Like giraffes, lions, hyenas and grey kangaroos, female Burrunan dolphins (Tursiops australis), a species of bottlenose dolphin endemic to southern Australian coastal waters, form social bonds with kin and other females in similar reproductive condition, while maintaining moderate and loose social bonds with some same-sex individuals, according to new research from Flinders University.
“Just like in human communities, Burrunan dolphins tend to form family groups, with those females most closely related genetically forming close social relationships in specific areas,” said Dr. Fernando Diaz-Aguirre, a researcher in the Cetacean Ecology, Behaviour and Evolution Lab and the Molecular Ecology Lab at the Flinders University’s College of Science and Engineering.
“These close social groups among related females appear to be vital for them while raising young calves, or for those without calves who also combine due to similar biological requirements related to feeding and mating.”
“As well as key pointers on social evolution and behavior in these highly complex marine mammals, our study also provides important information for their conservation.”
In the study, Dr. Diaz-Aguirre and colleagues used generalized affiliation indices, combined with social networks, reproductive condition, and genetic data to investigate drivers of associations in female Burrunan dolphins.
The analysis was based on photo-identification and genetic data collected through systematic boat surveys over a two-year study period.
Female dolphins formed preferred associations and social clusters which ranged from overlapping to discrete home ranges.
Furthermore, matrilineal kinship and biparental relatedness, as well as reproductive condition, correlated with the strength of female affiliations.
In addition, relatedness for both genetic markers was also higher within than between social clusters.
“Depending on kinship and other ties, specific females and their young either live in Kellidie Bay, Mt Dutton or near Port Douglas in South Australia — giving key clues for reducing anthropogenic threats such as boat strikes, entanglement in fishing gear, or habitat displacement due to aquaculture and pollution,” Dr. Diaz-Aguirre said.
“The study sheds light on how dolphin societies are developed and maintained, including special adaptations such as hunting skills, and how social learning is passed from one generations to the next,” said Dr. Luciana Möller, also from the Cetacean Ecology, Behaviour and Evolution Lab and the Molecular Ecology Lab at the Flinders University’s College of Science and Engineering.
“Our field studies are not only important for understanding the evolution of complex animal societies, but for providing information to conservation managers to sure the future survival of these unique dolphin populations.”
“Small resident populations of dolphins are particularly vulnerable to changes in the environment, and represent sentinels of the health of coastal ecosystems.”
The study appears in the journal Scientific Reports.
F. Diaz-Aguirre et al. 2020. Kinship and reproductive condition correlate with affiliation patterns in female southern Australian bottlenose dolphins. Sci Rep 10, 1891; doi: 10.1038/s41598-020-58800-2