Characterizing maternal and alloparental care in wild killer whales

Many long-lived mammals, including humans, invest heavily in extended and extensive care for offspring. In many species, this care is not only provided by parents, but also by other group members: termed alloparental care or behavior. Alloparental care can be critical for social development, reproductive success, and ultimately, fitness. Therefore, understanding what drives individuals to engage in alloparental care remains a subject of long-standing interest in animal behavior. However, studying fine-scale parental and alloparental behavior patterns and development in wild species—especially marine species—presents a significant challenge because of the need for both long-term demographic and fine-scale behavior data. The southern resident killer whales (Orcinus orca ater) are a critically endangered, closed population of wild, free ranging cetaceans that have been closely studied by the Center for Whale Research for almost 50 years, with individual identification and maternal relatedness known for every individual. Using drone footage from 2018–2023, I performed focal follows on all calves present in the population to characterize their behavior as well as the behavior and identities of their close associates (mainly mothers and potential alloparents). I identified key behaviors associated with maternal and alloparental care in the population (i.e. escorting calves in infant and echelon position, physical contact, and closely associating) and characterized how time spent in these behaviors varies by the age and sex of calves and their behavior partners. I found that calves spend a greater proportion of time with their mothers in infant and echelon position compared to others, and that calves spend a greater proportion of time in close proximity to at least one other individual compared to alone. These results suggest that alloparental care does occur in wild killer whales, including through behaviors not previously described. I also identified which age/sex/relatedness classes participated in alloparental care and tested two hypotheses that provide evidence that there are likely different benefits driving participation in alloparental care from different individuals (i.e. the “learning to parent” and “play” hypotheses). Both related and unrelated females participated the most in the more costly alloparental “care” behaviors of escorting calves in infant and echelon position, and both related and unrelated juvenile males participated more in physical contact and maintaining close proximity with calves. These results provide evidence that there are likely different drivers of alloparental care and behavior in wild killer whales that vary based on alloparent age/sex/relatedness to calf. These results provide important insights into behaviors and interactions that shape wild killer whale calf development, providing a foundation for further investigation into what impacts calf survival and successful reproduction in southern resident killer whales.<p></p>

Author dc:creator

• Rachel John (21045617)

• alloparental care
• offspring care
• cetacean
• killer whale
• Southern resident killer whale
• maternal care

Statement dc:rights

• All rights reserved

Identifier

10779/exe.32841350.v1

OAI identifier oai:identifier

oai:figshare.com:article/32841350