It’s time for another trifecta. The first article comes from Science, and suggests that, contrary to earlier opinion, once cats start purring, it is self-sustaining, and needs no further effort from the cat. Click to read:
One of the most delightful sounds to a cat lover is their feline friend’s rumbling noise when they get a little scritch behind the ears. Yet how cats produce their contented purrs has long been a mystery.
A new study may finally have the answer. Domestic cats possess “pads” embedded within their vocal cords, which add an extra layer of fatty tissue that allows them to vibrate at low frequencies, scientists report today in Current Biology. What’s more, the larynx of these animals doesn’t appear to need any input from the brain to produce such purring.
At first I thought the paper, which used eight larynxes (or “larynges”) taken from dead cats, involved killing cats. Well, it did, but not from the experiment. Here’s from the paper:
Eight domestic cat larynges (Felis catus) were investigated in this study. An overview of the specimens is given in Table 1. The larynges were harvested from animals that had to be euthanised due to terminal disease unrelated to the respiratory tract in veterinary clinics in Vienna, Austria. The animals’ owners gave their explicit consent for the larynges to be investigated postmortem.
So it’s okay for me to report it (I wouldn’t have otherwise). From the Science summary:
Domestic cats are small, with most weighing about 4.5 kilograms, and researchers had puzzled over how these animals manage to generate the low-frequency vocalizations—typically between 20 and 30 hertz (Hz)—involved in purring. Such frequencies are usually only observed in much larger animals, such as elephants, which have far longer vocal cords. And whereas big cats such as lions and tigers are capable of loud roars, domestic cats are only able to produce low-frequency purring.
Most mammal vocalizations, including other cat noises such as meowing and hissing, are produced in a similar way—a signal from the brain causes the vocal cords to press together, and the flow of air through the larynx causes the cords to knock against each other hundreds of times per second, producing sound. This process, known as flow-induced self-sustained oscillation, is a passive phenomenon: Once the vocal cords start to vibrate, no further neural input is required to keep them going.
But in the 1970s, scientists proposed that purring was different. The so-called active muscle contraction hypothesis holds that domestic cats actively contract and relax their laryngeal muscles about 30 times per second in order to purr. The idea, based on measurements of electrical activity in the laryngeal muscles in purring cats, caught on and has been a common explanation for cat purring ever since.
Here are the “glottal muscles”—muscles in the larynx that drive the vocal cords, opening and closing during a spontaneous purr
More from the Science summary:
To conduct the work, scientists removed the larynges from eight domestic cats, all of which had been humanely euthanized because of terminal disease and were investigated with the full consent of their owners. The researchers pinched the vocal cords together and pumped warm, humidified air through them. By isolating the larynx this way, the scientists guaranteed that any sound produced was occurring without muscle contractions or any input from the brain.
The team was able to produce purring in all of the larynxes—a “great surprise,” says lead author Christian Herbst, a voice scientist who holds dual appointments at the University of Vienna and Shenandoah University. Without any active neural control, all eight larynges produced self-sustaining oscillations at frequencies between 25 and 30 Hz—suggesting purring doesn’t necessarily require active muscle contractions.
The new experiment instead suggests that purring, like meowing and hissing, is a passive phenomenon that plays out automatically after cats’ brains provide the initial signal to purr, the researchers conclude. That explanation “is much more in line with what we know about how vocalizations are produced in other vertebrates,” says Karen McComb, an expert in animal behavior and cognition at the University of Sussex who wasn’t involved in the study.
But there is a reasonable objection, too:
However, David Rice, a biomechanical engineer at Tulane University who has conducted research into the mechanics of cat purring, isn’t fully convinced. He says there’s no guarantee that living cats’ vocal cords behave the same way as the surgically removed cords from the study. Just looking at excised larynges, he says, is “akin to removing the mouthpiece from a wind instrument and analyzing its sounds in isolation.”
Herbst suspects that purring is probably driven by a combination of neuronal control and self-sustaining oscillation—but it will be difficult to ever know for certain. As he notes, a cat will usually only purr when it feels safe, comfortable, and content—something that wouldn’t be possible if the felines had uncomfortable probes inserted into their larynxes. Until scientists find a way around that conundrum, this particular cat will likely remain in the bag.
He has a point, but I’d put my money on the first “endogenous purring” hypothesis. Still, purring means something, because it’s initiated by stimulation from the brain, including the pleasure of being petted.
Here’s the world’s loudest purring cat:
Merlin, a rescue kitty from Torquay, Devon (UK) now has plenty to make a noise about after being confirmed as having the world record for Loudest purr by a domestic cat.
From The World of Kitsch, we have a series of cat-shaped buildings. Click to see:
But there are only six, and no captions to show where or what they are. Readers might try a Google image search and tell us below what these buildings are and where they are located.
This is the best one by far: a real building!
A maneki-neko building, which may be a bus shelter:
Note: this is not a cat!
Neither is this one!
Many of you have older cats with arthritis. If so, here’s an article from the Pittsburgh Post-Gazette (click headline to read) that may help your ailing moggy:
A precis: here’s the new drug you can inject at home:
Earlier this year, Liz Schwinn noticed that her 18-year-old cat, Mango, wasn’t as playful or as social with her four other cats as she used to be.
During Mango’s annual exam, Schwinn mentioned this to her veterinarian, who said he had been having encouraging results with Solensia, a new drug for feline osteoarthritis.
Osteoarthritis occurs when tissue in the joints starts to wear down, causing bones to rub against one another. Not only does this make moving harder, but it can also cause severe pain.
It was difficult to treat in cats because there were few effective solutions that could be safely used long term and as any cat owner knows, it’s hard to administer oral medications.
Approved for use in 2022, Solensia is a once-a-month injection to relieve the pain associated with osteoarthritis. Its active ingredient, frunevetmab, is a monoclonal antibody designed specifically for cats that targets Nerve Growth Factor, a key driver of osteoarthritis pain. By targeting NGF, Solensia reduces pain signals and helps to control the animal’s pain.
Schwinn and her husband, Mike, who live in suburban Cleveland, have noticed a definite improvement in the six months that Mango has been treated with Solensia.
“It’s made her more active and social,” she said. “She’s out and about more with us instead of sleeping in the bedroom. And we haven’t seen any negative effects.”
Since Solensia can be injected subcutaneously, under the skin, the Schwinns opted to purchase it from their vet and administer it at home, thereby eliminating the stress of taking Mango to the vet once a month.
If you have an arthritic cat, I give the advice you always see on television: “Ask your doctor!” (or in this case your vet). And click on the screenshot below to go to the Solensia page for vets:
Many animal lovers feel passionately about animal rescue (and rightfully so) but it takes an extra special person to rescue animals on a daily basis. Whether they’re part of a rescue organization or are a one-person show, it’s inspiring to see the ways they change animals’ lives simply by following their passions.
One cat foster mom is saving lives across Iowa thanks to her efforts in fostering, rescuing, and trap-neuter-release. She recently answered a call about three gray cats who had been abandoned in a local park, and–as the September 25 video shows–she had no trouble winning over the confused felines. The poor babies had no clue where they were!
The Tik Tok video (click on arrow to go to the video with sound, and you’ll want sound):
h/t: Merilee, Divy, Ginger K.