Penguins are sociable. During breeding, these birds gather in large colonies on the coasts of Subantarctic islands and on the main land. Their multi-vocal calls are usually loud and heard over the entire colony. But what is their behavior while at sea foraging? To solve this mystery, Korean biologists applied video cameras on Gentoos to film and eavesdrop on the animals while at sea. The results were stunning: Even while swimming and diving, Gentoos communicate amongst each other using short calls. However, the exact nature of these calls is yet to be determined.

Gentoo penguins are the third largest penguin species. They are generalists and feed on many different sources, from krill to fish. As a Subantarctic species, they have started to colonize the Antarctic mainland only recently, thanks to climate change. Picture: Michael Wenger
Gentoo penguins are the third largest penguin species. They are generalists and feed on many different sources, from krill to fish. As a Subantarctic species, they have started to colonize the Antarctic mainland only recently, thanks to climate change. Picture: Michael Wenger

Gentoo penguins are very communicative: during breeding season, these 75 centimeters large birds emit their loud, trumpet-like calls almost endlessly. However, when going into the water, things change dramatically, according to latest research results. “Many penguin species forage in groups”, says Noori Choi from the Korean Polar Research Institute in Incheon. The birds mainly feed on krill and fish during their communal dives. To this end, groups of penguins synchronize their dives. The advantages of these group fishing activities remain unclear yet. Also, if and how they communicate with each other was not known until now. To find out, the scientists mounted mini-cameras on 26 penguins from a colony on Subantarctic King George Island and added sensors for acceleration and depth. This entire spy package was taped on the birds with water-repellent tape on the head of the animals. As soon as a penguin went for a dive, the camera and the microphone started to record the behavior and the sounds for up to eight hours while the sensors recorded dive depth and duration.

The Korean researchers used mini-cameras with microphones to observe the penguins during their dives. The cameras had been attached to the penguin heads which did not hinder the animals on their foraging behavior, according to the scientists. Picture: Won Young Lee
The Korean researchers used mini-cameras with microphones to observe the penguins during their dives. The cameras had been attached to the penguin heads which did not hinder the animals on their foraging behavior, according to the scientists. Picture: Won Young Lee

The footage showed that around half of the birds also emitted calls while diving. The records displayed one to two short bursts of calls. “Compared to the multisyllabic mating calls of the Gentoos, these off-shore calls were structurally simpler and significantly shorter”, the researchers reported. The calls usually lasted less than three seconds. Thanks to the cameras, the scientists also observed the situations in which penguins would call and the resulting behavior: Typically, one single animal emitted the off-shore call but without getting a response from neighboring penguins. Instead, the call seemed to form the group anew and all birds would swim in the same direction. “This could mean, that off-shore calls are not for communication between animals in an existing group, but rather being a signal for grouping itself”, say Choi and her colleagues. Such an off-shore call usually led the group to swimming to another spot in the ocean within a minute.  The advantage of this group formation “on order” during the dives could only be explained partially by Choi and her colleagues. “Maybe playback-experiments at foraging sites could give us more information on the functions of such off-shore calls”, the research note. “Also, equipping more animals within the same diving groups with cameras could help, to gain a better insight on the interactions during the dives.”

The Korean Antarctic Station “King Sejon” on the Subantarctic King George Island is one of two Korean stations. Occupied all year round, it offers room for 90 people in summer and houses 17 during the winter.
The Korean Antarctic Station “King Sejon” on the Subantarctic King George Island is one of two Korean stations. Occupied all year round, it offers room for 90 people in summer and houses 17 during the winter.

Source: Nadja Prodbegar, Bild der Wissenschaft