Marine Marvels: How Animals Optimize Swimming Depth for Energy Savings
A groundbreaking study reveals a engaging energy-saving strategy employed by a wide range of marine animals. Researchers from Swansea and Deakin Universities have discovered that marine mammals, birds, and reptiles consistently swim at similar relative depths when traveling and not actively feeding. This behavior, they found, considerably reduces energy expenditure during long journeys.
The international research team, led by Dr. kimberley Stokes, Professor Graeme Hays, and Dr.Nicole Esteban, analyzed data from six institutes across five countries. Their comprehensive study encompassed various species, including sea turtles, penguins, and whales. The results consistently showed that these animals swim at approximately three times their body length from the surface. This “sweet spot,” as the researchers describe it, minimizes the energy wasted on creating surface waves and reduces the overall vertical distance traveled.
This contrasts with semi-aquatic animals like mink, which swim closer to the surface, expending more energy battling wave formation. For marine animals undertaking extensive migrations, minimizing energy consumption is crucial for survival, especially during long-distance journeys.
While the principle of reduced drag at depths exceeding three times an object’s diameter has been understood for some time,applying this to wild animals presented meaningful challenges due to limitations in tracking technology. This new study, published in the Proceedings of the National Academy of Sciences (PNAS), overcame these hurdles. Researchers used advanced techniques, including high-precision depth recordings (accurate to within 1.5 centimeters) for little penguins and loggerhead turtles, combined with motion data and video footage from animal-borne cameras.This data was then compared with satellite tracking data from green turtle migrations and existing research on penguins and whales.
The findings revealed a remarkable consistency: these animals, whether “commuting” to feeding grounds or undertaking long-distance migrations without feeding, maintained optimal swimming depths predicted by physics. This suggests a remarkable evolutionary adaptation for energy efficiency.
“There are of course examples where animal swim depth is driven by other factors, such as searching for prey, but it was exciting to find that all published examples of non-foraging air-breathing marine animals followed the predicted pattern. This has rarely been recorded as of the difficulty in retrieving depth data from animals that migrate over large distances, so it was great to find enough examples to show a common relationship between swim depth and body size from animals across the size spectrum from 30 cm to about 20 m in length.”
Dr. Kimberley Stokes, lead author of the study, highlights the significance of this discovery, emphasizing the challenges in collecting data from migrating animals and the breadth of species included in the study, ranging from small penguins to massive whales.
This research offers valuable insights into the remarkable adaptations of marine animals and underscores the importance of continued research into their behavior and conservation.
