Siobhan

Siobhan the humpback whale

The Story of Siobhan

Siobhan (pronounced sha-VAHN.) is a female humpback whale that was named by the Jenny family of Washington State, who are adoptive parents in Pacific Whale Foundation's Adopt a Whale program.

The name Siobhan is of Irish origin. It is a variation of the name “Joan” which is a feminine form of the name “John.” While this whale lives in the Pacific Ocean—thousands of miles away from Ireland—it’s fitting to note that it is was identified in Hawaii, which is an “island state,” just as Ireland is an “island nation.”

Pacific Whale Foundation researchers first became acquainted with Siohban on April 13, 2010, off the coast of Maui. Maui is the second largest of the Hawaiian Islands, with a land area of 729 square miles. Like all of the other Hawaiian Islands, Maui is volcanic in origin. Haleakala, a dormant volcano rising more than 10,000 feet above sea level, is a major geographic feature on Maui. Older than Haleakala is the extinct and eroded volcano known as Mauna Kahalawai or simply, Kahalawai, is also often called the West Maui Mountains. These massive mountains help to shield the south and west shores of Maui from the tradewinds that blow from the northeast.

Off Maui’s south and west shores is a relatively shallow area of ocean, bordered by the nearby islands of Molokai, Lanai and Kahoolawe. In some areas, the ocean here is only about 100 feet deep. This shallow water region, sheltered from the strong trade winds by the towering presence of Haleakala and the West Maui Mountains, offers a uniquely protected area in the midst of the vast deep ocean. It is in this four-island region that the majority of Hawaii’s humpback whales are found in the winter months.

The humpback whales come to Hawaii in winter to mate and give birth. When Siobhan was sighted off the coast of Maui in April, 2010, she was with a calf. The pair was located in an area known as Ma’alaea Bay. She and the calf were very active and were breaching and pec-slapping repeatedly. (Pec slapping occurs when the whale slaps its long flippers down on the surface of the sea, often creating a loud noise.)

We believe that Siobhan’s calf was born earlier in winter. Gestation for humpback whales ranges from ten to twelve months. We often start seeing tiny newborn calves in December; by January, it’s commonplace to see them. Typically, the calves that we see in April are larger and more active. It’s not unusual to see a calf breaching or slapping its tail or pec fins repeatedly. On one whalewatch, we counted as a calf tail slapped more than 40 times.

The calf’s nourishment comes entirely from its mom during these early months of life. The mom produces about 100 to 130 gallons of thick, fat-rich milk each day. Compared to the milk of domestic animals, this milk is superfood. It contains 40 to 50 percent fat, compared to the 2 to 17 percent fat content of domestic animals, and much less water – just 40 to 50 percent, compared to 80 to 90 percent water found in the milk of domestic animals. On such a diet, it’s no wonder that the calf grows rapidly, at the rate of about a foot a month.

Like all humpback whale moms in Hawaii, Siobhan produced all of this milk for her calf at a significant nutritional cost to herself. Hawaii’s warm ocean waters do not sustain the large quantities of small schooling fishes and euphausiids (krill) that make up the diet of North Pacific humpback whales, so the whales do not engage in feeding behaviors while here. Instead, the females provide nourishment from their own fat reserves. During a winter in Hawaii, a nursing mom can lose 25% of her body weight.

Lactation by the mom is believed to occur for eight to twelve months. Fortunately, as summer approaches, the mom and calf migrate northward to their cool water feeding areas, where mom can eat again. For Hawaii’s humpback whales, these feeding areas stretch from southern British Columbia in the east to the Bering Sea in the west. It’s a 2,500 to 3,000 mile journey to reach the northern feeding areas.

While our encounter with Siobhan was limited, we believe she likely behaved in much the same way as other mother whales while caring for her calf. Mother whales engage in a lot of contact with their calves, using their head and pectoral fins to nudge and corral their youngsters.

Caring for a calf is hard work, and a mother whale like Siobhan does it all alone. Males do not provide any assistance in raising the calf. A mom’s efforts to raise her calf are not always successful. Researchers estimate that 25 to 30 percent of all newborn calves will not live past their first year. The long migration, attacks by predators such as sharks and orcas, entanglements with marine debris and ship collisions all take their toll on calves.

Fortunately, female whales like Siobhan have an average birth interval of only 1.7 years, once they reach the age of almost twelve years old. Thanks to these dedicated moms, and the protection provided to whales by the international ban on commercial whaling, the humpback whale population in Hawaii is increasing steadily—very good news for all who care about these majestic marine mammals.

Siobhan Sighting Map

Siobhan sighting map

Species: 
Whale
Area: 
Hawaii