Nature's Irish Mammies - EWTS #026

Senan: Hello, and welcome to another season of Enough with the Science.

Joe: Season three! Episode one, we're back!

Senan: Yes, I'm Senan.

Joe: Yes, and I'm Joe. More of this madness. How do we get away with it? I don't know, I just don't know. So, what is on the cards today, Senan?

Senan: Yes, we're back with a new batch of episodes.

Joe: Brilliant, brilliant work there. I like what you did there. [laughter] So, we are talking about…

Senan: Bats.

Joe: Bats. Very good.

Senan: But before we get to that, it was a fantastic summer here in the south coast of Ireland, wasn't it?

Joe: It's a pity that it's over. It went very quickly in some ways, but it's good to be back too, though.

Senan: It is good to be back.

Joe: And I know several of our fans from around the world, because we have a large listenership in Southeast Asia, apparently…

Senan: Yes, we have. [laughter]

Joe: Have been crying out for new episodes. So, we're back with a bang, and we're going bat crazy.

Senan: We're back with a bat.

Joe: We're back, we're going bat crazy. So, how did Bruce Wayne become Batman? You know like Spider-Man got bitten by a spider. But Bruce Wayne didn't get bitten by a bat, or he didn't bite a bat, or like…

Senan: I think he just woke up one morning and had the idea.

Joe: He just decided, "I'm going to be Batman."

Senan: I think that might have been it, yeah. And of course, didn't he have a cave somewhere, so that probably gave him the idea, because you know, bats and caves.

Joe: Obviously they went, right, let's pick an animal. We'll pick an animal and then just extrapolate out all the things that he'll be able to do as that animal. I wonder was there a list? I wonder was the bat the first thing they came up with?

Senan: I don't know. Maybe he started off with echidna, or I don't know, what's that rodent with the two nostrils? Capybara, maybe Capybaraman doesn't quite have the same ring… [laughter]

Joe: You realise some people are going to have to look that up now? [laughter] And now they don't know how to spell it, because how do you Capybara, how do you spell that? [laughter] But I think we're going to find out today actually that he picked a darn good mammal to try and be like.

Senan: Bats are amazing. I know a lot of people, the idea of bats just gives them the creeps. Basically a flying rodent. They're not actually rodents, by the way. [laughter] But there's just some incredible stuff about bats. So, let's just talk about why we're doing an episode about bats.

Joe: That's a good start. Why are we doing an episode about bats?

Senan: There's all kinds of reasons. Number one, they have a famously tough immune system; as far as we know, the toughest immune system of any mammal.

Senan: They live far longer than any small mammal is entitled to. They are the only mammal that has powered flight. Some mammals are gliders, but these are the only guys who actually have properly powered flight.

Joe: Humans!

Senan: Huh?

Joe: Humans.

Senan: Humans not using their own body parts.

Joe: All right, okay. Fair enough. [laughter]

Senan: And you know, there's a huge number of bat species. They're mammals like us, right? If you were to take a very long piece of paper and write down the names of every single species of mammal, one in five would be bats. 20% of all mammal species are bats.

Joe: Okay, so roughly how many mammal species are there?

Senan: There's 1,500 bats, so I would imagine that gives you about 7,500 mammal species, give or take. 1,500 species of bats is pretty amazing.

Senan: And the range of sizes. Remember they're mammals, right? They've got the same basic body layout as us; the same organs in the same places; they have four limbs; they have warm blood like us; they gestate their young in a womb and have live births; they feed their young with milk, etc.

Joe: So, they qualify as mammals. They've got the mammal passport.

Senan: Absolutely, definitely. Because they're mammals, they're much more closely related to us on the evolutionary tree of life than we'd say birds are, which are effectively dinosaurs. Birds would be more closely related to reptiles than they would be to mammals, right?

Joe: Okay, so they're mammals, but they're not rodents.

Senan: A rodent is a subclass of mammals, including rats and mice and various other small things like that.

Joe: Okay, and bats are a subclass of mammals…

Senan: But bats are their own other order, thing, yeah. But the range of sizes, bearing in mind that they have all the same body equipment that we have internally. The smallest one is the size of a paperclip and weighs two grams, the bumblebee bat, it's in Asia.

Joe: They probably don't have an appendix.

Senan: Why not?

