Science News in Brief: From cats on catnip to ancient European money

Your cat isn’t just getting high off catnip

For a lesson in euphoria, look no further than a house cat twined around a twig of silver vine. When offered a snipping of the plant, which contains chemicals similar to the ones found in catnip, most domesticated felines will purr, drool and smoosh their faces into its intoxicating leaves and stems, then zonk out in a state of catatonic bliss.

But the ecstatic rush might not be the only reason felines flock to these plants, new research suggests. Compounds laced into plants like silver vine and catnip might also help cats ward off mosquitoes.

Other papers have pointed to the insect-deterring effects of catnip and similar plants. But the new study, published recently in the journal Science Advances, is the first to draw a direct link between the plants and their protective effects on cats.

“It’s a really interesting observation, that such a well-known behaviour could be having this unappreciated benefit for cats,” said Laura Duvall, a mosquito researcher at Columbia University in New York who wasn’t involved in the study.

Catnip and silver vine contain iridoids, a suite of chemicals that seem to potently tickle pleasure circuits in cats.

To pinpoint the evolutionary roots of this plant-feline connection, a team of researchers led by Masao Miyazaki, a biochemist and veterinary scientist at Iwate University in Japan, corralled a menagerie of cats – some domestic, some wild – and monitored their responses to an iridoid extracted from silver vine.

Presented with scraps of paper dosed with iridoid, most of the cats initiated a ritualised rolling and rubbing.

The researchers next rubbed silver vine iridoids on the heads of several house cats, or allowed the felines to apply the substance themselves, and placed the animals within reach of dozens of thirsty mosquitoes. The insects nipped at the faces of un-anointed cats, but largely snubbed the felines that had gone gaga for the vines.

The new findings suggest that cats, which can contract heartworm infections from mosquito bites, might also glean some medicinal benefits from their botanical tussles, said Mikel Delgado, a cat behaviour expert at the University of California, Davis who wasn’t involved in the study.

In a one-off experiment, Miyazaki slathered his arm with iridoids and stuck it in a mosquito cage. The insects steered clear – but feasted on an untreated limb. “We hope to use it for humans in the future,” he said.

— Katherine J Wu

Electric eels hunt in packs, shocking prey and scientists

In August 2012, Douglas Bastos, then a graduate student at Brazil’s Instituto Nacional de Pesquisas da Amazonia, was exploring a remote waterway in the Amazon rainforest when he came across a small lake teeming with electric eels.

Electric eels, which despite their name are actually a type of knifefish, were believed to be solitary creatures. And yet before Bastos’s eyes were more than 100 of them. Then things got even more jolting.

Bastos watched, astonished, as the writhing mass of eels began corralling groups of tetra fish into tightly packed balls and bombarding them with synchronised electric attacks that sent them flying.

“When I saw the tetras jumping after the attacks, I was in shock,” Bastos said. “Group hunting is a rare event in freshwater fishes.”

Two years later, Bastos and researchers from the Smithsonian National Museum of Natural History returned to the area to study this unusual phenomenon. The findings of their study, published recently in the journal Ecology and Evolution, overturn the idea that electric eels are exclusively solitary predators and raise new questions about the lives of these little-understood fish.

When the researchers returned to the site, along the banks of Brazil’s Iriri River, they confirmed that the electric eels Bastos had observed in 2012 were Volta’s electric eels, a recently discovered species that can reach 8 feet and are capable of producing 860-volt electric shocks – the strongest electric discharge of any animal.

For the past 250 years, scientists believed that all electric eels belonged to the same species, but in 2019, research conducted by C David de Santana, a Smithsonian researcher, proved that there are at least three species, the largest and most electrified being the Volta’s electric eel.

Bastos and de Santana analysed over 70 hours of footage of Volta’s electric eels conducting highly coordinated group hunts. At dawn and dusk, the slimy, snakelike creatures would congregate in shallow water and start swimming together in large circles. After corralling thousands of tiny fish into dense balls, the eels split off into cooperative hunting parties with two to 10 members.

These parties would then surround the schools of terrified tetra and launch joint electric attacks, sending the tetra leaping out of the water. When the electrocuted fish splashed down, the eels quickly devoured them.

Although the researchers weren’t able to measure the voltage of the coordinated electric attacks, they estimate that 10 Volta’s electric eels working together could create an electric current strong enough to power 100 light bulbs.

