Orcs use algae to massage

The orcas detach stems of giant brown algae and use it to massage each other, a behavior which would constitute the first observation of manufacturing tools by marine mammals, according to a study published yesterday.

Cetaceans (dolphins, orcas, whales) have certainly already been observed using “tools” to drive out their prey. But this new discovery, published by the scientific journal “Current Biology”, is of another order, because orcas have been seen selecting and cutting stems of giant brown algae. This stem is then used in pairs by two orcas, which drive it on their bodies for an extended time.

The scientists of the Center for Whale Research (CWR) and the University of Exeter (England) observed this behavior on several occasions and in all the age groups of a population populating the Salish Sea, between the state of Washington, in the northwest of the United States, and the large island of Vancouver, Canada. This observation was made possible thanks to the precision of drone images made on a population of orcas yet studied for fifty years.

The orcas are not content “to find a piece of algae and use it”, but “modify it to do something really different,” said Michael Weiss, director of research at the CWR. “This is why we say that they make or shape a tool.” This practice could have a role in the attenuation of stress, social relationships or for the good health of the skin of these cetaceans, advance researchers.

Farm and flexible, the stem of these algae is “as a full -fledged watering pipe, with a slippery exterior surface”, characteristics which “make it an ideal grooming tool”, according to Michael Weiss. This type of practice is “very rare” in animals, which use the tools mainly for the quest for food, according to Darren Croft, professor at the University of Exeter. In the case of orcas, “it can be a health problem or linked to the skin, but it seems very likely that this is linked to a social challenge, to a need to have intense and significant social interactions,” he explained.

In their paper, scientists hypothesize that it is a “unique” cultural trait of this orcan population, called “residents of the South”, of which only 73 individuals left in July 2024. These cetaceans are threatened by the disappearance of their prey and pollution, while the fields of brown algae where they make their tools are declining because of global warming. “Although there are thousands and thousands of orcas in the world”, it is a question of protecting a “unique society”, “a unique set of ecological behaviors and interactions”, concludes Michael Weiss, stressing that the future of this population was “very dark”. (AFP-FTR)