Common minke whale

Description

The common minke whale is the smallest of the rorquals,and one of the smallest baleen whales (second smallest only to the Pygmy right whale).In the North Atlantic,Norwegian whaling vessels in 1940 allegedly caught individuals of up to 10.7 m (35 ft) in length,but they were likely only measured visually in comparison to objects of known dimensions aboard the ships themselves – the longest caught in subsequent years were typically only up to 9.4–10.05 m (30.8–33.0 ft) in length.In the North Pacific,Soviet vessels operating out of the Kuril Islands claimed to have caught two males of 12.2 (40 ft) and 12 m (39 ft) and a female of 10.7 m (35 ft) – the first two were landed in 1951,the third in 1960.These likely represent undersized sei whales,part of the massive misreporting of whaling data by the Soviet Union in the North Pacific and elsewhere The longest measured by Icelandic scientists were an 8.7 m (29 ft) male and a 9 m (30 ft) female,while the longest caught by the Japanese in the western North Pacific were 8.5 m (28 ft) males and a 9.1 m (30 ft) female – the latter caught off eastern Hokkaido in 1977.For the dwarf form,the longest reported are a 7.62 m (25.0 ft) male caught in May 1973 and a 7.77 (25.5 ft) female caught in May 1970,both taken off South Africa Males caught in the western North Pacific and weighed whole on a truck scale averaged between 2.85 and 4.23 metric tons (3.14 and 4.66 short tons) (range: 0.86 to 6.36 metric tons,0.95 to 7.01 short tons),while females averaged between 1.93 and 3.63 metric tons (2.13 and 4.00 short tons) (range: 0.84 to 8.35 metric tons,0.93 to 9.20 short tons) At sexual maturity,males and females in the North Atlantic average between 6.16–6.75 m (20.2–22.1 ft) and 6.03–7.15 m (19.8–23.5 ft),while in the North Pacific they average between 6.3–6.8 m (21–22 ft) and 7.1–7.3 m (23–24 ft).At physical maturity,males and females in the North Atlantic average between 7.9–8.17 m (25.9–26.8 ft) and 8.42–8.5 m (27.6–27.9 ft),while in the North Pacific they are slightly smaller,averaging only 7.5 and 8 m (25 and 26 ft),respectively.At birth,they are estimated to be 2.5–2.8 m (8.2–9.2 ft) in length and weigh 150–300 kg (330–660 lb).They are thought to be weaned at about 4.57 m (15.0 ft) in length.For the dwarf form,they are thought to reach sexual maturity at around 6.2 m (20 ft) for females and 6 m (20 ft) for males and are estimated to be about 2 m (6.6 ft) at birthAppearance Northern form Common minke whales are among the most robust members of their genus,the greatest height of their body being one-fifth their total length.They have a narrow,pointed,triangular rostrum with a low splashguard.Their prominent,upright,falcate dorsal fin averages about 30 cm (12 in) in height – range 7 to 77 cm (2.8 to 30.3 in) – and is set about two-thirds the way along the back.They are dark gray dorsally and clean white ventrally.The lower jaw projects beyond the upper jaw and is dark gray on both sides – though,like the dwarf form,it can have a white mandible blaze at the rear corner of the right lower jaw.An indistinct light gray rostral saddle may be present,and a few individuals can have pale,thin blowhole streaks trailing from the blowholes.A thin,light gray,forward-directed chevron,called the shoulder streak,lies between the pectoral fins.Two light gray to whitish swaths,called the thorax and flank patches,join ventrally in the mid-lateral region,with the former the brighter of the two.The pectoral fins are relatively small,averaging about 73 cm (about 2.4 ft) in length (maximum: 1.38 m,or about 4.5 ft).They have a transverse,white band on their outer margins,which is the most distinguishing feature of the species.In most individuals (about 94% in the western North Pacific) it is a clear white band,but in a minority of cases (about 6%) it only forms an obscure white band – about 29% of the individuals sampled from the Sea of Japan had this type of flipper band.The smooth-sided flukes average about 2 m (6.6 ft) in width and can be nearly 3 m (about 9.8 ft) wide.They are light gray or white ventrally and bordered by dark gray.The baleen plates,which number about 230 to 360 pairs and average about 20 by 10 cm (7.9 by 3.9 in),are creamy white with a fine white fringe – a small percentage in the western North Pacific (mainly larger individuals) have a thin black band along the outer margin.They possess 50 to 70 thin ventral pleats,which only extend about 47 percent of the body length – among