Animal migration

Animal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migration in ecology. It is found in all major animal groups, including birds, mammals, fish, reptiles, amphibians, insects, and crustaceans. The trigger for the migration may be local climate, local availability of food, the season of the year or for mating reasons. To be counted as a true migration, and not just a local dispersal or irruption, the movement of the animals should be an annual or seasonal occurrence, such as Northern Hemisphere birds migrating south for the winter; wildebeest migrating annually for seasonal grazing; or a major habitat change as part of their life, such as young Atlantic salmon or Sea lamprey leaving the river of their birth when they have reached a few inches in size.Migratory behavior is persistent and straightened out movement effected by the animal’s own locomotory exertions or by its active embarkation upon a vehicle. It depends on some temporary inhibition of station keeping responses but promotes their eventual disinhibition and recurrence. Animal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migration in ecology. It is found in all major animal groups, including birds, mammals, fish, reptiles, amphibians, insects, and crustaceans. The trigger for the migration may be local climate, local availability of food, the season of the year or for mating reasons. To be counted as a true migration, and not just a local dispersal or irruption, the movement of the animals should be an annual or seasonal occurrence, such as Northern Hemisphere birds migrating south for the winter; wildebeest migrating annually for seasonal grazing; or a major habitat change as part of their life, such as young Atlantic salmon or Sea lamprey leaving the river of their birth when they have reached a few inches in size. migration can take very different forms in different species, and as such there is no simple accepted definition of migration. One of the most commonly used definitions, proposed by Kennedy is Migration encompasses four related concepts: persistent straight movement; relocation of an individual on a greater scale (both spatially and temporally) than its normal daily activities; seasonal to-and-fro movement of a population between two areas; and movement leading to the redistribution of individuals within a population. Migration can be either obligate, meaning individuals must migrate, or facultative, meaning individuals can 'choose' to migrate or not. Within a migratory species or even within a single population, often not all individuals migrate. Complete migration is when all individuals migrate, partial migration is when some individuals migrate while others do not, and differential migration is when the difference between migratory and non-migratory individuals is based on age or sex (for example). While most migratory movements occur on an annual cycle, some daily movements are also referred to as migration. Many aquatic animals make a Diel vertical migration, travelling a few hundred meters up and down the water column, while some jellyfish make daily horizontal migrations, traveling a few hundred meters across a lake. Irregular (non-cyclical) migrations such as irruptions can occur under pressure of famine, overpopulation of a locality, or some more obscure influence. Seasonal migration is the movement of various species from one habitat to another during the year. Resource availability changes depending on seasonal fluctuations, which influence migration patterns. Different species also might migrate for reproductive purposes. Pacific salmon is an example of a species migrating to reproduce. Every year pacific salmon travel upstream to mate and then return to the ocean. Temperature is also a driving factor of migration that is dependent on the time of year. Many species, especially birds, migrate to warmer locations during the winter to escape poor environmental conditions. Circadian Migration is where birds utilize circadian rhythm (CR) to regulate migration in both the fall and the spring. In circadian migration clocks of both circadian (daily) and circannual (annual) patterns are utilized to determine the birds’ orientation in both time and space as they migrate from one destination to the next. This type of migration is advantageous in birds that during the winter remain close to the equator, and also allows the monitoring of the auditory and spatial memory of the birds’ brain to remember an optimal site of migration. These birds also have timing mechanisms that provide avians with the distance required to travel in order to reach their destination. To regulate the migration patterns of these birds, the mammalian circadian clock is utilized. This clock allows the avians to determine when the appropriate time is to migrate, which location will best help the birds regulate their metabolism, and whether land or water travel will be most advantageous for these migrating species. Tidal Migration is the use of tides by organisms to move periodically from one habitat to another. This type of migration is often used in order to find food or mates. Tides can carry organisms horizontally and vertically for as little as a few nanometers to even thousands of kilometers. The most common form of tidal migration is to and from Intertidal zone during daily tidal cycles. These zones are often populated by many different species and are nutrient rich. Organisms like crabs, nematodes, small fish, corals, and other species cycle to these areas as the tides rise and fall typically about every twelve hours. The cycle movements are associated with foraging of marine and bird species. Typically, during low tide smaller or younger species will emerge to forage because they can survive in the shallower water and have less chance of being preyed upon. During high tide, larger species can be found due to the deeper water and nutrient upwelling from the tidal movements.Tidal migration is often facilitated by Ocean current. The currents carry organisms at a faster speed than if they were to just swim. These long-distance currents often bring organisms to breeding grounds and nurseries. Breeding ground often end up being near or in intertidal zones. This occurs due to the food and nutrient richness of these areas, it makes it an ideal place for offspring to grow. Although migration and animal dispersal are similar in that animals are moving from one less advantageous area to an area with more advantages, there are many differences between the two. In migration, an animal is moving under some form of a cycle or pattern, like seasonal, tidal, or even circadian. This can be seen in Sage sparrows, who move on a seasonal bases with the help of environmental triggers. Migration is different from dispersal where the animals are moving to a new location and not returning to the original site. Dispersal is heavily reliant on chance and the organism’s ability to find a home with the necessary resources to survive. The organism may look at many places before picking a home. This ability to disperse is seen for many reasons, like social status or sex. A study by the Journal of Avian Biology found that the female bird will disperse, which is different from mammals where the male will disperse. This was largely related to mating techniques and caring for young, as the female bird will take care of her eggs in solitude while female mammals will raise in a community.