#WhaleWednesday – Bryde’s Whale

The Bryde’s whale (pronounced “broo-dess”), is named after Johan Bryde who helped build the first whaling factory in Durban, South Africa in 1909. Sometimes known, appropriately, as the “tropical whale”, this is the only baleen whale species that lives all year-round in warmer waters near the equator.

The identity and number of species in the “Bryde’s whale complex” however is still unclear. In addition to the “ordinary” Bryde’s whale, with a worldwide distribution in the Pacific, Indian and Atlantic oceans, one or more smaller forms which tend to be more coastal in distribution have also been described. For the moment, the taxonomic status of the smaller forms is unclear and there may be several additional species and/or subspecies however currently two are recognized; offshore Bryde’s whale, and Eden’s whale.

Bryde’s whales are closely related to several other fast swimming, medium-to-large whales all with a similar body shape and which may be confused with each other when viewed at sea. This group includes sei, minke and fin whales.

The Bryde’s whale has three parallel ridges on the top of its head. Like other rorqual whales, the Bryde’s whale has numerous grooves (between 40 and 70 throat pleats) running along the underside of the lower jaw to the belly which allow its mouth to expand when feeding. As with some of the other baleen whales, the Bryde’s whale primarily eats schooling fish and sometimes krill and other planktonic crustaceans. The Bryde’s whale has a slender body which is smoky blue-grey in colour with a sickle-shaped dorsal fin. The body is often mottled with some scars caused by parasites and/or cookie-cutter sharks. The flippers are slender, pointed and relatively short – approximately one tenth of their body length. The broad, distinctive tail flukes are rarely seen above the surface.

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The Bryde’s whale usually feeds alone, although mothers and calves often feed together. It is known to make sudden changes of direction when feeding both on the surface and underwater. Sometimes inquisitive, the Bryde’s whale can be seen approaching or swimming alongside boats. It has irregular breathing patterns, and will often blow four to seven thin, hazy spouts, followed by a dive, usually about two minutes long, although it is capable of staying below the surface for longer. They have also been see to blow or exhale whilst underwater. When surfacing between dives, the Bryde’s whale rarely shows more than the top of its head.

Bryde’s whales become sexually mature at 8-13 years of age and may mate year round. The peak of the breeding and calving season may occur in the autumn. Females breed every second year, with a usual gestation period of 11-12 months. Females give birth to a single calf that is about 11 feet (3.4 m) in length, that is nursed for about 6-12 months.

Wildlife

A long standing prohibition on the operation of factory ships north of 40°S, put in place to prevent hunting of rorqual whale’s at their lower latitude breeding grounds, allowed the Bryde’s whale to escape most of the historical exploitation of rorquals, as it occupies this region all year round. Only populations in the North Pacific may have been affected, as whaling vessels in this region were allowed to operate at lower latitudes, but even this threat was mitigated by the international moratorium on all commercial whaling implemented by the International Whaling Commission (IWC) in 1986. Although pelagic whaling by Japan was subsequently resumed in 2000, it is under scientific permit, and limited to catches of 50 individuals per year.

The main concern is that, while assessed as a single species, the Bryde’s whale appears to be abundant, but if it is in fact a complex of several separate species, some populations may be so small that they warrant threatened status and require conservation action.

Video: Bryde’s Whale Feeding in Raja Ampat

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#WhaleWednesday – Sei Whale

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The Sei Whale is identified by a dorsal fin, 38 to 56 ventral grooves (throat grooves that allow their throat to expand during the hug intake of water during filter feeding). Sei whales are also baleen whales, meaning that instead of the common mammal tooth form, baleen whales have plates for filtering foods in and water out, specifically sei whales have two rows of 300 to 380 baleen plates. This whale is known to be 14 to 20 m long and weighs about 20 tons – females are generally 1-2 m longer than males. The sei whale is dark gray or bluish grey on the back and sides with a greyish white area on the ventral grooves of the lower jaw and underbelly.

The sei whale is one of the fastest cetaceans, reaching speeds of up to 50 km/hour. Sei whales have a more regular dive sequence than most others and is known to stay near the surface more consistently. The sei whale normally blows once every 40 to 60 seconds, for about 1 to 4 minutes, and then can dive for 5 to 20 minutes. During the shorter dives, the sei whale rarely descends deeper than a few feet, so its progress can be followed by “fluke prints” or swirls left by the beat of the tail just below the surface. The sei whale seldom breaches, however the dorsal fin and back remain visible for longer periods of time than with other large whales.

Fluke Prints – the path of the unseen whale

Sei whale groups mostly consist of 2-5 individuals, however thousands may aggregate where plenty of food is available. Like the other baleen whales, sei whales feed by skimming and swallowing surface plankton, mainly copepods (tiny marine crustaceans) but also euphausiids (krill, shrimp like crustaceans).

