True love or bullying? Humans record humpback whale mating for the first time, and it's all males...

Spring is here, everything is coming back to life

It's the season for animals to ___ again....

Reproductive behavior is the cornerstone of the evolution of all kinds of life on Earth. For most organisms, this task requires the joint efforts of both a male and a female.

Every summer, humpback whales forage in polar waters, and in autumn and winter, they migrate to tropical waters to breed. Since the 1970s, scientists around the world have mostly observed the various social behaviors of humpback whales in autumn and winter, including play, courtship, and reproduction. But strangely, the sexual behavior of humpback whales has always been a mystery , and communication between the sexes has never been recorded.

Figure 1 Source NOAA

The reasons are: first, for the protection of whales , humans are not allowed to approach humpback whales within 100 meters; second, among cetaceans, the penis of males is usually hidden in the genitals , which helps the whales maintain a streamlined body. Males only expose their penises when they have sex, but this usually happens under the water, making it difficult to observe.

Figure 2 Schematic diagram of humpback whale genitals Source: hwrf.org

But recently, in a report published in the journal Marine Mammals, humans recorded the sexual behavior of humpback whales for the first time.

Humpback whale sexual behavior revealed for the first time

In January 2022, two photographers living in the Hawaiian Islands, Lyle Krannichfeld and Brandi Romano, were lucky enough to encounter two humpback whales while out on a boat. When the boat stopped, the two humpback whales actually swam slowly towards the boat. So they immediately awakened their professional instincts and put their cameras into the water to capture the natural beauty of the humpback whales.

However, as they were filming, they discovered something was wrong. How come the two humpback whales were swimming side by side one second, and then playing the "horse riding game" one second up and one second down?

Figure 3 Source: Lyle Krannichfeld and Brandi Romano

They observed that a humpback whale (codenamed B) would always "sneak attack" another humpback whale (codenamed A) from behind, grab it with its pectoral fins, and then stick its body to it, with a dark shadow similar to genitals appearing on its abdomen. Only then did the photographer realize that the two humpback whales might be mating.

To confirm whether this was sexual behavior among humpback whales, the two photographers contacted Stephanie Stack, a researcher at the Pacific Whale Foundation, and explained what they had seen.

Image 4: Lyle Krannichfeld and Brandi Romano

Through the descriptions and photographic evidence of the two photographers, Stephanie gave a "good news" and a "bad news".

The good news is:

This is indeed sexual behavior between humpback whales.

The bad news is:

Both are males .

How can she tell that they are all males? It is actually very simple, because the tail fin image of each humpback whale is unique, just like a human fingerprint . By observing the tail fin and cross-checking it with the data in the whale database, the basic information of each whale can be obtained.

Figure 5. The tail fin of a humpback whale. Source: Grorge Ofei

Through comparison, Stephanie confirmed that the two humpback whales exposed this time were both males, and the age difference between them was 13 years.

Since they are two male humpback whales, the question is: what does their behavior mean?

Same-sex attraction or the survival of the fittest?

When we see males with males, it's hard not to think of same-sex behavior.

In fact, homosexual behavior is not uncommon in the animal kingdom. There are records of same-sex behavior among animals such as bonobos, flamingos, dragonflies, and bison on land, and many cetaceans in the ocean also engage in same-sex behavior, such as bottlenose dolphins, killer whales, gray whales, and bowhead whales.

Figure 6 Bottlenose dolphin Image source NOAA

There are many reasons for same-sex behavior in the ocean, such as forming social bonds, relieving stress, practicing mating, etc. Regarding the behavior between the two male humpback whales this time, researchers speculate that it may be to release energy that has nowhere to go.

Because male humpback whales are often in a higher hormonal state during the breeding season, and under the influence of hormones, if there is no opposite sex around them, they will follow their instincts and look for other objects to release their energy.

Figure 7 Source: Research Attachment

Another possibility is that male humpback whales compete for females during the breeding season.

During competition, humpback whales sometimes display the S-position - an indication of threat or stress overload , characterized by a drooping tail fin and a slightly raised head, making the humpback's body look like the letter S.

Figure 8 The body of the humpback whale in the lower part has twisted into an S shape. Source: Research Attached Figure

In the photo, one of the humpback whales (codename B) seems to be showing its dominance, while the other humpback whale (codename A) is in an S-shape. More importantly, the humpback whale (codename A) that is pressed under is also sick.

Compared to the humpback whale (codenamed B) riding on top of it, it was thinner and had a large wound on its chin (probably caused by a ship collision), which showed that it was in poor health. It was also covered with whale lice (Cyamus boopis), a parasite that lives on the skin of cetaceans and reproduces rapidly when the host is sick or injured.

Figure 9: The humpback whale (codenamed A) has a broken jaw and its body is darker in color. Source: Research attachment

As the saying goes, "strike while the sick is at it", facing the sick and injured humpback whale (codename A), the other humpback whale (codename B) demonstrated its superiority to the female through suppressive behavior . It is not only stronger but also healthier than the other, thus winning the favor of the female.

Overall, although this recording is not a true humpback whale mating, it also allows researchers to learn more about the mating process of humpback whales and the postures they may adopt.

In the future, with the popularization of mobile phone cameras, you and I may be able to capture the actual mating behavior between male and female humpback whales with our mobile phones.

References:

An observation of sexual behavior between two male humpback whales

https://onlinelibrary.wiley.com/doi/10.1111/mms.13119

Humpback Whale Sex Observed for the First Time Ever, between Two Males

https://www.scientificamerican.com/article/humpback-whale-sex-observed-for-the-first-time-ever-between-two-males/

Author: Fish

Winner of the Silver Award for Outstanding Science Popularization Works of China Science Writers Association

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Editor: Dong Xiaoxian