Joe: Because we don't use the appendix anymore. I wonder do bats…

Senan: Interestingly now, that's not entirely true. There is some evidence now to suggest that our appendix is a place where our gut microbiome maintains a reservoir. So, if you say go through a tummy infection where you've the runs and everything gets cleared out, there's a little reservoir of your gut microbiome in your appendix that then repopulates your gut after you get better again.

Joe: So, they may have an… Okay, I take that back.

Senan: I don't know for sure, but broadly speaking, they have everything we have, just smaller.

Joe: Tiny. It's like someone miniaturised…

Senan: In the case of the guy who's the size of a paperclip, exceptionally tiny. The biggest one is a thing called the giant golden-crowned flying fox; is a bat, not a fox. But he has a 1.7-metre wingspan.

Joe: You don't want to run into him. I wouldn't like to run into him now, that's 1.7-metre wingspan. How big is his body, though? Is his body the size of a tennis ball in the middle of that?

Senan: You'd probably fly into him, not run into him. [laughter]

Joe: I wonder how big his body is.

Senan: His body, I'd imagine you're probably talking about something like a small cat or something, I don't know.

Joe: Kind of a Henry the Hoover? Is that one of those size of bats? [laughter]

Senan: Not that big, I don't think. [laughter] Much smaller than that.

Senan: Most of them eat insects, right?

Joe: Except for the vampires.

Senan: The vampires we will come to in a moment. [laughter] The vampires have an outsized reputation. [laughter] Most of them eat insects, a few would be eating fruit, and some of them are hunters, but don't hunt insects, they hunt other things; in fact, there are even some bats that eat other bats.

Senan: To get back to the vampires, out of the 1,500 species, only three bat species are actual blood drinkers.

Joe: As far as I'm concerned, that's three species too many. [laughter]

Senan: They have some interesting adaptations for that. The way the enamel on their teeth is arranged ensures that their teeth stay exceptionally razor-sharp. Why that's an advantage to a blood-drinking creature is that when they bite, say a deer or a cow or something to get at the blood…

Joe: Or a human.

Senan: The creature doesn't really feel the cut initially, because the tooth is so sharp. And they have an enzyme in their saliva, which some boffin in a laboratory named draculin, which thins the blood.

Joe: Stops it coagulating.

Senan: That means that the blood flows freely out of the wound they have inflicted, and they can just lap it up with their tongue.

Joe: That's a lovely image for your afternoon or evening, wherever you are.

Senan: I apologise for ruining people's dinner. [laughter] But let's talk about flight, because as I said, they're the only mammal that actually has powered flight. And you might think, I said a while ago they have the same body layout as us, you might think, well hang on a minute, they have wings, that's not the same as us.

Joe: You would think that! You would think that! When you go like, "Yeah, the same body layout, where's our wings? Where are our wings?"

Senan: But the reality is the bones that we have as our fingers are the bones that they use for the ribs of their wings. So, they just have very long, thin fingers with skin flaps in between them, that is what their wings are formed out of. Again, it's just a variation on the same design of bone structure that we have.

Joe: Except creepier.

Senan: A little bit perhaps. [laughter] Except for the thumbs, right? The thumbs are not elongated. They're short, they have little claws on them that helps them if they've to climb on anything, and they have this hooking mechanism. You know bats are famous for hanging upside down when they're asleep.

Joe: See, this is the problem, because I thought it was from their feet.

Senan: There you go now, yeah. It's these little hooky thumb things on their wings. They have some kind of locking mechanism in the cartilage or the tendons in those thumbs, that once they latch on, it locks, and they don't need to exert any more effort to stay latched on.

Senan: Even in fact, dead bats have been found still latched on. The locking mechanism is so good in their thumbs that they don't even need to be alive to still hold on.

Joe: Its something that kills them… [laughter]

Senan: That is a certain interpretation [laughter] that you could put. Isn't it just, you know, you've got your facts and I've got mine. [laughter]

Senan: Another difference from birds' wings; lots of differences from birds' wings, to be honest. The first thing is birds' wings are, generally speaking, very aerodynamically shaped, right? So, birds can get away with a lot of gliding. They don't need to flap their wings all the time; they can do a hell of a lot of gliding, and that saves a huge amount of energy.