Mating season ranges from November to February in the Northern Hemisphere and from May to July in the Southern Hemisphere. Females generally give birth to a single calf every other year in winter, after a gestation period of 10.5 to 12 months. Although little is known about their breeding habits, some data indicate that sei whale migration is loosely organized around sex, age, or reproductive function. This presumably relates to mating strategies, but at this time nothing is known of their mating habits or calving grounds.

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The sei whale species was intensively exploited worldwide after blue and fin whale stocks have been reduced. In 1980, it was estimated that the Southern Hemisphere population had been reduced to around 24,000 from an initial level of 100,000 or so. In the North Pacific there was a decline from 42,000 in 1963 to just 8,600 in 1974, while figures in the North Atlantic are the most uncertain, although some surveys have suggested a figure around 10,000. Since 1985, the International Whaling Commission has officially halted all commercial whaling of this species. However, today 50 sei whales are killed annually by the Japanese whalers in the North Pacific in Japan’s “scientific whaling” program.

Sei whales inhabit all ocean and adjoining seas except in polar regions, feeding in cold water during the summer and migrating to warm tropical and subtropical waters during the winter. In the western North Pacific, sei whales are most common in the south-west Bering Sea to the Gulf of Alaska, and offshore in a broad arc between about 40 degrees North and 55 degrees North across the Pacific.

In the North Atlantic, sei whales can be found from the coast of Labrador, and along the coasts of Greenland and Iceland. In the East Atlantic, sei whales migrate north to northern waters off Norway, Shetland, Orkney and the Faeroe Islands an occasionally, Svalbard. Sei whales are also present in the Denmark strait

Sei Whale Feeding Frenzy video:

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#WhaleWednesday – Bowhead Whale

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One of just three year-round Arctic whale species, bowheads, are famous for their massive bow-shaped heads, designed perfectly for one of their main challenges: getting through think sea ice to breathe. Bowheads are able to use their large reinforced skulls and powerful bodies to break through ice 20cm thick. Although Inuit hunters in Alaska have reported whales surfacing though approximately 60cm of ice. Their Heads make up about a third of the total length – which in adults can be up to 20 metres – newborn calves are about 4 metres long and weigh 2-3 tonnes.

Bowhead whales are also known in quiet Arctic waters for their intense bouts of social group interactions, involving tail and flipper slapping, as well as breaching (leaping entirely out of the water) – which is an impressive feat for whale that weigh up to 100 tonnes.

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Whales are close to the top of the food chain and important indicators of overall health of the marine environment. The bowhead whale’s conservation status is listed as “Least Concern” overall, however some populations, such as the East Greenland-Svalbard population are endangered.

Data has shown that bowhead whales may be among the longest-lived animals on earth. Based on the recovery of stone harpoon tops in their blubber, and from analysis of eye tissue, scientists believe that the life span of bowhead whales can be over 100 years.

Bowhead whale, Arctic

Like the other ice whales (beluga and narwhal), bowheads also have no dorsal fin, enabling them to move easily under the sea ice. Bowheads can dive for over 30 minutes at a time. They typically spend the entire year in Arctic waters, their travels shaped by the melting and freezing of the ice, and seasonal movements to a series of spring-summer productive feeding areas. They have a very thick layer of blubber – approx 40-50cm – which serves primarily as an energy store to see them through the annual cycle.

Bowhead whale, Isabella Bay, Nunavut, Canada

Bowheads are baleen whales, with about 250-350 keritanous baleen plates on each side of their upper jaw. These massive vertical plates – up to 4.6m long in fully grown individuals, the largest of any whale – to filter their food from the hug open-mouth gulps of water that they take. Bowhead whales need to eat about 100 tonnes of food annually, mainly tiny crustacean zooplankton. Most of their annual feeding occurs in the summer months, and much of that in the Canadian waters.

The bowhead whale has been a victim of the appeal of its long baleen plates and thick blubber – the most economically valuable whales. Hunted by commercial whalers until the last century for whale oil and baleen, bowhead whales are still recovering slowly from their economic extinction. While some populations are faring better as a result, it will take many more decades for this long lived and slow reproducing species to recover to its pre-whaling numbers. Inuit in Canada, Greenland and Alaska are allowed a limited subsistence hunt for bowhead whales.

Threats: Modern threats to bowhead whales include sea ice retreat and changes to food web dynamics due to rapid climate change and ocean acidification. Bowheads are also affected by direct and indirect impacts of increased development such as oil and gas exploration, commercial shipping, and fishing.

The Canadian and Alaskan governments have attached satellite radio transmitters to a sample of bowhead whales, in order to better understand seasonal movements and habitat use of these Arctic giants. This information can be used to identify and protect the most important areas used by these whales, and to help plan further human activities, like shipping and development, in these sensitive, quiet arctic waters – the bowheads’ home – and in all decisions regarding the future of Arctic marine systems facing rapid climate and economic change.