Around the world, millions of animals are on the move in migrations that will leave you awestruck. For example, six million antelope cross from South Sudan into Ethiopia during the seasonal Great Nile Migration.
And one million wildebeest make a risky dash across the Mara River each year, hoping they don’t end up in a crocodile’s jaws as they ford the waters from Tanzania to Kenya.
But there’s a lesser-known migration – and it’s actually the biggest in the world. Every day, 10 billion tonnes of marine animals move between the ocean’s twilight and sunlight zones in a phenomenon called the diel vertical migration (DVM).
During the daytime, many zooplankton (animal plankton that are the driving force for this migration), hide from predators in the twilight zone’s dark waters. Because photosynthesis can’t occur here, their main food source of phytoplankton (plant plankton) isn’t available.
Then, at night, the zooplankton rise towards the surface to feast on the phytoplankton, other zooplankton and marine snow that are abundant in the waters of the sunlight zone. By feeding at night, there’s less risk of being seen – and eaten – by much larger predators. Many other creatures in the food chain join the migration.
Top image: a herd of tiang undertake the Great Nile migration. Credit: Mike D. Kock/Getty Images
