Cetacean strandings happen when whales, dolphins, or porpoises end up on the beach or in very shallow water and can’t get back to the sea on their own. Sometimes just one animal is stranded, but other times groups of them get stuck together, especially species that live in tight social groups, like pilot whales.

The origin of cetacean strandings is undoubtedly linked to a combination of environmental or natural and anthropological factors that directly result in disorientation and the weakening of the affected animal. However, in recent years, the number of stranded cetaceans found in the Canary Islands has increased alongside the growing pressure of human activities on the marine habitat (André et al., 2001).

Specifically, collisions with vessels are a major cause of strandings in the Canary Islands, becoming an increasingly serious concern.

The work by Carrillo and Ritter (2010) reports a high number of ship collisions in the Canary Islands, with most incidents occurring around Tenerife and having a particularly significant impact on sperm whales, beaked whales, and pilot whales. Most collisions resulting in serious or fatal injuries are caused by vessels 80 meters in length or longer (Grassa et al., 2019). In the Canary Islands, both cargo ships and ferries pose a risk of collision with cetaceans, but high-speed ferries are especially implicated due to their speed and frequent routes near key whale habitats. These collisions are a risk not only to the animals, but also to passengers on board.

On May 21st, a female sperm whale approximately 9.8 meters long and weighing 8.4 tons was found stranded on Los Roques beach, in the municipality of Fasnia, Tenerife. A necropsy revealed that the whale died from a severe head trauma, with a clean cut over 2 meters long, consistent with an almost immediate death caused by a collision with a large vessel. In addition, a second dead individual with similar injuries was found floating nearby, although it has not yet washed ashore.

In sperm whales, females reach sexual maturity around 8 to 9 meters long, usually at 7 to 10 years old. Reproduction is demanding because pregnancy lasts about 14 to 16 months, followed by a long lactation period of up to two years. The female in this case, measuring 9.8 meters, was likely just starting or recently entered her reproductive stage and may have reproduced only once or not at all. The other individual, a juvenile not yet sexually mature, also hadn’t contributed to population growth. Losing both is a serious blow to the already vulnerable sperm whale population in the Canary Islands.