Senan: The bats, unfortunately, although they have efficient wings, they are not aerodynamically shaped, so they can't glide. They have to flap all the time, and they have to flap really fast all the time; they burn through huge amounts of energy. We'll come back to that in a while.

Senan: Another difference is that the skin flaps that are between the finger bones that basically form the wing structure, that's living tissue. Unlike feathers on a bird, where once the feather has been grown, it's not really a living thing anymore, it's a bit like a fingernail.

Senan: With the bats, that skin in between, those skin flaps, they have blood vessels and nerves in them, and they can self-repair if they get damaged and so on.

Joe: And if they fly into you, they can feel your face.

Senan: Yes, they certainly can, yeah. I'm sure they would love to hug us with their long fingers and slimy skin. [laughter]

Senan: Anyway, most of them, as we said, they roost upside down. Most of them start flight or take off by just unhooking from whatever they're hanging on to and falling. Gravity gives them a bit of speed, and then they spread their wings and start flapping, and off they go. So, they have this kind of weird way of taking off.

Senan: But that's not to say, there's a bit of a myth that bats can't take off from the ground; it's not true, bats can flap…

Joe: I've never heard that.

Senan: Well, there you go now.

Joe: There's a myth, and busted in the same, just in 30 seconds, there's a myth I never knew existed, and it's been destroyed.

Senan: Well, you know, we aim to be efficient here on this podcast. [laughter]

Joe: That is hugely efficient. [laughter]

Senan: And the reason for that, of course, is that you perpetually try to limit me to 30 minutes. [laughter]

Joe: It's never worked so far. [laughter]

Senan: And it's not going to work today. [laughter]

Senan: They have this enormous metabolism and energy consumption that they need to maintain flight. One of the side effects of that is that the metabolism products, like the exhaust, we'll call it, of all that energy they're burning, builds up dangerous chemicals in their system.

Senan: They have evolved extra methods in their biology to cope with all these dangerous by-products of high metabolism that could damage their system if they didn't eliminate them. We'll come back to that in a while.

Senan: Also because of the huge energy demands that their muscles for their wings require to maintain flight, their heart is capable of an incredible range of activity.

Senan: There was a really interesting study done where somebody managed to fit heart monitors into a bunch of bats in a cave somewhere. These heart monitors were able to be monitored remotely, so wirelessly, the scientists' equipment could connect up and count the heartbeats of each bat in the flock; I don't know if flock is the right word for bats.

Joe: No, it's definitely not. Surely we know the collective noun for bats. I'll look that up. I'm going to look that up.

Senan: A battery, perhaps? [laughter]

Joe: Continue, continue, I'm going to find what this is.

Senan: While these bats were asleep in the cave during the day, because they're night hunters, their heart rate dropped to like a few beats a minute, which is much lower than a human heart rate would ever be.

Senan: And that's because what their sleeping is actually what they call torpor; it's a much deeper sleep than what we do, and their body is nearly switched off when they're in daily torpor. So, they're only beating at a few beats a minute.

Senan: But within a couple of minutes of them leaving the cave in the evening to start hunting and starting to fly, that heart rate climbs up to 900 beats a minute. That's a huge change.

Joe: That's mental.

Senan: To put that in perspective, the average human heartbeat will go between 60 and 150 beats per minute. That's kind of the range most people's heart rate. If you're exerting yourself enough to reach 150 beats per minute, you're really sweating, you're really going at it; you're sprinting, or you're cycling at like 40 kilometres an hour or something.

Joe: You know like for the bats, 900 beats a minute is 15 beats a second.

Senan: That's unreal, isn't it?

Joe: That is just, I mean, your brain doesn't go there.

Senan: Think of this, you're talking about a heart, for most of them a heart that's like the size of, I don't know, a raisin, and it has all the valves and chambers and things that our heart has, and it's just going hell for leather. It's pretty amazing.

Senan: Evolution has equipped the bat with that because that was necessary to make flight possible for them.

Senan: Considering there's 1,500 species, evolutionarily speaking, it's a very successful design. The oldest bat fossils we have are 52 million years old, and even then, the fossils show a fully formed wing capable of flight.

Senan: So, it's a design that's been around for more than 50 million years. Evolution has made 1,500 different versions of it that we know of, and probably a couple of thousand others that have gone extinct.

Joe: So, it's going to get to the perfect one that's going to take over.

