Disease Investigation in Norwegian Killer Whales (Orcinus orca): Challenges and Needs for Improving Free-Living Cetacean Health Assessments.

Knowledge of the occurrence and etiology of cetacean diseases remains limited in northern areas, including in the Arctic and sub-Arctic. In November 2023, three killer whales (Orcinus orca) were observed in northern Norway exhibiting abnormal behavior, including inability to swim upright, loss of directional control, short and shallow dives, and lethargy. These unusual cases occurred within a 2-wk period and in the same area, suggesting a common underlying condition. However, due to the lack of diagnostic biologic samples, the cause of disease remains speculative. Herein, we discuss possible differential diagnoses based on the available data, including infectious disease, exposure to biotoxins, and blast trauma. Disease in live free-swimming killer whales in Norway has not been documented previously. These cases illustrate the significant challenges of investigating disease in wild, live cetaceans and emphasize the urgent need for improved surveillance, field diagnostic tools, and response protocols. Suggested developments include the implementation of ready-to-use kits for blow, fecal, and environmental DNA sampling; drones equipped with sampling devices and thermal sensors; and mobile laboratories to support on-site diagnostics. Collectively, these tools could significantly improve early detection, investigation, and management of similar unusual events in wild cetacean populations.