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The toughest animal migrations on the planet

The toughest animal migrations on the planet

By Joe Riis

Numerous species, from butterflies to caribou, face incredibly long and challenging walks. According to Jamie Gillooly, a biologist at the University of Florida, birds are probably the ones that face the most impressive migrations, both in terms of distance and For example, waders and passerines reduce the size of their digestive organs before and during migrations to lighten their load. Once the migration is over, they grow back, says Gillooly, who recently co-authored a study on body mass and migration with Princeton University's Andrew Hein. It is led by the tiny Arctic tern, which flies "from the Arctic to the Antarctic and vice versa," says Gillooly. On its tortuous route, this bird weighing just over 100 grams, travels about 71,000 kilometers. Yes, you read it right. In fact, thanks to a recent follow-up study, it is estimated that throughout its entire life, the Arctic tern migrates approximately a distance of 2.4 million kilometers - which is equivalent to three round trips to the Moon! –.Hugh Dingle, author of the bookMigrations: The Biology of Life on the Move, explains that the terns perform this feat in a matter of days, but "stop and feed during the trip." Good thing Carsten Egevang, lead author of the study on the matter, adds that these birds take various detours on their way north in spring, going from Antarctica and passing through Africa and South America until finally reaching the Arctic. But terns remain an enigma for researchers, as the reason they travel so far is unknown. In the category of the most impressive non-stop journeys, the clear winner is the colipint marlin. Tracking these small long-beaked waders on their flight from New Zealand to northern China found that they were not stopping to feed, drink or rest, says Gillooly. A tagged colipint needle traveled 11,500 kilometers in a single trip. non-stop from Alaska to New Zealand. This is the longest non-stop flight ever recorded. In addition, the bird even "slept" during the trip by turning off one half of its brain each time. "The only times they have to consume a lot of energy is in the areas of equatorial calm", a region of the Pacific around Ecuador with calm air and unpredictable weather, adds Dingle. "If not, they follow the winds and make the trip in two or three days." In fact, this tailed needle consumed all the accumulated fat deposits during its marathon journey: more than 50% of its body weight.
The water!

But if what we are talking about is migration by number of animals, sardines take the cake. Every year a gigantic group of sardines roam the waters of the Indian Ocean in search of warmer waters. During the "Sardine Run" - the name by which it is popularly known - they face a dangerous 1,500 kilometer journey along the coasts of South Africa.

Banks have been registered that reach 15 kilometers in length and between 30 and 60 meters deep. In fact, their magnitude is such that they can be observed from space satellites.

And of course, this massive migration also attracts various predators: dolphins, sharks, seagulls, cormorants and even sea lions are invited to this huge free fish buffet.

Extraordinary insects

Monarch butterflies can boast of being the stars among migrating insects, covering nearly 5,000 kilometers in their migrations, despite the drastic reduction in their migrations.

But Dingle also talks about cornleaf aphids, which he calls "wandering underdogs." This species is indigenous to the United States and Canada, and is normally found in cornfields, hence its name. They use their jaws to pierce the plant and extract the sap, from which they obtain the necessary food.

Despite their size - about 2 millimeters long - these insects travel approximately 1,000 kilometers from Texas to Illinois in search of food, attracted by the light yellow color of the new plants.

"They have to reach a goal: new growing plants," says Dingle.

These bugs counteract their slim chances - since they are the favorite prey for birds and other animals - creating "hundreds and hundreds of aphids," he adds.

In addition, the dry weather favors them, as it prevents the development of pathogens that can be deadly for corn leaf aphids.

What about mammals?

But even the migrations of large mammals can go unnoticed. In fact, it was only recently that mule deer were found to migrate approximately 150 miles through Wyoming, traversing highways, fences and rivers.

Caribou in Arctic regions move from boreal forests to tundras and from tundras back to boreal forests each year, Dingle says. Once they reach their destination, they spend several months feeding on pastures, consuming up to five kilograms a day.

In addition, it is the female caribou that start the migration route, and weeks later the males and the young follow them. Although their journey is not that long when compared to other migrants - approximately 1,000 kilometers - it is a difficult journey as walking consumes more energy than flying or swimming.

After all, hoofed mammals cannot propel themselves with the wind.

And finally…

It is also necessary to add that the difficulty of animal migrations is often overestimated by us humans, says Dingle. Most species have adapted well to their lifestyle.

Actually, for most animals, the hardest part is reaching adulthood, he says.

So whether or not it is "arduous" depends on the eye - or the hoof, wing or fin - of who looks.

Ecoportal.net National Geographich http://www.nationalgeographic.com.es/


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