Animal migration

Many animals go on long trips.

They move to find food.

Some go to find a mate.

They may also go to stay warm.

Some birds fly very far.

The Arctic tern flies the most. It goes from the top to the bottom of the world.

Scientists track these trips. They use small tools to follow them. It is a big journey!

Many animals go on long trips. We call this animal migration.

Animals move for many reasons. They may look for food. They may move to find a mate. Some move to find a better home.

Some trips happen every year. This is seasonal migration. Birds often fly south to stay warm in winter.

The Arctic tern flies the longest way. It flies from the Arctic to the Antarctic and back.

Other animals move with the tides. Tides are the rising and falling of the sea. Crabs and small fish move with these waters to find food.

In Africa, many animals move together. This is a mass migration. One million wildebeest move in a big circle.

Scientists study these trips. They use tags to track animals. Some tags use GPS. This helps show where animals go.

Animal migration is a very common way that living things move. It involves animals traveling long distances, usually at the same time every year. This movement happens in almost every major animal group. You can see it in birds, mammals, fish, and even insects. Some animals move because the local weather changes. Others move to find enough food or to find a mate. For a trip to be called a true migration, it must be a regular seasonal event.

There are many different ways these trips work. Some animals follow a seasonal pattern to find better habitats. For example, many birds fly to warmer places to escape the cold winter. Some fish, like the Pacific salmon, swim upstream to reproduce. Other animals use the tides to move between different areas. Crabs and small fish move in and out of the intertidal zone as the water rises and falls. This helps them find nutrients or stay safe from predators.

Scientists have studied these patterns for a long time. In the past, people used folklore to explain why animals appeared or vanished. They once thought barnacle geese grew from goose barnacles! Today, researchers use much better tools to track movements. They used to use simple identification tags like bird rings. Now, they use electronic devices like radio-tracking collars. Some even use GPS or Argos Doppler tags to find exact locations.

Different species show us amazing numbers and distances. The Arctic tern has the longest journey of any bird. It flies from the Arctic to the Antarctic and back every single year. Reindeer also have one of the longest land trips, traveling 5,000 kilometers in North America. In Africa, the Serengeti features a massive movement of 1.7 million wildebeest. Even insects like the globe skimmer dragonfly cross oceans between India and Africa.

Migration is a way for life to stay connected to what it needs. Just like you might move to a new room to find your toys, animals move to find survival. Some migrations are obligate, meaning the animal must make the trip. Others are facultative, which means the animal can choose to go or stay. Even butterflies like the monarch participate in a relay. No single butterfly finishes the whole trip; instead, many generations continue the journey together.

Animal migration is the relatively long-distance movement of individual animals. This behavior usually occurs on a seasonal basis. It is the most common form of migration found in ecology. You can find this phenomenon in all major animal groups. This includes birds, mammals, fish, reptiles, amphibians, insects, and crustaceans. Migration is not just a local dispersal or a sudden movement called an irruption. To be a true migration, the movement must be an annual or seasonal occurrence. It can also be a major habitat change that is part of an animal's life.

Zoologists study migration through several different concepts. One common definition comes from the zoologist J. S. Kennedy. He suggested that migration includes four related ideas. First, it involves persistent straight movement. Second, it is the relocation of an individual on a scale larger than daily activities. Third, it involves seasonal to-and-fro movement of a population between two areas. Finally, it includes movement that leads to the redistribution of individuals within a population. Scientists also distinguish between obligate and facultative migration. Obligate migration means the individuals must migrate to survive. Facultative migration means individuals can choose whether or not to migrate.

Different types of migration are driven by different natural cycles. Seasonal migration happens when species move between habitats during the year. This is often caused by changes in resource availability. Temperature is another major driving factor for seasonal movement. Many birds migrate to warmer locations to escape poor winter conditions. Some species, like Pacific salmon, migrate specifically to reproduce. They swim upstream to mate and then return to the ocean. Other animals use circadian migration. This relies on circadian rhythms, which are internal biological clocks. Birds use these daily and annual rhythms to regulate their orientation in time and space.

Other animals use the movement of water to guide their journeys. Tidal migration involves using tides to move between habitats. This helps organisms find food or mates. Tides can carry organisms horizontally or vertically. This movement can span from a few nanometres to thousands of kilometres. Many species move in and out of the intertidal zone during twelve-hour tidal cycles. Crabs, nematodes, and small fish often use these zones because they are rich in nutrients. During low tide, smaller or younger species might emerge to forage in shallow water. During high tide, larger species may be found in the deeper water.

Each animal group has unique migratory strategies and distances. About 1,800 of the 10,000 bird species migrate long distances every year. The Arctic tern holds the record for the longest bird migration. It flies from the Arctic to the Antarctic and back each year. This journey covers at least 70,000 kilometres. In the insect world, the globe skimmer dragonfly makes the longest ocean crossing. It travels between India and Africa. Some butterflies, like the monarch, use a generational strategy. No single individual completes the entire migration. Instead, successive generations continue the journey through mating and reproduction.

Mammals also participate in massive, coordinated movements. The Serengeti features a "great migration" in Africa. This is an annual circular pattern of movement. It includes approximately 1.7 million wildebeest and hundreds of thousands of other animals. These include gazelles and zebra. Some mammals, like reindeer, have very long terrestrial migrations. In North America, they can travel up to 5,000 kilometres per year. Grey wolves also move great distances over a year. One recorded grey wolf covered a cumulative annual distance of 11,200 kilometres.

Scientists use many tools to track these complex movements. In the past, they used traditional identification tags like bird rings. These were recovered later, but they did not show the actual route. Modern researchers now use electronic tracking devices. Radio-tracking collars can be followed by hand, in vehicles, or in aircraft. GPS tracking allows for very accurate position broadcasts at regular intervals. Another option is the Argos Doppler tag, also called a Platform Transmitter Terminal. This sends data to polar-orbiting satellites. By using the Doppler shift, scientists can estimate an animal's location at a lower cost and weight.