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Science
Volume 42 Issue 19 • Sept. 13-19, 2012
now in our 42th season

Among the Whales

by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station

I have friends visiting me from the Pacific Northwest and Texas this weekend and I have enjoyed taking them around the island to the many places that makes Nantucket so special. One of my favorites is the Nantucket Whaling Museum, which not only instills wonder at the size and beauty of whales, but also reminds me that we are especially lucky to be able to view these animals in the wild around the island. Over the past few years I have written about several individual species that have either washed ashore or been seen from local vessels. Nantucket's proximity to popular feeding grounds and exposure to the open ocean results in it becoming an inevitable resting place for marine mammals in trouble.

Where once islanders made their living by hunting down these mammoth creatures, we now marvel at and financially benefit from their presence. A small minke whale swam into Nantucket Harbor a few weeks ago to both the delight and consternation of islanders. There is no definitive answer for why this mammal decided that the middle of August Race week was a good time to take a jaunt in the harbor. The most likely reason for its foray is that it was chasing small bait fish into the harbor and didn't realize it made a mistake until it had practically booked a ticket on the Steamship slow boat. This happens somewhat frequently with common dolphins that get caught up in the chase of their prey and soon find they are ricocheting between cuspate spits along Coatue and the inner harbor shoreline on the south side.

I wasn't surprised to find out that the World Wildlife Fund ranks Massachusetts as the 10th best place in the world to whale watch. The best time for whale watching in Massachusetts is from April to October, although whales have been spotted in Bay State waters as early as mid-March and as late as early November. Whales migrate to Massachusetts to feed on mackerel, herring, krill, and other schooling fish that breed in these nutrient-rich waters. As soon as the cold weather settles in, however, whales travel to warmer waters to mate and give birth.

Several types of whales migrate to Massachusetts during feeding season. The most common sightings are humpback whales, which range in length from 35 feet to 55 feet and weigh nearly 37 tons. Also common are finback whales, ranging from 45 feet to 70 feet and weighing 40 tons. Minke, right, and pilot whales are also spotted in Massachusetts waters. On rare occasions, smaller species, including sperm, beluga, sei and blue whales, have recorded. Whales seen within 30 miles of Nantucket on local whale watches or that have washed ashore over the past ten years include finbacks, humpbacks, pygmy sperm, dwarf sperm, minke, and northern right whales. Over the past few years I have written about the dwarf (Kogia sima) and pygmy sperm (Kogia breviceps) whales that beached themselves here just because I had never heard of either of these until they appeared on our shores.

Common or northern minke whales (Balaenoptera acutorostrata) are members of the baleen whale family and are the smallest of the "great whales" or rorquals which include the humpback whale, the fin whale, the Bryde's whale, the sei whale and the blue whale. The scientific name for minke whales translates to: "winged whale" (Balaenoptera) with a "sharp snout" (acutorostrata). Its close relative, the Antarctic minke whale or southern minke whale (Balaenoptera bonaerensis) shares many traits but inhabits the waters of the Southern Ocean for most of the year. Minke whales received their common name from a Norwegian novice whaling spotter named Meincke, who supposedly mistook a minke whale for a blue whale (www.nmfs.noaa.gov/pr/species/mammals/cetaceans/minkewhale.htm).

Minkes are relatively small whales with sickle-shaped dorsal fins located two-thirds of the way back on the body and white bands on their flippers, Minkes are pretty sleek for whales and typically exhibit no visible breath (spout). Like all the rorquals, the minke is a fast swimmer, capable of reaching speeds of 18-24 knots (16-21 mph). The minke can be curious, and has been known to approach ships, even at times keeping up with moving vessels.

Whale observers always look for long-distance cues such as spout patterns and fluke and tail behavior to identify whales at a distance and the minke rarely lifts its tail. Our harbor visitor was an excellent example of a minke and was estimated by Captain Blair Perkins of Shearwater Excursions (one of our many local New England Aquarium stranding volunteers) to be 20-25 feet long. The National Oceanic and Atmospheric Administration (NOAA) estimates there are 185,000 minke whales in the Atlantic. They prey on small schooling fish (like anchovies, dogfish, capelin, coal fish, cod, eels, herring, mackerel, salmon, sand lance, saury, and wolfish) and crustaceans.

