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Nature Notes: Minke Whale and Friends

Ed Robinson
September 11, 2023

The middle of August found me wandering around the mud flats in eastern Maine with binoculars plastered to my face. A fair question would be why not slog around in Harpswell’s mud flats? Well, at my age I take any excuse to travel in order to see new habitats and fascinating species. The occasion was the Downeast Migration Birding Festival hosted by the Cobscook Institute, near Lubec. Every time I travel to this quiet part of our state, I find wonderful new sights and sounds, and wonder how it can be so ignored by visitors during the peak of vacation season. I guess the tourist maps all end at Acadia National Park! Tough luck for those who miss out on the amazing 20 preserved parks of Cobscook Shores assembled by the exceedingly generous Butler Family Foundation.

You might ask why I would be interested in bird migration in the middle of summer rather than early autumn? The reason is that some of the longest-distance avian migrators get started on their journeys south while we are still stuffing ourselves with lobster rolls and watermelon. Birds like the American golden plover or the white-rumped sandpiper have been known to begin departing breeding grounds in the far northern Arctic regions in late July or early August, getting a jump start on journeys that might carry them far down the coast of Argentina. The remote beaches and flats of Downeast Maine are prime habitat for untold thousands of birds to refuel during their migrations before another leg of a journey that might involve single flights up to three days straight. A Bar-tailed Godwit carrying a GPS tracker was reported by scientists as flying from Alaska to New Zealand non-stop, an amazing 7,500 miles over the Pacific Ocean!

While I find it challenging to try to sort out and identify a wide range of birds milling around on the bays and beaches of the beautiful Bold Coast, there was another reason to attend the festival. Over four days we twice had the opportunity to board large whale watch ships for several hour journeys in the waters around Eastport, including the exciting run through Head Harbor Passage and into open seas past the scenic Head Harbor Light. Weather and water conditions are highly variable in this area but we had fair skies and moderate ocean conditions for our trips. The scenery is spectacular and the wildlife viewing is hard to beat.

The birds on offer vary considerably from those we see around town. Ring-billed Gulls and Black-legged Kittiwakes are common, and Arctic Terns take center stage out there. I always enjoy seeing the gorgeous Black Guillemots, Razorbills and Common Murres buzzing around the ship. With professional guides on-board we were able to observe a huge variety of birds including scarce Northern Gannets and my first Great Shearwaters, soaring on strong breezes as if life is nothing more than a soaring exhibition. The highlight was spotting two rare birds who were hundreds, if not thousands of miles from their normal territories – two Little Gulls and a stunning Sabine’s Gull. Even the guides were jumping around for those beauties!

hump of whale sticks out of water on gray day

A minke whale feeding near Eastport, Maine (Ed Robinson photo)

Whale watching captains being what they are, there were also regular announcements regarding the large mammals around us. With the presence of sizable schools of baitfish, we enjoyed dozens of harbor porpoises on all sides. Harbor seals were easily spotted resting on rocky shoals or feeding below sea birds diving for fish. The day before we arrived the ship’s crew had spotted a finback whale and bottle-nosed dolphins, with humpback whales seen on occasion. The excitement for our group ramped up when two minke whales began feeding close to the ship. Thank goodness the ship managed to stay upright despite everyone running to the starboard rail to see the whales.

There is considerable confusion around the naming of whales, including the whale we call the minke. To be specific, it is properly called the common minke or northern minke to distinguish it from two close relatives, the Antarctic minke and the dwarf minke. Going back more than 1000 years, this whale has been known by many different names including the piked whale, little piked whale and little finner (from a time when whalers mistook the common minke for a small finback whale).

The minke falls in the family of baleen whales, those whales that use rows of hundreds of fringed plates in their mouths to sift food from ocean waters. The baleen plates are not made of bone as are the teeth of an orca or sperm whale but rather keratin, the same material found in hair or fingernails. To further clarify matters, the minke (Balaenoptera acutorostrata – “winged whale with sharp snout”) is the smallest among the rorquals, those baleen whales that have rather short heads, short but broad baleen plates and furrowed throat skin. The minke is the smallest of the ten species of rorquals, thus its vernacular name in some circles of lesser rorqual.

