Welcome to Stuff to Blow Your Mind production of iHeartRadio.
Hey you welcome to Stuff to Blow Your Mind. My name is Robert Lamb.
And I am Joe McCormick, and we're back with part two in our series on the theme of licking with
the tongue. In part one of this series, we talked about the role of licking in ancient Egyptian magic, which spans everything from the blessed licks and laps of the cow goddess Hathor to the sorceress violence of the crocodile who licks off the protective spells of the dead, and that discussion led to some diversions to talk about things like the adaptive function of the snake's forked tongue licking the air and the role that plays in chemo sensation
and research about when children acquire a disgust reaction to contamination of food surfaces by licking. After that, we took a hard pivot into candyland and talked about the frankly shocking amount of research that has gone into the question how many licks does it take to get to the center of a tutsi pop, which is a deep rabbit hole that becomes more philosophically interesting that the longer you gaze into it.
Yeah, I keep thinking about those TUTSI roll experiments. I think pretty much most, if not all of them were I think, at least on some level and in some phase approached with a fair amount of wit and whimsy. But you get the sense that like, once these scientific minds started digging into it, like it just becomes irresistible. It's just you've got to follow it through and put in the work.
So we're back today to talk about licking some more. And I promised that in today's episode we would talk about wound licking behavior in animals, So I think that's where we want to start. First of all, just Rob, I've got a few photos for you to look at in the outline here that are various statues of a Catholic saint. No as I'm a little confused about how to pronounce this guy's name because it's spelled different ways
in different languages. I believe it's Saint Roche or Saint Rock, sometimes spelled r o c h, sometimes spelled r c K or rck e or rch e anyway, a Catholic saint widely associated with hospitals, and with the Black Death.
I was looking at a gallery page about him and some artworks of him from the Met Museum, which are talking pointing out that very often depictions of this saint, he is shown with his left hand touching a sore on his thigh, which that explains why so many of the images of this saint he looks like literally like he's trying to show a little leg, like he's lifting something up. He's like, hey, have a look at my thigh here.
Yeah, in many cases too, or in some depictions it's like he's wearing shorts, so with like both legs on full display.
Yeah, into these leggy outfits. Often also he has a dog beside him, and both the showing of the sore on his leg, there's like a sore on his thigh showing this bulge or sore on his thigh and the dog beside him connect to this legend about the Saint that he at one point was traveling. I think he was on a pilgrimage and he became very ill. I don't know if he got the plague or some other illness. The boil or the bulge would sort of connect to
the idea that he got bubonic plague. But he fell ill and he collapsed somewhere, But then he was miraculously healed by a dog, a dog that brought him bread and licked his wounds.
And in fact, in these various depictions you'll see the dog either carrying the bread, holding the bread up to the man, or sometimes looks like maybe the bread is on the ground next to the dog. I guess the dog brought it and dropped it like here you go.
And in fact, this is not even the only major figure in Christianity to be part of a dog licking sores or dog licking his wounds motif that is said about the poor man Lazarus in the story in the Bible. Do you remember the rob Oh? Yes, the parable Jesus tells like he's ill and he falls down and the dogs lick his sores. It always seemed kind of gross.
And by the way, I just I'll explain more about this as we go on in a few minutes here, but I want to say at the top, having a dog lick your wounds is not a reliable way to be healed of illness or to treat injuries.
Yes, no matter what you might hear on Instagram or TikTok about the latest wound healing trend that's sweeping the nation.
It's all natural, it really is, but there are reasons even though it's not actually advisable, there are reasons why people get there mentally to think, oh, a dog healed me by licking my wounds. So in the last episode we talked about the licking of injuries in the Egyptian magical context and how that was probably modeled on the observation of animals licking their wounds in nature. So I was wondering, first of all, which animals do and do
not lick their wounds. Unfortunately, I don't think I can issue any kind of categorical taxonomic statement on this. It's not like, oh, mammals do it, and no other animals do. The best I can do is offer a kind of generalization and incomplete list of animals that have been observed
licking cuts and punctures in the skin. The behavior does seem to be most prevalent in mammals, though not present in all mammals and probably not completely limited to them, But animals that lick wounds include rodents like mice and rats, and a lot of the research on the biology of wound licking has been performed in mice and rats. For example, there's research showing that in domesticated brown rats, wounds heal fast or when the rat is able to reach the
wound with its mouth to lick it. And this in itself kind of highlights some features of wound looking adaptations, One that they do seem to help things heal, but also that in a lot of animals, self directed licking is going to be limited by what parts of the body the animal can reach with its own mouth. Some animals are more flexible than others.
Right, right, right, So certainly we think about our own case, like we cannot lick every part of our own body that we might desire to lick because.
