News and notes about science

Your cat may or may not love you, but it knows your scent

Cats tend to have their own ideas about what they should be doing, which may or may not align with the wishes of their owners. But in a study published in the journal PLOS One, a team led by Hidehiko Uchiyama, a professor of animal science in Tokyo, established that cats respond differently to the scents of their owners than to the odors of strangers. That suggests your cat knows what you smell like, in addition to what you look and sound like.

The researchers recruited 30 cats and their owners to participate in the study. The cats’ owners captured their own scents by rubbing cotton swabs behind their ears, between their toes and under their armpits. Eight more people who don’t own pets and didn’t know the cats’ owners were recruited to be “odor donors.”

Each of the study cats, in the comfort of its own home, was then presented with an array of test tubes containing the smelly cotton swabs from its owner, a stranger and a blank control. A camera recorded the cats’ reactions to the test tubes. The cats spent more time sniffing the samples from the strangers than from their owners — an indication that the cats could recognize their owners’ scents and devoted more time to exploring ones they’d never smelled before.

The team also analyzed videos of the cats sniffing the test tubes and observed the cats predominantly using their right nostrils to smell the strangers’ test tubes. These findings seemed to corroborate previous studies of other animals, including dogs, which also led with their right nostrils when exploring strange scents.

These plants protect larvae from wildfires

Living things have long needed to find ways to survive wildfires. Some of them, researchers recently discovered, can even build their own flameproof panic rooms.

Galls are outgrowths induced on plants by other organisms. In some instances, they form when parasitic insects like midges, moths and wasps release substances that prompt the plant to produce more cells. Galls shelter the larvae of the insects that made them grow, and they protect newborns from predators, parasitoids and adverse weather conditions. It turns out that this perfect nursery can also protect some insect larvae from the flames and heat of wildfires.

The discovery, announced in the journal Ecology, came from Jean Carlos Santos, an ecologist in Brazil, who was working in Minas Gerais, a state in the Cerrado, a region of savannas in the heart of the country. At that time, in 2012, “a massive fire erupted in the area.

While walking through the area devastated by the flames, he cut open the galls of Solanum lycocarpum, a common plant living in the Cerrado that is also known as wolf’s fruit. These galls were made by females of the Boheman weevil, which lay their eggs on the wolf fruit’s shoots, inducing thick, multichambered galls that host many larvae.

To his surprise, weevil larvae were still hanging on inside. “This was both fantastic and intriguing!” Santos wrote in an email.

Santos came back to the area a few days later with his students. They collected dozens of galls from 40 wolf fruits; some had been exposed to the fire and some had not. Back in the lab, the team cut the galls open and checked whether the weevil larvae and pupae survived.

The galls were at a height on the plants where they “were clearly exposed to extreme heat from the fire. All the galls in the burned areas bore signs of charring,” Santos said. “Initially, we assumed that no insects could have survived within the galls.”

Despite that, the survival rate of larvae sheltering in burned galls was about 66%. Inside 20 galls, all larvae survived; in 23, only some came out alive; while in nine galls all weevils succumbed to the flames.

A genetic clue to why men are taller than women

Men are taller than women, by an average of about 5 inches. But why? A new study suggests it partly involves a gene called SHOX, known to be linked to height. SHOX is present on both the X chromosome — females have two X chromosomes — and the Y chromosome; males have one X and one Y. A research team suspected SHOX could explain differences in height by having a different effect on the X and Y chromosomes.

To investigate, researchers asked if an extra Y chromosome boosted height more than an extra X chromosome. Studying genetic databases, the group found 1,225 people with either missing or extra X or Y chromosomes. And an extra Y did give more height than an extra X.

The placement of the SHOX gene is near the end of the sex chromosomes. In females, most genes on one of the two Xs are inactive. But one region where the genes remain active is at the tip of the X. The SHOX gene is close enough to the tip that it is not quite silenced. In men, the X, with its SHOX, is fully active. So is the Y. This means that a woman, with two X chromosomes, will have a slightly lower dose of the SHOX gene than a man, with an X and a Y. The SHOX effect may account for nearly a quarter of the average difference in height. Other features of male sex hormones cause most of the rest of the difference.

This article originally appeared in The New York Times.

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