Jellies as Prey, Benny the Beluga, Time-sharing Dolphins

A lion’s mane sea jelly (Cyanea capillata).

INTERESTING STUFF ON THE WEB

Jellyfish have generally been regarded as more nuisance more than key players in the ocean food web. But they may be much more significant than has been previously thought, according to a study described in the online magazine Anthropocene.

While they have long been considered “tropic dead ends” ignored by predators, in fact they’re regularly consumed by marine life as diverse as fishes, penguins, turtles, crabs, octopuses, sea cucumbers and crustaceans.

They’re still low-calorie organisms – their gelatinous tissues are 95 percent water. But there are a lot of them – a swarm of tiny jellies can be quite large, for example – and they’re predators themselves. Predators of jellies can also take in the undigested tissues of fishes and other prey remaining in jellies’ stomachs.

As opposed to limited direct observation of jellies, they examined jelly lifestyles through isotope analysis of predators’ tissues, DNA analysis of fecal and gut sampling and use of animal-borne cameras.

A beluga whale – normally found in Arctic seas – has been in residence in the Thames River in southern England since September, reports an article in Hakai Magazine. He’s become a fan favorite. They named him Benny

Actually, his age and sex are not known. But his presence has inspired Benny-themed Christmas cards, tea brews and beers. Also much media attention. And also, concerns for his safety. While prey like flounder are abundant in the lower Thames, so are ships. It’s a major shipping lane.

The city council in Gravesend launched a “#KeepBennySafe” campaign, which included canceling a barge-based fireworks display in November. The Port of London Authority warns incoming ships to watch out for the whale. And, Hakai reports, the local tea shop has begun working to reduce its use of plastic bags as a general environmental concern. Still, locals say, for Benny’s sake, they want him to go home.

A group of dolphins in the northern Adriatic Sea have divided into two groups that “time-share” their hunting grounds – a behavior not previously known among marine mammals, according to a report in Science Magazine’s daily newsfeed.

The population of 38 bottlenose dolphins (Tursiops truncatus) has split into groups of 19 and 13 animals each (with six animals loosely making up a third group). The larger group tended to hunt in the morning, following fishing vessels in the Bay of Trieste. The 13-member smaller group hunted in the same area, but not in relationship to fishing vessels, in evening hours. They rarely saw each other.

 

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