The animals grow to about 35 feet and can weigh up to 20,000 pounds. They live up to 50 years and reach sexual maturity between three and eight years of age. Minke whales can be very active at the surface, breaching and "spyhopping" (a term for raising their heads vertically out of the water) while making clicking and, up until recently unidentified, "boing" sounds.

You might recall last year that we had a juvenile humpback whale wash up on Smith's Point in July. Humpbacks are seen relatively frequently around Nantucket. Humpback whales (Megaptera novaeangliae "mega" for "giant" and "ptera" for "wing") may grow to be fifty-five feet long and they are usually black with long white flippers, knobby bumps on their heads and distinctive, variably sized dorsal fins. These are showy exciting animals on a whale watch with spectacular breaching maneuvers, exhibiting flamboyant tail lifting while diving with distinctive black and white patterns underneath. Their signature bubble net fishing techniques are icing on the cake. During the spring, summer, and fall, these whales are found most often around the sloping sides of the banks and ledges of the Gulf of Maine, Georges Bank, and the continental shelf south of the Islands. Humpbacks are baleen whales that feed on mostly small schooling fish like sand lance, herring, young mackerel, and krill. Each whale eats up to 1 1/2 tons (1,361 kg) of food a day.

Because their feeding, mating, and calving grounds are close to shore and because they are slow swimmers, the humpback whales were an easy target for early whalers. The International Whaling Commission (IWC) gave them worldwide protection status in 1966, but there were large illegal kills until the 1970s. Population estimates vary from 35,000 to 70,000 individuals depending on the source.

North Atlantic Right whales (Eubalaena glacialis which means "good, or true, whale of the ice") are the most seriously endangered whales with a population teetering between 400-500 animals. According to a census of individual whales identified using photo-identification techniques, the latest available stock assessment data (December 2010) indicates that a minimum of 361 recognized individuals were known to be alive in 2005. More than 450 North Atlantic right whales are thus thought to exist at present; almost all living in the western North Atlantic Ocean. Vessel strikes and entanglement in fixed fishing gear are the two greatest threats to their recovery. They migrate between their feeding grounds in the Gulf and Maine, the Bay of Fundy, and in Cape Cod Bay and their calving grounds down south off the coasts of Georgia and Florida.

North Atlantic Right whales are stocky (they prefer big-boned) mostly black whales with no dorsal fins and rough white patches called callosities on their heads. They can be identified at a distance from their spouts which appears as a V-shaped pattern of water vapor due to their partitioned blow holes. When they dive they usually lift their black, triangular tail high. They eat zooplankton, including copepods (tiny crustaceans), euphausiids (small shrimp-like crustaceans), salps (gelatinous tunicates) and cyprids (barnacle larvae). Unlike other baleen whales, right whales are skimmers: they feed by removing prey from the water using baleen while moving with their mouth open through a patch of zooplankton.

Our other local cetacean denizen is the fin whale (Balaenoptera physalus), also called the finback whale, razorback, or common rorqual. Finback whales can be up to 80 feet in length and their dorsal fin is very far back on their dorsal (back or upper) side. They are the second longest animal in the
world and the second in size after the Blue Whale. Finbacks are grayish, sleek whales with tall, curved dorsal fins. Their heads are asymmetrical with darker markings on the left side and lighter marking on the right side. The reason for this unusual coloring is unknown, but some scientists have speculated that fin whales circle schools of fish with the white side facing the prey and frightening them into denser schools that are easier for the whale to catch. Other scientists theorize that this lighter color is mostly pointed downward as they swim on the right side to feed. Of course a few have to swim on the left side just to mess with that theory. Similar to the minke whale, finbacks rarely lift their tails while swimming. Like other baleen whales, fin whales have two blowholes positioned in a V-shape while toothed whales have only one blowhole. They have a broad, flat rostrum (upper part of the head). Their throat grooves or ventral pleats, in addition to streamlining their shape, allow their throat area to expand tremendously during feeding. In the North Atlantic, they prey on krill and small schooling fish (e.g. capelin, herring, and sand lance) which they can scoop up while swimming on their sides at speeds from 6-10 mph while side-feeding and up to 25 mph while lunging into balls of fish.

