Cetaceans are marine mammals commonly known as whales, dolphins and porpoises. There is traditionally an arbitrary distinction between the large and small cetaceans. The group of large cetaceans comprises whalebone whales (rorquals, baleen whales, etc.) and the sperm whale. As for the term "small cetacean", it means all toothed whales except the sperm whale: killer whales, dolphins, porpoises, etc.
Descendants of land animals, cetaceans have existed for over 50 million years. Present in all the oceans (including the North Sea), they play a key role in marine ecosystems. Many species, especially large whales undertake long migrations between their breeding and feeding grounds (e.g. humpback whales can travel more than 10,000 km every year). Given the migratory nature of these animals, their protection requires international collaboration. Cetaceans live in accordance with complex social organisations and have amazing cognitive skills: some species show an intelligence and self-awareness comparable to those of apes and elephants.
Currently there are around 85 species of cetaceans in the world. These are the sentinels of the marine environment: threats to them also affect the entire marine environment. Since cetaceans are especially sensitive to them, they act as a kind of indicator of the health of the oceans. Among threats to the cetaceans, some are well known (hunting, bycatch, etc.) while others, such as the use of powerful sonar, are still new and not well known. Since many species are critically endangered in terms of their population, the international community is investing in research, conservation measures and mitigation.
At present, it is acknowledged that there is no justification to the killing of whales, whether for hunting or for scientific research.