noise pollution are the biggest threats to orcas today. The decline in fish populations is a direct problem affecting resident whales that rely on them for food. In turn, fish feed the seals, sea lions, and penguins that transient orcas consume. When food supplies are limited, reproductive rates plummet and mortality increases.

Entanglement in fishing gear is a common risk to killer whales. Entangled whales may drag fishing gear for thousands of miles, or be unable to swim at all. Entanglement can lead to fatigue, malnutrition, injury, and death.

Environmental toxins enter the ocean through pesticide runoff, oil spills, sewage contamination, and runoff from wastewater treatment plants. Toxins climb up the food chain and collect in the bodies of large animals that live for decades. This resulting bioaccumulation has an adverse effect on the reproductive and immune systems of orcas. Oil spills directly impact prey species that orcas rely on for food.

Vessels as well as industrial and military activities cause noise pollution in the ocean. Orcas use sound for hunting, communication, and navigation. When noise is present, orcas call more loudly, which expends more energy. They also travel more and hunt less in the presence of noise and vessels.

A lone killer whale.


Orcas are protected under the Marine Mammal Protection Act of 1972, which prohibits harassment, capturing, hunting, killing, or collecting marine mammals in U.S. waters or by any Unites States citizen.

The Southern Resident Killer Whale is the only orca population listed as endangered, and thus has further protections through the Endangered Species Act. This population lives off of Alaska and the West Coast of the United States.