Urohidrosis: A Case of the Urine Sweats

to look these up for yourself when I give you the names. So the examples I'm about to mention would be three stork species. One is Seconia episcopus, this is the wooly necked stork. Another one is Micteria lucocephala, which is the painted stork, and another is Leptoptalus creminifer, the Marrabou stork. Now, these are all storks with long, thin legs, I would say very roughly, you know, body length or

longer standing in an upright posture. And in the pictures I've provided for you, rob these come from a paper that we're going to talk about just a minute. You can see in patches that the legs and feet have a natural pigmentation.

out pretty well. This is a paper in the journal Scientific Reports, and I apologize if I pronounced any of the author's names wrong here. It is by Julian Kabeo Vergel, Andrea Soriano, Ridondo Auxiliadora Viegas, Jose A Maseroje M. Sanchez Guzman, and Jorge S.

water content from freezing solid or turning into steam. But beyond those extremes, animals also need to keep their body temperature within a fairly narrow range to protect cellular function and facilitate the chemistry of metabolism, like there are certain enzymes in the body that don't work right if they're outside of a certain temperature range and so forth. And there are broadly two different ways that an animal species can be oriented with respect to the regulation of body temperature.

These are ectothermy and endothermy. Endotherms, also known as warm blooded animals, generate their own internal heat from metabolism, so they burn food energy and use homeostatic mechanisms like shivering and sweating and so forth to keep body temperature within a very tight range. Mammals and birds are generally endotherms.

They primarily regulate their temperature with internal mechanisms. Ectotherms, on the other hand, sometimes called cold blooded animals, regulate their body temperature mostly with the help of the outside environment. So these are the animals that you would think of as sun basking or cooling in water in order to manage their body temperature. Ectothermic animals include most reptiles, amphibians, and fish. Though to be clear, the cut between ectothermy

and endothermy is not a clean cut. There are a lot of kind of blurry cases in between, just sort of a generally helpful distinction. Now, there are advantages to each of these major strategies. We could come back and go deep on this someday, and we've talked about it somewhat in the past, I believe, But a very simplified version is that endotherms animals that primarily generate their own

heat through metabolism, they can do a lot more. They can sustain more muscular activity, they can grow more powerful brains, they can survive in a greater range of different climates you know you don't usually see like reptiles and extremely cold climates and so forth. But they also require a lot more food. Ectotherms are efficient because they don't leave the motor running all the time. They can usually go much longer in between meals and can survive rough patches

by kind of going dormant. Now, because this paper is focused on birds, we're in the domain of the indotherms, the warm blooded animals that primarily generate heat through their own internal metabolic mechanisms, but even endotherms can't regulate everything internally, and the authors begin the paper by discussing various ways that endothermic animals do still have to protect themselves from external heat stress, from getting too hot because the environment

is too hot. And some of these defense mechanisms against overheating are physiological and some are what you'd probably call behavioral, and the authors say that typically the first response, the first priority response, in the responses you go through when you're encountering heat stress is behavioral, and this could involve the selection of cooler microclimates, going to cooler places from warmer places, or what they call heat dissipating behaviors, and

there are many different kinds of heat dissipating behaviors in nature. This could mean something as simple and as familiar to us as reducing physical activity. You know it's hot out, you stop moving around so much, or moving out of the sun and into the shade, or things like getting in the water for a swim. Being submerged, even in what feels like fairly warm water, actually removes heat from

the body quite efficiently. The author is mentioned later in the paper that the thermal conductivity of water is twenty five times that of air. So you might have had this experience before where you know, even in a pool that doesn't feel very cold, the water feels nice and warm. You spend too long in the pool, you really will start to chill out and you need to get out of the water and warm up.

kind of crouch. But in the heat, if you're overheating, you don't want your legs touching each other, and you don't want your arms touching your body. You want to splay out maximally to have maximal surface area, which means heat can escape your body with the greatest efficiency.

