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Wednesday, May 31, 2023

Caño’s Story: Baby Humpback Learns to Dive

You might not think that a whale needs to learn how to dive, but it does, just like children need to learn to walk. Born along Costa Rica’s Pacific coast, baby humpback whales learn to swim, dive and be good whales. Offshore of the OsaPeninsula, we watch whales grow up throughout the year, every year.

A baby humpback whale needs a lot of help from its mother, plus a lot of milk. Every day, little whales drink more milk than would fit in your refrigerator. A mother whale usually swims and floats right next to or just under the little one. Often the baby will rest on the adult’s back, to be brought to the surface whenever it needs a breath.When mom swims, the little whale gets sucked along in a special slipstream of water currents made by the big whale as she slowly fins along. Much of the time, the new baby does not need to do much – just go for a ride and breathe.

A mother whale with a newborn does not go far; she stays close to the shallow, protected bay where she gave birth, and where she may have been born herself. A newborn humpback whale probably stands a much better chance of surviving its first weeks in a place where there is not a lot of big wind and waves. To migrate to and then survive in the higher latitudes of feeding areas, a little whale must practice diving and coming to the surface to breathe, with help and teaching from its mother and perhaps other whales.

A baby humpback is awkward and clumsy; it rolls around and seems unable to get all that blubber to dive down. When a humpback whale wants to dive, it lifts its tail out of the water, and this pushes the whale down quite a bit, making it much easier to dive. This action is called a flukes-up dive. While some whales learn it faster than others, it seems to take the little ones many days to get it down pat. I watched one little humpback learn to dive like this after practicing for a fortnight.

The little whale, named Caño by area schoolkids, started life with her tiny dorsal fin bent over. She was about as big as a bottlenose dolphin. A couple of days later, by the time she had learned to float and breathe sometimes on her own, the little fin stood straight up. Soon, Caño was swimming around for short distances. She then began to practice lifting her little whale tail up – the first step in diving down.

At first, Caño’s tail flukes would flop to one side, or not come up high enough to push her down underwater. She tried again and again. One day, as she was working on her flukes-up dive, a boat came and began to drive right at her, making her mom come over and stop her practice.

The boat and its people bothered the little whale for a while, and then another boat came and did the same. If this kept happening, learning to dive would have taken the young whale a lot longer.

The boats finally went away, and she went back to practicing diving as we watched from a distance, floating with our motors off.

Another day, she almost swam into a commercial fishing boat’s long line. The tough line, if wrapped around a fin, could slowly saw it off. Again, Caño went back to practicing her flukes-up dive. This little whale was diligent and persistent.

One sunny day, Caño executed a perfect flukes-up dive into the blue Pacific. She stayed down almost four minutes, the longest we had seen her dive. Her mom breached halfway out of the water afterwards. A few days later, Caño and her mom were swimming near Caño Island Biological Reserve, more than 20 kilometers away.

About two weeks later, Caño faced her biggest challenge yet. A pack of giant dolphins, each longer than a car, decided they wanted a bite of the little whale. The huge dolphins, known as false killer whales or pseudorcas, had been attacking whales in the area. We saw more than a dozen pseudorcas chase a big humpback, repeatedly surfacing right alongside the whale as it swam at high speed. The humpback was huffing harder then I have ever heard a whale breathing, with wheezing, haggard blows. About the same time, Caño showed up around our boat with big bite marks on her tail. Maybe she was just big enough to get away. Somehow, Caño survived to fin her tail.

The little whale was getting into shape for a very long trip. Costa Rica is a great place to get big, but colder waters have greater productivity, and thus are the best place in the world to eat enough to stay big. The largest animals in the world, such as blue and fin and humpback whales, like to feast in cold waters that are home to massive quantities of fish, shrimp and krill.

Humpbacks born during the dry season in Costa Rica head north; many are photographed off California. Others born here in the wet season are sometimes photographed in the Antarctic Ocean. Tico humpbacks head north and south because that’s where the food is. But Costa Rica’s protected Pacific bays are among the best places for a tiny humpback whale to be born, grow big on mother’s milk and learn how to dive.



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