Humpback and grey whales still migrate along the same routes used by their ancestors millions of years ago
- Baleen whales use the same migratory pathways as their ancestors
- Fossilised crustaceans revealed the related animals follow similar routes
- Pacific coast of Panama has served a meeting point for several whale subpopulations for at least 270,000 years
Whales use the same ocean highways as their ancestors millions of years ago.
The giant mammals migrate huge distances around the world over the course of the year to feed in cool waters while travelling south to breed in warmer regions.
Chemical evidence stored inside fossilised barnacles showed that the migrations have remained similar over millennia.
It is thought the movement patterns originated five million years ago when oceans began having wildly different properties depending on proximity to the equator.
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Pictured is a Pleistocene-aged fossil whale barnacle from the eastern Pacific Coast. Chemical evidence stored inside fossilised barnacles showed that the migrations have remained similar over millennia
Ancient barnacles hitched a ride on large baleen whales, a group which includes humpback and grey whales.
Study leader Larry Taylor, from the Smithsonian tropical research institute (STRI) and a doctoral student at the University of California, Berkeley, said: ‘Most modern [baleen] whales undertake annual migrations that allow them to feed in cool, seasonally productive, high-latitude waters in summer before returning to warm, tropical waters where they breed in winter.
‘In the northeast Pacific, migration routes span from breeding areas in Central America, Mexico, and Hawaii to feeding areas in the Gulf of Alaska, Bering Sea, and California Current system.’
He says the behaviour and traits of these animals is linked to the way oceans developed to have short-term fluctuations.
‘During the Pliocene and Pleistocene the world’s oceans became characterised by increasingly strong seasonal upwelling and patchy productivity distributions, and long-distance migrations are thought to have first become selectively favoured at this time,’ he added.
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Proving this hypothesis and determining a start point of whale migration habits remained difficult as little evidence remains of the long-ago giants.
He said: ‘Instead of looking for clues to migration patterns from the whale’s bones, we used hitch-hiking whale barnacles instead.’
Co-author Dr Aaron O’Dea added: ‘Whale barnacles are usually species specific – one species of barnacle on one type of whale.
‘This gives the barnacle several advantages – a safe surface to live on, a free ride to some of the richest waters in the world and a chance to meet up with others when the whales get together to mate.’
Ancient barnacles hitched a ride on large baleen whales – including humpback and grey whales
As whale barnacles grow, their shells record the conditions by taking up oxygen isotopes from the water.
By carefully reading the unique isotope signatures left in the shells, the barnacles can reveal the water bodies the barnacle passed through, helping reconstruct the whale’s movements over time.
The study, published in Proceedings of the National Academy of Sciences looked at a number of fossil and modern whale barnacles from the Pacific coast of Panama and California.
The study provided evidence that the oxygen isotope composition of modern whale barnacle shells reliably records migration pathways.
The analysis of fossil whale barnacle shells from three Pleistocene localities also showed they displayed isotope profiles similar to those of modern specimens.
Mr Taylor said: ‘The signals we found in the fossil barnacles showed us quite clearly that ancient humpback and grey whales were undertaking journeys very similar to those that these whales make today.
‘It seems like the summer-breeding and winter-feeding migrations have been an integral part of the way of life of these whales for hundreds of thousands of years.’
Co-author Associate Professor Seth Finnegan at UC Berkeley added: ‘We want to push the technique further back in time and across different whale populations.
‘Hunting for fossil whale barnacles is easier than whales, and they provide a wealth of information waiting to be uncovered.’
The findings also suggest the Pacific coast of Panama has served a meeting point for several whale subpopulations for at least 270,000 years, according to the authors.
HUMPBACK WHALE POPULATIONS AND ITS THREATS
Humpback whales live in oceans around the world. They travel incredible distances every year and have one of the longest migrations of any mammal on the planet.
Some populations swim 5,000 miles from tropical breeding grounds to colder, plentiful feeding grounds – this is why it is difficult to estimate population size, according to the NOAA.
Of the 14 distinct populations, 12 are estimated to number more than 2,000 humpback whales each and two are estimated to number fewer than 2,000.
Humpback whales live in oceans around the world. They travel incredible distances every year and have one of the longest migrations of any mammal on the planet
Some populations (such as those off eastern and western Australia) are believed to number in excess of 20,000 animals—a remarkable recovery given that the same populations were almost eradicated by whaling almost sixty years ago.
By contrast, the smallest known population is one which inhabits the Arabian Sea year-round, and may number as few as 80 individuals.
Threats to humpback whales include decline in food like Krill due to a combination of climate change and industrial-scale fishing.
Humpback whales can become entangled by many different gear types including moorings, traps, pots, or gillnets.
Once entangled, if they are able to move the gear, the whale may drag and swim with attached gear for long distances, ultimately resulting in fatigue, compromised feeding ability, or severe injury.
There is evidence to suggest that most humpback whales experience entanglement over the course of their lives, but are often able to shed the gear on their own.
Inadvertent vessel strikes can injure or kill humpback whales.
Humpback whales are vulnerable to vessel strikes throughout their range, but the risk is much higher in some coastal areas with heavy ship traffic.
Underwater noise threatens whale populations, interrupting their normal behaviour and driving them away from areas important to their survival.
Sound has been shown to increase stress hormones in their system and mask the natural sounds humpback whales require to communicate and locate prey
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