"This study showed little penguins gained no benefit in capturing prey when from hunting in groups, suggesting individuals may forage in groups to improve detection of prey or avoid predation but, once they find prey, it is every penguin for themselves," lead author Grace Sutton of Deakin University said in a press release.
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The study was conducted at two breeding little penguin colonies located in southeastern Australia: London Bridge and Gabo Island.
Sutton and colleagues Andrew Hoskins and John Arnould got the footage by taping "penguin cams" to the bodies of the small flightless birds. The cameras were very lightweight and small, so as not to impede the penguins' movements. The cameras were also simply taped to the birds' bodies, and were then removed after a single foraging trip per penguin.
Many of the penguins, as Sutton indicated, hunted in groups. She and her colleagues suspect that fear may drive this behavior. The penguins themselves don't want to be eaten by predators, so it is a bit safer for them to be in a group.
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In addition to more eyes, ears and other senses detecting predators, all of these senses could also improve finding prey, which might save an individual's energy.
The authors could see no signs that the penguins were coordinating their moves to improve prey capture, as some other marine species, like whales and dolphins, are known to do.
However disorganized their hunting groups were, the little penguins predictably went after large schools of fish when behaving in this manner. Their favorites appeared to be anchovies and a fish called "sandy sprat," or white pilchard.
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The little penguins also enjoyed munching on small shrimp-like crustaceans called krill.
The penguins were additionally spotted eating a lot of jellyfish, which has not been reported much before. The researchers suspect that the jellyfish's "rapid deterioration means that they may often be overlooked in diet studies." In other words, there is not much to digest, so once a jellyfish is eaten, there is little evidence of the unfortunate victim left behind.
The researchers continued, "In the present study, individuals were observed to consume both whole small jellyfish and the inner portions of larger jellyfish, which are the most nutritious components."
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Other than that, jellyfish are like the junk food of the sea, at least for penguins, the scientists indicate.
They explained, "While jellyfish are relatively easy to capture due to their slow mobility, they are generally of low nutritional content."
Jellyfish might also be tasty to the little penguins, but the palate of most animals, even widely studied ones like dogs and cats, largely remains a mystery. Nevertheless, the latest study provides a clue: Sutton and her team determined that 28 percent of all observed consumed prey items were jellyfish.
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In future, the researchers hope to learn more about little penguin social dynamics, such if individuals preferentially choose whom to associate with when hunting, and for how long they might do so. The answers to such questions could shed light on the optimal ways that many group-living predatory species, not just these penguins, maximize their energy conservation and fitness.