Animal migrations are one of nature’s most wonderful spectacles. Thousands of migrating animals carry out long journeys together to reach more favourable climates where they can feed and reproduce. Animal migration occurs on land, in the air and under water and is cyclical as the species return to their place of origin once the season has ended. These displacements also often bring drama as predators strike along the way.
One of the largest and most striking migratory species is salmon, whose life cycle continues to surprise those who study it. Salmon are born in freshwater rivers and months later migrate towards the sea, where they remain until they have reached sexual maturity (on average three years). They then begin the journey back to the waters where they were born. This journey is a spectacular odyssey as they must swim upstream against the current, overcome obstacles and avoid predators. Once they have returned to their place of origin, a mating ritual begins that usually lasts several hours while the female builds the nest where she will spawn.
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Whales, whose natural habitats are the cold waters of the planet’s polar regions, often travel thousands of miles each year in search of warm waters to give birth to their calves. The migration process of this species, which travels at 15 km per hour on average, has been documented by marine biologists. The migration begins between September and October and the first to set off on the journey are the mature whales. They are then followed by the pregnant females and finally by the younger whales. They stay in warm waters for three to four months and begin the return in March when the crustaceans on which they feed are more abundant in cold waters.
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Despite their fragility, millions of monarch butterflies migrate 4,000 km each year from the forests of southern Canada and the northern United States to reach Mexico. This movement southwards begins between August and October with the aim of mating in the warmer forests. They return north in spring. This phenomenon is repeated annually. It should be noted that although this species has a lifecycle of between eight and nine months (although there is a type of Monarch butterfly known as Methuselah which lives for only three to four months), migration is not interrupted as the offspring make the return journey.
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The massive migration of Alaskan seals to the warm waters of the South Pacific Ocean is led by the female of the species. Once they reach the warmer waters, the female seals give birth to their young. They then remain beside their pups for two or three months before embarking on the journey back north. On their return to the cold waters of Alaska, the females join the harem of one of the males to restart the reproductive cycle. It has been documented that some males do not migrate and instead wait for their females in Alaskan waters.
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The migration of African sardines is considered by scientists as the most important migration in terms of the numbers involved. This phenomenon takes place in South Africa each year during spring. The aim of the species is to reach warmer waters (18 to 20 degrees Celsius), to feed and reproduce. Researchers have documented that the shoals of migrating sardines can reach up to 20 km in length, 15 km in width and more than 50 metres in depth. The millions of sardines that make up the shoal travel 1,174 km from Cape Agulhas to the shores of Durban.
Canadian sandhill cranes
The sandhill crane, which inhabits in the wetlands of Alberta in Canada, makes an annual migration between November and December. It flies to a stopover in Nebraska in the United States and then onto Chihuhua in northern Mexico (3,600 km away) for breeding and feeding purposes. This species, like other large migrant species, makes the movement en masse. Flocks number about 600,000 individuals on average. This migration has become a source of entertainment for tourists on the banks of the Platte River and the Rowe Sanctuary. The female sandhill crane lays two eggs and the incubation period takes between 30 to 35 days.
Wildebeest migrate distances of more than 3,000 km in herds of up to a million. It is known as the Serengeti-Masai Mara migration (from Tanzania to Kenya). The peculiar thing about this migration is that it is done in a circle, as the wildebeest look for green pastures created by the rainy season. The migration begins in June and the herds face many predators (especially in the Mara River). They reach their objective in September and start out on the return journey in October. An estimated 400,000 wildebeest are born ever year. Herds of zebra are often seen looking for fresh food with the wildebeest.
African and Asian elephants migrate in family units (females and children) or in large groups that range from 10 to 70. They travel between 300 km to 500 km in search of food and water. Elephants are very sociable and the herd is led by the oldest female. This elephant will take charge of marking pathways and dealing with the security of the herd. When there is danger, older elephants protect the younger members. The male elephants travel alone or in the company of other males.
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Emperor Penguins inhabit the cold waters of Antarctica and migrate in large groups, travelling more than 70 km to breed. Once they have reached mainland breeding sites, where they congregate in their thousands, the penguins select a partner and remain with them for the rest of their life (20 years on average). This species mates in climates of up to 40 degrees below zero. Once the female has laid her eggs, the couple alternate brooding. They also take turns at returning to the Antarctic waters to feed.
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The Arctic Tern is a seabird that makes the longest migration of all animals. It makes a pole to pole round trip of more than 70,000 km to achieve two summers, one in the Greenland Sea and the other in the Weddell Sea in Antarctica. Arctic Terns are tiny birds, weighing just 100 grammes and they make use of wind currents to facilitate their journeys. They have a life cycle of about 35 years.