Of our wound cut on the elbow. You're out of luck. Yeah. Also, animals that lick their wounds include many primates humans. Also, to some extent, there does appear to be at least some latent wound looking instinct in humans, though obviously lots of humans don't do it, and there are good reasons not to do it if you have other options, which most people do, but most I don't know about. Most many primates seem to have a wound looking instinct. Monkeys
and apes or observed to lick wounds in nature. Some carnivores, including domestic dogs and cats, lick their wounds. Of course, some wild ungulates, such as deer bears lick their wounds. Maybe not all bears, but some bears at least. There are some reports that horses occasionally lick wounds, but I don't know. I was trying to sort this out. Evidence
on that seems mixed to me. But it's also not just mammals, especially if you expand the definition of licking a little bit, like I see some reports online of anecdotal reports of people who keep reptiles like certain lizards, talking about the lizard's licking wounds. But again, the evidence
is a little fuzzy. In this case, however, there is a scientifically recognized behavior in some ant species where injured worker ants will be brought back to the colony for medical treatment, which essentially amounts to having their wounds licked
by first aid ants. It's not exactly licking with a mammalian tongue, but the wound treating ants will get the injured ant, and maybe it's been injured on a raid against a bunch of termites, and they'll get the injured ant and bring it back and treat the wound site by touching it with their mouth parts and applying saliva,
which helps prevent infection and promotes healing. According to a twenty eighteen article by Frank Verhon and Linsen Mayer in the species Megaponera analysis, they found that quote lack of treatment. Lack of treatment by this licking procedure increased mortality from ten percent to eighty percent within twenty four hours, most likely due to infections. So being able to get this licking treatment from the other ants makes a huge difference
in survival rates. So if a bunch of animals do lick wounds, that raises the question why what are the potential benefits of wound licking. It turns out there are a bunch first, and I think this one is underappreciated in some sources that really focus exclusively on the healing properties of saliva. The first thing to mention is the
mechanical cleaning of the wound area by the tongue. Licking the wound can remove necrotic or dead tissue, especially if it's only very loosely attached at this point can remove dead or dyeing tissue from the wound area. This is called dibridement in a surgical context. And licking also, more importantly probably removes dirt and other material contaminants from the environment from the site of the injury. This is really important because dirt and other contaminating solids and some liquids
are potentially microbial delivery vehicles. They have bacteria and other microbes on them and in them. And if say a little fleck of soil remains in an open wound, the microbes that are densely packed in that soil can move from the fleck of soil to the exposed tissue and cause an infection. And so licking with the tongue mechanically scrapes that fleck of soil out of the wound so that it doesn't become a landing craft for a microbial army.
And note that this is the same reason that doctors would advise you to wash a wound as soon as possible after you get hurt. Washing a wound out with water, soap, and water performs the same function as licking. Here it physically removes contaminants that bring a payload of germs with them.
So basically, whatever is in a dog saliva, there may already be things far worse than dog saliva in the wound. Yes, so the tongue can just physically remove those again, almost like you were rinsing out a wound, which of course the dog can't do because it doesn't have access to modern medical science and so forth.
Exactly, Yes, so the dog's tongue, for the dog, is the best it can do because it doesn't have clean running tapwater. Second, when animals lick a wound, they not only get rid of the bad stuff, but they also introduce substances to the wound through their saliva that may help the wound heal. Some examples here antimicrobial enzymes in our saliva that selectively kill germs on contact. A common example here is the enzyme lysizyme. This is found in
a bunch of our body fluids. Actually it's in spit, but also tears nasal and epithelial mucus in milk, and also in non human body fluids like egg whites. Lysisyme selectively attacks GRAM positive bacteria by dissolving their cell walls. So if bacteria made horror movies, lysizyme might be a good candidate for a melt movie monster. You know, it just kind of it melts you. It dissolves your you know, the outside of the cells. Another anti my chrobial in
saliva is called lactoferrin. This is a protein that prevents bacteria from growing by starving them of iron. Bacteria need iron atoms to reproduce, and lactoferriin bonds to free iron, making it unavailable for the bacterial cells. This is called iron sequestration. Removes the iron from them and so that they can't get what they need in order to grow and survive. And that's not even a whole list. Animals just have a big host of antibacterial agents in their saliva.
And note that these antibacterial agents in the saliva wouldn't be evolved exclusively for the application to external wounds. They play a big role in protecting the body in the mouth, like they're doing stuff for your body in your mouth, for your digestive system, and for your mouth cavity. Spit also contains things that are not just antimicrobials, but things that can actively speed up the healing process in the
affected tissue. And this includes his statins. These are proteins that also have antimicrobial properties, but in addition to that, they promote healing by causing what's called epithelial migration. They cause epithelial cells to migrate to the exposed tissue surface and close the wound. And saliva also has growth factor proteins like epithelial growth factor and nerve growth factor, and
you can see some of these influences at work. Actually, if you have ever noticed that injuries inside your mouth tend to heal a good bit faster than injuries on your outer skin.
