Gray Seals Can Monitor Blood Oxygen Levels to Prevent Drowning, Study Reveals
A groundbreaking study by researchers at the Sea Mammal Research Unit, School of Biology, University of St Andrews, UK, has uncovered a fascinating ability in gray seals—they can monitor their own blood oxygen levels to prevent drowning. The findings, published in the journal Science, provide new insights into how marine mammals regulate their breathing while diving.
How Gray Seals Detect Oxygen Levels
All mammals need oxygen to survive, and prior research has shown that land mammals rely on carbon dioxide sensors to signal when they need to breathe. In humans, chemoreceptors near the carotid arteries detect rising COâ‚‚ levels, triggering symptoms like dizziness, air hunger, and even panic. However, marine mammals, including seals, can hold their breath for extended periods, leading scientists to explore whether they use a different mechanism to regulate diving behavior.
To investigate, researchers conducted controlled experiments with six adult gray seals in a test pool. The pool featured a feeding station and a designated breathing chamber where oxygen and carbon dioxide levels could be precisely adjusted. With the pool covered, the seals could only surface for air in the breathing chamber, allowing researchers to analyze their responses to different air compositions.
Key Findings from the Study
The scientists tested four air compositions:
- Ambient air (normal oxygen and carbon dioxide levels)
- High oxygen (twice the normal oxygen levels)
- Low oxygen (half the normal oxygen levels)
- High carbon dioxide (normal oxygen with COâ‚‚ levels 200 times higher than usual)
By measuring the seals’ dive durations, researchers observed a direct correlation between oxygen levels and time spent underwater. Seals stayed submerged longer when oxygen levels were high and surfaced sooner when oxygen was reduced. Surprisingly, elevated carbon dioxide levels did not influence dive duration, suggesting that seals rely primarily on oxygen monitoring rather than COâ‚‚ build-up.
Implications of the Research
These findings suggest that gray seals possess a unique physiological mechanism to track their blood oxygen levels, allowing them to surface for air at the right time and avoid drowning. This ability differs significantly from land mammals and highlights the specialized adaptations of marine life for underwater survival.
Reference:
J. Chris McKnight et al., Cognitive Perception of Circulating Oxygen in Seals is the Reason They Don’t Drown, Science (2025). DOI: 10.1126/science.adq4921.