Generally, the perfect factor for a penguin is to float.
Magellanic penguins change their technique for navigating residence primarily based on the power of ocean currents, researchers report July 17 in PLOS Biology. In calm waters, penguins head nearly straight again to their colony after fishing journeys. However in sturdy currents, they observe the move — rising journey distance, however conserving vitality.
From September to February, Magellanic penguins (Spheniscus magellanicus) stay in South America, breeding in colonies alongside the coasts of Chile and Argentina. Grownup penguins will journey over 100 kilometers in a single journey to search out small fish, squid and shellfish to feed their chicks.
“They leap within the sea, they swim out a good distance, they seize a maintain of the fish, after which they swim again, after which they offer the meals they catch to the chicks,” says research coauthor Rory Wilson, a biologist at Swansea College in Wales.
Lengthy ocean journeys require not solely an ideal sense of course but in addition the flexibility to expertly negotiate ocean currents, says David Grémillet, a biologist on the French Nationwide Centre for Scientific Analysis in Montpellier. Sea turtles, for instance, use currents to propel themselves on lengthy migrations. Suppose Crush in Discovering Nemo. However currents may sweep animals, together with penguins, off their meant course.
Whereas penguins are completely able to swimming in opposition to sturdy currents, Wilson says that it’s not essentially the perfect technique. “Why would you catch all that fish after which spend all of the vitality simply swimming in opposition to the tide?”
To determine if these penguins had a greater technique, Wilson and colleagues used GPS gadgets and motion loggers to trace the searching journeys of 27 grownup penguins from the San Lorenzo colony, within the Valdés Peninsula of Argentina, below totally different present situations.
Some grownup penguins swam for almost 30 hours in the hunt for meals earlier than beginning their lengthy journey residence. Their return journeys, which might last as long as 16 hours, all the time began off with the animals pointing straight towards their colonies. However what they did subsequent trusted how the ocean was wanting that day.
In calm waters, the penguins swam in an nearly straight line again to their colony. However on days with sturdy currents, the penguins’ homeward journeys adopted a special path.
“[The penguins] weren’t into actually arduous work and silly ways,” Wilson says.
As an alternative, they swam in s-shaped trajectories that adopted the peninsula’s pure tide sample. As a result of the tide reversed course throughout their lengthy journeys, the animals didn’t drift too far off target. The longer journeys supplied additional fishing alternatives and saved vitality, in response to calculations of the hassle wanted to swim at a given pace.
This means that these penguins assess the present’s power and course to decide on the perfect navigation technique, Grémillet says.
Penguins most likely know when to float by a mix of intuition and expertise. “They’ve these genetically decided, tough person manuals of the ocean,” Grémillet says. However younger penguins additionally constantly observe the adults and be taught from their conduct.
It’s unclear how the penguins sense the power of ocean currents, Wilson says. People and different animals sense currents primarily based on which course the water drags them relative to visible landmarks, like a mountain or a lighthouse. However within the open ocean, the place most of those penguins’ journeys happen, there aren’t many landmarks to make use of.
How animals sense the course and power of ocean currents is “one of many large mysteries of animal navigation,” Grémillet says.