Hmmm, I mean that that can be a kind of a paradox to consider because sometimes wounds inside your mouth are a little more irritating then wounds on your outer skin, so they might feel like they hang around longer. So I don't know, I'll have to really calculate on this one.
Well, they might actually hang around longer, depending on things like if you keep if something keeps irritating them or keeps reopening the.
Wound a sharp the wheat, then yes, yeah, if.
You keep cutting it open over and over, like, because you're using your mouth in a way that like you know, you could actually just keep stuff away from a cut on your skin, so there could be ways that something in your mouth would last longer, but it is typically the case that abrasions and cuts on the oral mucosa
heal faster than on the outside of the body. And one reason for this not the only reason, probably, but one reason is the presence of these healing factors and antimicrobial agents within the saliva, so a lot of benefits in spit. Spit could do a lot for an open wound, but these benefits do not come free. Wound looking, in fact,
has a very high cost. It comes with risks. At the same time that it removes contaminants, provides antimicrobial enzymes, and stimulates healing, it also so introduces problems of its own. For example, failure to regulate the wound looking behavior can lead to overlocking, which itself almost creates new wounds or makes the wound worse kind of keeps it from healing.
It can irritate or further injure the skin. A common example is that you know a dog just it has a wound looking instinct, but it can't turn the instinct off, so it just keeps licking a wound, making it actually worse and worse, So the injured dog will need a cone because it doesn't know when to stop.
Okay, so that sometimes the cone is for that, I know. Sometimes a cone with an animal is also to keep them from licking off a medication, which of course they have not evolved to understand. Like for the natural world dog, the best medicine is the dog saliva. The idea that there is a better medicine out there that did not come from their mouth is an impossible idea.
Right, So there can be multiple reasons for I mean, it can ye keep a dog from removing medication, can keep a dog from tearing out stitches, and can also just keep a dog from over grooming or overlicking a wound site. But maybe even more importantly, wound licking while
it removes some contaminants and microbes, it introduces others. The mouth is not sterile, so it's going to be delivering bacteria from the mouth cavity to the wound and this does come with genuine risks, especially if the animal's oral health is poor, or if it has mouth infections, or if the animal's immune system is compromised, or if the animal just has an oral microbiome that is more dangerous to cross link to open wounds. So you might imagine
that this could be the case with carnivores. A carnivore licking its wounds, that might be a riskier behavior than a herbivore licking its wounds on average, but still a lot of carnivores do it, so the benefits still seem to outweigh the costs in nature. So if it comes with these dangers, you can, you know, maybe contaminate the wound with bacteria from the mouth. If it comes with these dangers, why does the behavior continue? Why does it
persist in nature? It just seems like it's a case of trade offs, and on average, the wound looking instinct does more good than harm in the animals where it persists, it helps and it causes harm, and it does a little bit more of the former than the latter. So it's the evolutionary math works out.
Yeah, does it allow the individual animal in question to live long enough to do more reproduction? Essentially, like it kind of boils down to.
That, Yeah, Or if it just you've got a wound and it makes things worse forty percent of the time, but makes things better seventy percent of the time, I'll take that you know, you know odd, or I guess the math I just proposed didn't work out, but seventy thirty I guess yeah, I just I don't know what the real numbers are. But anyway, with the knowledge of germ theory and modern medicine, we don't have to go
with this math. Fortunately, because by washing out a wound with clean water and soap and applying clean pharmaceutical antimicrobials to the wound site, you can basically get all of the benefits of wound looking with none of the risks. Now, another interesting thing about wound locking is that there are two different versions of this behavior. There's the main kind we've been talking about, which is self directed wound loocking
licking your own cut or scrape. But there's also what's called communal wound looking, licking the wounds of others of your species. I found a good quick review of the research on communal wound looking in the background section of a paper called Licking their Wounds Social Response to Trauma
by free ranging Bison. This is by Thomas Young, Kayleye. Thacker, and Christopher Lewis, published in the journal Ethology in twenty twenty three, and they talk about how communal wound looking has broadly the same hygienic and healing acceleration benefits as self directed licking, but with some interesting added factors. One is that if animals in a group lick the wounds of other animals, this allows the treatment of wound sites
that the animals cannot reach with their own mouths. So this gets around the flexibility problem.
Right, especially if you're dealing I mean, you could be dealing with human beings again, but especially if you're thinking about large herbivores.
