22 May 2019
It’s long been a whale-eat-whale world
Published online 10 January 2019
Knowledge of the evolution of whales eating other whales is pushed back to 35 million years ago by a fossil find in Egypt.
Fossilised whale remains found in Egypt reveal convincing evidence that an ‘apex predator’ whale at the top of a food chain preyed on a smaller whale species. “This is the first direct evidence of the diet of the extinct whale Basilosaurus isis,” says researcher Manja Voss of the Museum für Naturkunde Berlin (Natural History Museum).
Voss describes B. isis as a 16-meter giant that roamed the ancient Tethys ocean around 35 million years ago. This body of water can be regarded as the precursor of today’s Mediterranean Sea.
The details of the diet of an animal that lived so long ago were deduced from the stomach contents of a fossil discovered in Egypt’s “Valley of Whales”, Wadi Al-Hitan, about 150 km southwest of Cairo. The remains within the B. isis fossil include fragments of juveniles of the smaller contemporary whale species Dorudon atrox, and these bear bite marks that can be attributed to B. isis.
One key motivation behind this study is to understand more about the evolution of whale feeding behaviour. Modern orcas are known to eat other whale species, but when this activity evolved is debated.
“Our finding confirms that killing and eating their own kind already occurred in the Eocene, and so was present very early in the evolution of whales,” says Voss. The discovery also confirms a predator-prey relationship between the two most commonly found species of whales in Egypt’s Wadi Al-Hitan.
“Such findings also help us to better understand today’s marine ecosystems, which can assist effective protection of the present biodiversity,” Voss adds.
Voss, M. et al. Stomach contents of the archaeocete Basilosaurus isis: apex predator in oceans of the late Eocene. PLOS One 14, e0209021 (2019).