Humpback Whales Off Our Coastby Jim Rapp
Earlier this summer, the residents of Bethany Beach in Delaware awoke one morning to find that a dead ocean giant had washed ashore. They gathered around the body, gazing in awe at the 33-foot marine mammoth that had been delivered in the dark by the previous high tide.
Scientists at the scene announced that the colossal carcass belonged to a juvenile male Humpback Whale. The 33-foot length indicated that he was between 1 and 2 years old, and weighed around 33,000 pounds. The young whale was roughly the length and weight of a small motor home.
A preliminary investigation of the partially decomposed body found a gash in the whale's neck that may have been caused by the strike of a ship's propeller. Following the harvesting of its organs to perform a necropsy, or animal autopsy, the dead whale was buried in the sand along the Delaware coastline, just a short distance from its ocean home.
The story of the dead whale made the news as far away as Philadelphia and Washington, D.C. Beached dead whales often make headlines, as do sightings of these mysterious marine mammals when they venture out of the Atlantic and into our shallow Chesapeake and Delaware Bays. Newsrooms know that we are fascinated by whales, dead or alive.
The dead humpback was likely migrating near the Delmarva shore when the presumed blunt force trauma from the propeller ended its' short life. Thousands of Humpback Whales migrate north along the Atlantic seaboard during the spring. During migration, humpbacks stay near the ocean surface, where they are more likely to encounter shipping traffic.
Lucky whale watchers on Delmarva sometimes see them performing magnificent aerial acrobatics, such as jumping out of the water, a behavior known as "breaching," or slapping the ocean surface with their immense tails, fins and heads. Whales can also be seen when they surface to breathe through a blowhole located on top of their massive head. With each breath, they release a spout that may be 20 feet tall.
Humpbacks migrate from winter calving grounds in the warm, tropical Caribbean Sea to feed in the cold, bountiful waters found at higher latitudes, such as the Gulf of Maine. They spend the majority of the summer feeding on plankton, tiny crustaceans known as krill, and small fish, such as herring, mackerel, and sand eel.
Humpbacks gorge themselves on up to 3,000 pounds of food each day in the summer, which is necessary for surviving the lean winter months. During the winter, they will live off of the fat reserves stored in their blubber.
Humpback Whales are filter feeders. Fibrous, comb-like plates known as baleen, act as filters in the whale's mouth. Baleen is made of keratin, the same protein that makes human hair and fingernails. Humpbacks can have up to 300 plates of baleen inside their mouths, which are worn down at the edge by their giant tongues to form a bristly fringe.
When feeding, the whales gulp enormous mouthfuls of water filled with tiny prey animals. As the mouth fills with water, their pleated throat expands and balloons outward. When the whale brings its immense jaws together, the water is strained out through the baleen, and the plankton, krill and fish that remain are swallowed.
Humpback whales are known for their skill in hunting large, swarming shoals of small invertebrates and fish. They can blow air bubbles around their food to herd or disorient their tiny, swimming prey. One social hunting technique, known as "bubble netting," is unique to humpbacks.
A bubble net forms when a group of humpbacks swim in circles around their prey, blowing air bubbles as they swim. As the circles get smaller, the bubbles form a net that captures the food. While some whales are busy making bubble circles, others dive deeper to push prey toward the surface. When the bubble net is set tight and the prey are corralled into dense groups, the whales will burst upward with their huge mouths open, swallowing the food-rich water in one big gulp.
Named after the arching, above-water hump that forms near their dorsal fin when they prepare to dive, Humpback Whales can grow up to 60 feet long and weigh 40 tons. Females tend to be larger than males. Even baby humpbacks are big -- a newborn weighs about one ton at birth. Humpbacks normally live for 45 to 50 years.
Their body coloration is dark grey, with patches of white on their fins and belly. The gray and white color pattern on the underside of the twin flukes of the humpback's tail is unique to each animal, and can be used much like a human fingerprint to identify individuals. Humpbacks also have round, wart-like bumps on their heads and on the edges of their fins. Three different species of barnacle can be found growing on their bodies.
Humpback whales have long pectoral fins, which measure up to 15 feet in length. Their long fins help the humpback slow down when swimming, or go backwards. Their scientific name is Megaptera novaeangliae which translates to "big-winged New Englander." Although they are found in all of the world's oceans, Europeans gave the humpback its Latin description after documenting them in the waters off New England, hence the unusual name.
In their Caribbean wintering grounds, male Humpback Whales gather and engage in aggressive, and sometimes very physical, mating activities. Behaviors include lunging at each other with their heads above water, dramatic bubble displays, and violent tail thrashing. Males occasionally make physical contact when they breach and land on top of one another. These fights can cause injuries ranging from bloody scrapes to death.
During the breeding season, males also sing beautiful, complex songs that can last up to 20 minutes and be heard 20 miles away. A single male may repeat the same song over and over again for hours. Within a population of humpbacks, all males sing the same version of the song, but the song changes slightly over time. Scientists understand very little about why Humpback Whales sing.
Females usually breed once every 18 months to two years, and are pregnant for about 11 months. The one-ton newborns are 13 to 16 feet long at birth. The whale calves nurse from their mothers in the warm, shallow water, gaining weight from the nutritious milk and laying on blubber before migrating to colder water in the summer.
Mother humpbacks are affectionate with their babies, and will protect them by swimming close together and touching them with their flippers. Males do not help in raising the young.
From the 1600s through the mid-20th century, humans hunted Humpback Whales in the North Atlantic for oil, meat, and baleen. The population fell by an estimated 90% before a 1966 moratorium was put in place by the International Whaling Commission.
Today, Humpback Whale populations are increasing in much of their range. Apart from trauma caused by ship and propeller strikes, threats to humpbacks include entanglement in commercial fishing gear, marine pollution, harassment from unethical whale watching operations, and seismic air gun blasting associated with offshore oil and gas discovery. To learn more about seismic air gun testing proposed in the Atlantic off the Delmarva coast, please visit this website.
We hope you have the good fortune to one day witness a living, breathing and breaching Humpback Whale from one of our beautiful beaches. Enjoy your summertime wildlife watching wherever you go, and we'll see you outside, Delmarva.
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