Senan: Sooner or later, it'll perfect the design, yeah. [laughter]

Joe: I knew it! Another thing to worry about. [laughter]

Joe: Now, I just give you a go. There's apparently three different words that can be used… four different words, and they all begin with C, for a gang of bats. Gang's not one of them. [laughter] Do you want to go? They all begin with C.

Senan: Collection? [laughter]

Joe: No. [laughter]

Senan: Concert?

Joe: That would be a good one, but no. [laughter] So, relying on AI: a colony.

Senan: A colony of bats.

Joe: A colony, which I think…

Senan: A colony is very generic to nearly any creature, isn't it?

Joe: A cloud.

Senan: A cloud of bats, okay. [laughter]

Joe: Or a cauldron.

Senan: A cauldron of bats, is that because the association with witches?

Joe: Yeah, but a colony seems to be the…

Senan: Colony of bats.

Joe: Colony of bats, yeah. I think the other ones are just like AI getting a little bit beyond itself…

Senan: Because I was hoping it was going to be something more specific than that, because for example, crows, a murder of crows is one of my favourite ones.

Joe: I would have liked cauldron. I thought a cauldron of bats would be very good.

Senan: Cauldron is, I wonder how official is that? Maybe it is official.

Joe: No, it's not. It's really not, that's like kind of, that's AI gone nuts.

Senan: Okay, fair enough. [laughter]

Senan: Let's talk about another one of their unique features, which is their sonar or their echolocation. Again, a fairly unique feature. Dolphins and whales have something like it for underwater, but for bats, it works differently.

Joe: Are they the only three?

Senan: I don't know, to be honest, if there's others. There may well be, but I'm not sure.

Joe: I think Irish mothers. [laughter] Irish mothers when they're shouting at their children out the window. I assume there's some sort of sonar, like, "Come in for your dinner!" They know exactly how far away you are. [laughter]

Senan: Another myth to bust: blind as a bat. Bats are not, in fact, blind. [laughter] But the problem, of course, is because they hunt at nighttime in complete darkness, good eyesight doesn't really help you even if you have it. [laughter]

Joe: But then it is technically correct to say you're as blind as a bat, because you are not blind and neither are bats.

Senan: That is a very good point. [laughter]

Joe: So, you can still use it!

Senan: I'm pretty sure that will score me a few points on some TV quiz show someday. [laughter]

Senan: Evolution has equipped them with echolocation. So, they emit these high-frequency chirps; they listen for the sound bounces off say a moth that they're hunting, and they listen…

Joe: I'm imagining it's kind of like when your smoke alarm runs out of battery, that sort of sound. That's what I'm hearing when I think of a bat chirp.

Senan: Yeah, but I suppose much, much higher frequency. Our hearing tops out at round about 20 kilohertz, so we can't hear anything more high-frequency than 20 kilohertz. And in fact, you and I probably are back down to 17 or 18 because of our age. [laughter]

Joe: There's no need to bring that up. [laughter]

Senan: But the bats, their chirps are up to 100 kilohertz, so like much, much higher frequency than ours. And probably the reason for that, I would think, is that higher frequency gives them higher fidelity, so they can discern more details in what they hear coming back if it's a higher frequency signal.

Senan: Their brain does some incredible calculation. They emit this chirp, they listen for it coming back; they're able to work out to within a centimetre or two exactly how far away their prey is from them.

Senan: Just to put that in perspective, 1/100 of a second, a sound will travel two metres, right?

Joe: Okay.

Senan: That means at 1/1,000 of a second, the sound is travelling 20 centimetres.

Joe: And they can do it to two centimetres.

Senan: They can do it down to two, so probably down to 1/10,000 of a second, they're able to time it, or better probably. That's an incredible feat for a tiny little brain, and they're doing it multiple times a second; they're firing off several chirps a second.

Joe: And processing that.

Senan: Not only are they telling how far away it is, they're able to tell which direction it is, because the difference between what they hear in their left ear and their right ear…

Joe: It's like they're hearing in 3D.

Senan: One side will be a little bit louder, and one side will get the signal back fractionally before the other side. So, that's enough to tell them the direction.

Senan: They're able to tell how fast it's moving because of something called the Doppler shift, which the classic example for that is the ambulance noise. When you're walking down the street and you hear an ambulance coming behind you, as it passes you, you notice the tone of the ambulance siren goes down a little bit as it's moving away from you; it sounds a bit lower than it was when it was moving towards you.

