Role of sociality in the response of killer whales to an additive mortality event.
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When killer whales lose their kin, their own chances of survival suffer too.
Social animals gain a lot from group living by joining forces to forage for food, protect against predators and raise their young.
A team that included researchers from Deakin University used a long-term study of killer whale (Orcinus orca) pods around the sub-antarctic Crozet Islands to observe the impacts of seven years of illegal fishing that inadvertently killed off half the orca population.
They noticed that surviving whales from disrupted pods tried to ingratiate themselves into other pods, sometimes moving erratically between groups. But death rates remained unnaturally high even after the illegal fishing had stopped. This suggests that the bereaved whales did not bond strongly enough with new groups to reap the benefits.
Understanding how sociality affects animal resilience to population decline could help conserve highly social species.
- PNAS 116, 11812–11817 (2019). doi: 10.1073/pnas.1817174116