Patterns of foraging ecology in a highly mobile, socially complex marine predator

Abstract

Social structure plays a key role in shaping ecological and evolutionary dynamics in group-living animals, yet its influence on genetic connectivity and foraging ecology remains understudied in wide-ranging marine predators. Here, we used mitochondrial DNA (mtDNA) sequencing and stable isotopes of carbon (δ13C) and nitrogen (δ15N) to evaluate matrilineal and ecological connectivity in a highly mobile, socially complex marine predator, the false killer whale (Pseudorca crassidens). We analysed skin samples (n = 164) collected from three different Southern Hemisphere regions: a stranding event in Falkland Islands (nS = 19), biopsied animals from Australia (nB = 7) and a combination of stranded and biopsied animals from Aotearoa New Zealand (nS = 52, nB = 86). We designated sets of samples as separate partitions (n = 8) based on sampling region, sample type and/or time of sampling. Haplotype number and diversity were low within sample partitions representing (known or presumed) social clusters of false killer whales, with significant overall and pairwise differentiation (FST = 0.89, p ≤ 0.01; ΦST = 0.94, p < 0.01), consistent with distinct matrilineal groups. These social clusters each had narrow isotopic niche regions (less than 2‰2) with little or no overlap between them (less than 5%), suggesting ecological separation. These findings highlight the value of complementary datasets in understanding both genetic and ecological divergence in wide-ranging social mammals.