Yeah, yeah, But also this is interesting there could be secondary social benefits which are parallel to the benefits of social grooming. Young and co authors note that group wound looking might trigger a release of the hormone oxytocin and other associated neurotransmitters, which could help reduce the stress of animals after a traumatic incident and could help strengthen social
bonds among group members. So oxytocin chemically counteracts the effects of the hormone cortisol or stress hormone, and is thus used internally to deactivate the body's stress response. This can be really useful because while the stress response stress hormones are good for you in an emergency, like if you are about to run or fight for your life, they quickly become a harmful burden on the body if you are not about to run or fight for your life, so you want to turn them off whenever you don't
need them. I think we could all use that and find a way to turn the stress hormones off more often. Oxytocin is also importantly involved in forming social bonds between individuals. It plays some kind of role in complex cognitive and social effects like love, devotion, and loyalty. Though it's important to flag some caveats here because the role of oxytocin
socially and cognitively I think sometimes it gets oversimplified. Oxytocin is not the only hormone that is involved in this stuff, and it's also not like an automatic love potion that just mechanistically makes us love people when it is released. Love and loyalty and related emotions are complex and multi causal, and even the chemical influences that feed into them are many.
But oxytocin is important, and so it's if it is released by this communal wound looking behavior the same way that it is sometimes released during grooming behaviors that could signal that that communal wound looking plays some role in
strengthening or regulating maintaining social bonds within a group. Communal wound looking has also been observed in rodents, in primates, and in this study by Young and co authors, it was observed in social ungulates, specifically bison in northwestern Canada, which had been shot with tranquilizer darts so that they could be tagged for tracking the author's right quote. The day after being darted, we observe three different adult bison
lick the wounds of the two wounded bison. Both bison were less than three meters, were within less than three meters of each other during this time, and all of the observed wound looking occurred in less than ten minutes. Our observation provides an additional example of communal wound locking in free ranging mammals and extends it to a social ungulate. Benefits to bison of communal wound looking are perhaps largely social, and that kind of brings me back to thoughts about
these stories of dogs licking humans wounds. You know, this is an even further thing where it's like a cross species wound looking behavior kind of makes me think that that is cross species wound looking, I doubt is something that is directly specifically an evolved adaptation, but probably more like a you know, a misapplication of a general wound licking impulse that's primarily probably focused on a dog's own kind or its own ancestors.
Yeah.
Yeah, And I guess that one of the things that potentially complicates all of this, or a least adds another dimension, because so many things in animal behavior they're they're not so cleanly defined by one category. Is that of course, I mean just looking at the dog, right. A dog will also lick you in the face when there's not a wound there, That's right. One of my friend's dogs routinely just licks my pants the whole time I'm over at his house, and I'm not sure exactly why.
Yeah, so there could be multiple different motivations going on for that kind of licking. Like it could be a social grooming kind of thing. It's a social behavior that is, you know, to help dogs relate to each other and maintain their relationships, something about bonding. It could be a it could just be a you know, like taste and texture thing like a dog is you know, it likes something it's getting from this licking feeling or from the
licking taste there. It might I wonder if dogs licking human wounds could just be because they're getting some salty there.
I mean, yeah, all of these things are kind of in play with some topics related to the cat we're about to get into, because I didn't really I didn't specifically look at cat wound licking though, as we already mentioned, like they are a type of organism that does this, but I was looking at various other forms of social licking, and yeah, it's one of these areas where there are a number of different overlaps and some competing and potential
potentially overlapping theories as to why they engage in it, And a lot of it does come down to like social activity, the release of potential release of hormones, and how it makes the individual cat feel to groom or be groomed. So moving on to cats, then, if you have ever lived with a cat, I know that they have various tactile ways to make their feelings known. You may receive the scratch, you may get the wet and nose boop, the rub the head butt, the making of biscuits.
Of course, the coveted lap set. You may also find yourself licked.
A connoisseur of pet affection may notice a textural difference in cat licks and dog licks. I find that the dog's tongue is somewhat softer. The cat's tongue is somewhat rougher.
Yes, due to the papilla on the cat Tonguehich I'll get into. It's like it's essentially their comb. As you've observed, cats will rigorously groom themselves with their tongue, and the papilla on their tongue allows them to essentially, you know, they work like the again, the teeth of a comb. And that's why it's a little bit scratchy. And that's why being licked by a cat is often a ticklish affair, one that caused for a certain amount of what's going on? Why is it happening? Sort of reaction.
When I think about the cat's tongue, I pretty much always think of the eighteenth century English poet Christopher Smart, who wrote I think some of the best cat poetry of all time, in a section known as for I will consider my cat Jeffrey after the first line in the section in his devotional Christian poem Jubilate Agno, meaning rejoice in the lamb. Smart wrote this when he was confined to a mental institution in London called Saint Luke's Hospital for Lunatics. This was roughly in the middle of
the eighteenth century. I know I've brought this poem up on the show before at some point.
Yeah, because I remember one line in particular. Now that I'm looking at it again.