Fin whales were severely overhunted in the 19th and 20th centuries and are still hunted by commercial vessels from Iceland and Japan and aboriginal subsistence vessels from Greenland. Estimates suggest that the population of the remaining fin whales in the all the world's seas range from less than 100,000 to roughly 119,000. As with many whale species there is a division of species between northern and southern hemispheres. The fin whale that inhabits the North Atlantic is the Northern fin whale, (Balaenoptera physalus physalus) which is smaller than and distinct from the southern fin whale (Balaenoptera physalus quoyi). Fin whales are more gregarious than other rorquals, and often live in groups of 6–10, although feeding groups may reach up to 100 animals.

Another relatively common marine mammal visitor is the long finned Pilot whale (Globicephala melas). Like the orca, the long-finned pilot whale is really a dolphin (Delphinidae family). Six of the larger species in the Delphinidae, the Orca and the Pilot (long-finned and short-finned), Melonheaded, Pygmy Killer and False Killer Whales, are commonly called whales, rather than dolphins; they are also sometimes collectively known as "blackfish."

A female pilot whale beached itself twice and eventually died in June of 2011 near Smith's Point. Pilot whales are often involved in mass strandings off of Cape Cod. During the summer of 2000, there was a mass stranding of 11 pilot whales on Nantucket on the 4th of July. The weather was clear and calm and the animals showed no obvious underlying health problems as opposed to other mass strandings that can be linked to storms or unusually high or low tides. From the New England Aquarium (NEAQ) website: "The term "mass stranding" refers to events in which groups of distressed cetaceans (whales, dolphins, porpoises) come ashore alive. They can involve anywhere from a few to several hundred animals. Mass strandings regularly occur in several parts of the world (primarily Australia, New Zealand and Cape Cod), yet so far we have no universally accepted, comprehensive explanation for this syndrome. In many cases, the animals show no obvious signs of health problems other than those resulting from coming ashore. Although mass strandings typically occur during winter months and at times of severe weather, they can occur at any time of year and under any conditions. Once a cetacean comes ashore, a cascade of physiological changes occurs, often resulting in shock and death. Because the species typically involved are extremely social, the bonds that hold groups together are perhaps strong enough to supersede the survival instincts of individual animals. Although we don't know what specifically might set off a mass stranding event, we know that once animals start coming ashore, it's extremely difficult to stop the process from continuing and escalating. Affected animals will relentlessly follow one another ashore, as if crippled by widespread panic, even when there is clear access to open water. Gregarious offshore species such as Atlantic white-sided dolphins (Lagenorhynchus acutus) and long-finned pilot whales (Globicephala melaena) are particularly known to mass strand in New England, mainly on Cape Cod." Sometimes it does not pay to be one of those friendly party people.

It is important to remember that all marine mammals are protected under the 1972 Marine Mammal Protection Act. This year marks the 40th anniversary of this critically important legislation which has ensured that our children and grandchildren will be able to see these creatures in the wild.

The New England Aquarium (NEAQ) oversees the Nantucket Stranding Team volunteers on island and local volunteers go through extensive NEAQ training before they are allowed to work with the team. The aquarium is authorized by the National Oceanic and Atmospheric Administration's Fisheries Service to respond to marine mammal strandings of whales, dolphins, porpoises and other animals. Anyone spotting a stranded marine mammal on Nantucket is urged stay away from the animal, and to call the NEAQ's 24-hour stranding hotline at (617) 973-5247.

 

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