Even as Cape Cod sits this morning under even more snow *sigh*, movements are under way that signal that spring is here. Our trees are beginning to fill with migrating birds, while off shore, baby humpback whales are on the move at their mother’s sides. They are are beginning to arrive in the northern waters they will call home for the first year of to the delight of whale watchers.
The baby humpback whales we encounter at Stellwagen Bank National Marine Sanctuary were not born here. Because the waters in the Gulf of Maine are very cold in the winter and spring, baby humpbacks would likely not survive long, as they are born with very little fat on their bodies. For this reason, most breeding and calving activities take place in the Caribbean Sea at the Silver and Navidad Banks, underwater seamounts located near Puerto Rico and the Dominican Republic. Interestingly Silver bank is the sister sanctuary of Stellwagen Bank National Marine Sanctuary and was designated as a marine mammal sanctuary by the Dominican government in 1996.
Migration route of western Atlantic humpback whales.
Since the waters are bathtub warm, the babies are protected from hypothermia as they accumulate an insulative fat layer of blubber. Additionally, the waters of the Caribbean are more saline, or saltier, than northern waters. Saltier water makes things float better, and that helps the baby whale float as they practice swimming. Also, the whales’ only significant predator, the Orca or killer whale, is largely absent from these relatively unproductive waters.
Following a gestation period that begins roughly 12 months prior, a single calf, never twins, is born tail first. The mother assists the baby to the surface for its first breath. Big babies in any sense, calves are born at ten feet long and one ton in weight! Able to swim, but still unrefined in their abilities, the babies often catch rides behind the dorsal fin on its mother’s back to break the drag as they gain size and strength from their diet of milk provided by the cow. This is why Caribbean whale watch guidelines differ from ours here. These calves have no experience with anything beyond mom; they are new-borns and must be given plenty of space.
A very young humpback whale in the crystal clear water of the tropics.
Hearty eaters, baby humpback whales will consume an estimated 50-100 gallons of fat and protein rich milk per day! The milk is expressed from mammary glands that are hidden away in folds of skin along the mother’s belly. The baby nudges the mother to stimulate feeding and she pumps the milk through contractions into the babies’ mouth. This sounds simple and familiar enough except when one considers that baby whales cannot form a tight seal with their lips and lack the muscles necessary to suckle. The result is a method of feeding whereby the baby receives the thick, viscous milk while docked at its mothers teat, much like a airplane receiving in-flight fueling! And this method is highly effective; in thirty-plus years of whale watching, we have never seen a single drop of spilled milk around nursing humpback whales!
During the first few months of life, the calf grows quickly. It is not unusual for a baby humpback whale to gain 100 pounds of weight per day in the first six months of life. Its swimming abilities are practiced and refined, and at about four months old, the cow and calf will begin their northward migration towards Cape Cod and the productive waters of the north. Everything is at stake for the cow at this time. as she has ben living off her accumulated fat stores from the year before to sustain not just herself, but also her baby. She must begin to feed to sustain herself, and to produce milk for her young or risk perishing.
This is why, at the beginning of the whale watch season, many of the first humpback sighted are cow/calf pairs. The mothers arrive, and begin feeding while the calves swim along side. At four or five months old, the calves are akin to toddlers. They are curious about the world around them, and as the season progresses, they will make longer forays further from mom’s side to explore and play.
A close approach by a humpback whale calf.
Play is very important in the life of all young mammals. Through play, they learn about their bodies abilities and limitations. Their primary, and most enduring role-models for behavior are their mothers. If she frequently flipper-flaps, her calf may do so as well. If she uses bubble traps in feeding, the calf will likely do so later in life as well. Behaviors are often performed in tandem, with both mother and baby active at the same time. This can result in show-stopping whale watch action!
The calves will begin feeding alongside their mothers as their baleen grows in; usually by six months of age. Many of the first feeding attempts are simply mimicking the cow’s feeding strategy, and successful attempts are unnecessary as the calf continues to receive milk. By fall the calves will have doubled or tripled in size and are more difficult to tell from smaller adults. They will often be feeding continuously with the adults and their feeding attempts have a new purpose.
As the whale watching season draws to a close, the cow and calf humpback whales begin to leave the Gulf of Maine and Stellwagen Bank as they head back toward the Caribbean. At some point, the female will stop nursing and the cow/calf bond will break. From that point on, the young whale will be on its own for the rest of its life. Having provided care for the baby, the mother humpback will head south to recharge, and the calf will often begin to associate with other young whales until all return north the following year. Last year over fifty new calves visited Stellwagen’s waters. We hope this year there will be more and that you can join us to see them!