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purrsistence
Apr. 21st, 2019 08:18 pmEarlier this week, T got a blood pressure cuff and a cheap stethoscope, to be used to practice taking blood pressure and heart rate counts. Roomie M and I have already been informed that we're probably going to be the model patients, which is fine: it's not as if I haven't signed on to be a living anatomical aid before, and this requires way less effort on my part. But it does mean I have to sit still, and I'm not great at that. So after they tested a blood pressure/heart rate exam on me, I snagged Dent (who happened to be napping nearby) and volunteered him to have his heart rate measured. No blood pressure cuff, but there isn't a reason you can't practice on a cat, right?
It turns out there is certainly a reason not to practice getting heart rates on Dent: he purrs under his breath constantly, just quiet enough not to be heard unless you hold him up to your ear like a conch shell. He was actively annoyed with me the first time I held him up for the stethoscope--he'd been napping! why was I disturbing a nap and a good cuddle?--and still he purred. We took to trying to sneak up on him over the course of the day to see if we could startle him into not purring, in case it was the human attention. Nope--he purrs regardless, quietly and happily, and never, ever, ever stops. Eventually T got a heart rate by waiting until he was asleep and surprising him into pausing.
I also learned this week that cat purrs are apparently almost unique among vocalizations inasmuch as they aren't produced via the myoelastic-aerodynamic theory of laryngeal vocalization: that is, most tetrapod animals make noises by pushing air through vocal folds which vibrate at particular resonances, which means you can replicate the sound if you force the air through an excised larynx from a dead animal. This is also the way that most cat vocalizations work. Purring, though, happens when cats actively vibrate muscles in their larynxes, which is why cats can purr and breathe at the same time. You can vocalize while inhaling as well as exhaling, but the noise never sounds quite the same from inhale to exhale.
As far as I know--and I was listening to Tecumseh Fitch, who is probably the most knowledgeable living expert on the mechanisms of vocalizations across vertebrates--cats are very unusual for being mammals who vocalize this way. There was some thought that perhaps elephants might, too, when they make big infrasonic calls--but nope, it seems that they use the more common MEAD mechanism to make those calls too.
(We had a symposium at work about animal vocalizations, and so I'm perked up and thinking hard. I found out that bats sing, too--including the Mexican free-tailed bats who are so beloved in Austin--and I ought to follow up with that later.)
It turns out there is certainly a reason not to practice getting heart rates on Dent: he purrs under his breath constantly, just quiet enough not to be heard unless you hold him up to your ear like a conch shell. He was actively annoyed with me the first time I held him up for the stethoscope--he'd been napping! why was I disturbing a nap and a good cuddle?--and still he purred. We took to trying to sneak up on him over the course of the day to see if we could startle him into not purring, in case it was the human attention. Nope--he purrs regardless, quietly and happily, and never, ever, ever stops. Eventually T got a heart rate by waiting until he was asleep and surprising him into pausing.
I also learned this week that cat purrs are apparently almost unique among vocalizations inasmuch as they aren't produced via the myoelastic-aerodynamic theory of laryngeal vocalization: that is, most tetrapod animals make noises by pushing air through vocal folds which vibrate at particular resonances, which means you can replicate the sound if you force the air through an excised larynx from a dead animal. This is also the way that most cat vocalizations work. Purring, though, happens when cats actively vibrate muscles in their larynxes, which is why cats can purr and breathe at the same time. You can vocalize while inhaling as well as exhaling, but the noise never sounds quite the same from inhale to exhale.
As far as I know--and I was listening to Tecumseh Fitch, who is probably the most knowledgeable living expert on the mechanisms of vocalizations across vertebrates--cats are very unusual for being mammals who vocalize this way. There was some thought that perhaps elephants might, too, when they make big infrasonic calls--but nope, it seems that they use the more common MEAD mechanism to make those calls too.
(We had a symposium at work about animal vocalizations, and so I'm perked up and thinking hard. I found out that bats sing, too--including the Mexican free-tailed bats who are so beloved in Austin--and I ought to follow up with that later.)
