[I] Migration is a natural phenomenon that has fascinated humans for centuries and is important to ecosystem health. [II] It is observed in species across the animal kingdom, from the tiniest insects to the gargantuan blue whale. [III] Every year, millions of animals set out on an epic journey searching for food, shelter, and mating opportunities. [IV]
The Great Migration
Between December and April, wildebeest migrate through the Serengeti Plains of Tanzania. In February, the female wildebeest bring forth more than 400,000 calves in a three-week period. In April, the rain stops, the plains become dry and the wildebeest population sets off in search of fresh grass. First, they head west, then north towards Kenya, then south back to the Serengeti where they began their journey. In total, it’s a return journey of about 1,000 miles, and it is taken by 1.7 million wildebeest.
The journey is necessary but dangerous. Facing not only the risks of starvation and drowning but the wildebeest must also look out for predators along the way. The stronger ones run on the outside of the herd while the young animals stay on the inside.
When wildebeest cross a river, they can look disorganised, but experts have shown that the herd are actually using something called ‘swarm intelligence’. This means that no one wildebeest is the leader but instead they explore and overcome obstacles as a group.
Multigenerational Relay
Monarch butterflies spend their summer in Canada and the northern USA where there are plenty of nectar plants and not many predators. However, they cannot survive the cold winters of the north. Thus, in September and October, they begin a long journey south of over 2,500 miles to Mexico via the southern USA.
When spring arrives, the monarchs start their return journey north; the population cycles through three to five generations to reach their destination. Along the way, females lay eggs on milkweed plants, which the caterpillars use for food after hatching. This new generation of butterflies complete the journey their great-great-great-grand-parents started. It is still a mystery to scientists how the new generations know where to go, but they appear to navigate using a combination of the Earth’s magnetic field and the position of the sun.
(Adapted from C-21 Smart & National Geographic)