by Nataly H. Aranzamendi
The lives of young Emperor Penguins have long been a challenge to study, owing mostly to their harsh Antarctic habitat. But now, scientists are beginning to get some insight into their early years. Let’s find out more about their secret journeys.
Emperor Penguins are the only penguins breeding through the tough Antarctic winter. Adult Emperor Penguins perform difficult journeys during the breeding season in order to feed themselves, and repeat these journeys later to feed their offspring.
There are two key feeding periods during breeding for Emperor Penguins. One is after egg-laying, which occurs approximately between autumn and mid-winter in the Southern Hemisphere. At this time, females need to rebuild their body reserves, so they march towards the sea for feeding, while the males stay on the ice incubating the egg.
The second critical period takes place during the chick rearing period, from mid-winter to December when the female comes back and it’s the male’s turn to eat something and collect food for the chick. After these long journeys and summer begins to bring life to the surrounding ecosystems, the food becomes close enough and plentiful enough that both parents can alternate this role more frequently.
Feeding places of breeding Emperor Penguins are often found around their colonies in open water areas surrounded by sea ice or in pack-ice regions further off-shore. Both areas provide a variety of food items for breeding penguins, e.g. Antarctic krill, Antarctic silverfish or glacial squid, which are very important for their survival.
However, to date, we have been unaware of what happens with juvenile Emperor Penguins after they fledge. Where do they go when they leave the colony for the first time? Young Emperor Penguins depart in December and travel far north mostly to ice-free waters, but their journey from there on has remained unknown, only until recently.
Since juveniles leaving the colony for the first time are probably still learning their best foraging techniques and the best places to eat, scientists have always assumed that young penguins went far away avoiding the sea ice during winter.
In a recent study following young Emperor Penguins, scientists have untangled this journey, giving us further clues about their behavior during their first years of life1.
Scientists gathered information on penguins’ journeys by putting transmitters on 15 juvenile penguins. To be more specific, they looked at their trajectories, traveling distances, depth and temperatures for almost a year since they left their natal grounds.
The maximum distance that a penguin traveled was 7800 km and the farthest distance from the colony was 3500 km. The penguins first traveled north to approximately 53 degrees South latitude and then later around March they started heading back south, remaining around sea-ice. This was a surprise for researchers, as they expected penguins staying in ice-free open waters year round. Instead they remained around sea ice areas at most times (49% of the total recorded trip).
Penguins were mostly active during the day (63% of their time diving) when dives were the deepest, and then during twilight (32%). Nocturnal dives only occurred in 5% of the cases.
Young Emperor Penguins explored their environment in different ways depending on the season. During summer, just after they departed the colony, they started their journeys diving in the sea ice around the colony and slowly going northwards into open water. At this time, the dives were the shallowest and it was only later during winter when the deepest dives were recorded. The reason why penguins explore deeper waters and the variation found throughout seasons is most likely related to prey availability.
Areas around ice support abundant food resources, particularly under ice. It provides a substrate for ice algae and zooplankton, which could explain the shallow dives of penguins at daylight and twilight. In autumn, krill larvae and other crustaceans are more abundant outside the sea ice, therefore the movement patterns are outside the region of the sea ice. In winter, krill migrate to deeper waters and the penguins are forced to follow them.
Photo source: Ian Duffy from UK [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)]
A question that remains unanswered is how do young penguins know where and when to forage? It is likely that foraging strategies are learned with exploratory behaviors during the first months of life in the water. But perhaps there are additional genetic predispositions leading the way as well. Finding out more about the capacity of young penguins to rapidly learn about prey distribution in an efficient way is crucial for their future, as young birds are often more sensitive to environmental fluctuations than are adults. The future of this charismatic species will therefore be better predicted and understood if we keep studying these mysterious and unknown behaviors.
Did you know all this about Emperor penguins? They have quite the life! Let us know what you learned and/or think. Also, please help us continue to learn more about penguins by donating to Penguins International. We more than appreciate your support!
You can also read more about penguins in the following blogs:
Labrousse, S., Orgeret, F., Solow, A. R., Barbraud, C., Bost, C. A., Sallée, J. B., … & Jenouvrier, S. (2019). First odyssey beneath the sea ice of juvenile emperor penguins in East Antarctica. Marine Ecology Progress Series, 609, 1-16.