Balaenoptera acutorostrata

Description and Fascinating Facts

The Minke Whale is the smallest baleen whale with 50–70 throat grooves. It is a rorqual whale (Family Balaenopteridae, which includes blue, Bryde’s, fin, humpback, minke and sei whales). These long, slender whales are much more streamlined than other whales. They have a pointed snout, paired blowholes, and a broad, flat rostrum (upper part of the head). The throat grooves, in addition to streamlining the shape of the whale, allow the throat area (called the cavum ventrale) to expand tremendously during feeding. Minkes are the most abundant baleen whale and have a characteristic white band on each flipper (absent on southern minke whales), contrasting with its very dark gray top colour. They have two blowholes, like all baleen whales. Minke whales grow to be about 7.8–9 m long, weighing about 5,400–6800 kg (15,000 lbs). Females are about 0.6 m (2 ft) longer than males, as with all baleen whales. The largest minke whale was about 10.5 m (34 ft) long weighing 8600 kg (18920 lbs). Minke whales have a snout that is distinctively triangular, narrow, and pointed (hence its nicknames “sharp-headed finner” and “little piked whale”). The minke whale’s skin is very dark gray above and lighter below, sometimes with pale trapezoidal stripes behind the flippers on the top. These whales are stocky, having a layer of blubber several inches thick. They have 50–70 throat grooves, running from the chin to the mid-section. The minke whale has two long flippers (up to one-eighth of the body size), a small dorsal fin, and a series of small ridges along the its back near the fluke (tail). They either travel singly or congregated in small pods of about 2–3 whales. Minke whales can dive for up to 20–25 minutes, but usually make shorter dives, lasting about 10–12 minutes. Just before diving, minkes arch their back to a great degree, but the flukes do not rise out of the water. They breathe air at the surface of the water through two blowholes located near the top of the head. At rest, minke whales spout (breathe) about 5–6 times per minute. The spout of the minke whale is a very low, almost inconspicuous stream that rises up to 2 m above the water. Minke whales begin exhaling before they reach the surface, which minimizes the blow. They make very loud sounds, up to 152 decibels (as loud as a jet taking off). They make series (trains) of grunts, thuds, and raspy sounds, usually in the 100–200 Hertz range. These sounds may be used in communication with other minke whales and in echolocation.

World Range and Habitat

Minke whales live at the surface of the ocean in all but polar seas and frequent the Pacific Northwest during spring and fall. Minke whales normally swim 4.8–25 kph (15.5 mph), but can swim up to 29–34kph (21 mph) in bursts when in danger. Feeding speeds are slower, about 1.6–9.8 kph (6 mph).

Feeding Behaviour

Minke whales (like all baleen whales) are seasonal feeders and carnivores. They sieve through the ocean water with their baleen. They filter out small polar plankton, krill, and small fish, even chasing schools of sardines, anchovies, cod, herring, and capelin. They have the same diet as blue whales. The baleen plates in minke’s jaws have about 300 pairs of short, smooth baleen plates. The largest plates are less than 30 cm (1 ft) long and 13 cm (5 in) wide. The fine textured baleen bristles are fringed and with white bristles. 

Reproduction

Minke whale breeding occurs mostly in the late winter to early spring while near the surface and in warm waters. The gestation period is about 10 months and the calf is born near the surface of the warm, shallow waters. The newborn instinctively swims to the surface within 10 seconds for its first breath; its mother, using her flippers, helps it. Within 30 minutes of its birth the baby whale can swim. The newborn calf is about 2.8 m (9 ft) long and weighs about 454 kg (1000 lbs). The baby is nurtured with its mother’s milk. The mother and calf may stay together for a year or longer. Minke whales reach puberty at two years of age and have a have a life expectancy of over 20 years. It is estimated that there are about almost 800,000 minke whales worldwide.

Warnings and Comments

The story of this whale’s name illustrates its blighted history. Minke was an 18th-century Norwegian whaler; infamous for regularly breaking the rules concerning the sizes (and therefore species) of whales that he was permitted to hunt at that time. Soon all the small whales became known as “Minke’s whales”. Eventually, it was formally adopted as the name for this small species.