What is migration?
When most people think of migration, they only think of birds migrating south for the winter. There are however, tons of different species that take part in migration events for many different reasons. Animal migration occurs when individual animals move a relatively long distance, usually on a seasonal basis. Many different species take part in migration including birds, mammals, fish, reptiles, amphibians, insects, and crustaceans. There are multiple environmental factors that can trigger for the migration. Some of these include the local climate, the availability of food, what season it is, or mating reasons. To be considered a “true migration”, and not just a local dispersal or irruption, the movement of the animals should occur annually or seasonally. Examples of this include birds migrating from the Northern Hemisphere to the south for the winter or wildebeest migrating annually for seasonal grazing.
Migration is an adaptive response to certain seasonal or geographic variations of resources. The changes in seasons provides a drastic different in the duration and intensity of solar energy received in each hemisphere. It also allows the animals that migrate to take advantage of favorable food and weather conditions in different areas for different tine periods. Animals can travel hundreds to thousands of miles away from their current habitat during migrations.
How do the animals know where to go?
Migration of Red Crabs
Red is the most common color for Christmas Island Red Crabs but they can also be found in orange and very rarely purple. They are a large crabs, an adult crabs body shell can measure up to 116mm across. This body shell encloses their lungs and gills. The claws of these crabs are usually equal sizes however, they are able to regrow missing claws.
The Christmas Island Red Crab is a species of land crab that is native to Christmas Island and Cocos (Keeling) Islands which are located in the Indian Ocean. There were an estimated 43.7 million adult red crabs on Christmas Island alone, but this number dropped drastically after the yellow crazy ant was accidentally introduced. It is believed that these and have killed between 10–15 million crabs. Christmas Island red crabs are most known for their annual mass migration to the sea to lay their eggs in the ocean. The crabs only migrate during the rainy season, and if there is not enough rain, they will halt their migration.
The video below shows some great footage of the migration and explains a little more about it.