the shortest relative to body length among the rorquals,second only to the sei whale.Dwarf form The dwarf minke whale has similar proportions to the northern form,with an upright,hooked dorsal fin set about two-thirds the way along the back that is up to 32 to 34 cm (13 to 13 in) in height.It has 55 to 67 ventral grooves.Its baleen – 18 to 20 cm (7.1 to 7.9 in) in length – is mostly white,with up to 45 per cent of the posterior plates shading from black to dusky gray along their outer margins The dwarf form has the most complex coloration of any baleen whale.Dark gray fields and capes alternate with light gray and white blazes,patches,and streaks.The dark gray spinal field lies above an ivory white ventral field.This spinal field extends down into a nape field,which separates a light gray rostral saddle and a light gray,triangular,usually forwardly peaked thorax patch.The nape field,in turn,extends even further down into a dark throat patch,which reaches down to the ventral pleats and extends back to the front of the pectoral fins.Further back the spinal field extends into a dark thorax field,which usually forms an inverted triangle between the thorax patch and the light gray flank patch.This flank patch can be separated into an anterior and posterior flank patch by a dark triangular or even wave-like flanThe common minke k infill.Finally,the dark peduncle field covers the posterior portion of the caudal peduncle to the tips of the dorsal side of the flukes,which are white ventrally and thinly bordered by dark gray The most prominent features on the dwarf minke whale are the white flipper and shoulder blazes.The former covers the proximal two-thirds of the pectoral fin and continues along its leading edge,while the latter connects to the thorax patch aboveThe common minke whale is the smallest of the rorquals,and one of the smallest baleen whales (second smallest only to the Pygmy right whale).In the North Atlantic,Norwegian whaling vessels in 1940 allegedly caught individuals of up to 10.7 m (35 ft) in length,but they were likely only measured visually in comparison to objects of known dimensions aboard the ships themselves – the longest caught in subsequent years were typically only up to 9.4–10.05 m (30.8–33.0 ft) in length.In the North Pacific,Soviet vessels operating out of the Kuril Islands claimed to have caught two males of 12.2 (40 ft) and 12 m (39 ft) and a female of 10.7 m (35 ft) – the first two were landed in 1951,the third in 1960.These likely represent undersized sei whales,part of the massive misreporting of whaling data by the Soviet Union in the North Pacific and elsewhere..A variably sized,dark oval auxiliary patch (formerly called a "flipper oval") lies behind the pectoral fin,often appearing to merge with the dark gray distal flipper patch,which occupies the distal third of the pectoral fin.This auxiliary patch is often completely separated from the thorax patch by the white of the shoulder blaze and a vertical extension of the ventral field,but can also narrowly or even broadly attach to it.A mandible blaze usually covers the posterior third of the right lower jaw,while the left side is normally dark gray.Similarly,a white eye blaze is usually present on the right side,but rarely on the left.The rostral saddle likewise shows asymmetrical coloration,extending further on the right side than on the left and having a more well defined posterior right margin;the left,meanwhile,often has a diffuse posterior margin.A white peduncle blaze extends up from the ventral field,being bordered on each side by light gray double caudal chevrons,which extend down from the peduncle field and flank patch,respectively.A variably shaped,thin,light gray line,called the nape streak (analogous to the "shoulder streak" or "chevron" of the northern form),extends laterally down the back between the pectoral fins.It can point forward,backwards or form a straight line;this variability can help to identify individual whales.A pair of light gray blowhole streaks extend posteriorly behind the blowholes,often curving to the left – the left more strongly than the right.Occasionally fine ear stripes may be present behind the opening of the auditory meatus,while dark or light speckling or streaking can occur along the flanks as well as what are called tiger stripes – "parallel,dark,usually vertical stripes" Like Bryde's whale (and occasionally blue and fin whales),dwarf minkes can exhibit auxiliary ridges on either side of the central ridge of the rostrum.