I just love it. It's too long to read in full here, but I love it so much. I have to mention the part leading up to the part about the tongue, but then also one other highlight from later. So the section leading up to the tongue line goes like this, He's celebrating all of He's just adoring his cat, Jeffrey's celebrating all of Jeffrey's virtues. And Smart writes, for he is the quickest to his of any creature, for he is tenacious of his point. For he is a
mixture of gravity and waggery. For he knows that God is his savior. For there is nothing sweeter than his peace when at rest. For there is nothing brisker than his life when in motion, for he is of the Lord's poor, and so indeed is he called by benevolence perpetually poor Jeffrey. Poor Jeffrey. The rat has bit thy throat. For I bless the name of the Lord Jesus, that Jeffrey is better, for the divine spirit comes about his
body to sustain it in complete cat. For his tongue is exceeding pure, so that it has in purity what it wants in music.
Beautiful.
It really is beautiful. And that last line, So that's the line about the tongue. It's exceeding pure, it has in purity what it wants in music. I don't know if there's a meaning there that is going past me through cultural context or beliefs about cats at the time, but my interpretation is cat mau is just as good as human mouth, even though cat mouth cannot talk. Cat licks better than or equal to human words.
Yeah, yeah, I would. I would agree with that. Like, I'm not a huge fan of my cat licking me, but when she does, I do acknowledge that it. I mean, I don't want to overstate it and be like it is an act of love or whatever, but at the very least. It is a neutral act, and I know that I am in okay graces with the animal at the moment. That's what we go to go for in this household, sustaining neutrality.
I think it's okay to call that love. You understand, you know, you understand the differences in cats and humans. But still there's there's something there that you know, you can make that metaphorical.
Leave yeah, as long as yeah, I know, I'm calling it love, So it's fine.
The one other passage I wanted to read here, this is from sort of the end of the section about Jeffrey Smart rites. For by stroking of him, I have found out electricity. For I perceived God's light about him, both wax and fire. For the electrical fire is the spiritual substance which God sends from Heaven to sustain the bodies, both of man and beast. For God has blessed him in the variety of his movements. For though he cannot fly,
he is an excellent clamberer. For his motions upon the face of the earth are more than any other quadruped. For he can tread to all the measures upon the music. For he can swim for life or he Can.
Creep, Joe, you will be delighted to know that for He Can Creep is the title of an episode of the latest season of Love, Death, and Robots, and it is about a poet and a sanitarium and his beloved cat named Jeffrey stands against the forces of darkness and it's rather good.
I haven't seen that show, but really tempted to watch now because yeah, I love for my cat Jeffrey.
Yet features the voice of Jim Broadman as Christopher the Poet.
Well, there's other stuff I couldn't get to here, so I just recommend anybody who wants to go look up the four I will consider my cat Jeffrey section of the poem Jubilate Agno. You can find it online.
It's great, excellent, excellent. You know, I recently watched part of a series started it watching it with my kid, titled Night of the Living Cat. It is a Japanese animated series based on a manga and Takashi mi k played a hand in it. But it's so far at
least it's totally age appropriate. But it's super fun because it's obviously a parody of zombie and apocalypse films, except The whole idea is that cats carry some sort of a virus, and if they come into contact with you, and certainly if they lick you, you too will become a cat. And so the population of the planet is swiftly becoming a population of cats.
Whoa.
So that's very much an inversion of the Christopher Smart idea about the purity of the tongue.
Well, the show is pretty fun and that it also plays with the fact that even though humans recognize that the cats are bringing their destruction, they also still love cats, and so they can't bring themselves to do violence against cats or anything of that nature. It's just like a heartbreaking affair. It's pretty fun though so far, so I'd like that premise. Yeah, all right, Well, getting back into licking. Licking is of course just one way that cats communicate
and or get information about the world. They may lick your skin out of curiosity, if you particularly. Theories vary on all this, but one idea is that they might lick you because your skin is salty, or you have something on your skin that is interesting. And I'm not sure there's a firm answer on any of that, but
it just may be part of the scenario. So if your cat is licking you and there doesn't seem to be any rhyme or reason, it could just be that where they're just like, oh, salty interesting, or oh lotion interesting. Of course, as with any domesticated or semi domesticated animal, depending on how you view cats, the relationship that we have with house cats is complicated by all of this, of course, and in some ways whatever we have going on with the cat is a perversion of what would
occur in nature. So in some ways, the best way to understand what they're licking of us means we have to look at how they interact with other cats in their natural environment, So especially looking at colonies of cats where a number of cats have essentially come together or kind of aggregated in such a way that they don't have to worry so much about food, they're not competing with each other, and they will find some sort of stability.
Doesn't mean they all get along with each other, though, because cats will have and I've seen this term used multiple times, they will have preferred associates. To be clear, they do not have friends, they have preferred associates, which which I like. It sounds like cat legal eese.
Maybe I've just got film noir on the brain because of the stuff we've been doing on Weird House Cinema. But I'm thinking of like Humphrey Bogart's associates in the noir films, people that he's not exactly lovely with, but you know, they they sort of have a working relationship.
