Mai Sakai, a lecturer at the Department of Fisheries, Faculty of Agriculture, Kinki University, Kamogawa Sea World, and the research team at the Wildlife Research Center at Kyoto University clean the body surface with the social behavior of rubbing the opponent with the pectoral fins that are seen in many dolphins. It was revealed that it has a hygienic function.
The social grooming found in primates and birds has a hygienic function to clean the body surface by grooming other individuals, and a social function such as tension reduction and care behavior between parents and children. It has been reported to have both.
As a similar behavior, dolphins have observed a social behavior of rubbing the other person with a pectoral fin, and it is known that they have some social functions such as a reconciliation function.However, there have been no reports to support whether rubbing also has hygienic functions such as social grooming.
Therefore, the research team observed the rubbing of three pairs of bottlenose dolphins raised in Kamogawa Sea World, and found that the old skin peeled off from the part rubbed by the rubbing.
Dolphins also perform self-rubbing by rubbing their bodies against the object, but as a result of observation of bottlenose dolphin mothers and children, it was confirmed that old skin was peeled off in 53% of self-fluffing and 19% of rubbing.In addition, a significant negative correlation was found between the number of times of rubbing and the number of times of self-fluffing, that is, a relationship in which one increased and the other decreased.This means that rubbing has the same functions of maintaining and caring for the body surface as self-fluffing.
Further observations showed that in all mother-child pairs, the mother rubbed the child more often than the child rubbed the mother.It was also suggested that rubbing is one of the care behaviors between mother and child, because the mother is more likely to be a scraper when her child is the other person than when the other individual is the other person.
This is a result that clarified that not only terrestrial animals but also marine mammals, dolphins, have social behaviors that have both social and hygienic functions.
