Longest Animal Migrations: Arctic Terns, Whales and Caribou

What counts as a migration?

A migration is a regular, usually seasonal movement between two areas, such as a breeding site and a feeding site, followed by a return. That rules out one-off wanderings, however far they go. Some migrations are completed by single animals many times in their lives; others, like those of some butterflies, are a relay in which no individual makes the whole trip.

Distances depend on how they are measured. A straight line between two points on a map is far shorter than the real, zigzagging route an animal flies or swims, so modern tracking studies, which record the actual path, often give much larger figures than older estimates.

1. Arctic tern: the longest migration on Earth

The Arctic tern (Sterna paradisaea) breeds around the Arctic, including Iceland, Greenland, Scandinavia, Britain and northern Canada, then flies to the edge of the Antarctic pack ice for the southern summer. By following summer at both ends of the world, it probably sees more daylight than any other animal.

In a 2010 study, tiny light-sensing tags weighing about 1.4 g (0.05 oz) showed that terns from Greenland and Iceland flew an average of 70,900 km (44,000 mi) a year, with a maximum of 81,600 km (50,700 mi). They did not fly straight: they followed S-shaped routes down the Atlantic that use prevailing winds. A later study of a tern from the Farne Islands off northeast England recorded about 96,000 km (60,000 mi) in ten months, crossing the Indian Ocean and reaching the South Pacific.

Arctic terns can live for more than 30 years, so the oldest birds may fly well over 2 million km (1.2 million mi) in a lifetime, about three round trips to the Moon. Learn how other birds compare in which bird has the longest migration?

2. Sooty shearwater: a figure eight across the Pacific

Sooty shearwaters that breed on islands off New Zealand make one of the longest migrations of any animal. A 2006 tracking study found that they fly a giant figure-eight loop across the entire Pacific Ocean, feeding off Japan, Alaska or California during the northern summer, and covering an average of about 64,000 km (40,000 mi) in roughly 200 days. Some birds have been estimated at up to 74,000 km (46,000 mi) in a year.

3. Bar-tailed godwit: the longest nonstop flight

The bar-tailed godwit (Limosa lapponica) holds the record for the longest nonstop flight of any bird. Godwits of the subspecies baueri breed in Alaska and fly straight across the Pacific to New Zealand and eastern Australia, without landing, eating or drinking. In 2007, a satellite-tagged female flew 11,680 km (7,260 mi) from Alaska to New Zealand in about eight days. In 2022, a five-month-old juvenile flew at least 13,560 km (8,430 mi) from Alaska to Tasmania in 11 days and 1 hour.

Before leaving, godwits store so much fat that it can make up more than half their body weight, and their digestive organs shrink to save weight. On the way north in spring they take a different route, stopping to refuel around the Yellow Sea, for a round trip of about 29,000 km (18,000 mi).

4. Gray whale: the longest regular mammal migration

The gray whale (Eschrichtius robustus) of the eastern North Pacific feeds in summer in the Bering, Chukchi and Beaufort seas, then swims south along the coast of North America to warm lagoons in Baja California, Mexico, where calves are born. The round trip covers about 16,000–22,000 km (10,000–13,700 mi), traveling day and night at an average of about 8 km/h (5 mph).

In 2011, a female from the small western population, tagged off Sakhalin Island, Russia, crossed the Pacific to Mexico and back, a journey of about 22,500 km (14,000 mi) in 172 days, one of the longest migrations recorded for any mammal. See how far do gray whales migrate?

5. Humpback whale: from polar seas to the tropics

The humpback whale (Megaptera novaeangliae) migrates between cold, food-rich polar waters and warm tropical breeding areas, and has been recorded traveling up to about 8,000 km (5,000 mi) in one direction. Humpbacks from the Antarctic Peninsula, for example, breed off Colombia and Costa Rica.

Researchers identify individual humpbacks from the black-and-white patterns on the underside of their tail flukes. In 2024, scientists reported a male photographed off the Pacific coast of Colombia and later off Zanzibar in the Indian Ocean, at least 13,000 km (8,000 mi) apart, the greatest distance yet recorded between sightings of the same humpback.

