When it comes to understanding the migration patterns of whales and figuring out why different species migrate in different ways it is important to understand what the purpose for their migration is because not all whales migrate for the same reasons.
Some whale will migrate in order to get to their local feeding or mating grounds as they tend to have specific locations where they gather for these two different activities.
While not always the case whales that migrate between feeding and mating seasons tend to migrate towards cooler waters during the warmer summer months in order to stock up on food and replenish their supply of blubber and will migrate towards warmer waters during the colder winter months in order to mate and give birth to their offspring.
Other cetaceans are not concerned about their mating/feeding grounds and will migrate in order to maintain their food supply.
Marine mammals that migrate for these purposes will travel wherever their prey migrates to so that they can continue feeding without having to worry about finding new prey.
While there are whales that follow fairly predictive migration patterns there are also some whales do not follow a normal migration pattern.
These marine mammals may meet up at their local mating grounds and once their mating season ends they will wander off in whatever direction suits them.
Lastly there are whales that do not migrate.
These types of whales tend to inhibit the same environment all year long and may only travel short distances to meet other whales or avoid environmental changes such as large ice caps that may block their ability to surface for air.
In order to simplify there reasons here is a short list of 4 common reasons why whales migrate.
- They migrate for mating and feeding purposes.
- They migrate primarily to maintain their food supply.
- They are wanderers and travel the world without any notable migration pattern.
- They do not migrate and maintain a fixed distance from their home location all year round.
When it comes to whales, dolphins and porpoises there are currently around 90 known species of cetacea in existence today.
Within the many different species there are several different types of migration patterns that have been found to occur among the various species.
Here is an example of 4 different species of whale that follow different migration patterns.
Humpback whales are a migratory species and are commonly known for making one of the longest migration trips of any animal.
During feeding season they can often be found swimming near the upper and lower hemispheres gathering food.
When mating season comes around they make their yearly trip towards the center of the equator (to tropical environments) where the temperature is warmer and they can mate and bare offspring.
Humpback whales can travel distances of 16,000 miles during these trips and will fast during their migration living off of stored energy in their fat reserves.
Killer whales typically prefer living in cold water although they can be found swimming in all of the large oceans of the world from the Arctic and Antarctic to the tropical regions near the center of the equator.
Unlike humpback whales which follow certain migration patterns killer whale tends to migrate toward wherever their food source goes.
In some regions the migration of killer whales are influenced by fish and various other pray that occupy the area.
Note: Although the killer whale uses the word “whale” in its name it is actually considered a dolphin.
While these whales do migrate towards warmer tropical climates during mating periods male whales don’t follow a particular route or have any notable migration patterns.
Males are largely solitary creatures and typically leave their nest as they mature creating their own paths and traveling to various parts of the world while the female whales stay more central to their mating grounds in order to mate and give birth to their offspring.
Unlike other species of whale that migrate between seasons bowhead whales typically maintain a fixed location all year round.
These whale are often found swimming in the Arctic/sub Arctic waters and may make short trips to other area’s in the upper northern hemisphere such as the Bering sea, Beaufort sea and Chukchi sea.
While they are non migratory these whales may move from one location to the next during certain times such as when looking for a mating partner, trying to locate food or when certain areas become too cold and begin forming large ice caps.
Reproduction and migration
Although not always the case a whales gestation period (length of pregnancy) may have an impact on when, where and if these marine mammals migrate to new locations during certain times of the year.
For instance the killer whale has one of the longest known gestation periods which can last up to 17 months.
These marine mammals do not migrate long distances in order to mate or give birth to their offspring and can mate any time of the year.
If killer whales did migrate to different grounds to give birth it is likely that their gestation period would overlap their feeding and breeding season (assuming they had one) causing them to give birth in their feeding grounds or in the middle of a migration.
The narwhal and beluga whale also have longer gestation periods that exceed the 11 – 12 month cycle of other whale species.
Both of these whales may travel from one area to another within their respective grounds but they do not migrate over large distances from cold to tropical environments the way other whales do and it is likely that if they did they would have a hard time giving birth to their young in a specific location as it would overlap with the seasons.
Whales such as the blue whale and humpback whale have a 11 – 12 month gestation period which allows them to give birth in the warmer environments where they mate and become impregnated rather than having to give birth in a different environment.
This makes the process of reproduction much simpler for marine mammals that are migratory and provides their newborn offspring with the opportunity to be born in a warm, secure environment rather than having to deal with scattered births in their feeding grounds or during their long migration trip, which would cause all sorts of issues such as keeping their pods together and ensuring that the child is able to survive a long migration trip right after birth.