“ For San Blas you will see the stork and if you don’t see it, snowy year ” or “ For San Juan the stork begins to fly ” are some examples of typical sayings that refer to the migration of, in this case, the storks, such as indicative of a specific time of year. Like all sayings that have their origin in popular knowledge, it is a very interesting idea, since these animal migrations are very common and many people carry them out, but do you know why they do it exactly? Apart from storks, do you know other animals that also migrate?
What is animal migration
In order to understand why animals migrate, you must first know what migration is. The migration of animals is neither more nor less than the movement of a population periodically from its original habitat to another where they settle for a certain period of time. These migrations are studied from ecology, biogeography or zoology.
These migrations are phenomena that occur in nature to maintain the ecological balance or balance of all the ecosystems that participate in this event, both the departure and arrival ecosystems as well as those intermediate ones through which these migrant individuals pass.
What is ecological balance? Discover the answer in this other article that we recommend.
The migration of animals usually lasts several days depending on the distance they have to travel and they are different between the different species that carry them out. For example:
- Birds are often helped by trade winds and other air currents.
- Amphibians or invertebrates also take advantage of water currents.
On the other hand, animal migration are not usually individual events, rather animals usually migrate in groups . However, what is really unknown even today is how the species of animals that migrate from one place to another orient themselves. In fact, there are various theories such as, in the case of birds, the orientation of the Sun and the stars. Theories that take the Earth’s magnetic field as a reference are also considered.
why do animals migrate
Once we know what migrations are, the big question comes. Why do animals migrate? It seems that this behavior is something instinctive in the species that perform it.
Migrations are linked to certain events to fulfill different purposes, but as a common denominator for all of them we find the main objective of all forms of life: survival .
The 3 fundamental objectives of migratory animals are the following:
The differences in temperature :between the different seasons of the year: this is perhaps the most well-known reason of all. Species migrate due to these temperature changes that become very low during the winter and, on the contrary, very high during the summer, so the species move away and ensure their ability to survive in other areas during these extreme periods.
Reproduction and foraging : It may not be so obvious, but many animals are forced to move away from their usual habitats to mate safely or to find food in other areas where competition is not as high.
Flee from their predators : again it is not one of the first reasons that comes to mind, but it is logical. The animals move away from those areas where they feel threatened by other species and seek new refuges where they can protect themselves.
examples of animals that migrate
There are many animals that migrate, although we always think of birds. But, apart from birds, what other animals tend to migrate? To the surprise of many, so do fish, invertebrates and mammals, for example. Animals migrate through the air, water, or land, depending on their habitat.
Next, we are going to delve a little deeper into each of the groups of animals that migrate and we will comment on some examples.
migrating birds
Birds are the migratory animals that generally travel the greatest distances during their migratory journey, such as shearwaters (seabirds that can fly up to 910 km a day), swallows or the little golden plover .
In addition, birds can be classified according to when they migrate, that is, what time of year they decide to move away from a specific site. Taking the Iberian Peninsula as a reference, we can distinguish between:
- Wintering birds : that flee from the cold of the north and spend the winter here on the peninsula, such as the common crane ( Grus grus ).
- Summer birds : By contrast, they flee the heat of Africa like the Barn Swallow ( Hirundo rustica ) and spend the summer here; or birds of passage.
- The white stork (Ciconia ciconia) : migrates to Africa in winter avoiding crossing the Mediterranean Sea, which is the most striking part of its migration period. The reason? It seems that the winds that are helped by what we discussed earlier only occur over land areas.
- The Canada goose (Branta canadensis) : one of the typical ones that form V groups in the skies during migration. This species prefers and seeks warm climates, as well as better availability of food sources.
fish that migrate
Some species of fish also happen to be migratory animals, the most famous being the Salmon ( Salmoninae) migration . Many species reproduce in fresh water, where the young of the fish develop and, once they reach adulthood, they migrate to the sea where they grow, feed and mature sexually. Finally they return to the rivers, which they cross against the current to reproduce in them.
