Interactions Between Killer Whales (

Cetacean interactions can be diverse and complex, spanning agonistic to affiliative behaviors. While killer whales are known for complex hunting strategies and a wide range of prey worldwide, they also engage in various non-predatory interspecific interactions. This study describes two encounters off south Iceland, on the 23rd of June 2022 and the 20th of June 2023, where neonate pilot whales were observed with killer whale groups. No other pilot whales were sighted in the area for the duration of these encounters. The killer whale groups, of mixed age and sex classes, engaged in slow travel, foraging and social behaviors throughout the encounters. The pilot whale calves were seen surfacing in front of killer whales or in echelon position, and at times being lifted out of the water. Photo-identification revealed that, while different individual whales participated in each event, all were likely fish-eating specialists. The interactions with the calves displayed no clear signs of predation. We explore several hypotheses for the function of these interactions, which appear suggestive of play behavior (whether affiliative or agonistic in nature), or possibly practice hunting, or epimeletic behavior. However, because neither interaction between killer whales and a pilot whale neonate was observed from start to end, the true motivation and function of the interactions remain unknown. Our observations not only highlight the complexity of these interactions but also underscore the broader importance of investigating interspecific encounters among cetaceans and other mammals, where such behaviors can offer insights into ecological and social processes.