The Short, Sad Life of a Humpback Whale Calf
by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station
Just last week we had another “washashore” come onto the island, and this one was a heartbreaker. Nantucket’s location out to sea and the prevailing currents encircling the island means we often collect the floating carcasses of recently deceased whales, dolphins, and seals. Our newest arrival is a juvenile humpback whale that washed up on Smith’s Point in Madaket after being seen floating in the water south and west of the island. As I write this article, the New England Aquarium is assembling a team of experts to come to Nantucket on Monday, July 18, to perform a necropsy on this animal with the assistance of local officials and trained Nantucket Stranding Team members. A sad but important goal for scientists in the event of the appearance of a beached, relatively rare animal is to get as much information as possible while it is still somewhat intact.
From the American Cetacean (Marine Mammals) Fact Sheet (http://www.acsonline.org/factpack/humpback.htm) we find that the scientific name for a humpback whale is Megaptera novaeangliae. Humpbacks are in the class Mammalia; order Cetacea (Marine Mammals), Suborder Mysticeti (from a translation error from Aristotle for “the mouse, the whale so called”) and Family Balaenopteridae (Baleen Whales). The humpback whale is one of the rorquals, a family that also includes the blue whale, fin whale, Bryde's whale, sei whale, and minke whale. The term “rorqual” is French, which itself derives from the Norwegian word røyrkval, meaning "furrow whale.” Rorquals have two characteristics in common: dorsal fins on their backs, and ventral pleats running from the tip of the lower jaw back to the belly area. These ventral pleats are longitudinal folds of skin that allow the mouth to expand immensely when feeding. The humpback has a distinctive body shape, with unusually long pectoral fins and a knobbly head.
The long pectoral fins give the humpback the genus name, Megaptera which come from the Greek word “mega” for "giant" and “ptera” for "wing” (very “dinosaurian” sounding). The humpback whale was first identified as "baleine de la Nouvelle Angleterre" by Mathurin Jacques Brisson in his Regnum Animale of 1756. In 1781, Georg Heinrich Borowski described the species, converting Brisson's name to its Latin equivalent, Balaena novaeangliae. Early in the 19th century Lacépède shifted the humpback from the Balaenidae family, renaming it Balaenoptera jubartes. In 1846, John Edward Gray created the genus Megaptera, classifying the humpback as Megaptera longpinna, but in 1932, Remington Kellogg changed it to Borowski's novaeangliae. At this point, I would have called them “Gary” just to settle the arguments. The common name is derived from the curving of their back when diving. The species name means "New Englander" and was probably given by Brisson due the regular sightings of humpbacks off the coast of New England.
The long black and white tail fin (fluke), which can be up to a third of body length, and the pectoral fins have unique patterns, which make individual whales identifiable. Several hypotheses attempt to explain the humpback's pectoral fins, which are proportionally the longest fins of any cetacean. The two most enduring mention the higher maneuverability afforded by long fins, and the usefulness of the increased surface area for temperature control when migrating between warm and cold climates. Humpbacks also have “rete mirable,” Latin for “wonderful net” a heat exchanging system of closely aligned arteries and veins, found in humpbacks, sharks, and fish and used to transport heat or oxygen or stabilize and control metabolism. The shape and color pattern on the humpback whale's dorsal fin and flukes are as individual in each animal as are fingerprints in humans. The discovery of this interesting fact led scientists to be able to start intensive "photo-identification" of individuals in order to not only identify them but also track their movements and monitor their populations. This ability to distinguish humpback whales provides information about their population, migration, sexual maturity, and behavior patterns. A photographic catalogue of all known North Atlantic whales was developed and is currently maintained by College of the Atlantic (http://www.coa.edu/allied-whale-microsite.htm).
Adult male humpback whales measure 40-48 feet long (12.2-14.6 m) and adult females are slightly bigger averaging 45-50 feet (13.7-15.2 m) long. They weigh 25 to 40 tons (22,680-36,287 kg). Humpback whales feed on krill, small shrimp-like crustaceans, and various kinds of small fish. Each whale eats up to 1 and 1/2 tons (1,361 kg) of food a day. As a baleen whale, it has a series of 270-400 fringed overlapping plates hanging from each side of the upper jaw, where teeth might otherwise be located. These plates consist of a fingernail-like material called keratin that frays out into fine hairs on the ends inside the mouth near the tongue. The plates are black and measure about 30 inches (76 cm) in length. During feeding, large volumes of water and food can be taken into the mouth because the pleated grooves in the throat expand. As the mouth closes, water is expelled through the baleen plates, which trap the food on the inside near the tongue to be swallowed. Humpbacks were recently discovered to use a “bubble net” to encircle fish that they drive into the net in order to herd large groups of fish into a tighter ball that they can then swim underneath and engulf in one big swallow. They usually do this as a group but can do it alone if needed. This video link http://www.youtube.com/watch?v=vJvfjiCTvq4 shows the awesome beauty and precision of this method of corralling fish.
