Sperm whales – in the dark blue of the sea

Last year, for example, we observed a large adult male sperm whale that had only arrived a few days ago and had not yet joined any companions. During the morning we saw him jump out of the water twice, which seemed very impressive given his size. In the afternoon we found our big, strong, lonely sperm whale not so lonely anymore. He had gathered a proud group of 11 sperm whales around him. Including many females, some young sperm whales and also a baby. At approximately 17 meters, it was by far the most impressive sperm whale in this family. Did he attract the attention of the other whales with his jumps in the morning? Did he perhaps even call them together? The fact is that we saw him swimming alone days before and in the morning, but after the jumps he had a whole family gathered around him.

Of course, he was only interested in females that were ready to mate, because that was the reason for his long journey from the Arctic here to Dominica. He wants to mate, but this isn't very easy with a full-grown bull of his size.

In male sperm whales, puberty begins at an average age of 9 years, when they have reached a size of 9 - 10 meters. However, spermatogenesis, or sexual maturity, is not completed until the child is around 20 years old.

However, sexual maturity in female sperm whales begins much earlier. With an average age of 9 years and a height of 9 meters, they are already taking part in reproduction. Sexually mature females usually ovulate in spring (January to July). Off the Azores, for example, the peak of mating has been observed between March and May.

The size of the testicles is also important in other whale species. In males that fight for a particular female and drive their rivals away, such as humpback whales, the testicles are relatively small. In males, which mate with many females as often as possible and do not hinder their rivals, as has been observed in right whales, the testicles are much larger.

The erectile tissue of the penis is surrounded by elastic and collagenous tissue, which is permeated by blood vessels and nerves and covered by a thick layer of muscle packages. Camels also have a comparable muscular penis. However, the corpora cavernosa portion of the relatively long and mobile penis is very small compared to other mammals.

The female sexual organs are typical of mammals. The ovaries are located in approximately the same place as the testicles in male animals. The uterus is comparable to those of carnivores and pigs, but develops slightly differently in toothed and baleen whales. In immature whales, the uterus still consists of two so-called uterine horns that are identically formed.

However, later in toothed whales the left uterine horn develops wider because that is where the fetus generally develops. In baleen whales, however, the fetus can develop in both uterine horns.

The fertilized egg implants very loosely in the mucous membrane and therefore has the advantage that there is only minimal bleeding after birth. The relatively long cervix has a thick, muscular wall and extends into the interior of the vagina. The vagina merges into an elongated fold (vulva) with two pairs of lips, which lies directly in front of the anus.

For example, the birth date of a pregnant dolphin can be predicted based on the distance between the suckling slits. In dolphins kept in dolphinariums, the distance between the nursing slits of pregnant females is measured daily shortly before birth. A distance of 40 mm is normal. But when birth is imminent, the distance is 60 mm. In addition to the body temperature dropping from the normal 98 - 99o Fahrenheit (36.7o - 37.2o Celsius) to 96o Fahrenheit (35.6o Celsius), these are sure signs that birth is imminent.

But how does an adult sperm whale bull, 18 - 20 meters long, manage to find the even further away vagina with his two meter long penis, which is about 10 - 12 meters away from his eyes, in order to mate? And all this without hands?

As already described above, the whale's penis is moved with the help of many muscles. This explains its movements, but not how these movements are coordinated.

In 1994, Günther Behrmann wrote an extremely interesting paper on the “movement coordination of the penis during copulation”. For this purpose, he examined porpoises and his results were unique.