the authors call rapid physiological adjustments. This is things that the body does we would usually think of as involuntarily to try to remove heat faster. And these can vary across different types of animals, but it could include things like in humans, sweating, in other animals, panting, or increasing the breathing rate to dissipate more heat from the lungs and the respiratory system. Now, the authors point out that in birds, one of the most common physiological mechanisms for

removing heat is what they call panting. I've seen some sources reject that terminology because maybe because they think it incorrectly implies it's the exact same thing that dogs do, but either it's similar either way. For birds, panting involves rapid breathing with an open mouth, so they might hold the bill open and breathe in and out very rapidly to purge heat through evaporation from the warm, moist tissues

inside the mouth, throat, and lungs. This is also sometimes accompanied by another response called googler fluttering g u l R fluttering, which means like they would, the bird will vigorously vibrate the muscles and membranes inside its throat while panting to further increase evaporation and the purging of heat. Now, these physiological adjustments they do work. They will purge heat from the body and help avoid hyperthermia, help the animal

cool down, But they're also very costly. They're costly and thus risky to the animal because they can waste important resources like energy and water. Birds can lose a lot of water through panting and fluttering, and in addition, the authors mentioned that panting in birds can force potentially undesirable

changes in blood chemistry. So if you're an animal in the wild fighting for survival, you have these physiological mechanisms, these sort of rapid body adjustments that you can rely on if you have to, but you would like.

is to start sweating bullets. In their introduction, the authors of this paper introduce a concept from zoology called heat dissipation limit theory, which argues that in indotherms, the problem of how to deal with excess heat produced by metabolism limits how much which energy you can take in and

by consequence limits reproductive output. So the author's right that under this theory, heat dissipation behaviors could really be crucial to the evolutionary success of a species because they allow more chemical energy to be devoted to foraging and reproduction and things like that, rather than to physiological mechanisms simply

for getting excess heat out of the body. And the authors mentioned that the sort of research context of this paper is that thermoregulatory behaviors and animals are increasingly being studied because of the current and future increases in heat stress on wildlife due to global warming, where the ability of an animal species to deal with heat stress without resorting to costly physiological mechanisms may be the difference between

adaptation and extinction. So this is something that is probably just going to get more and more attention from people who study wildlife, especially as the heat stresses of environments

are changing more rapidly. Now, another interesting fact about how birds protect themselves against overheating has to do with what the authors call quote unfeathered and well vascularized appendages, meaning parts of the body that are bare so not covered in feathers and parts of the body containing a lot of blood vessels, and examples here would be the bill, the bird's bill around the mouth, and the legs because these parts of the body are typically not insulated by

feathers and lots of blood flows through them, and for these two reasons, these parts of the body can be utilized pretty well as what the authors call thermal radiators to purge excess heat, and this is especially the case for storks. The storks belong to the In scientific classification, they belong to the family Sickniady, which storks typically have long, bare legs and most often live in warm or hot

climates with little shade. So storks have an internal mechanism for making use of these thermal radiators in the body. For making use of the long legs for temperature management, storks can actually alter the blood flow to their legs, constricting the blood vessels down there when it's cold out so less blood is flowing through and there's less heat exchange, and then dilating the blood vessels in the legs when it's hot, promoting more heat loss from the body down

in the legs. But in the case of storks, the use of the legs as thermal radiators. Goes one step further, and here's where we get back to the topic for today, eurohydrosis the author's right quote. Notably, storks can deliberately excrete onto their legs when exposed to increasing environmental temperatures, a phenomenon known as eurohydrosis. When overheated, storks repeatedly direct liquid excrita toward their legs, only one leg at a time,

which usually evaporates before reaching the toes. So it's hard to imagine this from a human perspective, but the more you think about it, the more it does make biological sense. Imagine you're out in the sun on a blazing summer day. The heat's really getting to you. You have a few options to cope. You could stop moving around and flop down in a chair. You could get out of the

sun and into the shade. You could hop into a pool, or if those options are not really available to you at the moment, you could poop all over your own legs, one leg at a time, and then hope that that helps cool you off.

