Whales can migrate over such long distances to find breeding and feeding areas, as well as to avoid cold waters during winter.
Whales have developed a wide range of anatomical features that allow them to undertake incredible migrations over very long distances. Firstly, their streamlined bodies reduce water resistance, which saves energy for these marathon journeys. Their powerful flippers and highly developed horizontal tail fin provide them with propulsion and stability, making it easier to swim thousands of kilometers. They also have a thick layer of fat, called blubber, that stores the energy needed to travel far without eating for long periods. Finally, their ability to hold their breath for very long periods, thanks to adapted lungs and muscles, gives them the advantage of covering great distances without constantly surfacing. These adaptations partly explain their extraordinary endurance.
Whales primarily migrate to meet essential biological needs such as reproduction and calving. They alternate between nutrient-rich feeding areas in cold waters and warmer waters that are more conducive to giving birth. Females, in particular, prefer these warm waters where their calves benefit from a more welcoming temperature and easier monitoring against predators. These long journeys also facilitate encounters between males and females to ensure reproduction at regular intervals. This migratory strategy optimizes the survival chances of the young and thus perpetuates the population in the long term.
Whales spend a good part of the year in polar or temperate regions, where they find plenty of food, primarily krill and small fish. However, these food-rich areas are not ideal for giving birth and nursing their young, as the waters are cold and predators are numerous. As a result, to ensure the survival of their babies, whales migrate to warmer waters, usually in the tropics. They travel thousands of kilometers to arrive in safer and more comfortable places where their calves will be born. The problem is that once they reach these breeding grounds, whales hardly eat for several months and live off their fat reserves built up during the period of abundance. This explains why the annual migration cycles are closely linked to the times of food abundance and reproduction.
Whales often take advantage of ocean currents to migrate without too much fatigue. These true "highways of the seas" allow them to save energy during their long journeys. Water temperatures also influence their routes: they generally prefer warmer waters to give birth to their young and colder waters when they are looking for food-rich areas. Additionally, seasonal variations and climate changes affect the abundance of plankton and small fish that they feed on, thus prompting whales to travel to where environmental conditions are most favorable for them.
Whales can navigate using several natural tricks. They notably use the Earth's magnetic field, a kind of built-in compass, to determine their position and stay on course over very long distances. Some species rely on the position of the sun or stars as visual landmarks. Others memorize the underwater landscape: shapes of coastlines, underwater mountains, or variations in the seabed serve as familiar reference points. Whales also use their exceptional hearing to identify specific sounds from particular geographic areas, such as the sounds of waves against an unusual shore. All of this combined allows them to navigate accurately during journeys of thousands of kilometers each year.
Some whales, such as the gray whale, undertake annual migration journeys exceeding 20,000 kilometers round trip, making them part of the longest migrations of any mammal.
Whales can sleep while swimming. To avoid drowning, their brain rests by alternating between each hemisphere, allowing the animal to continue breathing regularly while moving forward.
During their long migrations, whales use various means to navigate, including Earth's magnetic fields, the position of the sun, stars, and even underwater topography as reference points.
The blue whale holds the record for the largest animal ever to have existed on Earth, even surpassing dinosaurs in size, with a length of up to 30 meters and a weight of up to 150 tons.
Whales likely use a combination of magnetic sensitivity, visual memory of coastal and underwater landmarks, as well as acoustic perception, allowing them to interpret sound signals over vast distances.
They primarily migrate to meet specific biological needs. Cold areas, rich in food, are suitable for their intensive feeding in summer, while they prefer warm seas, which are safer and conducive to raising young and breeding during winter.
During their long migrations, whales may encounter various dangers such as collisions with ships, acoustic pollution from human activities, accidental fishing, and even disruptions or changes to their routes due to climate change.
The humpback whale generally holds the record for the longest migrations, traveling up to about 25,000 kilometers round trip each year, often between its breeding grounds and feeding areas.
The average migration speed of whales varies by species, but it generally ranges from 5 to 15 km/h. This moderate speed allows them to conserve their energy over the thousands of kilometers traveled.
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