In 2020, a deceased orca found in Russian waters provided valuable insights into the dietary habits of Bigg's orcas, a subgroup with distinct genomes and feeding preferences. The orca, measuring 6.3 meters in length, was discovered with a stomach filled with an unusual meal – six whole sea otters and a seventh lodged in her throat. This marks the first direct evidence of orca predation on sea otters in the Commander Islands off the eastern coast of Russia.
Scientists conducted an autopsy on the orca and found 256 upper and lower parts of cephalopod beaks in her gastrointestinal tract, suggesting that these orcas also consume squid. While the cause of death is challenging to determine conclusively, the researchers speculate that the otter lodged in the orca's throat led to asphyxiation. Clear signs of vaginal prolapse were also observed, but the researchers suggest that this may be a secondary factor.
The findings pose intriguing questions about the dietary habits and adaptations of Bigg's orcas. The orcas typically prey on seals, sea lions, whales, dolphins, and porpoises, making predation on sea otters rare. The researchers ponder whether consuming cephalopods and otters is a specialised behaviour within this pod, possibly arising due to competition for more typical prey or changes in the availability of their usual food sources.
The tragic discovery sheds light on the complexities of orca behaviour and raises inquiries about the impact of environmental changes on their feeding strategies. As orcas are increasingly recognised as having distinct regional populations with unique behaviours, understanding their dietary preferences becomes crucial for conservation efforts and adapting to a changing climate.