These whales are black, dark brown or gray in color and svelte by whale standards, reaching just over 30 feet in length and a maximum weight of 10 tons. Females average slightly larger than males, perhaps to support the birth of a calf that often exceeds 700 pounds. The most recognizable part of the minke might be the tall, sickle-shaped dorsal fin located well back on the body. While the dorsal fin is often exposed when the whales breach for air, they rarely display their tail fins or flukes, unlike the humpbacks. There is often a pale whitish mark behind the head and over their flippers, and the underside is white. Calves are usually darker in coloration than adults, presumably to help in avoiding predators like the orcas.

Minkes seem to be relatively tolerant of boat traffic especially when feeding, and they have been observed approaching boats when the boats are quiet on the water. The first sign that a minke is in the area is often the emerging snout and a “blow” or exhalation that sprays water up to 10 feet high. Our captain told us the whales tend to surface three times for air before arching their bodies high in the water for a deeper dive. If the whales are actively feeding near the surface they may be sighted repeatedly over an extended period or they may dive for 10 to 15 minutes. In an earlier visit to West Quoddy Head Light we observed a pod of minkes feeding actively for more than an hour.

Favored food species include crustaceans, plankton, eels, and small schooling fish like herring and mackerel. The whales have been observed plunging through schools of prey while taking in large amounts of water than is then expelled. Sea birds, attracted to the concentrated prey just below the surface, are often associated with minke whale foraging.

Minke whales are believed to have a potential life span up to 50 years but they are not tracked as closely as the larger whales, such as the endangered right whales so often in the news here. Sexual maturity is believed to occur after several years when the whales are nearly fully grown. Breeding and calving generally occurs during winter months when the animals are in warmer waters near the equator The female has a gestation period of nearly 11 months and gives birth to a single offspring around 10 feet long and up to 1000 pounds. The calf grows quickly on nutrient rich milk squirted from the mother and is weaned at four to six months.

two gray and white whales swim together in bottomless blue

Minke whales courting (iStock photo by Baddpix)

Gatherings of minkes are normally just a handful of animals but in far northern waters groups up to 400 whales have been observed. The species has not been well studied by scientists, so little is known about their social structure. A range of vocalizations have been recorded including grunts, thumps, clicks and a sound described as a “boing.” The significance of the various sounds is yet to be determined.

The minke whale seems to tolerate a wide range of ocean conditions and may be spotted close to shore or in deep offshore waters, especially during migrations. They migrate seasonally, probably timed to remain in contact with favored food species, and may cover thousands of miles during their journeys. The distribution of minke whales varies by age, reproductive status, and sex. It appears that mature males are more likely to move into polar regions while females remain in warmer coastal waters, especially during calving season or when accompanied by juveniles.

Common minke whales are thought to have one of the highest populations among whales and they are found in most waters around the world north of the equator. Historically they were not pursued by commercial whalers given their speed and relatively small size compared to behemoths like the sperm, right and blue whales. This perhaps helps to explain their higher numbers since the depletion of larger whales left more food available for minkes. Most of the historic harvests were done by natives in small boats, since there was less danger in pursuing this smaller creature.

In US waters, minke whales are not endangered or threatened, but they are protected under the Marine Mammal Protection Act of 1972. Globally minkes are pursued by the remaining few whaling nations – Greenland, Japan, and Norway – ostensibly for research purposes but whale meat continues to appear on dinner plates in those countries.

A prime risk for whales that favor coastal waters is becoming entangled with fishing gear of all sorts, from herring weirs to seine nets, lobster lines to groundfish trawls. Shallower waters also increase the risk of boat strikes which can cause serious injuries or death. Scientists are worried about increased boat traffic in warming Arctic waters given the seasonal concentration of whales in those regions. As we learn more about the ways in which undersea mammals use sounds for communication and locating prey, there is increasing concern about man-made noises that may be disruptive or deadly for them. High pitched or high intensity noises such as pounding steel pilings for piers, oil rigs and fixed offshore wind turbines are a hot topic for study.

Finally, minke whales are now confronted with the same challenges of pollution and climate change that we have reviewed for so many other species. Plastic wastes, changing sea ice conditions, disruption to prey species movements, warming seas and altered ocean currents are serious concerns. Declining prey species populations can easily cause nutritional stress and disease for the minke, with a resulting fall off in reproduction rates and life spans.

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