The Bowhead Whale, A True Icebreaker
The Bowhead whales is one of the largest marine mammals known to man, second only to the killer whale. Adults can reach sizes between 46 to 59 feet, the oldest individual recorded was aged at 200 years old. With the remains of historical weapons such as harpoons and spears in individuals being found to date back to the 1800s, a period where the populations of Bowhead whales were reduced dramatically due the trend of whale hunting. The remaining populations of the species are distributed through the northern hemisphere, where they take advantage of the annual fluxes of currents and food resources. Whales species are known to migrate as water temperatures change,but the Bowhead whale, Balaena mysticetus, remains in the Arctic ocean all year round.
When travelling across the northern hemisphere the bowhead travels in solitude or forms pods consisting of up to 4 individuals at a time. The process of migration is done seasonally when travelling with the currents of the Arctic ocean, between the Beufort and Bering seas. Within the spring, whales can have been seen emerged at the seas and bays across the northern hemisphere, between Russia and Alaska. The distribution is dependent on the range of ice coverage within different areas. In the spring, a high abundance of zooplankton and blooms of copepods draws the whales to areas, previously heavily covered in ice during the winter, allowing the whales to feed in bulk at the surface of waters. Each species of whales has their own tolerance to cold temperatures and ability to reach different depths, using their physical and biological adaptions to survive their environment.
The skeletal structure of the bowhead whale consists mainly the spine and neck making up 2/3 of its total length with the head filling the front third. In prospective the skull takes up over 30% of the animal’s body length. The reason for having such a largely structured head is due to the species inhabiting waters which are glazed over with a layer of ice up to 2ft thick. The strength and size of the skull allows the whales to break through the ice with ease, when coming up for oxygen.
The image in figure 2. shows the sheer size of the animals head compared to the rest of its body, the force when emerging gives enough push to crack the ice. The angle of the whales body at the waters surface give enough opportunity between the ice crack to obtain oxygen through its blowholes. Not the greatest of divers amongst the whale species, it can only reach depths of 500 feet but is pushed to restore air in its lungs in short intervals, its time underwater is on estimated between 15 minutes to an hour.
Where it lacks the adaptation to dive for long periods of time, it has the thickest layer of blubber compared to that of its relatives like the killer whale (Orcinus orca) and others. The thick layer of blubber is an insulator against the cold-water temperatures, whilst allowing a layer of protection to its body against predators. The overall weight of a Bowhead whale can vary between 75-100 tonnes, meaning it’s not the most agile swimmer in the ocean, reaching speeds between 2-3km per hour.
Feeding & Diet
To maintain such a large mass to perform bodily functions, requires the consumption of large quantities of food to keep balance of energy levels. Reaching an age of 200 years old has been down to the ability of individuals in the Bowhead whale populations having a slow metabolism. Its slow lethargic movements allow it to be more resourceful with its energy levels, fuelled by its diet. The mouth of the species is where it gets its name from with the bow like shape. With the absence of teeth, the mouth is built up with a filtration system known as a baleen. Measuring up to three metres in length, the largest of any whale species.The baleen functions like that of syphon, water is pushed through the hairs attached to the baleen plates and the contents within are left behind. The whale keeps it mouth open constantly, allowing tonnes of water to be filtered continuously whilst it swims, small organisms such as krill, copepods, plankton etc. are examples of what is consumed by the species.
The most common predator to whale species is humans, with the trend of whaling dating back to the 1300’s and subsiding in the 1900s when species became more protects. With the heavy reduction in populations of whale species worldwide. The tradition of whale hunting has been due to the large body mass of the whales providing a food resource with meat and the other bodily parts being highly valued. The bowhead whale has not escaped this phase of resourcing due to its high value blubber, this was shown in specimens collected with spears and harpoons that dated to be as old as 200 years old, which helped age the oldest individual of the species. Other than humans, the Bowhead whale is prey to its larger relative the killer whale. Its slow movement and often solitary behaviour makes the species easy target for pods of killer whales. Its only defence being its large size and thick layer of blubber being able to withstand hits but over time an individual can be killed, as shown in the video below. The process of killer whales attacking a Bowhead can be seen, with turns taken in applying blows to the prey until left dead in the water.
The Bowhead species was registered under the IUCN as endangered and close to extinction in 1965, a time where intense whaling was occurring. A modern assessment in since 2008, shown the populations have become stable and are increasing. The protection of the species has proven beneficial, with the limitation to whaling in a modern era allowing the populations to bounce back from near extinction. But now the reduction of ice ranges in the arctic region is decreasing due to climate change, a consequence of men effecting the species habitat for the future. It’s worth keeping a close eye on the development of the species over the coming years with stable populations still in chance of decreasing with the limitations of their habitat.