Killer whales know how to be friends: they often spend time with species of the same age and gender.

In a study carried out by the University of Exeter and the Center for Whale Research (CWR), the authors, with the help of

drones studied how the social relationships of killer whales are built. 

Based on 40 years of data collected by the CWR on southern killer whales, the authors note that these animals are endangered in the Pacific Ocean.

The results show that killer whales spendspend more time interacting with certain individuals in their pack, and tend to prefer friends of the same sex and age. The authors also looked at instances where the whales surfaced together, since acting in unison is a sign of social bonding in many species.

Another feature of behavior in society istactile contacts: the authors compared their number with the interactions of two close people. In many species, including humans, physical contact tends to help calm and relieve stress. 

The study also found that whales become less socially active as they age.

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