Extraordinary Animal Migrations and How Scientists Tracked Them

In October 2022, a young bar-tailed godwit known as B6 flew from Alaska to Tasmania without landing. A solar-powered satellite transmitter on its back recorded the southbound flight of about 8,425 miles in 11 days. The endpoint was especially telling. Many of the birds nesting in Alaska head to New Zealand, but this juvenile turned toward Australia.

The light logger carried by each bird in a 2010 study weighed only 1.4 grams. Its readings let scientists estimate location from daylight and piece together a year’s travel. The longest trip measured in the study was more than 50,000 miles, including travel within the Southern Ocean. The birds also took different routes going north and south.

A female fitted with a satellite tag off Sakhalin Island, Russia, crossed the North Pacific and visited three gray whale breeding areas off Baja California. The tag kept working as she returned to Sakhalin the following spring. Researchers estimated the full round trip at about 14,000 miles, an exceptional journey even for a gray whale.

After nesting in Papua, Indonesia, a leatherback crossed the Pacific to feeding waters off Oregon and Washington. Her satellite-linked transmitter returned locations for 647 days. Taken together, those points gave a minimum of about 12,800 miles for the whole tracking period, which included travel after she left the North American coast.

GPS collars on eight female Burchell’s zebras revealed a migration between the Chobe River floodplain and Nxai Pan National Park in Botswana. All eight crossed the river and headed south. The two seasonal ranges are about 310 miles apart when measured as a straight-line round trip. The return route was less direct, so the zebras traveled farther.

In a 2019 comparison of land migrations, scientists put the Porcupine caribou herd’s round trip at about 840 miles by measuring the straight-line distance between seasonal ranges and counting the trip back. Adding the distances between GPS fixes in newer studies can tell you more about how far caribou actually walk over a year.

To find out where the monarchs wintering in central Mexico had grown up, scientists compared chemical signatures in the butterflies’ wings with patterns across the summer breeding range. Most of the 597 butterflies they sampled pointed to the U.S. Midwest. Wing chemistry can connect a winter colony to a broad region even if nobody tagged the individual insects.

In 2018 and 2019, researchers fitted 26 European eels from the Azores with pop-up satellite tags. Five tags surfaced within the boundaries of the Sargasso Sea. The researchers located one eel within the presumed spawning area. The tags gave scientists direct evidence of adults reaching the region where they had previously found larvae.

A pop-up satellite tag documented the outward leg of a shark named Nicole’s journey from South Africa to Western Australia. The tag was gone by the time she returned. Researchers matched notches in her dorsal fin and markings on her side to earlier photographs, confirming a round trip of more than 12,400 miles in just under nine months.

Globe skimmer dragonfly Where had the dragonflies passing through the Maldives grown up? Researchers tested the hydrogen in the wings of 49 migrants, comparing it with geographic patterns in rainfall. Northern parts of the Indian subcontinent were the most likely source. The result points to a journey over the ocean and gives an origin region, though it leaves the exact flight path unknown.

Two photographs of the underside of a humpback’s tail connected sightings off Brazil and Madagascar a little over two years apart. The shortest practical route between the two places was more than 6,000 miles. Photographs established the same whale reached two distant breeding areas, leaving the route and any stops she made in between open.

White-eared kob Counting from the air and following GPS collars revealed different parts of the Great Nile Migration. A survey released in 2024 estimated around six million antelope across four species, most of them white-eared kob. Later maps showed seasonal routes of white-eared kob and tiang across South Sudan and identified Ethiopia’s Gambella National Park as a dry-season refuge for some kob.

Light-sensitive loggers revealed that three great snipes leaving their Swedish breeding area flew roughly 2,900 to 4,200 miles nonstop to tropical Africa. They passed over stretches of land suitable for a rest. The surprise was how much time they stayed in the air when they could have landed.

Satellite tracking traced this hawk’s southbound migration to Argentina from breeding sites as far north as Canada. Birds from different parts of North America converged in eastern Mexico and used a much narrower route farther south. Individual tracks showed where some hawks lingered for days or weeks before moving on.