Some species of birds, fish, mammals, and insects can gather in large flocks of millions to trillions of birds.
Red crab
During the rainy season, flocks of millions of red crabs on Christmas Island, Australia, migrate to the sea to start a new breeding season. The migratory journey of red crabs will start from the forests of Christmas Island to the Indian Ocean coast. The number of red crabs in migratory crab herds can range from 40 million to 120 million. During the red crab migration season, signs prohibiting roads for vehicles and pedestrians are placed in many places in the area.
In October-December every year, when it starts to rain, red crabs migrate on a large scale to the coast to reproduce. Each crab must cross a distance of 8 kilometers within 9 to 18 days. The reason they can travel such a long distance is because when the breeding season comes, crabs secrete a lot of crustacean hyperglycemic hormone (CHH) to help increase the amount of glucose in the blood, ensuring enough energy for the crabs. long journey. When reaching the coast, female crabs will mate with male crabs in burrows that have been dug by the male, and after mating, female crabs will continue to crawl out to sea to lay eggs. Contrary to other land crabs on the island, red crabs are the only crustaceans whose males accompany their females on their migration to the sea.
Wildebeest
This species of antelope can gather in large herds of up to tens of millions of animals. A huge herd of antelope can be more than 140 km long. However, today the number of wildebeest is not as large as before due to hunting, habitat loss and disease.
Every year, some populations of blue wildebeest in East Africa undertake a long-distance migration, seemingly timed to coincide with the rainy season and grass growth. Their migration timing during both the wet and dry seasons can vary significantly (monthly) from year to year. At the end of the rainy season (May or June in East Africa), wildebeest migrate from dry season areas when there is a shortage of water. When the rainy season started again (a few months later), they quickly returned to the same area. Factors considered to influence migration are food abundance, available surface water, predators and phosphorus content in grass.
Herring
Gathering in schools is a common characteristic of fish species. However, herring is the species with the largest number of fish concentrated in schools among fish species. According to researchers, the number of fish in a school of herring can reach tens of millions, covering tens of square kilometers. Fish live in large groups to limit the risk of being eaten or concentrated during spawning time.
Herring is a type of fish similar to apricot fish but larger, with greenish skin, small bones, long, thin body, and two equal jaws. Fish have small or missing teeth, thin round scales that fall off easily, some species have comb scales, and the fish's abdominal spine has serrated teeth. Herring have the habit of migrating in large flocks. Herring lives in surface water, usually has no hiding place, has an elongated body, normally developed even fins, a strong tail, and swims quickly.
In Vietnam, fishermen often call the herring species they catch by unique names. Accordingly, there are two types of herring: red herring and false herring. The herring is flat, has many blue-white scales, white meat, fragrant, fatty but has many bones. Mistaken herring is round, has less scales, and has more meat, but the meat is red and not as delicious as herring.
Krill shrimp
Krill shrimp are small crustaceans that live in large schools. The density of individuals in a herd can reach 10,000 - 30,000 individuals per cubic meter. They can be found in every ocean in the world, but the largest population of krill shrimp is found in Antarctic waters. The size of a giant krill shrimp colony is usually about 10 km long and 30 m deep.
Although krill shrimp are small, they are extremely important to the survival of the ocean and are concentrated in the largest numbers in Antarctic waters. Overexploitation of krill not only severely reduces ocean biodiversity, but also affects marine fish stocks and the world's fishing industry.
Although individual krill shrimp are small, unimpressive, and vulnerable in dangerous, predator-filled ocean environments, giant schools of krill shrimp are a vital link in the marine food chain. , converting plankton cells into energy suitable for many animals that rely on them to survive. The list of such animals is considerable, from tiny fish, to seabirds, to the largest fish alive today on earth: the blue whale. This giant fish can eat 2,500 kg of krill per day.
Locust
Swarms of millions of locusts are a nightmare for farmers. Many locust swarms even have trillions of locusts. One of the records for giant locust swarms was recorded in North America in 1875. The size of this locust swarm is estimated to be about 500,000 km2, equivalent to the area of California, USA. There are about 12.5 trillion locusts.
The record for the largest swarm in the animal world belongs to grasshoppers. In East Africa in early 2020, a cloud of desert locusts swept across the sky, spanning thousands of square kilometers. "It was like a black blanket covering the sky, so dense that it was difficult to see the clouds," described researcher Emily Kimathi at the Center for Insect Physiology and Ecology in Kenya.
200 billion is a staggering number, but data from the past shows that locust swarms can grow much larger under ideal environmental conditions. In 1875, a meteorologist named Albert Child was stunned to see grasshoppers streaking across the sky in a giant swarm that covered much of the western United States. The species is the Rocky Mountain grasshopper, and Albert estimates it covers an area of 512,800 square kilometers.
This historical event is today also known as "Albert's locust swarm". Based on meteorologist estimates, their number could be as high as 3.5 trillion. This is believed to be the largest number of animals in a herd that humans have ever recorded.
