Blue whales (Balaenoptera musculus) ~ Aquatic Mammals Blog

Blue whales (Balaenoptera musculus)

Taxonomy & Identification

Blue whales are included into order Cetacea, Suborder Mysticeti, and family Balaenopteridae. The Blue whale is the largest animal ever known, however, size alone is not enough to distinguish it from other rorquals, as its size substantially overlaps with that of adult Fin and Sei whales. Like all rorquals, the blue whale is slender and streamlined. The head is broad and U – shaped (like a gothic arch). when viewed from above and relatively flat, when viewed from the side. Along the center of the rostrum, there is a single prominent ridge, which ends in an impressive "splash guard’ around the blowholes. The flippers are long and pointed, and the dorsal fin is relatively small, variably shaped (sometimes reduced to just a nubbin), and placed about three-quarters of the way back from the rostrum tip. The broad, tapered flukes have a relatively smooth tailing edge and a prominent median notch. When viewed through the water surface they may appear dappled or uniformly light blue. The spout is tall and slender, reaching 10-12 m in height. Northern hemisphere subspecies (Balaenoptera musculus musculus) are 23-27 m long (with females growing larger than males). Newborn whales are about 7-8m long. Adults can weigh up to 180,000kg, but most weigh between 72,000 and 135,000kg.

Behavior

Blue whales are considered to live at least 70-80 years of age and perhaps more. Though blue whales can reach a speed of 32 to 36 km / h, they usually sail at a speed of 2 to 8 km / h when feeding and traveling. If pursued by predators such as killer whales, ships, and interact with other blue whales, they can reach much higher speeds. After breathing 6 to 20 times at the surface over 1 to 5 minutes, blue whales usually dive for 5 to 15 minutes. 20-minute dives are also not uncommon. 36-minute dives have been recorded in the St. Lawrence, Off California. Most of the time, they separately feed on planktons mainly Krill, small shrimp-like organisms. It can eat approximately 7500 pounds of krill per day. They also have a row of 300-400 baleen plates on each side of the mouth, which are black in color and range in length from 50 cm in front to 100 cm in back. When mating, they made as couples or small groups. In resting times after feeding, they wished to isolate from their pod. But they spend more time on their courtship and mating. When they are a couple or small groups rising, spouting, surfacing and diving are done almost at the same time. The Blue Whales were observed diving on many occasions and each time they fluked before diving. Always one individual decided the swimming direction and others followed them. But they never gathered as big groups like sperm whales or dolphins. The majority of them liked to live as isolated individuals from groups.

oceanfacts.net/vaquita-porpoise-driven-to-extinct-by-humans/

Acoustic power

All blue whales have in common featured of very long and low frequency or amplitude modulated signals units that make up the frequency content and number of components which seem to have greater acoustic power than any other animal. Blue whale's calls are generally infrasonic and too low for humans to hear. It was 186 dB compared to the source levels which are one of the loudest and lowest sounds produced by any animal. Early records indicated that long-term calls can only be made by a male. These calls, which vary geographically specific among populations in the Eastern, North Pacific, and around the world, are described in some detail.

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