on the show before. I think we did an invention series on the history of air conditioning, The Invention of air Conditioning, where we talked a lot about evaporative cooling, and it's come up in a biological context as well. But the short version is that the phase transition from liquid water into water vapor requires a lot of heat energy to take place. So water that is evaporating into the air cools down very rapidly and in turn cools whatever it is touching, such as your body if it's

on the surface of your skin. And if you ever want to do a simple experiment in your home. To see evaporative cooling at work, you can try this is kind of fun. You can get two bottles of water at the same temperature room temperature bottles of water, and you put them both in front of a fan, and now one you just sit there with nothing, you know, by itself, but the other one wrap the bottle in a wet towel, set them both in front of the fan,

and then come back in like half an hour. The regular bottle will not have cooled off significantly, but the bottle that you wrapped in a wet towel will be very cold because as airflow from the fan causes the water in the wet towel to quickly evaporate, it will suck heat from the water in the bottle and make

it cold. I think this is an old trick that like people traveling in desert climates, you know, without artificial cooling used to use where they would you know, they'd have like a big jug of water, like a big skin of water, and to keep it cool as they're

traveling in the hot desert sun. They would also get like a cloth and wet it at the beginning of the day and wrap it around the outside of this skin of water, and as the water evaporate from the hot cloth on the outside through the day under the hot sun, it sucks heat from the water inside and makes the water very cold. And evaporative cooling is why sweating cools the body. You know, as sweat evaporates from your skin, it steals heat energy from your body and

it cools you off. Now, of course, sweating has a downside, which is that it causes you to lose water and electrolytes. So when you're hot and sweaty, it's very important to keep hydrated. To compensate for the water loss. Exercising in the hot sun one oh one, you got to drink

lots of fluids. The same is true for birds. Now, birds don't sweat, they don't have sweat glands, they can't sweat, but they do have their own evaporative cooling techniques, and as we talked about, the panting is one of those techniques where they can use evaporative cooling in their respiratory system with the open bill rapid breathing, and eurohydrosis is

one of these techniques. The author's right that eurohydrosis is relatively rare among birds, because it requires ready access to a lot of drinking water, but plenty of bird groups

have been observed to do it. They list New World vultures, storks, condors, gannets, and boobies, and eurohodrosis has been known about for a long time, but the authors say there still has been relatively little investigation of what exactly are the environmental and physiological factors that determine it, like what causes one bird group to use eurohydrosis and another group to not use it. So the authors came up with a systematic way of

looking into this. Now, this particular study relied on essentially repositories of scientific media, like imagery of birds from various field locations that was associated with metadata, so that you could try to correlate images of birds doing certain things

and the environmental data about them. So this was not a direct field test with variables that the authors could manipulate, but they were just trying to establish correlations between like environmental factors and factors about the bird's bodies, along with observations of do these birds poop on their own legs or not? So what environmental factors did they find correlating.

more likely to engage in eurohydrosis. They also found that it was more common among stork species that forage on dry land as opposed to those that commonly inhabit water bodies and forage by wading, which kind of makes sense to me, Like, if you can get your legs wet without pooping on them, all the better, right, Some storks are not in a position to spend as much time hanging out in the water.

more likely to do this to help cool their bodies. Now, there were some other hypotheses that had been put forward by these authors and other authors that were not confirmed in this research. It had been hypothesized that stork pigmentation would be correlated to the use of eurohydrosis. The idea is maybe that birds with darker pigmentation absorb more heat from the sun, but this was not supported by the survey.

They did not find that correlation. It had also been hypothesized that eurohydrosis would directly correlate to the latitude where birds live, with tropical species practicing it more. This was also not strictly supported, though again there's some complications because some of these birds, you know, they will travel live at different latitudes different parts of the year, and again, warmer, more open environments did predict it, it was just not

strictly latitude. Another thing that was not supported was a hypothesis about body mass. This was something that the authors of this paper predicted. They thought that higher body mass would predict more eurohydrosis because the animal would have more water reserves to take advantage of. Like, if you're a bigger animal, you can drink more water, store more water in the body. You can also you've got more to waste in pooping on your own legs to cool off.

