Whales migrate to different locations depending on where they live or where they often roam to rest, feed, frolic, and mate. Southern right whales, for instance, migrate during summer to waters near Antarctica and go to South America, Australia, New Zealand, and South Africa during mating season. The humpback whales that live in hemispheres cross to the other side of the world during breeding and feeding seasons. These aquatic placental marine mammals undertake some of the longest migrations in the animal kingdom. For instance, the humpback whales cover a distance of 22,000 kilometers every year with the help of their massive tail fin.
Some whale species migrate to the tropics or the region of the Earth that surrounds the equator. Some scientists believe that it could be to search for food or to give birth. But a new study that appeared in the peer-reviewed journal Marine Mammal Science has explained that they do so to maintain healthy skin.
Migrating to the Equator to Shed Skin
Authors from the Oregon State University and the NOAA Fisheries West Coast Region explained that skin molting, which is the process when animals shed their old skin or body coverings so that new skin will be revealed, is a significant physiological need that could be met if whales go to warmer waters. This is why they begin migrating to the equator during the start of the winter season. Small whales and female whales move first in groups during their migration.
Oregon State University Marine Mammal Institute’s marine ecologist Robert Pitman, who is the study’s lead author, said that whalers believed in the past that whales travel to the equator for calving or to give birth. Although this has been the theory for more than a century already, scientists could not agree on the reason why. Pitman and colleagues said that during their months-long migration, most of the whales would fast because of reduced food opportunities even in the tropics. Why would they have to go through all the trouble and still not get enough food there? The answer is that warm water speeds up the process of skin shedding.
Warm Water Helps Whales Maintain Healthy Skin
They went on to say that just as mammals on land regularly shed skin, feathers, or fur, it happens with whales too. The team proposed that whales in the cold waters of Antarctica have to conserve their body heat, so this process requires diverting the blood flow away from the skin, reducing skin cell regeneration and stopping the normal shedding of skin. To help them recover their skin metabolism and shed their skin healthily, they need an environment that will not reduce their body heat. This drives them to migrate to warmer water.
How Did They Come Up With Their Theory?
To come up with their new theory, scientists studied the movement of whales for more than eight years. They used 62 satellite tags on killer whales and found that the four whale types that feed in the freezing Antarctic waters migrated as far as 7,000 miles or 11,000 kilometers round trip. The majority of these migrations even happened non-stop and were quite fast. The whales just went straight north and then went back in cold waters. These migrations happen in about 5.5 months.
Pitman and his team also captured a photo of newborn whale calves in the Antarctic region, proving that whales do not have to go to warmer waters just to give birth. Although there are larger whales that have given birth in warmer waters during their migration, it could be because they just had to bear their calves while in the area. The tropics' water may have also sped up the growth of their calves because the environment has fewer killer whales, their predator.
Just like humans, dolphins and whales continuously shed their outer skin cells. Although people may not see it happening, we lose about 30,000 to 40,000 dead skin cells every minute on the surface of our skin. Scientists in the recent study observed that whales living in the cold waters of Antarctic are usually discolored by microscopic diatoms in “thick yellow film.” This is an indication that they are not experiencing normal skin mold or “self-cleaning.”
Early whalers also noticed that blue whales have heavy diatoms coating on their white bellies. They also assumed that whales without the said coating had just recently arrived from the tropics because as whales shed their skin, diatoms are removed.
There were also recent studies that have found that Antarctic killer whales with high concentrations of diatoms on their skin may have gathered a potentially harmful bacteria, according to science and technology platform Phys.org.
John W. Durban, co-author of the study and a senior scientist at the SEA Inc., said that feeding is “so good” in the waters of Antarctic that a relatively warm-blooded and small killer whale can exploit the resources in it but still maintain healthy skin because their migration behavior has also evolved.
Whales and Whaling: Statistics
Endangered species conservation organization World Wildlife Fund (WWF) shares that whales roaming throughout the world’s oceans and communicate using mysterious and complex sounds. Blue whales can reach more than 100 feet in length and can weigh up to 200 tons, which is as much as 33 elephants combined. As of today, there are only around 400 North Atlantic right whales existing and the number of other species varies. These species include the gray whale, bowhead whale, fin whale, and sei whale.
Despite a ban on commercial whaling and trade of international whale produces, there are still countries that continue the commercial whale hunts. These include Norway, Japan, and Iceland. More than 1,000 whales are killed every year because of such purposes. The blue whales were almost exterminated in the 20th century because of commercial whaling. Database company Statista shared that in 2005, approximately 2,310 whales were killed by humans. The number decreased to 1,321 in 2012 but slightly increased to 1,486 in 2017.
The number of whales killed worldwide in 2000 reached 487 and these were only “catches under objection.” These numbers do not include aboriginal subsistence whaling catches and those with special permit catches. The catches under objection grew to 639 in 2005, 574 in 2008, 591 in 2011, 763 in 2013, 844 in 2015, and 606 in 2018.
Our oceans are filled with amazing species of all shapes and sizes. Understanding whale migration can create significant contributions to the growing body of research, management, and conservation on the species.