They tolerate, into some sense, depend on each other. Yeah, so among preferred associates you encounter a number of different actions. There's something called alla rubbing. This is when they rub their bodies and tails against each other as a form of social bonding and communication. So I think everyone has seen an example of this and with cats and other cats, but also anytime they rub against especially if they rub against your legs, this is seen as an extinct as
an extension of this behavior. Now I'm not sure about feet because speaking mainly from my experience, rubbing against my feet often quickly devolves into play and play biting of my feet, and of course levels of play are going to occur, especially in younger cats, but even in older cats, and then indoor cats is kind of a forever kitten
scenario by some estimates. So again, another example where you can't just talk about the social behavior among preferred associates, because it could descend into play at any point, and that's another factor in everything.
I know.
This is asking you to get inside the mind of a cat, which may be impossible. But you've talked before about your cat having a habit of attacking your feet out from underneath furniture. Do you get the sense that your cat in the moment is thinking of your feet as part of your body or are the feet just something that's moving? Does that make sense?
That's a complicated question and one that I've I've heard more broadly explored a lot of times just talking about what do cats think humans are? And I've heard the argument that, you know, they think that we're other cats, and if they think that there were other cat, other cats, then it makes sense to engage in play with us. Play generally takes the form of fake fighting.
I know.
Another thing that my cat will do is come up next to my foot, my sockt foot, PLoP down next to that foot, way too close to my foot, as if inviting me to rub against her. And even if I don't rub against her, she may just start attacking my foot. So so like that's one way, But then there's there's also the idea that cats see us as part of their environment as well, so like we we also have sort of like a deep personified status to some degree where we are just part of the place
that they are comfortable with. And I mean, we can certainly understand that when they use us as a heated bed and just want to sit on this all the time during the colder months.
Are we warm moving furniture?
Yeah, So I don't know. I'm willing to bet there's maybe a little bit of both of these scenarios going on. And you know, the cat is going to have a you know, probably from our standpoint, a perplexing understanding of other beings, Like they're not going to perceive other beings the same way we do. We're going to and it's probably a lot easier to understand their perception of definite prey or predator status organisms.
Maybe it was not a meaningful question, No.
No, I think it's a fascinating quest when I think about all the time I lock eyes with this creature across the room, and I'm like, what does she think I am?
Like?
What am I to her? And indeed, then I turn around. What is she to me? I don't know. These are difficult questions to ask. But coming back to alo rubbing, there is this seeming we might think of it as an emotional context to it as well. I was reading
two thousand five Understanding Feline Signaling and Social Interactions. This is from the proceedings of the North American Veterinary Conference by Sharon L. Crowell Davis, and she pointed out that in many ways this just is this rubbing of cats against each other, and indeed a rubbing of a cat against your leg. It's in many ways like a hug, like it's comforting to them in the same way that like other activities they do seem to be based purely
on comfort. Like for instance, cats will often be in physical contact with each other while they are sleeping and during the during cold months or cold environments, and again cold by a cat standards, which is a little different than human standards. It makes sense, right while they're sharing each other's body heat. But they'll also do it even
if thermoregulation doesn't seem to be an issue. If it's you know, hotter, warmer, and so forth, it may be that they do these things, you know, just because it is comforting to do them, and that gets to straight up grooming as well. In the of licking a fur, this is something that may be acquired and when they're kittens it's comforting behavior. It might also be a way to mark others. As we'll discuss a little bit more. And as Carole Davis points out, humans have this terrible
sense of smell. We just can't we can't smell at all, We've discussed as many times before, at anywhere close to the same level as even a cat, and certainly not
a dog. So just it becomes very difficult for us to understand or comprehend the olfactory lives of animals like this, Like not only not just like a chemical understand like we can sort of break down the chemical understanding of chemical markers, but in terms of like translating that into our like sort of larger understanding of how animals operate in the world, it can be challenging.
Yeah, they have an information rich relationship to the environment on a dimension that where we come nowhere close.
Right, But getting back to where we're talking about with dogs, with cats too, licking and grooming or soothing behaviors, it stirs the release of endorphins. They may lick themselves, other cats or humans, or also materials in the home, and this can certainly spill over into excessive licking that may be a sign of stress or some other situation, but in general, it's like this is a calming action that they can partake of.
Now.
On top of that, of course, cats are famous for their use of self licking to fastidiously clean their own bodies, a self grooming process that takes up a substantial portion of their waking hours. I've seen different estimates on that this mostly I've seen an estimate of between thirty and forty percent of their waking hours, and this can amount to something like five hours apparently of just endless grooming.
Cat owners will have noticed this, especially if your cat does want to treat you like a couch and then is like, hey, I'm not just going to sit here and watch television with you, I'm also going to clean myself. And then you're like, I don't want this anymore, and you have to push them off or gently push them off, or maybe you can put up with it. I find it a little hard to put up with, but but yeah,
I've also seen like eight percent estimates. But anyway you cut it, they spend a lot of time self grooming, looking after their fur, cleaning it. And as I mentioned earlier, part of it is, you know, using those little barbs in their tongue, the sandpaper of their tongue to physically clean their furs. There's a little backward facing barbs and helps remove like little particles from their fur, kind of getting back to the womb cleaning that we were talking about earlier.
