01.09.2024 – Bachelor party

As a special welcome into the month of September, we sighted Sperm whales (Physeter macrocephalus) this morning. The largest of all Toothed whales (Odontoceti) spend about 75 % of their daytime feeding (they’ve got to work on a maximum of 70 tons of body weight!). Feeding activity means about 45 minutes looking for squid in the depths, at an average of 700-1000 meters of depth, followed by 5 to 10 minutes at the surface to refill the oxygen storages in the body. These timings count for females, males regularly stay an hour or more underwater. Why is there such a difference? Well, the diving time in Sperm whales is related to their size. And these whales have an extreme sexual dimorphism: Females measure a maximum of 12 meters, but males can reach up to 20 meters! For the same reason we were able to tell this morning that the animal blowing in the distance was a male. The larger the whale, the more powerful their blows. We only spent a few moments with him until he decided to go for another squid hunt. The dive of a sperm whale is probably the most incredible moment of the sighting. They expose a bigger part of their heads, the large tailstock and the fluke to dive vertically into the depths. Unfortunately, this also means, it is unlikely to see him again during our short trip out at sea (Note to myself: propose a full-day-trip. Who’s with me?). Luckily for us, our spotter on land had already sighted two other individuals a bit further away from land. And this time, we managed to have some more precious minutes around the two. Puzzling to me, it seemed once again like large, male individuals. It is believed that sperm whales live in very strong social units which eventually never separate – but these are females taking care of calves and juveniles. As the males grow older, they separate from their family unit to spend a more solitary life. In fact, we often see large male adults on their own. In this case, a minimum of three individuals in a nearby area, with apparent synchronised movements and dives? Well it has been suggested that especially young adult males form so-called “Bachelor groups”. Group standings of adult males and observations of “preferred companionships” (repeated sightings of the same adult males together) demonstrate: These boys might not be as antisocial as it was thought, after all.

By Sarah Kather

Sightings of the day

Ribeira Brava

09:30 Sperm whales, Rough-toothed dolphins, Bottlenose dolphins

Stenella

09:30 Sperm whales, Blainville’s beaked whales, Rough-toothed dolphins, Bottlenose dolphins

14:00 Atlantic spotted dolphins, Striped dolphins

17:00 No sightings