Last week I heard a fascinating talk by a whale biologist from Hawaii. Her name is Rachel Cartwright and she opened her seminar with a personal story of being on a boat for the first time in Alaska and seeing humpback whales. That first encounter touched her in a way that would shape her life and career. She eventually followed in the footsteps of Marine biologist Rachel Carson, who studied humpback whale migrations-(perhaps it was the similarity of their names?). Rachel Carson is best known as the author of the book “Silent Spring” published in 1962, which started a large environmental movement.
On the deck of that wildlife tour boat in Alaska Rachel Cartwright was treated to a special event: the humpback whale’s bubble net feeding behavior. Her wildlife guide informed her that the whales were feeding in Alaska’s waters for the summer and would soon leave to spend their winter in the warmer waters of the Hawaiian Islands, mating and giving birth. Rachel eventually made her way to Hawaii to verify the story. She did not stop at that, she became the lead scientist in the Keiki Kahola project researching the biology and health of the humpback whale population, specifically by studying calving mother whales and their “little ones”.
Bubble net feeding is a behavior specific to humpback whales. A group of whales dives under a school of fish and releases air from their blow holes while swimming in circles. The air ascends to the water surface as big bubbles. These bubbles create a barrier to the fish, keeping the school trapped inside the whale circle. In complicated patterns, the whales then swim in from below with their mouths wide open to take huge gulps of fish. The grooves in their throats extend to take in the large volume of water, which is subsequently pressed out through the baleen with an enormous tongue, leaving only the fish in the whale’s mouth to be swallowed. This peculiar and highly sophisticated group behavior is often observed on whale watching tours out of Juneau or Seward, but never in Kodiak. I am not sure about this, but my guess is that the ocean bottom and topography of Chiniak Bay is just not right to make this work.
When I guide wildlife tours in the summer, we have on several occasions had the privilege to observe mother humpback whales with their calves after they had made their first large journey from Hawaii north to Kodiak. On some lucky days, we witnessed the young whales breaching, leaping out of the water into the air, not once but several times. One day, with the boat full of photographers with long lenses on their expensive cameras, a whale gave such a show, that I was worried it set an impossibly high bar for future adventure delivery. People asked me why the whale was doing this, and I had no real answer for them other than “I don’t really know”.
In the talk, Cartwright mentioned this behavior of young whales. Curious why whale calves would seemingly waste so much energy when according to all contemporary knowledge whales were pressed to eat enough calories, she decided to study this behavior. Let’s back up to what we know: Humpback whales leave Alaska between September and late October to swim to Hawaii. They do not feed in Hawaii, though they may take advantage of abundant food if they encounter it during the migration. Calories are needed to manage their daily metabolism, constant swimming, a two-way migration between Hawaii and Alaska and for reproductive females to give birth to a baby the size of a Subaru Forester, and nurse such a big baby. All the while the whales do not eat for the entire time when they are not in Alaska.
First, I learned that there is a lot of misinformation online for the facts around whale reproduction, nursing and early growth, especially the amount of milk a whale calf drinks per day (it is NOT 150 gallons or 500 Liters-this is a myth). Obviously, it is not easy to just take a sample of milk from a whale, or weigh and measure a few calves and their moms every week. Some information researchers are still using today comes from logbooks written in the whaling days. In some cases, the information is taken from one whale species and extrapolated for another species. All that introduces error and leads to a certain degree of false information.
In the case of humpback whales it seems that the numbers used to describe the fat content of whale milk were from another species, and the calorific need of the calf higher than what the Hawaiian research group calculated. They also found that mothers with calves had a better nutritional status than females without calves. While this seems counterintuitive, if interpreted together with the total numbers of calves seen per season, the conclusion was that only well -nourished females conceive, while those with low body mass index did not have calves. Thus, as a population, whales self-regulate their numbers and fat is beautiful.
So, why do the young whales splish and splash around and jump out of the water? Of course, I am biased and think that they are simply overjoyed to finally see Kodiak! It seems that the researchers found another explanation: Next to haemoglobin, which is the means to storing oxygen in the bloodstream, whales also have a lot of myoglobin, which allows them to store oxygen in the muscle tissue itself. This is one of the tricks that enables them to dive deep and for a longer time. Apparently, calves do not have high levels of myoglobin. To activate production of myoglobin in their muscles, they must exercise. The more they exercise at the surface, the better they get at deep diving!
In addition, there was also some evidence that in times of food shortages, some whales may change their migration routes. In some areas, sightings of mother - calf pairs diminished, while at the same time more were seen in areas, where they previously were rare. There is so much that we don’t know about the world of the animals we share this planet with. I hail all those researchers who follow their heart to unveil some of these wisdoms of animals that have owned this world long before naked beach apes appeared. Thinking about what messages I took home from the humpback whale talk, I think there are three: 1. Don’t believe everything you read on the internet, 2. There is so much intelligence in the amazing depths of the ocean that it is unwise and somewhat arrogant to assume we have it figured out and 3, we should leap for joy as often as we can, because exercise enhances the ability to survive.