Orca mothers endure a lengthy period of pregnancy followed by up to two years of nursing, caring for their offspring throughout their lives by hunting and sharing food with their adult children. A recent study in the journal Scientific Reports, led by biologist Sharon Kay, sheds light on the physical toll of motherhood on these marine mammals. The research focused on northern resident killer whales, a threatened species under Canada’s Species at Risk Act, living in the coastal waters of North America.
The study revealed that after giving birth and nursing, orca mothers experience a significant decline in body fat levels, which can last up to three years. Some mothers struggle to regain their pre-pregnancy condition, with the number of living offspring being a key factor influencing their body fat levels. By using drones to capture images of the whales, researchers analyzed changes in the white patches above their eyes to assess body condition.
According to co-author Amy Rowley, the fatness behind the whales’ heads plays a crucial role in their overall body condition. The study of 66 adult females highlighted the challenges these mothers face in maintaining their body fat levels due to the demands of caring for their offspring, including finding food and sharing it. This research contributes valuable insights into the societal pressures faced by these animals, alongside ongoing human impacts such as chemical contaminants, noise pollution, and climate change.
Experts emphasize the importance of understanding the impact of maternal investment on orcas, particularly in the face of multiple stressors that could further exacerbate body fat decline and threaten their survival. The study underscores the complex dynamics of orca populations and the need for conservation efforts to mitigate human-induced stressors on these iconic marine mammals.