But this was actually not the case. This might have to do with the fact that these storks all had access to water bodies for regular drinking, even if they didn't spend a lot of their time waiting around in that water, so maybe internal water stores were less of

a concern. Looking beyond storks, the authors note that even other bird groups that practice eurohydrosis, like New World vultures, boobies, and gannets, they all tend to breed or forage in hot, open land areas under the sun, and they also tend to have relatively large and highly vascularized legs, so there seemed to be some common environmental and physiological pressures at work.

Now some other interesting observations from their conclusion I thought one was that when comparing different ways of cooling the body at the cost of energy and water reserves, the authors conclude that eurohydrosis is actually cheaper than panting, which was kind of surprising to me that that was counterintuitive, but they said this is supported by the fact that birds who have the adaptation tend to engage in leg pooping at a lower temperature threshold than the temperature threshold

for panting. So I think kind of like how if you're a human, humans will typically resort to like changing into short sleeves before they will resort to like jumping into an ice water bath. You know, one is like a more severe, costly activity than the other, and it seems like for these birds, panting is the more severe, more costly, and risky activity. The authors also note that other animals, apart from birds, use alternative evaporative cooling methods,

not just not just sweating like we do. They say, some mammals produce excess saliva when hot and then use evaporative cooling through the mouth or even cool the body by like drooling or licking on themselves on the outside and then allowing that saliva to evaporate. Rob I know, you've got an alternative evaporative cooling method to talk about in a minute, But they end up saying that there

could be some tradeoffs involved here. There's possibly that this is not a strong not something strongly established, but a possibility is that there could be a tradeoff between mate signaling based on the pigmentation of bird legs and the cooling benefits of euro hydrosis. But this is yet to

be fully explored. But the idea here would be if this were the case that it helps you advertise mating fitness better, if like the correct pigmentation on your legs is showing, and that by pooping all over your legs this like changes the way you look and sort of downgrades your mating appeal. So there could be some push

and pull there, but that wasn't very well established. But more briefly, I did want to mention a second paper that involved three of the same authors as the previous paper because it had some interesting follow up on this

and involved a or direct method. And so the second paper was by again three of the same authors, Kabeo, Vergel, Viegas and Gutierres, and this one was called keeping Cool with poop Eurohydrosis lowers leg surface temperature by up to six degrees celsius in breeding white storks, published in Ecosphere in twenty twenty three, and this study was a direct attempt to measure that the magnitude and duration of the evaporative cooling that you get from eurohydrosis in free ranging birds.

This study used observations of eurohydrosis in white storks or seconias econia, paired with thermal imaging and microclimate measurements to see like exactly how much benefit the leg pooping was providing. Now, this next part in the abstract did make me laugh. They write, quote, we show that eurohydrosis can reduce leg surface temperature by up to six point seven degrees celsius, which is actually four point four plus or minus one

point zero four degrees celsius. Yet its cooling effect was of short duration, lasting no more than two point five minutes,

and decreased with time since defecation. Which actually that makes sense, right, because like, if you're trying to work through evaporative cooling, as the bird poops on its leg, it will be very it will have a great cooling effect while the poop is still very wet, but then as it evaporates, it will dry up, and then it will provide less of a cooling benefit and may even have some negative effect.

twenty seven point five minutes of cooling per hour. If they do it eleven times, almost half of the time of the hour is in cooling mode. So the authors estimate that eurohydrosis can cover quote four percent of the daily field metabolic rate for an adult stork.