Senan: That's to do with the sound wave either being slightly compressed or being slightly stretched by the movement of the thing that's creating the sound. And they're actually able to use that effect to determine what the speed of movement of the creature is.

Senan: And they even, although this hasn't been proven definitively, but by observing what bats are doing, it seems like they can even detect the texture or the shape. So, for example…

Joe: Now they're two very different things.

Senan: Is it a leaf, or is it a moth? That kind of thing, you know.

Joe: So, is it corduroy, is it… [laughter]

Senan: Maybe texture is the wrong word, but basically they're able to discern a lot about what it is without seeing it; a lot about the shape and so on.

Senan: The other thing is the loudness, right? A jet engine on a modern aircraft, 30 metres away from it, it's about 140 decibels of sound. Some bats can produce a chirp that's 140 decibels from 10 metres away or less. They're able to outshout a jet engine. That's incredible.

Joe: And what evolutionary advantage would that give them? [laughter]

Senan: I wonder is it in a case where there's an awful lot of bats together hunting, and they're trying to drown out the sonar of the guys that are around them? Potentially might be the reason.

Joe: Or let other bats know that there's a jet engine.

Senan: Or you know the way it could be a mating ritual thing, where you prove to your potential mate that you're particularly fit, because you're able to shout louder than the other guys that are trying to mate with her?

Joe: Like it's the basis for all the politics in the world! [laughter] "I can shout louder than you!" [laughter]

Senan: Bat politics, who knew we were going to end up in bat politics?

Senan: But that level of noise begs the question, how are they not deafening themselves? Because you know, their ears are near where their mouth is.

Senan: And they actually have built-in earmuffs, which is kind of cool. There's a little muscle in their ear canal that closes their ears for a fraction of a second while they're making that chirp, so that they don't deafen themselves, and then opens their ears again so they can hear the echo coming back. It's pretty stunning what they can do.

Joe: I might have a use for that. [laughter] Just writing that one down. [laughter]

Senan: Anyway, the other thing they can do is, as they're closing in on their prey; remember they're hunting on the wing, so a moth is doing its damndest to get away from the bat. The moths will have, their prey will have evolved their own strategies for evading bats. Catching a moth in mid-air on the wing in darkness is no easy job.

Joe: I can't even do it with all the lights on! [laughter]

Senan: You need a pet bat, Joe. [laughter]

Senan: In the last second or two when they're homing in on their prey, some species can emit up to 200 chirps per second, just to give them more and more and more detail about what it is they're hunting.

Joe: Bats are all about big numbers. They're about big numbers in short times. [laughter]

Senan: And then you've got a handful of bat species that don't chirp at all; they just listen. They have really good ears for listening, and they know what the sound of the prey they want sounds like.

Senan: Presumably those are bats that have evolved in a quiet environment, that they don't need to make their own echo noises, they can just listen to whatever's going on around them and catch their prey that way.

Senan: And then of course, some of them, the ones that eat fruit, don't need to do it either; they can just find the fruit by smell. They're not all doing it.

Senan: And then of course, it's a bit of an arms race. Tiger moths, who are obviously a prey species for bats, some of those are able to emit their own high-frequency noises that jam the sonar of the bats that are hunting them, or confuse it.

Senan: And there are other species of bats that are able to jam each other to steal prey. Your man next door to me is homing in on a moth, I'm going to make noises that'll confuse him, and I'll steal the prey out from under him. So, it's a real arms race, as it always is with evolution.

Joe: Good nature, yeah.

Senan: Probably one of the things that scientists are most intrigued by is their longevity. There's a general rule of thumb for mammals: if you're small, you've a short life, that's kind of the rule of thumb. Mice, typically maybe two years or so; whereas elephants and whales and things can live for long, long, long times.

Joe: Tortoises are kind of in the middle.

Senan: Wasn't there Lonesome George, the tortoise from Darwin's time? He was brought back to Britain, I think, by Darwin, and he only died there a few years ago. And is it the Greenland shark? That's not a mammal, but the Greenland shark I think can live for two or 300 years as well.