Something paradoxically similar occurs with European and North American eels ((Anguilla anguilla) . In their adult state they live in the rivers, but they go to the Sargasso Sea during the reproductive season.
Other examples of species that migrate annually are:
- herring(Clupea harengus).
- Cod ( Gadus morhua).
- flounder (Pleuronectidae).
mammals that migrate
Some well-known examples of migratory mammals include the following, which migrate to find food sources and water holes to survive.
- The NU( Connochaetes).
- The elephant ( Elephantidae). Feel free to read Why Elephants Are Endangered .
- The zebra ( Equus zebra ).
- The caribou ((Rangifer tarandus).
- The antelope ( Antelope cervicapra). Check here Why the saiga antelope is in danger of extinction .
Another example is that of seals, the California sea lion, or whales , such as the humpback whale ( Megaptera novaeangliae ), the southern right whale ( Eubalaena australis ), or the gray whale ( Eschrichtius robustus ). These whales can travel up to 20,000 kilometers during their migrations between their feeding and breeding sites. It should be noted that both birds, fish and mammals migrate to warm places most of the time.
Reptiles and amphibians that migrate
Looking at the examples of reptiles, you are probably wondering which animals migrate. In that case, we bring you this list where we can highlight the following species of sea turtles as migrating reptiles:
- the green turtle(Chelonia mydas) : lives on the coasts near Brazil, but travels long distances to spawn on the beaches of Ascension Island (in the South Atlantic Ocean). These hatchlings quickly go to the sea and over time, they appear on these Brazilian coasts where the adult specimens live and feed.
- leatherback sea turtle (Dermochelys coriacea). In fact, it is the one that practices the longest migration, since it travels more than 4,831 km from its nesting beaches.
- Other examples of turtles: such as the loggerhead sea turtle (Tortuga babaua) , the Kemp’s ridley sea turtle (Lepidochelys kempii) , the olive ridley sea turtle(Lepidochelys olivacea). Check out this article on Endangered Turtles for more information on the subject.
On the other hand, in terms of migrating amphibians we can find:
- The newt ( Pleurodelinae).
- The toad ( Bufonidae). Find out the difference between toad and frog in this post.
- The frog (Anura).
- The salamander ( Salamandra salamandra). Are salamanders poisonous?
Their migrations are annual and of few kilometers. In these cases, the migration occurs from those places where they hibernate during the winter to the rivers or ponds where they reproduce later.
invertebrates that migrate
Although we tend to forget about them, invertebrate animals also carry out migrations related to the search for food and the reproductive season.
A particular case is that of plankton (Plankton) , which perform daily “vertical” migrations. During the night the plankton is found in the most superficial layers of the water of the seas and oceans where it feeds and with the arrival of the day it descends up to 1,200 meters to flee from its predators and reduce its metabolism due to the lower temperature of the waters deeper, saving energy.
What animals migrate that are invertebrates? To our surprise, there are quite a few like:
- Crabs ( Brachyura ) : are other migratory animals that move to salty waters to lay their eggs, traveling distances of up to 240 kilometers.
- lobsters (Palinurus elephas): known for the great damage they cause to many crops in their path.
- Butterflies ( Lepidoptera ) : like the monarch butterfly ( Danaus plexippus ), which you can see in the image below, whose migration lasts longer than the life of any other species of butterfly (it can live up to 9 months) and which leads them to travel more than 5,000 kilometers from the northern United States and Canada to Mexico and California. Migration begins between August and October and they remain at their destination until March, when they return north. They are thus one of the few insects that can make transatlantic voyages. Do not hesitate to read this post about The Monarch Butterfly Migration where we explain everything in more detail.
- Dragonflies ( Anisoptera) : Belonging to the Libellula and Sympetrum genera , dragonflies are the last migratory animals on our list. The migration of animals like them is carried out in massive groups of individuals. Pantala flavescens stands out with the longest transatlantic migratory journeys of all insects (longer than the monarch butterfly). Travel between India and North Africa, round trip, traveling up to 15,000 kilometers.