Dear colleagues, Our study on the effects of conspecific scarring on all sex and age classes in three divergent killer whale populations is now published open access in Behavioral Ecology and Sociobiology at https://rdcu.be/eccmc Citation: van Weelden, C., Tixier, P., Doniol-Valcroze, T., Guinet, C. & Towers, J.R. (2025). Divergent killer whale populations exhibit similar acquisition but different healing rates of conspecific scars. Behavioral Ecology and Sociobiology 79: 39. https://doi.org/10.1007/s00265-025-03576-6 Abstract: Scars obtained from interactions with conspecifics may be caused by both playful and aggressive activities, making them useful when studying cetacean behaviour. This study investigates the effects of age and sex on conspecific scar acquisition and healing in three genetically distinct populations of killer whales (Orcinus orca) each with unique diets and social structures. The sample consisted of 50 of the most commonly photo-identified individuals from all sex and age classes in each of the Bigg’s, Northern Resident, and Crozet killer whale populations. The number of new scars annually acquired by an individual as well as how long it took them to disappear were extracted from annual photo-identification images of these individuals taken between the years of 2008 and 2021. Scar acquisition was analysed using a generalized additive model while scar healing was assessed using Kaplan-Meier survival curves. Results showed an inverse relationship between scar acquisition and age, as well as an effect of sex with males being more scarred than females amongst all age classes. No significant differences in scar acquisition between populations was found. Scar re-pigmentation was faster in Northern Residents compared to Crozet and Bigg’s individuals and varied amongst age classes, with scars on calves and juveniles disappearing more quickly than those on adults. These population- and age-based differences in healing may be due to scar severity, while results around scar acquisition suggest that the nature of physical interactions between sex and age classes in this species are homogenous despite cultural and genetic differences that have evolved between populations. Significance Statement: In several species of odontocetes, including killer whales, scars caused by the teeth of conspecifics are typically attributed to social behaviours associated with reproductive competition. Previous research has suggested that divergent but sympatric populations of killer whales each with unique diets, social structures, and behaviours have frequencies of scarring which differ amongst sex and age classes in each population. Using more robust data we conclude that rates of scar acquisition between these same populations and another non-sympatric population are remarkably similar when compared between sex and age classes, but that one population exhibited significantly different rates of healing. These results suggest that sexually selected behaviours have not diverged as strongly as ecological adaptations have in this species, but that scars are likely caused by mild to intense play and aggression which are specific to population, sex, and age class. Jared Towers Executive Director Bay Cetology