Cooperation by non-kin during birth underpins sperm whale social complexity.

We quantitatively document a sperm whale birth event, revealing collective support behaviors across kinship lines. Using high-resolution drone footage, computer vision, and multiscale network analysis, we studied the interactions within a Caribbean sperm whale unit comprising two matrilines. Our results suggest that a female family member led birth assistance and that after delivery, all individuals oriented toward and helped lift the newborn, taking turns in a coordinated, cross-kin effort. Despite historically observed foraging segregation, kinship barriers dissolved as all unit members contributed. These analyses provide evidence of birth attendance, or assistance, in a nonprimate species, a behavior long considered characteristic only of humans and their close relatives. Editor's summary: Whales have high levels of cognition and complex social lives, but studying this massive marine species has been challenging. Maalouf et al. used high-density drone imaging and advanced network analyses to reveal the dynamics of a sperm whale birth in the Caribbean. They found that other females assisted the mother, including those that were in different kin and social groups and were only distantly related to her. Such assisted births have thus far only been seen in primates. This observation confirms the suspected social complexity of whales and suggests that modern observational tools are likely to continue to reveal the secrets of other species that are difficult to study. —Sacha Vignieri [ABSTRACT FROM AUTHOR]