Senan: These guys, typically a lot of the same mouse-sized bats can live to be 30 years old, which for a mammal that size is unheard of. That's about nine times longer than you would expect a mammal that size to live.

Joe: Except for cats. [laughter]

Senan: They have discrete separate lives. They just go through several steps of reincarnation during the course of their existence to stay alive. [laughter]

Joe: Okay, but bats don't. Bats just plough along. [laughter]

Senan: There was one tiny example in Siberia where, now I don't know how they actually worked this out, but they have one that lived more than 40 years.

Joe: Right.

Senan: It's pretty amazing. And how do they do it? There's all kinds of theories, some more proven than others.

Senan: First of all, there's this torpor thing they do every day, this sleeping… Well, they don't die, that's probably how they do it, yeah. [laughter] And next week on… [laughter] That's that solved! [laughter]

Senan: This torpor that they do, this deep sleep they do during the day, is like hitting the pause button on their metabolism.

Joe: Stasis, it's like stasis.

Senan: It is, kind of like spaceship stasis. A lot of species will hibernate in the winter, that's a longer version of the same thing.

Senan: Of course, they live in caves, there's not many predators, and they're hanging out of the roof of the cave, there's not many predators up there to catch them. They live at nighttime on the wing, so they're flying around in darkness where there isn't very many predators then either.

Senan: And they have remarkably tough biology. They have genes for self-repair of their DNA that other mammals don't have, so they're able to detect and fix damage in their DNA that you and I are probably building up as a result of our ageing, that they're taking care of.

Joe: That's the second time you've mentioned that. Let that be the last! [laughter] Let that be the last!

Senan: I've bad news for you in the next point [laughter] also.

Senan: One of the hallmarks of ageing in mammals, including humans, is degrading of telomeres. I probably don't need to explain that any further, do I? [laughter]

Joe: Okay, good, thank you, goodnight! [laughter]

Senan: Your chromosomes, which are like the structures that your DNA are arranged into, have these protective caps on the end of each chromosome called a telomere, and it prevents the chromosome from getting damaged. As you get older, those telomeres degrade and break down…

Joe: When you look at that helix thing of the DNA, the chromosomes are the little, like the steps of the ladder, are they?

Senan: No. You're talking about the individual bases. We see that helix and we see these steps of a ladder, they tend to come in groups of four, and you're right down to the level of individual bases, which is as far down into the structure as you can go. Chromosomes are at a much higher level; they're like a bunch of a lot of those ladder things together. [laughter]

Joe: Okay, and then at the end of a chromosome there's a telomere.

Senan: A telomere, yeah, which is like a protective cap on the end of it. Your entire DNA genome is kind of folded up into a load of chromosomes, a bit like a herringbone kind of pattern, and at the ends of each one of the folds, there's this telomere cap thing.

Senan: One of the hallmarks of ageing for us and for all mammals really, is that these telomere caps degrade and break down and get shorter and shorter and shorter as you get older, and that means there's less protection for your chromosomes, and that tends to, that's one of the things that causes your biology to gradually weaken as you get older.

Senan: The bats have genes that allow them to repair their telomeres so that that degrading doesn't happen.

Joe: I can see pharmaceutical companies going ka-ching, ka-ching, ka-ching!

Senan: And that's only one example of what bats… There's loads of research going on, because if we can figure out how bats do some of the stuff they do at the biological level, there's great applications for us.

Joe: We'll be able to fly with our hands. [laughter]

Senan: I just can't wait for that one! [laughter]

Senan: Another thing that they do that's pretty good is, we, and again most mammals, have a mechanism that allows us to detect damaged DNA, damaged cells, damaged proteins, and hoover away that stuff; get rid of that stuff before it causes any problem in our bodies.

Senan: Bats have a far more active version of that. They're pruning away any damaged stuff the moment it happens. So, they have a much cleaner cellular biology, because this system is so active, it's just getting rid of all the junk before it causes any problems.

Senan: And this may be the reason why the next weird thing is believed to be true, and that is, it seems like there's an extremely low incidence of cancer in bats. Now, not the zero level that the naked mole-rats have, but still… [laughter]

Joe: You heard that right, you heard him right. I'm not even going to say anything. [laughter] Just, yep, continue.

Senan: We will do a naked mole-rat episode, because they're pretty cool too. [laughter]

Senan: It may well be, so at least some of the causes of cancer in humans; cancer, of course, is not one disease, it's hundreds of different diseases, so the causes are wide and varied.