The author's right quote, Gaining knowledge about behavioral thermoregulation in the heat is therefore crucial to better predict the future persistence and vulnerability of species under different climate warming scenarios. A lot of these species are going to be living in places where the local climate is increasing in heat over time. That's increasing the heat stress on animals that live in the wild, and some animals will be better

or worse able to deal with it than others. There was another question that came out because I saw some stuff online in discussions about eurohedrosis that was about possible other functions. It seems pretty clear certainly in storks it's playing a role in cooling the body, But is eurohidrosis just to cool the body or in some species. Could it be playing another role as well, Like I saw some ideas that it could possibly have an antibacterial function.

could the purpose be? And there is this idea that it is essentially kind of like when we reach for a container of a hand sanitizer, except for the vulture, whose, of course, you know, it's it's getting its talons into various you know, grotesque feasts there on the side of the road or in the wilderness and so forth. Occasionally it makes sense to sanitize those legs with an eye,

perhaps with a nice you know, coloacal wash. And so that is, that is the theory that there is an antiseptic nature of vulture defecation, and that it, you know, especially would be important for various scrapes and cuts on those appendages. And so I was reading about this in a twenty twenty two book, Vultures of the World, in which the author Keith l Builds and points out that at the time, at any rate, the antiseptic nature of vulture defication had not been like tested to the full.

So it's still kind of an open question. But this does seem to be a strong argument, again based in large part of the fact that they do seem to do it both in summer and winter, suggesting that disinfection might be at least an important part of the equation for like turkey vultures. Okay, now, an interesting fact about this.

I was not familiar with this, but the author here points out that in in US and Canada at any rate, vulture researchers are prohibited from using leg bands on turkey vultures because there's a risk of uric acid building up and cementing around the leg band because again they're pooping and peeing down those legs. If you have a band there for tracking purposes, it could you know, it gets caught there, it drives there, it's cements there, and this

could effectively hobble the bird over time. Eventually it's like too big of a weight for them to fly off with, apparently, or at least you know, it would get in the way they're flying, in their ability to carry out their

daily activities. So fortunately there are other methods for tracking them, things like wing tags and the like, but putting a leg tag on them as a no no. Now, before we get away from birds, I do want to point out that in looking I'm always interested to see if there's any kind of mythological or folklore tie in to a particular topic, and I really wasn't expecting much here, but I did find mention of this in connection to Amazonian mythology via a book titled an Amazonian myth and

Its History by Peter Goal that came out in two thousand and one. So the story involved here is referred to as the Sun and it entails a character who is at one point eviscerated, but in a nice way, like in a like a polite mythic way, like he's asleep and the creatures that are working for him remove his intestines. But at any rate, the story involves a character who's eviscerated becomes gutless, and by becoming gutless, can now eat and drink all he wants, but can also

never be satisfied. And this is a story that Giles says is apparently connected to observations of the wood stork who appeared gutless, because they are constantly excreting waste. You mentioned, like how often per hour they are excreting in order to cool those legs down, and it can lead to this observation. It's like, well, this animal poops all the time, and we don't do that. We you know, we know exactly, we know more or less what's happening when we consume

food and it becomes nourishment and so forth. Perhaps the stork is not giving it time at all, is just going straight through, and therefore, you know, there's just these kind of you know, ravenous but unsatisfied creatures.

are intestines. So as I understand that what we have here is we have an observation of nature, an incorrect hypothesis, or a very loose hypothesis that's maybe concerned more with the mythic purposes of the tale as opposed to anything else.

And then this bleeds into an anatomical mythology that presents something almost like a hungry ghost, you know, this idea of a being that cannot be satisfied because his digestive capabilities are just not intact, and that perhaps that's what we see when we see these storks as well.

adapted to thrive in very cold waters. However, as Roger L. Gentry discusses in the nineteen seventy three paper Thermoregulatory Behavior of eared Seals this is published in the journal Behavior, they have other means of thermoregulation that become necessary when these well insulated creatures are out of the water and caring about on the shore, on the rocks in the sun.