Yeah. Yeah.
On top of just the mechanical cleaning of their fur, self grooming also enables them to spread natural oils across their coat, helps keep it clean, waterproof and insulated. Also, as the saliva evaporates, it can also help cool them down as a means of thermoregulation. So that's seems to be in play as well. And then of course the act itself is self soothing. They are in there. You
could almost say happy place if they are self grooming. Now, when it comes back to the human question, I did find a nice little explainer article that tackles this and covers some of the ground we've already discussed. This was for BBC Science Focus from I think a couple of years ago by Thomas Ling, and he basically broke it down into three different theories. The trust theory that they're making a display of trust towards you. My cat is licking me because they are saying you, I trust you
are good, You are a preferred associate. Then there's the biochemical theory that there's something about your taste that's interesting, okay, salt your lotion or what have you. And then there's the possession play theory, and this is that they are marking you as their own. They're saying like, this person is my territory, this person is my property. And so going through each of these, starting with the trust theory, this is I think relatable to the oligrooming scenario, which
means at best or a preferred affiliate. This should not be confused with love. If we're talking, you know, purely scientifically about the scenario. Again, we humans can call it love, but maybe just understand that in the literature they're not going to call it that.
But yeah.
Studies have shown though that any supposed trust bond that a cat is associating with a human, it doesn't necessarily mean it's absolute. So cats tend to be pretty solitary in many cases, and in studies they found that they get along well with strangers almost just as well or as just as well as they would with other humans, which cat owners I think sometimes observe this because in our closed environments where we think about, oh, the cat, she's so social, she loves us so much, she just
wants to be around us. And I'm not discounting any of the social needs of cats, but it can also be a little bit alarming when a stranger comes over and it's like, cat's right in their lap and you're like, you want to be like, you don't know that person at all. Why weren't you said, in my lap? So, yeah,
that's one caveat to the trust theory. I think we've hit the biochemical theory pretty well, and then the possession play theory basically comes down to the idea that the cat's own smell is the most important thing to it in terms of its olfactory world, Like, it wants to make sure it smells like itself, so it will lick away any foreign smells in order to order to champion and establish its own smell, and there may be some level of territory marking when they lick or rub their
faces against humans, certainly like the face rubbing, which can lead to licking or follow licking. You know, you never know how it's going to go. You know.
I just had the thought that I wish I'd thought of this before we recorded, so I could look it up. But while I'm aware of lots of stories from legends where a dog licks a human's wounds, I can't think of anywhere a cat licks a human's wounds. Cat licks, or at least not in anonical literature that I know of, wound.
Related Yeah, that's interesting. Well, maybe we'll come back to that.
Yeah, all right.
To close out this episode, I would like to talk a little bit about eye licking. In the last episode, we discussed the idea of eye licking as it fits into the magical and mythic concepts of the ancient Egyptians. Naturally, a lot of social grooming animals will lick each other in the face and in the eye. Come back to a couple of examples of that, but I wanted to touch on a couple of examples of animals that definitely lick their own eyeballs.
Oh this is good.
Yeah, And of course it's interesting to us humans because most humans cannot do this. To be sure, there are way most most My initial thought was, and I like my original original draft of the notes, as I was kind of putting my thoughts to, I was like, well, humans can't look their own eyes, so of course we find this interesting. But then I dared to look a little closer, and there are certain individuals who can, by some definitions, lick their own eyeball. WHOA like, it's going
to come down to a few different measurements. So you know, facial spacing certainly, and you know there's a fair amount of variety there, but tongue size is the big one. I was looking around, and I believe the average human tongue link is between three and three point three inches. But you have certain individuals who have verified or unverified
claims for almost four inch tongues. And then there are at least claims and I don't know, maybe not certified, but to my eye eyes convincing arguments for four inch tongues. One in particular I was looking at, again not verified by Guinness as far as I understand, but one Adrian Lewis of the United Dates. You can look her up because she was kind of like she appeared on various news programs and like did social media and YouTube videos.
But she could stick out her tongue, which is allegedly four inches long, and then using her finger, guide the tongue up until it I think comes in contact with the eye, or perhaps could come in contact with the eye.
I'm speechless, I like you assume, would have said no human can lick their own eye. This is if this is true, it's flabbergasting to me.
Yeah, so it seems entirely possible that some humans can bring their tongue into contact with their eye, if not lick it in the same way that you know, an animal with a long tongue can't, like as well to get into in a bit like a giraffe and a a copy can do this like they can without a doubt lick their own tongue. Humans might have to have a little help, and therefore, you know, it's very hard to argue that there's any practical application for this.
