Published in PLOS Biology, a study tracked 27 adult penguins during their return trips from foraging in the ocean off Argentina. Led by the Max Planck Institute of Animal Behaviour, researchers found that instead of swimming directly back to their nests, penguins often followed curved, S-shaped paths influenced by tides. These routes helped them conserve energy and take advantage of feeding opportunities.
Co-author Professor Rory Wilson of Swansea University’s Animal Movement Lab explains: “We used small high-tech tracking devices with GPS and compasses, combined with detailed ocean current models. These revealed that penguins adjusted their swimming direction depending on the strength and direction of the currents. In calm water, they headed straight for home, but when the currents were stronger, they allowed themselves to drift sideways. This made their journey longer, but less tiring.”
This strategy also gave the penguins more chances to feed.
“The penguins were observed diving and foraging for food during much of their return journey,” said Professor Wilson. “As they got closer to the colony, they became more focused and swam more directly, often arriving within just 300 metres of their original departure point — an impressive level of accuracy after journeys of up to 75km.”
The researchers considered two logical strategies the penguins might use to return home. Theoretically, assuming that the penguins ‘knew’ where they were because they cannot see land when far out at sea, there would appear to be two obvious options as to how to get home. The ‘naïve’ approach would be always heading directly for the colony regardless of current strength or direction – something humans caught in rip tides or rivers are prone to doing. However, in strong opposing currents, this would require significant effort from the penguins.
Currents in their region may reach up to 4.5 mph – roughly equivalent to speeds of top Olympic swimmers. Although penguins can travel faster than this speed at about 4.5 mph cruising speed, it costs them significantly more energy. A smarter ‘navigator’s option’ is swimming at an angle so that combined effects result in overall movement towards the colony efficiently.
Surprisingly though according to Professor Wilson: “Actually penguins do neither! Their approach is more flexible.” Penguins sometimes swim with currents even if not taking them directly toward nests occasionally shooting past colonies down coasts yet sensing both presence & strength despite no visible cues: "Penguin seem able determine when they're current & roughly how strong it is understanding tidal cycle."