News and notes about science

Videos show narwhals using their tusks to play with their food

For an animal with an ivory appendage half the length of its body protruding from the top of its head, a narwhal moves in the water with surprising grace. “It’s almost mesmerizing,” said Greg O’Corry-Crowe, a research professor at Florida Atlantic University. “The precision with which they wielded their tusks, it wasn’t like a broadsword. It was like a surgical instrument or the bow of a violin.”

In research published in the journal Frontiers in Marine Science, O’Corry-Crowe and colleagues make the case that narwhals aren’t only showing off with their tusks — the appendages have a variety of uses that help the animals survive in the ocean.

The narwhal’s tusk was an inspiration for unicorn myths. It’s known that only males have them, with rare exception, and that a big tusk is something female narwhals look for in a mate. But the shy and elusive animals have been difficult to study.

With the help of local Inuit communities, the team of researchers identified a spot in the Canadian High Arctic to set up camp and fly drones. As O’Corry-Crowe and team studied their video recordings, they identified previously unobserved tusk behaviors. And one of those behaviors looked an awful lot like playing.

Narwhals sometimes chased arctic char but did not, strangely, try to catch and eat it. The whales even slowed down when necessary to keep the fish just off the tip of their tusks. When they did interact with the fish in these encounters, they used gentle taps or nudges — a stark difference from more aggressive uses of their tusks when they were seen hunting fish. And, in fact, the arctic char also didn’t seem to always be trying to escape the pursuing narwhals.

“They are not actually foraging on the fish, and we were hesitant to use the word ‘play,’ but that is really what it looked like,” said Cortney Watt, who is with Fisheries and Oceans Canada and is an author of the study. She said it was also possible older narwhals used such behavior to teach younger ones how to pursue prey.

Everyone in the city needs soundproofing, even spiders

There’s nothing worse than a noisy neighbor when you are trying to have a nice meal — even if that meal consists of liquefying the insides of your prey before sucking them back up.

New research shows that some spiders living in cities somehow weave soundproofing designs into the fabric of their webs to manage unwanted noise, which can make it difficult for them to find prey and detect mates. These spiders “are able to use their webs as both a hearing aid and hearing plug,” said Eileen Hebets, a biologist at the University of Nebraska-Lincoln and an author of a paper led by Brandi Pessman, a postdoctoral research associate.

Spiders don’t have ears like humans, so they don’t necessarily hear things in the traditional way. But sound produces vibrations that travel through the ground and into their webs via silk strands.

Pessman began wondering whether noise pollution might annoy the spiders enough to alter their web-weaving strategies.

In a new study, Pessman and Hebets rounded up arachnid city slickers and country bumpkins and placed each spider in a container with a speaker at the bottom that played either loud or quiet white noise. When the researchers played loud noise to the city spiders, they found that the webs they had built were less sensitive, transmitting fewer vibrations to the funnel. “Their webs were essentially quieter,” Pessman said.

These iguanas got carried away and ended up 5,000 miles from home

For decades, the native iguanas of Fiji and Tonga have presented an evolutionary mystery. Every other living iguana species dwells in the Americas. So how could a handful of reptilian transplants have ended up on two islands in the South Pacific, more than 4,970 miles away?

In research completed by a team led by Dr. Simon G. Scarpetta, an evolutionary biologist at the University of San Francisco, the case is made that the ancestors of Fiji’s iguanas crossed on mats of floating vegetation. Such a voyage across nearly 5,000 miles of open ocean would be the longest known by a nonhuman vertebrate.

Rafting — the term scientists use for hitching a ride across oceans on uprooted trees or tangles of plants — has long been recognized as a way for small creatures on land to reach islands, said Hamish G. Spencer, an evolutionary geneticist in New Zealand who was not involved in the study. Usually those are invertebrates, whose small size lets them survive a long way in an uprooted tree trunk.

Iguana species have made shorter crossings. In 1995, at least 15 iguanas were seen rafting 200 miles on hurricane debris from one Caribbean island to another. And ancestors of the Galápagos Islands iguanas made the 600-mile trip from South America on bobbing vegetation.

But a crossing to Fiji is a much harder challenge. Scarpetta’s team concluded that the Fijian iguana species — which belong to a distinct genus, Brachylophus — split off from their closest relatives around 30 million years ago, about the time volcanoes birthed the Fijian archipelago. “North America is the most probable area of origin for iguanas in Fiji, and overwater rafting is the best supported mechanism,” Scarpetta said.

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