Yeah, not a doctor, but I would not recommend it for the same base reasons why there are downsides to licking your wounds. You know, you don't want to introduce bacteria. The mouth is a bacteria rich environment. You don't want to introduce microbes into a different place in the body when you don't have to.
Yeah, yeah, So I'll come back to the mammal world real quickly because I have less to say about the mammal world, because the ocopy and the giraffe are great examples of related organisms. They both self groom via tongue licking, including licking of their own face, and they may lick their eyes in the process. They also lick each other during courtship. But the best example, the most exciting example of an animal licking its own eyes, you'll find this
with geckos. Geckos or of course, reptiles of the suborder Gekkota, of which there are at least fifteen hundred known species. There are a lot of geckos out there. All geckos can and do lick their own eyeball, and the main reason for their doing so, again, it's not just to show off on social media. They do it to clean their eyes and remove debris from their eyes, such as
little grains of sand, particles, and so forth. Some geckos, however, would seem to depend on this ability much more than others, as discussed by herpetologist Aaron M. Bauer in the book Geckos, The Animal Answered Guide. All geckos have eyelids, but if you read some descriptions of the scenario, will say, you know, a lot of geckos don't have islids. All geckos have eyelids, but only the thirty species of the u Blephylaridae geckos
can move those eyelids. So it's one thing to have eyelids, but can you actually make them.
Go up and down?
Oh? Okay, interesting, So the Ublephalaridae geckos, they close their eyes and blink, much like we do. The gecko that my child has, a leopard gecko, is one of these geckos. So you know, this gecko can blink his little eyes. And I'm not sure that I've actually observed him licking his own eyes, but according to the literature, he can and does do so. I just I don't watch him all the time. I don't know what he's up to most of the day.
Does the cat watch him?
No, they don't interact. We don't want to encourage that anyway. They're in their own little worlds, you know. Though one's name is Waffles and the other's name is mochi, so they're kind they're kind of siblings in that regard. So anyway, we've discussed the blithelarid geckos. The non eu blifferid geckos cannot move their eyelids. They have a structure called a spectacle or brill that covers the eye and it protects
it from abrasian and dryness. Bauer describes it as derived from a transparent lower eyelid that has become fused with the upper eyelid, so a trans and disc positioned directly over the eye, and it's it's very much you know, it's sometimes described as being like a scale. And indeed it is part of the gecko's skin. So when the gecko sheds its skin, which it will eventually eat. That's one of the magical things of having a pet gecko is when he goes into his hide to shed, he's
going to clean all that up. He's not going to let any of that god of waste. But when he does shed, that eyelid is going to come off with it. I believe it becomes like you can tell, it becomes like kind of translucent, or you know, not translucent, becomes kind of like gray. Perhaps before it comes off Wow delicious now. Additionally, some of these geckos also have eyelid like structures called extra briller fringes that partially cover the upper portion of the eye and can be partially raised
and lower, but they're not fold it's either way. The main function of self eyelid licking is to keep things clean and clear. However, they'll also just lick their eyes and faces to drink water droplets off their face. If they have water on there, why not, you know, free drink. They've also been observed licking their own face after eating or running, basically some sort of strenuous activity, but the reason for this isn't entirely understood. So in eating, of course,
bear in mind we're talking about geckos. They are little predators. They are eating live prey, so that there's an endurance aspect to that as well. Elsewhere in the book, Bauer notes that geckos often lick one another during courtship, and this is likely both tactile and chemical communication, with molecules on the tongue transferred to their vomeroonasal organ to then crunch the data about potential mates.
Oh coming back to like the like the snakes. Yeah, yeah, the Jacobson's organ.
Yeah.
So if you have a gecko out there, you know, to watch them a little extra in the next couple of days. See, first of all, recall what sort of gecko you have, and see what sort of eye licking us up to. And if you can lick your own eyeball, don't do it. For starters. I encountered similar things looking into this, the idea of humans locking eyeballs, because for a subset of the human population, there is a certain
eroticism to the licking of another human beings eye balls. Yeah, but you know, I mean, there's there's room for everything. I'm not going to shame anybody, but.
This is judging. I'm just surprised.
But this is not recommended by health experts. It's it kind of comes back to the dog looking a wound scenario. It's like, yeah, we have better ways to attend to the cleanliness of our eyes. So no need to have your eyes licked by even you know, even a trusted lover. But if you were a get go, I mean, go at it.
It's your way of life.
All right. We're going to go and close the book there, but we will be back so tune in for more episodes in the future. Just to remind it of the Stuff to Blow Your Mind is primary science and culture podcasts with core episodes and Tuesdays and Thursdays. On Wednesdays we do a short form episode, and on Fridays we set aside most serious concerns to just talk about a weird film on Weird House Cinema.
Huge thanks as always to our excellent audio producer JJ Posway. If you would like to get in touch with us with feedback on this episode or any other, to suggest a topic for the future, or just to say hello, you can email us at contact at stuff to Blow your Mind dot com.
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