{"id":25920,"date":"2019-01-04T00:05:33","date_gmt":"2019-01-04T08:05:33","guid":{"rendered":"https:\/\/hakaimagazine.com\/?post_type=custom_news&p=25920"},"modified":"2019-01-03T12:45:47","modified_gmt":"2019-01-03T20:45:47","slug":"penguins-love-jelly","status":"publish","type":"custom_news","link":"https:\/\/hakaimagazine.com\/news\/penguins-love-jelly\/","title":{"rendered":"Penguins Love Jelly"},"content":{"rendered":"

Some penguins like their fish with a side of jelly, a new study shows<\/a>. By looking at the DNA in the birds\u2019 poop, researchers found that they eat a surprising amount of gelatinous prey, including tiny tube-shaped animals called salps<\/a>. Knowing what\u2019s on the menu for penguins is important for understanding the health of not just these seabirds, but of their whole ecosystem.<\/p>\n

Catherine Cavallo, a PhD candidate in ecology at Monash University in Australia, is trying to turn seabirds into tools for learning about ocean environments. In particular, she studies little penguins<\/a>, which get their name for being the smallest of all penguins at just 30 centimeters high. These penguins stay close to home when they hunt, Cavallo says. That means observing what they eat could help researchers track changes in the local environment.<\/p>\n

The traditional way of studying an animal\u2019s diet is to examine its stomach contents or feces. \u201cIt\u2019s usually some random assortment of body parts and mush that are pretty hard to identify,\u201d says Travis Gerwing, an ecologist at the University of Victoria in British Columbia who wasn\u2019t involved in the new study. Even if you can tell what you\u2019re seeing, this method over-represents species with hard parts such as shells, bones, or beaks. Soft, squishy prey are more likely to disappear entirely in the digestive process, Gerwing says.<\/p>\n

So, instead, Cavallo and her coauthors used a newer technology called DNA metabarcoding. They collected hundreds of scat samples from little penguin nests at two breeding sites in southeastern Australia. Then they targeted and sequenced certain short segments of DNA within the feces. These genetic snapshots told them what kinds of life forms had passed through the penguins\u2019 guts.<\/p>\n

Most of the penguins\u2019 diet appeared to be fish, but the researchers also found gelatinous animals in 75 percent of the samples. The DNA of these animals made up almost a quarter of the total prey DNA in the study. Some of them weren\u2019t known to be penguin food. \u201cWe were expecting to find gelatinous prey in the diet, but the prevalence of salps was a surprise,\u201d Cavallo says.<\/p>\n

\"(Thalia<\/a>

This salp, Thalia democratica<\/em>, often grows in great swarms, and in the Tasman Sea it has reached densities of up to 1,312 individuals per cubic meter. Photo by David Shale\/Minden Pictures<\/p><\/div>\n

DNA metabarcoding is an imperfect tool though, notes Gerwing. \u201cIt\u2019s an amazingly powerful technique. That\u2019s actually one of its problems,\u201d he says. It can pick up the genetic signature of not just the little penguin\u2019s prey, but also the prey\u2019s prey\u2014whatever was in the belly of a fish the penguin swallowed, for instance, so long as that DNA survives being digested twice. Cavallo says that\u2019s unlikely to dramatically change her results, however, and knowing what the penguins\u2019 prey were eating is also valuable information.<\/p>\n

Cavallo thinks little penguin diets can help researchers study climate change. For example, salps and jellies are expected to fare better than others in a warming, acidifying ocean, and their abundance might be reflected in penguin poop.<\/p>\n

In an earlier study<\/a>, Jean-Baptiste Thiebot of the National Institute of Polar Research in Japan and his colleagues attached video cameras to little penguins and three other penguin species and saw them all eat jellyfish. But evidence for penguins eating gelatinous herbivores like salps has been more limited, Thiebot says.<\/p>\n

Thiebot wonders whether salps are a favorite food item for little penguins year round or just in the summer when salps are more abundant. He also thinks it would be interesting to know if their diets change over time. \u201cDo younger individuals tend to try those more? Or less?\u201d Perhaps age and hunting experience will affect a penguin\u2019s taste for jellies.<\/p>\n","protected":false},"excerpt":{"rendered":"

Some penguins like their fish with a side of jelly, a new study shows. By looking at the DNA in the birds\u2019 poop, researchers found that they eat a surprising amount of gelatinous prey, including tiny tube-shaped animals called salps. <\/p>\n

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