6. Leatherback sea turtle: crossing the Pacific

The leatherback sea turtle (Dermochelys coriacea), the largest living turtle, follows jellyfish across entire oceans. Leatherbacks nesting in Indonesian Papua cross the Pacific to feed off the coast of California and Oregon, and one tracked female swam about 20,000 km (12,400 mi) over 647 days, one of the longest journeys recorded for any reptile.

7. Caribou: the longest migration on land

Caribou, the North American name for reindeer (Rangifer tarandus), make the longest known land migrations. Each spring, herds such as the Porcupine herd of Alaska and Yukon walk from winter ranges in boreal forest to calving grounds on the Arctic coastal plain, and back again in autumn. A 2019 study comparing tracked land mammals worldwide found that caribou made the longest round-trip migrations, of more than 1,000 km (620 mi) a year, and counting all their wandering, some herds may cover several thousand kilometers in a year. Read more in how far do caribou migrate?

8. Wildebeest: the biggest migration on land

The Great Migration of East Africa is not the longest, but it is one of the largest. About 1.3 million blue wildebeest, along with hundreds of thousands of zebras and gazelles, follow the rains in a loop of roughly 800 km (500 mi) between Tanzania’s Serengeti and Kenya’s Maasai Mara. The details are in what is the Great Migration?

9. Butterflies and dragonflies: relays across continents

Insects migrate surprisingly far. The eastern population of the monarch butterfly flies up to about 4,000–4,800 km (2,500–3,000 mi) from Canada and the northern US to wintering forests in central Mexico. The butterflies that make the southward trip belong to a long-lived “super generation” that survives about eight months, while the return north is completed by their offspring over several generations.

The painted lady butterfly goes further still, with a yearly circuit of about 12,000–15,000 km (7,500–9,300 mi) between tropical Africa and northern Europe spread over up to six generations; see how far do painted ladies migrate? The globe skimmer dragonfly (Pantala flavescens) is thought to make a multigenerational circuit of up to about 18,000 km (11,200 mi) between India and East Africa, crossing the Indian Ocean.

10. European eel: a journey to the Sargasso Sea

The European eel (Anguilla anguilla) lives in rivers and coasts from Scandinavia to North Africa, but it breeds only in the Sargasso Sea, in the western Atlantic. Adult eels swim roughly 5,000–10,000 km (3,000–6,000 mi) to reach it, depending on where they start, and their tiny, leaf-shaped larvae drift back to Europe on ocean currents. Nobody had followed adults all the way until 2022, when scientists published the first tracks of satellite-tagged eels reaching the Sargasso Sea. The species is listed as Critically Endangered.

Other record-breaking travelers

• Northern elephant seals make two migrations a year between California’s beaches and feeding areas in the North Pacific, totaling roughly 18,000–21,000 km (11,000–13,000 mi) a year.
• Great white sharks can cross oceans: in 2003–2004, a female tagged in South Africa swam to Australia and back, more than 20,000 km (12,400 mi), in under nine months.
• Whale sharks have been tracked for more than 20,000 km (12,400 mi) across the Pacific over two to three years.

How scientists track migrations

For most of history, migrations were pieced together from sightings. Bird ringing, or banding, began in Denmark in 1899: a numbered metal ring on a bird’s leg tells where it was marked if it is found again.

Modern tracking is far more detailed. Light-level geolocators weighing as little as 1 g (0.04 oz) record day length and the times of sunrise and sunset, from which a bird’s position can be worked out once the tag is recovered. Satellite and GPS tags send locations in real time but are heavier, so they are used on larger animals such as godwits, whales and turtles. Whales and some sharks are also identified from photographs of their natural markings.

Insects are too small for most tags. Scientists study them with weather radar, which can detect swarms high in the air, and with chemical clues: the chemistry of a butterfly’s wings reflects the plants and water where it grew up, revealing its birthplace.

Longest migrations compared