The migrations they are movements of groups of living beings from one habitat to another. It is a survival mechanism that allows animals to avoid negative conditions in their habitat, such as extreme temperatures or food shortages.
The migrating animals They tend to do so on a regular basis, meaning that they make the same round trips at a certain time of the year (for example, in spring or fall). In other words, migration follows a pattern. For instance: loggerhead, dragonfly, plankton, salmon.
However, they can also occur permanent migrations.
When a group of animals is taken by man from their natural habitat to a new one, it is not considered migration, since it is not a natural process. In these cases it is called “introduction of foreign species”.
The migratory processes They are natural events that maintain balance in the ecosystems that participate in the process (the initial ecosystem, the intermediate ecosystems through which migrant groups pass and the ecosystem that receives them at the end of the journey).
On the contrary, the introduction of foreign species in a artificial it has both anticipated and unforeseen ecological impacts.
Biotic factors (animals that migrate) and abiotic factors that are used by animals, such as air currents or water, participate in migration.
Some abiotic factors can also be triggers for migrations, such as variations in light and temperature that occur with seasonal changes.
Examples of migrating animals
- Humpback whale (yubarta). Whale that transits all the oceans of the world, despite the great variations in temperature. During the winter they remain in tropical waters. Here they mate and give birth to their young. As temperatures rise, they move into polar waters where they feed. In other words, they move between feeding sites and breeding sites. They travel an average of 1.61 km per hour. These trips reach a distance of more than 17 thousand kilometers.
- Loggerhead. Turtle that lives in temperate seas, but migrates to tropical or subtropical waters in winter. They spend most of their time in the water and the female only goes up to the beach to spawn. They live up to 67 years. It is a large species, reaching 90 cm in length and an average weight of 130 kg. To carry out their migration, they use the currents of the North Pacific. They have one of the longest migration routes, compared to other marine animals, reaching more than 12 thousand kilometers.
- White stork. Large black and white bird. European groups migrate to Africa during the winter. It is striking that on this route they avoid crossing the Mediterranean Sea, so they make a detour towards the Strait of Gibraltar. This is because the thermal columns it uses to fly only form over land areas. Then it continues to India and the Arabian Peninsula.
- Canada goose. Bird that flies in groups forming a V. It has a wingspan of 1.5 meters and a weight of 14 kilos. Its body is gray in color but is characterized by a black head and neck, with a white spot on the cheeks. It lives in North America, in lakes, ponds, and rivers. Their migration occurs in search of warm climates and availability of food.
- Barn Swallow (Andorine). It is the swallow with the largest distribution in the world. Bird that inhabits Europe, Asia, Africa and America. It expands with humans because it uses human-built structures to build nests (reproduction). It lives in open areas such as pastures and meadows, avoiding dense vegetation, steep terrain and urban areas. When migrating, they also choose open areas and the proximity of water. They fly during the day, also during migrations.
- California Sea Lion. It is a marine mammal, in the same family as seals and walruses. During the mating season it is found on islands and the coast from southern California to southern Mexico, mainly on the San Miguel and San Nicolás islands. At the end of the mating season they migrate to the waters of Alaska where they feed, traveling more than eight thousand kilometers.
- Dragon-fly. It is a flying insect capable of transoceanic migrations. Mainly the species Pantala Flavescens performs the longest migration of all insects. The tour is back and forth between India and East Africa. The total distance traveled is approximately 15 thousand kilometers.
- Monarch butterfly. It has wings with orange and black patterns. Among insects, this butterfly performs the most extensive migration. This is because it has a much higher longevity than other butterflies, reaching 9 months. Between August and October, it migrates from Canada to Mexico, where it remains until March, when it returns north.
- Wildebeest. It is a ruminant with a very particular appearance, similar in bearing to a hair but with hooves and head more similar to those of a bull. They meet in small groups that in turn interact with each other, creating large conglomerations of individuals. Their migrations are motivated by the scarcity of food and water: they look for fresh grass with the change of season as well as rainwater. The movement of these animals is made spectacular by the intense sound and vibrations on the ground produced by their migrations. They make a circular trip around the Serengeti River.
- Shady shearwaters (dark shearwaters). Seabirds that live in the Atlantic, Pacific and Indian oceans. It is 45 cm long and with its wings spread over a meter wide. It is blackish brown in color. It can fly up to 910 kilometers per day. During the breeding season, it is found in the southern part of the Atlantic and Pacific oceans, on small islands around New Zealand or the Falkland Islands. At the end of that time (between March and May) they begin a circular route to the north. During summer and autumn it remains in the northern hemisphere.
- Plankton. They are microscopic organisms that float in water. The type of migration carried out by marine plankton is of much shorter periods and shorter distances than other migratory species. However, it is a significant and regular movement: at night it remains in shallow areas and during the day it descends 1,200 meters. This is because it needs the surface waters to feed itself, but it also needs the cold of the deep waters to lower its metabolism and thus save energy.
- American reindeer (caribou). It lives in the north of the American continent and when the temperature begins to rise they migrate towards the tundras that are even further north, until it begins to snow. In other words, they are always kept in cold climates but avoiding snowy seasons when food is scarcer. The females start the migration accompanied by the young before the Mays. Recently it has been observed that the return to the south is delayed, probably due to climate change.
- Salmon. Various species of salmon live in rivers during youth, then migrate to the sea in adult life. There they grow in size and mature sexually. Once they have matured, they return to the rivers to spawn. Unlike other species, salmon do not take advantage of currents for their second migration, but quite the opposite: they move upstream against the current.