Throughout human history, there have only been two recorded instances of this species being born. Who are we talking about?

For centuries, researchers have been trying to uncover the mystery of how and where the offspring of the largest animals on the planet are born. In fact, their births have only been witnessed twice in recorded history.

https://focus.ua/technologies/695140-za-vsyu-istoriyu-chelovechestva-zafiksirovano-lish-dva-sluchaya-rozhdeniya-u-etogo-vida-o-kom-idet-rech2025-02-25 07:46:58

The ocean covers more than half of the Earth's surface and is home to the largest animal on the planet — the blue whale. Before the onset of whaling, there were hundreds of thousands of blue whales in the ocean, but even today their population is estimated to be around 10,000 to 25,000. It is known that female blue whales give birth every two to three years; however, throughout human history, only two instances of blue whale calves being born have been recorded — both occurred decades ago, according to PHYS.org.

As a result, the birth of these marine giants remains a true mystery: the births themselves are very discreet, and calves are encountered much less frequently than scientists might expect based on the animals' pregnancy rates. Calves closely follow their mothers and are observed as mother-calf pairs, but why are there so few of them?

In a new study, a team from the University of Washington focused on uncovering the reason. The findings suggest when and where these "invisible" births actually take place and where blue whale calves spend their first months of life.

According to co-author of the study, Professor of Aquatic and Fishery Sciences at the University of Washington, Trevor Branch, he and his colleagues decided to solve the mystery by examining a range of hypotheses. The authors of the study believe that one of these hypotheses provides the best explanation: scientists typically conduct observations during the summer months when whales are feeding, while calves are born in the fall and winter and are weaned before returning to feeding grounds.

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It is known that in the summer, blue whales migrate to colder regions rich in krill for feeding, such as off the coast of California. In winter, when the females are ready to give birth, they return to warmer areas like the Gulf of California and the eastern tropical Pacific. About seven months after birth, and already at a colossal size of 16 meters, calves are weaned and stop interacting with their mothers.

At the same time, observations show that among various populations of blue whales, high pregnancy rates of 33-50% per year seem to contradict the average observed rate of 3.1% for mother-calf pairs.

The researchers explored other hypotheses and concluded that the timing of birth hypothesis best explains the observed patterns. Notably, among other hypotheses, scientists considered:

low fetal survival;
low calf survival;
low birth rates;
separation of calves from mothers.

According to Branch, their theory most convincingly explains the mystery of the missing calves: blue whales give birth to calves or deliver them shortly after leaving their summer feeding grounds, and wean them off at about seven months, just before returning. This explains why researchers, most of whom conduct field studies on blue whales during the summer months, rarely see mothers with calves.

One concern raised by the low detection rates of calves is that it could be a warning sign of low birth rates or calf survival. Fortunately, the results of the new study indicate that the situation with blue whales may be better than previously thought.