Blue Whale 

	Blue whale Rorqual bleu Balaenoptera musculus Other names: Sulphur bottom

Description

• Large, U-shaped head with massive splashguard in front of blowhole 

  

• Mottled, blue-grey colouration

• Small dorsal fin set far back on body

• Ventral grooves cover throat to navel

When it surfaces: Its explosive and sonorous blow can attain a height of six metres. The dorsal fin breaks the surface long after the blow is sighted. 

The largest of the ocean’s giants

It is also the largest animal to have ever existed on the planet! Power and majestic elegance guarantee every blue whale sighting to be an exceptional experience. Yet, this exceptionality is also true in view of the fact that it is such a rare and fragile animal. Uncontrolled whaling, which ended in 1955, decimated the North Atlantic blue whale population. It has been recognized as an endangered species in Canada since 2002. The blue whale retains much of its mystery for researchers; its bohemian nature adds a great deal to the challenges of studying this elusive animal.

Population, range and habitat

In the St. Lawrence: The blue whale patronizes deep, cold waters where thermal fronts and upwellings mix surface water, consequently increasing productivity and the accumulation of prey. This species is a seasonal summer resident of the Gulf and Estuary where its numbers peak in August and September. It can at times be observed very near shore. Certain individuals return to the same feeding sites on nearly an annual basis, while others are more irregular. They are capable of long and rapid travel. Based on observation and monitoring by MICS researchers, one blue whale covered a total distance of 400 km in two weeks, while the longest recorded voyage in 2007 was a 180 nautical mile (324 km), six-day journey.

Migration: Seasonal movements and wintering grounds remain poorly defined. Blue whale itineraries appear to adhere to prey concentrations. This leads them towards lower, more temperate latitudes along the East Coast of the United States, from the Gulf of Maine to Florida during their winter mating season. Researchers tracked one individual from the Grand Banks of Newfoundland all the way to Bermuda using acoustic monitoring in 1993. Some of these whales appear to extend their stay in the food-rich waters of the St. Lawrence for as long as possible; they swim at the limit of the ice pack, at the risk of becoming trapped. Observations from the Estuary and Gulf suggest that a few may even spend the entire winter here. A first in the St. Lawrence: during one aerial survey MICS researchers photographed and identified a blue whale in winter; it was swimming among the seal-covered ice sheets off Port-Cartier.

 Worldwide: The blue whales of the St. Lawrence are part of the North Atlantic population estimated at between 600 and 1500 mature animals. According to the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), a mere 250 mature blue whales swim the waters off Canada’s East Coast. Through an ongoing genetic study, researchers will be able to verify whether this population is whole or divisible into two populations: the western North Atlantic population and the Icelandic population. Blue whales are present both inshore and offshore throughout the world’s oceans.

Behaviour

Feeding: The blue whale is a gulp feeder. It feeds mainly on small planktonic animals called krill that live in swarms. A blue whale consumes up to four tonnes of krill per day, or approximately four percent of its weight.

At the surface: Three to four breaths per breathing sequences are the norm for this species. The blue whale will occasionally feed at the surface in a distinctive manner: it often rolls onto its side, revealing a distended throat pouch, a pectoral fin and one tail fluke. Approximately 15 to 18 percent of blue whales in the St. Lawrence fluke up as they dive.

While diving: Average dives last between 10 and 15 minutes, up to 30 minutes. Blue whales can dive to depths of 200 m. However, dives between the surface and 100 m are more common, as they represent the range in the water column where prey can be found during the day. 

Social behaviour: Solitary and nomadic by nature, blue whales sometimes swim in pairs or in small, impermanent groups. The nature and duration of these associations are not well known. Stable pairs that last from one day to several weeks are formed in the St. Lawrence from July onward. These pairs are predominantly composed of a male and a female. These associations may be precursors to mating that takes place in winter.

Vocal behaviour: Blue whales vocalize at low frequencies of 11 to 125 Hz. Vocalizations last from one to 13 s. Single note infrasounds of eight to 20 Hz can last as long as 30 s. These sounds are very intense with a volume of 186 to 198 db. Sounds are sometimes organized into sequences, repeated at uneven intervals. Travelling hundreds of kilometres through deep water, these vocalizations may be a form of communication for animals that are scattered throughout an ocean, or they may be used to “read” the underwater terrain to facilitate long distance navigation. They may also play a role in nuptial parades. Geographic variations in sound patterns could be used to differentiate blue whale stocks or sub-populations. The distinctiveness of vocalizations in the St. Lawrence suggests that blue whales here have adapted to an increase in shipping noise.

Reproduction

Blue whales attain sexual maturity at 10 years of age. Mating and calving occur in late autumn or winter. Gestation lasts 10 to 11 months. Nursing lasts seven months. Fewer than 20 cow/calf pairs have been observed in the St. Lawrence since 1979.

About scientific research

Using skin pigmentation patterns to identify individual animals since 1979, MICS presently has a total of 420 St. Lawrence blue whales on file in their catalogue. Other research groups working in the Gulf and Estuary are conducting various projects pertaining to blue whale acoustics, population dynamics and diving behaviour.

Blue whale  "Science and conservation" page.

	Compare

	Blue Whale