So there's a lot of fighting and squabbling for territory and for females, and it's a It can be a real endurance game for the males of you know, various seal species species because they're having to constantly fight and at the same time they have to maintain acceptable body temperatures, they have to thermoregulate, and they're not in the water at this point. The water is the author points out,

the ideal place for this creature to cool down. But you're fighting a territory war, in a mating war up here on the rocks. So getting back in the water is something you can do, but that is going to be like your last resort because you're giving up territory at that point, so you have to do other things. So Gentry discusses how, especially during the high temperatures in these environments, you'll see a few different behaviors. So on one hand, they will seek out shade or shade cooled rocks,

which you know, kind of the same thing. But it's essential to note that you know, rocks of course heat up in the sun, so being in the shade is one level of protection, but also being on rocks that are either currently or have just previously been cooled by

the shade is also worth thinking about. And so according to Gentry, during higher temperatures, these seals have been observed to stand on all fours and then annoy their flippers and bellies with urine, with the back of flippers being the key, because then they'll lay on one side and extend their now wet rear flipper into the air and this will be the way they carry out carry out

some evaporative cooling. He also notes that the males seemingly drink more water in the surf during this time period in order to provide more urine for thermal regulation when they're out on the shore. So, coming back to what we were talking about with the with the storks, if you're going to engage in something like this, you've got to keep you've got to keep the fluids flowing.

these females. And then occasionally here's some other male seal coming that is going to contest this situation, and then you know, there are various little squabbles about where the females are getting to lay about as well, and then you know sometimes and then this is also inevitably happening or a lot of the time it's happening on beaches that where people are also hanging around, so they're also human tourists, so there's a lot of and of course

when the seals decide they want to go somewhere, it's like it's time for the humans to move.

didn't have anything about the Galapagos in my notes. It's just as I was going through this part of the episode, it stirred a memory, and as is sometimes the case with memories that are recalled from the depths, sometimes it comes up with a little bit of incorrect information applied there. So,

without further ado, let's get back into the episode. Now, speaking of the Glapagos, this does bring me to the next question that I had, because when I was in the Glapagos, I did just a little bit of snorkeling in very cold waters, and I was wearing a dive

suit because it gets cold. And if you've ever gone diving or done scuba diving or snorkeling and you've worn a wet suit and the water's been cold, you might have done what a lot of people have done what I did as well, and that is urinate in the suit while you're in the water too warm. Things is

up a bit. This instantly came to my mind when we started getting into this, because yeah, like this seems like an example where humans can get in on the euro hydrosis action, right, sort of in the opposite direction, in the opposite direction, right, you know, can we just pee in our dive suits in order to warm things up? And you know, I was able to find a full article about this on dive SSI dot com. That's Scuba School's International.

And they point out that due to the mammalian dive response, you might need, you might have a heightened need to urinate in this environment, because a submerged mammal is going to experience a slowed heart rate during free diving, especially, it's going to narrow blood vessels in the extremities, and blood's going to shift to the core parts of the body all in order to conserve oxygen and maintain blood flow while holding one's breath, But more blood ends up

going to the core and then via the kidneys. This increases the urge to urinate. So you might find yourself in a situation where you're like, Wow, I just got into the water off the boat. It's cold, I need a pee anyway, Why don't we warm things up a bit? And so Yeah, they point out that this is a common bit of diver's lore, and the article states quote the wet suit itself works by trapping a thin layer of water between the neoprene that's a synthetic rubber and

the skin, which the body warms. This layer serves as insulation, keeping the diver warm in cold water. When a diver urinates in their wet suit, the initial warm sensation comes from the body warmed urine. However, this effect is fleeting.

When you pee your suit in order to warm up, you kind of like recreate something like that scenario again, we're like, oh, now now it's cold again. Because and part of this is the wet suit is not waterproof. It's permeable, so outside cold water will directly cool the layer of spreading warm urine in the suit. Now, all that being said, the article stresses that peeing in your wet suit is a common practice and it's not harmful.

You know, you may have some hygienic or some comfort concerns about it, but basically all they really advise on this is, look, if you do it, fine, but just you want to make sure you wash out your suit afterwards. I mean, you're going to be washing your suit out, but you know, if if you don't thoroughly wash it out, you could get some uh some some some urine odors

you know, in the material and so forth. But uh, and then again they stress that, yeah, you're gonna get a warm burst, but it's not going to be lasting. It's not It's just just going to be a burst.