Synchronous foraging observed in chinstrap penguins | Polarjournal
The South Shetland Islands on the west side of the Antarctic Peninsula are the best areas to see chinstrap penguins. The almost 55 cm tall penguins find ideal breeding areas with stones on land and enough krill nearby. The team in their latest study shows how they hunt them. Picture: Michael Wenger

Chinstrap penguins are among the few true Antarctic residents. The small black and white birds directly depend on krill around their breeding grounds. It has been known for some time that they go hunting for the small crustaceans in larger groups to optimise their success and also for protection. But now, for the first time, a U.S. research team has been able to show with video footage how the penguins synchronize their dives and foraging, while also sharing success equitably.

The study showed that three penguins had already joined forces on land and swam together from Livingston Island (South Shetland, Antarctica) into the open sea to hunt for krill. The birds, equipped with video cameras and loggers, showed synchronous dives during the hunt and also coordinated the hunt for the nearly 6-centimeter krill. “Synchronous diving among penguins has been reported,” the team writes in their paper. “But simultaneous observations of predation by synchronously diving individuals have not.” Further analysis showed that the penguins were equally successful at hunting. According to the researchers, the images and the data show that chinstrap penguins already form hunting groups on land in a way that is not yet known, synchronize their hunting and diving trips, and that this synchronization probably pays off for everyone.

The small clip shows the two birds equipped with video cameras diving and hunting together. The team had to evaluate a total of 9.25 hours of video material to arrive at the results. Video: Created from material in Hinke et al. (2021) Mar Biol 168(135)

Once again, coincidence played an essential role in the whole story. The research team led by Jefferson Hinke and his colleagues from the National Oceanic and Atmospheric Administration (NOAA), the Scripps Institute in San Diego and the organization Ocean Associates Inc. had actually equipped several animals with small video loggers and tapes as part of a study on the hunting and diving behavior of chinstrap penguins. This was done by two scientists, Laura Brazier and Stephanie Walden of Ocean Associates on near Cape Shirreff on Livingston Island. Tamara Russell of the Scripps Institute at the University of California, who had been involved in the analysis of the footage and data, explains in a post on Instagram, “Two penguins that had attached camera tags left the colony together, foraged together for hours, regrouped before foraging dives, and ate the same amount of krill.” According to the data, the animals spent a total of 9.25 hours together on the hunt and were very successful.

Chinstrap penguins are not the only penguins that hunt together. But the research group’s images are the first to directly show that the birds could all be very successful if they hunted together. However, further investigations are necessary. Picture: Michael Wenger

The authors of the study note in their paper that these are only initial results that should prompt further study. On the one hand, the researchers could not see any examples of clear coordinated behavior in the underwater images. Furthermore, the observations were only made on two animals. “While generalization from this small sample size is challenging, the results prompt questions for further research,” the team writes. More recordings will certainly be necessary to show whether and how the animals, which only measure around 55 centimetres, hunt their food in the cold waters of Antarctica. This is essential because the region where the animals breed and hunt is coming under pressure from ever warmer water from the north. Ice always forms later, which in turn is bad for krill. And when the main food source is missing, chinstrap penguins have to retreat further… but the question then becomes where. Because despite its size, Antarctica is not infinite.

The study area is located on Livingston Island, one of the South Shetland Islands. Cape Shirreff, where the breeding grounds of the chinstrap penguins are located, is the northern tip of Livingston. There are also two field stations (small picture), a Chilean field station (left) and the US field station operated by NOAA (right). Image: small = Joshua Stone, Wikicommons CC SA-BY 4.0; Map_ Michael Wenger via Google Earth

Dr Michael Wenger, PolarJournal

Link to the study: Hinke, J.T., Russell, T.M., Hermanson, V.R. et al. Serendipitous observations from animal-borne video loggers reveal synchronous diving and equivalent simultaneous prey capture rates in chinstrap penguins. Mar Biol 168, 135 (2021). https://doi.org/10.1007/s00227-021-03937-5

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