— Annie Roth

DNA reveals the real lives of ‘Game of Thrones’ dire wolves

The dire wolf, an animal many people know from its fictional incarnation in Game of Thrones was a heavy-boned, powerful predator that roamed North America up to about 11,000 years ago, or perhaps even later, preying on large animals like extinct horses, bison, sloths and even mammoths.

While it was nowhere near as big as its television version, the dire wolf was about 20 per cent larger on average than the grey wolf, and it was long considered a sister species, Canis dirus rather than Canis lupus.

But an international team of scientists reported recently in the journal Nature that the first sequencing of the dire wolf genome showed an unexpectedly large genetic separation between the two species, big enough that the dire wolf is not just a separate species but a separate genus. They resurrected an old name, Aenocyon, for the genus, first suggested in 1918 by John Merriam, a paleontologist, but soon discarded. The dire wolf is the sole species in the genus.

The last common ancestor of the gray wolf and the dire wolf was about 5.7 million years ago, the researchers reported. And another surprise was that the dire wolf didn’t seem to interbreed with other species – as dogs, wolves, coyotes and other canids do. In evolutionary terms, it met a lonely end.

Angela Perri, an archaeologist at Durham University in England, one of the leaders of the research, said of the new work, “a hundred years later we are saying that Merriam was right”.

What made the change possible was the effort made by the many scientific groups that participated in the project to find enough ancient DNA.

The problem was not a lack of old bones. The vast majority come from the La Brea Tar Pits in Los Angeles County, where the remains of about 4,000 animals have been recovered. Tar apparently plays havoc with recoverable DNA and until now, nobody had been able to sequence the dire wolf’s genome.

The researchers compared the dire wolf data with previously sequenced genomes of a number of other species, including wolves, foxes, jackals and dholes. The data showed how long ago the species split apart and how distant they are.

They were here at least 250,000 years ago, and they were still around, although nearing the end of their existence, when the first humans were arriving in the Americas, perhaps 15,000 years ago.

As to why the dire wolf went extinct and wolves survived, the authors speculated that its long genetic isolation and lack of interbreeding with other species may have made it less able to adapt to the disappearance of its main prey species.

— James Gorman

An ancient form of European money: Bronze rings, ribs and blades

The modern world runs on a constant flow of money that has its roots in simpler proto-currencies pioneered on regional levels by ancient peoples.

A pair of archaeologists believe they have identified a very early example of commodity money in Europe, used some 3,500 years ago during the Bronze Age, with denominations that took the form of bronze rings, ribs and ax blades. People at this time frequently buried collections of these ubiquitous items, leaving a wealth of scattered “hoards” across the European continent.

In a study published recently in PLOS ONE, Maikel Kuijpers, an assistant professor in European prehistory at Leiden University in the Netherlands, and Catalin N Popa, who was a postdoctoral researcher there, compared the weights of more than 5,000 Bronze Age rings, ribs and blades, sourced from over 100 hoards that contained five or more items.

The results revealed that 70 per cent of the rings were so close in mass – averaging about 7 ounces – that they would have been indistinguishable if weighed by hand. While the ribs and ax blades are not quite as uniform, the study concludes that the artefacts are similar enough to collectively demonstrate “the earliest development of commodity money in prehistoric Central Europe”.

“It is a very clear standardisation,” Kuijpers said.

While other researchers questioned some of their conclusions, they agreed that the study added to our knowledge of the economic activities of ancient peoples.

A central innovation of bronze is the ability to make duplicates by casting the metal in moulds. The study speculates that these near-identical copies gave rise, over time, to an abstract concept of weight, which laid the mental groundwork for the invention of weighing tools and technologies that emerged in Europe centuries later in the Bronze and Iron Ages.

Nicola Ialongo, a prehistoric archaeologist at Georg August University of Gottingen in Germany, said that the study offered “an important contribution to understanding how early monies work,” but that there was a less complicated explanation for how these standardised objects emerged.

“As the authors acknowledge, the regularity of their samples might simply be explained by imagining that the objects in their data sets were cast with a limited number of moulds, or that the moulds themselves had a standardised shape,” Ialongo said.

The authors counter that “weight mattered” because “there are indications that for some types of objects a deliberate effort was made to achieve a specific weight interval”.

— Becky Ferreira

© The New York Times