Wild Things

The weird and wonderful in the natural world

Sarah Zielinski

Wild Things

Wild Things

Lazy sunfish are actually active predators


Ocean sunfish (Mola mola) hang out at the water’s surface to warm up after diving deep to find food, a new study finds.

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If you spot an ocean sunfish (Mola mola) near the surface of the water, you might be amazed by its size. These are, after all, the biggest of all the teleost fish (the group of ray-finned fishes that includes many of the species we like to eat), and they can grow as large as 1,000 kilograms. You may also think the fish are nothing but lazy sunbathers. And that wouldn’t be an unreasonable guess — scientists used to think sunfish only drifted about in surface currents.

Then some researchers attached accelerometers to the fish and discovered they were active swimmers that could reach depths of 800 meters. But what were they doing in the deep?

To find out, Itsumi Nakamura and colleagues at the University of Tokyo attached instruments to seven sunfish caught in Funakoshi Bay on the east coast of Japan that could record the fish’s behavior and internal temperature. On some of the fish they also attached a still or video camera with a light to see and record what was in front of the fish — and what they were eating. The results of their study appear in the May issue of the Journal of Animal Ecology.

Over four to six days of recording, each fish traveled tens of kilometers; these were no lazy drifters. At night, they stuck close to the surface, within the top 20 meters of water. But during the day, the fish spent about 40 percent of their time in the top five meters of ocean and the rest diving to depths of up to 200 meters.

The cameras revealed that the fist were chasing after a variety of jellyfish and jellyfish-like creatures, mostly siphonophores. But the fish didn’t necessarily eat all of these creatures. When one sunfish approached a jellyfish, it ate only the gonads and oral arms; these bits are more nutritious than the bell.

The body temperature data showed that the sunfish lost a lot of body heat when they dove deep. When at the surface, the fish had body temps of 16° to 20° Celsius, similar to the ambient water temperature. When it dove, though, a fish’s body temp could decrease to as low as 12° C. Those hours lazing about in the sun, the researchers conclude, are needed to warm back up after a trip to the deep to catch a meal.

Plants,, Evolution

A protein battle underlies the beauty of orchids

By Sarah Zielinski 4:00pm, April 28, 2015
The petal-and-lip shape that draws pollinators to orchids results from a competition between two protein complexes, a new study finds.
Paleontology,, Evolution

Your toy stegosaurus may be a girl

By Sarah Zielinski 2:00pm, April 22, 2015
Male and female stegosaurs may have looked different, a new study finds.
Animals,, Oceans

Growth of mining on land may promote invasions at sea

By Sarah Zielinski 7:46pm, April 21, 2015
Ballast water taken in to keep ships stable could, when discharged elsewhere, release species that become invasive in their new homes.
Ecosystems,, Ecology

Before you plant this spring, consider the birds

By Sarah Zielinski 10:00am, April 20, 2015
A study of Chicago neighborhoods finds that the plants in private yards influence the variety of birds that live in the area.

How many manatees live in Florida?

By Sarah Zielinski 4:30pm, April 15, 2015
The most recent official count reports more than 6,000 manatees in Florida waters, but a new estimate may give a better picture of the population.

Flight delayed: There’s a coyote on the runway

By Sarah Zielinski 9:00am, April 14, 2015
A new study tallies up airport incidents involving carnivores and finds coyotes are the biggest threat.
Animals,, Oceans

Tiny sea turtles are swimmers, not drifters

By Sarah Zielinski 12:00pm, April 9, 2015
Young green and Kemp’s ridley sea turtles moved in different directions than instruments set adrift in the sea, which shows the animals were swimming.
Animals,, Ecology,, Climate

Eggs and other land foods won’t feed polar bears

By Sarah Zielinski 9:00am, April 5, 2015
Polar bears will not be able to survive on land by eating birds, eggs and vegetation, a new review concludes.
Animals,, Conservation

How human activities may be creating coywolves

By Sarah Zielinski 8:00am, April 1, 2015
Endangered red wolves will mate with coyotes when their partners are killed, which often happens because of human activities, a new study finds.
Animals,, Conservation

‘If you build it they will come’ fails for turtle crossings

By Sarah Zielinski 2:00pm, March 25, 2015
Turtles and snakes barely used an ecopassage built to make their movements safer. Scientists blame poor fencing that failed to keep them off the roadway.
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