Senan: But at least a part of a common cause of cancer is where cells or proteins or DNA have become damaged in some way and aren't cleaned up and are able to cause our biology to grow incorrectly.

Senan: So, one of the reasons it may be that bats have very little cancer is because the system they have for pruning away all that junk is very active, much more active than ours.

Senan: And of course, they have this superpowered immune system, which is one of the really, probably my favourite thing about bats of all time is how amazing their immune system is.

Joe: This is why you're in charge of this podcast. Only you could get excited about the immune system of bats. [laughter]

Senan: What do you mean I'm in charge? [laughter] You're the one trying to let me… [laughter]

Joe: Look, in this scenario, I was thinking today, like in this scenario, you are Batman, I am Robin, that's the way this podcast goes. And you have all the knowledge, I'm just picking away at it. [laughter]

Joe: So, yes, their immune system.

Senan: Their immune system. They carry some of the most scary viruses. Bats generally in their bodies, they just live their lives with some of the worst viruses you've ever heard of, like Ebola and some of those things, and even coronaviruses that we all know about.

Senan: And somehow, they're able to tolerate having these viruses in their system without them making them sick in the way that they make us sick. It's amazing. And that's not to say that they…

Joe: Do all bats have this, or do sick bats have this, or all bats have these kinds of things?

Senan: It's endemic in a lot of bat populations that just carry this whole pile of really serious viruses in their… Just like, you know, probably at this stage, the human population is carrying COVID-19, right? Because we…

Joe: Now, this might be a newsflash to some people, so just let him finish. [laughter]

Senan: In other words, there's viruses that we build up gradually in the population a resistance to, an ability to fight off without us getting sick.

Joe: Yeah.

Senan: And at this stage, it's rare enough that we hear of people getting sick from COVID, that I do anyway. But yet, it's got to be in the population still, I mean it was very contagious.

Joe: Right.

Senan: The point is that our bodies, not every single person, but most of us have evolved an immunity to it of some kind at this stage so that although it's in our system, you know, we don't really get sick from it.

Joe: Right, so we are like bats.

Senan: But I've just picked that one as an example. The fact is that in any population of mammals, there will be a set of viruses that have become endemic there and are just carried by that population without… The odd one gets sick occasionally from it, but generally speaking, it's not making the entire population unwell.

Joe: So, it's just that the viruses that the bats have are just lethal.

Senan: They're the ones that we regard as really serious, that we take… Ebola is obviously the poster child for this stuff, but there's lots of other really serious ones as well.

Senan: But it's interesting, they're not able to fight off everything. Rabies, which of course is deadly to humans, is also deadly to bats.

Joe: There's a happy thought for today! [laughter] Something can take us all out! [laughter]

Senan: And there's a sad one called white-nose fungus that kills off bats, and it doesn't…

Joe: But not humans.

Senan: I don't think I don't recall seeing any furry white noses on humans recently, except maybe Santy, but whatever. [laughter]

Senan: Anyway, what it actually does is it prevents them from sleeping, so they die from lack of sleep, which is pretty sad.

Senan: But the interesting thing about all these serious viruses that they carry, it doesn't seem like they're fighting them off in the way that we normally consider an immune system fights off things. It seems like they're coexisting with them. These things are active in their system, but not active enough to make them sick.

Senan: Their immune system is much more low-key. It's able to somehow damp down the activity of these really serious pathogens to the point where it doesn't make the animal sick, but is still active to some extent in the animal cells.

Senan: But at the same time, the immune system avoids it itself being triggered into a high state of inflammation, which is what would normally happen when you get infected by one of these things, because that in itself, the side effect of a very high rate of inflammation can actually kill you or make you very sick.

Joe: I wonder is it though as well though that they're so used to such a high metabolism… For example, if we got sick with something and suddenly our heart rate was 900 beats a minute… That would be a problem. But they're so used to that sort of…

Senan: There is a theory that the garbage collection system that they have had to evolve to deal with the waste by-products of that high metabolism probably is playing a role in keeping them from getting infected or made sick by these viruses that they're carrying.