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 (http://iwcoffice.org/conservation/estimate.htm).
Females typically breed every two or three years. The gestation period is 11.5 months, yet some individuals have been known to breed in two consecutive years. The peak months for birth are January, February, July, and August. There is usually a 1-2 year period between humpback births. Both male and female humpback whales vocalize, however only males produce the long, loud, complex "songs" for which the species is famous. Cetaceans have no vocal cords, so they make their famous songs by blowing air through their nasal cavities (basically glorified snoring!). The humpback whale lifespan ranges from 45–100 years which gives them plenty of snoring time. All the whales in the same area sing the same song; so North Atlantic humpbacks all sing the same tune. There are many theories for why males sing. They may be trying to impress a female, warn off another male, find other whales to set up a hunting group, or use it for echolocation. Perhaps they are bored. I highly recommend that you go online and listen to one of the many audio files of humpback whales songs if you are one of the two people in American who have not heard it. Their eerie, haunting songs have captivated researchers and the public for years. Humpbacks whales’ spectacular breaching maneuvers, their curiosity and “friendliness” in approaching whale watching boats, and their amazing feeding behaviors have made them an ideal whale for ecotourism, and whale watching provides an economic boon to parts of the world where these giants come in close proximity to the shore.
For several years, the UMass Boston Nantucket Field Station Grace Grossman Environmental Center has collaborated with the Provincetown Center for Coastal Studies (www.coastalstudies.org) an amazing collection of scientists and educators located in Provincetown doing excellent research on a variety of marine mammals. We also host scientists from the University of New England, collaborate with the New England Aquarium, and of course provide research and housing support for researchers from the various UMass campuses such as UMass Boston researchers Dr. Solange Brault, a pilot and right whale population expert and Dr. Meng Zhou, who studies the krill these whales eat in the Southern Ocean (Antarctica). This year, the field station has entered into a new collaboration with the Whale and Dolphin Conservation Society (WDCS), Shearwater Excursions (www.explorenantucket.com) and the Nantucket Marine Mammal Conservation Program (http://www.nantucketmarinemammalconservation.org). From the WDCS web site (http://www.wdcs-na.org/about.php): “Established in 1987,WDCS, the Whale and Dolphin Conservation Society, is the world's most active charity dedicated to the conservation and welfare of all whales, dolphins and porpoises (also known as cetaceans).
WDCS North America was born in 2005 with the merger of WDCS and the Whale Adoption Project.” According to WDCS: “the whale on Smith's Point has been identified based on observations on Saturday, July 16 as the 2009 calf of Isthmus. It is the 7th calf documented with Isthmus, who was ID'd in 1988 with her mother Orbit. Another of Isthmus's calves, Tofu, was also found dead at the age of 2. Tofu was born in 2005 and hit by a vessel in 2007. She was found floating and it took a lot of work to get her in for a necropsy — which was of absolute importance in identifying the cause of death. This calf was about to be named. It was last seen alive and well on April 30, 2011.”
It is important to remember that all marine mammals are protected under the 1972 Marine Mammal Protection Act. 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. Connie Merigo, director of the New England Aquarium’s rescue program reminds us that “only authorized, trained personnel should approach such animals along the shore.” 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.
It can be very difficult to ascertain the cause of an animal’s death unless very obvious signs of human interactions such as a propeller wound or cuts from entanglement in fishing gear are evident. Similar to what might occur during a human autopsy; an animal is measured, pictures are taken, a partial dissection is done, and samples are taken of various tissues and organs in what is called a necropsy. It may be months before toxicology results come back; some results from researchers have shown a saxitoxin, a paralytic shellfish poisoning (PSP) from contaminated mackerel has been implicated in humpback whale deaths.
On a happier note: New England is home to many museums dedicated to learning about whales from the hunts of years ago to the protection and science of their biology and behavior. Our local Nantucket Historical Associations’ Whaling Museum on Broad Street (www.nha.org) is one of the finest in the country. New Bedford also has an excellent whaling museum. You can see a humpback whale’s skeleton and learn more about them at the Whale Center of New England free, public Visitor's Center located near the Gloucester Maritime Heritage Center http://www.whalecenter.org/about-whale-center/visitor-center.html.
Next week we’ll continue this topic as we discuss the strange and unusual case of the ocean floor phenomenon known as whale fall. These have fascinated me for years, and I’ll introduce you to some of the weird creatures that have found a home when these massive and beautiful animals die. Until then, take some time to visit a museum, go on a whale watch or go online and learn more about whales. All the organizations mentioned in this column have a host of excellent resources on their websites. If you go to Smith’s Point, please stay a respectful and safe distance away from the whale, which by now is hosting a variety of bacteria and pathogens that you don’t want.