December 3, 2020 — New research shows that humans are taking a greater toll on killer whale populations than previously believed. Between pollution, overfishing and impacts with vessels — it doesn’t look good for the majestic, endangered creatures.
The most common human-related causes of death include infectious disease, malnutrition, congenital defects induced by chemical pollution, blunt force trauma from boat strikes and ingested fish hooks. These cases represent otherwise preventable deaths that can likely be reduced through further research and effort.
Researchers looked at blubber thickness and body length to determine an orca’s overall body condition. Not surprisingly, mature orcas tended to be healthiest prior to death and most often died from bacterial infections, emaciation and injuries caused by boat strikes, whereas calves were more likely to die from infectious disease, malnutrition or congenital defects and were typically healthy before their deaths. Understanding these interactions with humans is critical to ongoing management and conservation efforts for over 55,000 orcas worldwide.
Lead author Dr. Stephen Raverty from Canada’s Ministry of Agriculture and his team looked at pathology reports for 53 individuals stranded between 2001 and 2017, which revealed human activity to be a significant cause of death for orcas across every age group. The researchers published their findings Wednesday in the journal PLOS One.