Joe: And also, it's good to know that like in case we're invaded by aliens, that we just have to lob a few bats into their deep fat fryer just on the off chance that some of those viruses might be lethal to them. [laughter]

Senan: That actually would be, we really should edit that out of the audio, because the aliens will then know we're planning to do it.

Joe: Oh, wait. Yeah, they might have defence mechanisms against that. [laughter]

Senan: Because I'm sure the aliens are listening to us on a weekly basis.

Joe: Speaking of people listening to us, I know one question that's on the mind of a lot of our listeners is, do bats have any sense of time?

Senan: Possibly a bit better than mine! [laughter]

Senan: Anyway, we're going to very briefly rattle through some of the weird and wonderful bat facts before we finish. [laughter]

Senan: Vampire bats, they need regular meals; they can't go more than a few hours without a meal, right?

Joe: Like real vampires.

Senan: Like real vampires! [laughter] And in the bat cave, if a bat is starving, a vampire bat, their generous neighbour will actually regurgitate some blood and feed them an emergency…

Joe: I was actually shocked by that. I thought their generous neighbour would turn around and eat them. I thought that's where that was going.

Senan: But the really cool part about it is, experiments that have observed their socialisation, they actually remember who was kind to them, and if in the future they have to make a decision between feeding some bat that was never kind to them before and the one who was kind to them, they will always pick the one who was kind to them in the past.

Joe: This is a lesson for everyone.

Senan: What goes around comes around.

Joe: It's a lesson for… What goes around comes around, yeah. It's a lesson for everyone. [laughter]

Senan: Now, the coolest fact of today's podcast: we need bats for tequila.

Joe: Fundamental. They're fundamental to the future of mankind, so. [laughter]

Senan: Yeah, so that's it, no more hating on the bats. The reason we need bats for tequila is because tequila is made from a plant called agave, and bats pollinate agave.

Joe: So, bats are the pollinators, there's…

Senan: Do other insects pollinate it as well? Chances are they do, but bats are known to anyway.

Joe: Yeah, but bats are known to eat those insects. [laughter]

Senan: That's also real! Right. There's a cave in Texas. If you don't like bats, do not go anywhere near the Bracken Cave in Texas, because it is bat city; it is home to 20 million bats.

Joe: Why did they not call it Gotham? Why not? [laughter] Why did they not call it Gotham Cave?

Senan: They missed a trick. Yeah, I don't know. But that actually gives us a clue maybe for why they have such a strong immune system, because 20 million bats living cheek by jowl, if one of them gets sick, they're all going to get sick. [laughter] So, that could well explain that one.

Senan: They eat an enormous amount of insects, because of that high metabolism where they need all that energy for flying. If we did not have bats around, and incidentally, there are bats on every continent bar Antarctica, if we didn't have bats around, we probably would have a hell of a lot more insects annoying us than we do.

Joe: Aren't they actually protected? Aren't they protected here in Ireland?

Senan: There are certainly some species, whether all are, I'm not sure, but there are certainly some species that are protected, because I happen to know somebody who was planning to replace the roof on his house because the timber was rotting or something, and they discovered bats roosting in the roof, and he couldn't do it.

Joe: He couldn't do it?

Senan: So, the message really is, if you find bats that you don't want, don't tell anyone.

Joe: Oh my god, Joe! [laughter] You are so cancelled! [laughter]

Senan: Imagine I got cancelled for that, with all that's going on in the world! [laughter] Next week on Enough with the Science, it'll be, "Hello, I'm Senan, and I'm Senan too." [laughter]

Joe: This is my last podcast. [laughter]

Senan: We've kind of come to the end of bats. I suppose the parting message is that there's an awful lot of scientific research going on into bat biology, because potentially, if we could learn how their bodies are doing these wonderful things they're doing, we could apply that stuff to ourselves and solve autoimmune diseases, potentially limit cancer, solve virus infection, improve our longevity, you name it; this is a real one…

Joe: So, the bats are our saviours really.

Senan: The bats will be our saviours eventually.

Joe: They're a superhero, almost. I wonder is there a superhero… Like someone should write a book about superhero bats, somewhere.

Senan: Somebody should. Joe, patent that idea quickly, Joe! [laughter]

Joe: So, I think with that, that's the end of our first episode, season three. Welcome back, thanks for listening, and hope to catch you next time. I'm Joe.

Senan: And I am Senan, and hope you have a nice day doing whatever it is you're doing.