Migration is a type of behaviour where animals travel from their native habitat to another location in search of food, better living conditions, and sometimes for mating purposes. Migration is different from emigration in the fact that emigration involves the permanent movement of animals into a different location from their native habitat and settling there, whereas migration is seasonal movement and involves a journey back home at the end of the migratory period. Species like amphibians, crustaceans, reptiles, Pisces, and mammals migrate to faraway places. They usually migrate in flocks and often travel through sea, air, and land to reach their desired destination.
Now that you know what is migration, let's know its reasons, types and also the cause of occurrence.
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One of the main reasons for animal migration is food. During the winter season, when the temperature is well below the freezing point, food becomes a scarce resource vital for survival. Animals living in these regions migrate to warmer places where food is abundant and more easily available.
Another major reason for animal migration is climate. Animals who are not naturally equipped to survive harsh winters migrate to warmer climates to survive. The Monarch butterfly cannot survive in freezing temperatures. Thus they migrate in large numbers from Canada, all the way to Mexico, and flock together for warmth. At the end of the winter season, they return to their habitat, laying eggs on milkweed plants along the way.
The final vital reason for animal migration is for reproductive purposes. Animals might migrate to find a suitable mate, give birth to young ones, or raise them. Salmon, a riverine fish, migrate to the oceans to feed and grow. After spending about seven years in the ocean, they return to the rivers to mate and reproduce.
Animal migration is probably one of the most fascinating and studied animal behaviours. When animals migrate from their native lands in search of food and safety, they must travel an enormous distance to reach their destination, which is a test of their endurance and fitness.
Types of Migration
Animals may be classified into two groups depending on their reasons for migration.
There may also be another classification of the type of migration depending on animal behaviour.
Complete Migration: Every individual of the migratory species migrates to a different terrain every year. Example- Arctic Tern
Partial Migration: Some individuals of the migratory species migrate, while others stay behind. Example- American Robin
Differential Migration: Species have different patterns of migration based on age or gender. Example- Male American Kestrels migrate a shorter distance than female American Kestrels.
Interruptive Migration: These species either do not migrate at all or migrate all at once when food runs out in their habitat. Example- Blue Jays
Concept of Migration in Animals
Since it is dangerous and energy-exhaustive for an animal to travel a very long distance, scientists have concluded that animals only migrate when the benefits of migration outweigh the dangers it might face en route( predators, lack of food on the way, etc.) to its destination.
Some migratory animals examples are:
Humpback whales migrate in the summers and travel towards the polar ice to feed on krills and small fishes, while in winter, they travel back to warmer waters.
Christmas Island red crabs live in the forest lifelong but migrate to the oceans to reproduce.
Longfin eels are oceanic animals. However, their young migrate to freshwater and live their entire lives there. Towards the end of their lives, they migrate back to the ocean to reproduce. This migration happens over many years.
The Canada goose migrates 1000 miles north in search of food in winter while travelling as far as Texas in the summers to breed.
Concept of Migration Birds
Birds native to the Northern Hemisphere tend to move northwards during spring to feed on the multiplying insect population, growing plants, and better nesting locations. With winter, the availability of food drops, and the birds again move southwards. Although climate may be a major motivating factor for migration, many birds can withstand harsh climates as long as there is an adequate food supply.
Some migratory animal examples are:
The Siberian crane, a critically endangered migratory species native to the Arctic tundra of eastern and western Russia, migrates to China, Iran, and India during the winter season.
The Ruby-throated Hummingbird migrates to the North from Central America during the breeding season. They travel for over 900 miles, of which they fly nonstop over the Gulf Of Mexico for 500 miles.
The Bar-tailed Godwit is one of the most common migratory birds name. It is native to Alaska and migrates down south to Australia and New Zealand. They cross the Pacific Ocean in a nonstop flight for over nine days.