Desert Animals: How They Beat the Heat Without Water

A desert is usually described as a place with too little water. That is true and it is not the problem worth understanding.

The real constraint is an exchange rate. To get rid of heat, an animal has to evaporate water. There is no other exit into open air.

So a desert animal runs a heat budget that it can only pay for in water. Every adaptation it has is a way of avoiding part of that payment.

A camel's hump, a kangaroo rat's never-thirsty life, a thorny devil's skin and a sidewinder's strange walk are all the same idea wearing different clothes.

This post is about that rate, and about the animals who live inside it.

Albert Deccan. Dew. In a desert, water also arrives from the air as a liquid, not only as falling rain. CC BY-SA 3.0, via Wikimedia Commons.

A Desert Is a Heat Problem, Not a Thirst Problem

Where the water actually goes

Every animal loses water through the same four routes. Breath, skin, urine and faeces. In a cool place the first two are trivial. In a hot dry place they are the budget.

It helps to separate the two things the earlier version of this post ran together: how much water there is, and how easily the animal can get at it.

Deserts are not empty of water. They hold dew, fog rolling in off a cold sea, flash floods, groundwater, and a great deal of water locked inside plants and prey.

Arabian oryx have no standing water to drink at all. They live on the water inside the grasses they eat.

So the problem is rarely a shortage. It is delivery. The water is in the wrong phase, the wrong place, or the wrong part of the day.

The rate, and why it is expensive

Carrying heat away from a body into dry air takes evaporation. To turn liquid water into vapor needs energy, and the energy comes out of the body as heat.

That is the whole trade in one line. The animal pays water to move heat, and it pays again to pay for the water.

Every design choice on the list below is a decision about how to pay less, and the six options are not equally available to every animal.

Body size decides which problem you have

Across mammals, how much water an animal turns over each day tracks body mass closely, with a correlation above 0.9.

That is why a mouse in a desert is in far more trouble than a camel in the same desert. A small animal has a large surface for its mass, and it loses more for every gram it has.

A kangaroo rat deals with it by oxidising food for a living. A camel deals with it by being big, by traveling to water, and by being able to swell its red cells when it finally does.

Route out	Why it happens	What the animal does about it
Breath	Air leaves the lungs warm and wet.	Exhale it cooler and drier, and recover some of the water.
Skin	Water passes through the surface, faster when hot.	Insulate, get underground, or move the animal into cooler air.
Urine	Nitrogen waste has to leave in water.	Build a longer medulla and concentrate harder.
Faeces	Undigested food carries water with it.	Dry the faeces out and cut the volume.
Made in place	Oxidising food gives water out of the air.	Eat more fat, which returns the most water per gram.

Five routes, one exchange rate. The first four are losses and the last is income, and only one of them is under any directional control at short notice.

AntanO. A dromedary. The hump is a fat store, and fat is the best water substrate the animal has access to. CC BY-SA 4.0, via Wikimedia Commons.

Six Ways to Pay Less

Store the heat instead of shedding it

The cheapest trick is to change the question. Instead of cooling the body to a fixed number, let the number move, and dump the stored heat when the environment is cooler than the animal is.

Arabian oryx were tracked with implanted loggers for two years in the Saudi desert. Their body temperature moved through about 4 degrees across a summer day and only 1.5 degrees in winter.

The important detail is the shape of the day. Body temperature rose steadily from morning onward, which is what storage looks like. The animal absorbed heat all day and let it go at night, when the air was cooler than it was.

A second year of work confirmed that water is what drives this. In hot months the daily swing widened to about 5 degrees while the daily average body temperature moved less than half a degree.

The amplitude is the variable water controls. The average is not.

Charles J. Sharp. The Arabian oryx. Measured in the wild, its body temperature swings by about 4 C across a summer day. CC BY-SA 3.0, via Wikimedia Commons.

Cool the one organ you cannot lose

Send heat somewhere it costs nothing

Large, thin, well-vascularised ears are not decoration. A fennec fox runs blood through them and loses heat to the air by radiation and convection, which cost no water at all.

The pinna is under active control, not merely large. Blood flow to ear skin rises when an animal is hot and falls when heat must be held in. An ear is a radiator that can be shut.

Some hoofed mammals do something sharper. They push blood through a dense braid of arteries on the way to the brain, so the blood arriving at the brain has already given up heat to outgoing blood.

Arabian oryx held brain temperature about a quarter of a degree below the temperature of the blood in the carotid artery feeding it.

The comparison that proves the point is with the gemsbok, a close relative living at similar air temperatures but in a less arid place. The effect was larger in the Arabian oryx.

So the difference between them is not the heat. It is the dryness.

Drew Avery. The fennec fox. Large, thin, well-vascularised ears dump heat by radiation and convection, which costs no water. CC BY 2.0, via Wikimedia Commons.

Breathe it back out cold and half dry

Every breath puts water into the air. On an inhale the nose warms dry air and adds water to it. On an exhale it has to take that water back, or lose it.

The device for this is a countercurrent heat exchanger in the nose: thin blood vessels running beside the airway in opposite directions. Warm blood leaving the nose gives up heat to cool incoming air.

Camels do it unusually well, and the saving has been measured at about 60 percent against exhaling saturated air at body temperature. The trick is two tricks at once. The exhaled air comes out cooler, and it comes out less than fully saturated.

The same work shows how much the whole budget moves with body temperature. A dehydrated camel's temperature swung by as much as 7 degrees. Across that swing, its respiratory water loss ran from about 0.06 grams a minute to 1.2.

That is a twenty-fold range in one animal, controlled by one number.

Sweat on purpose, and choose where it goes

The earlier version of this post said that most desert animals do not sweat, to avoid losing water. That is backwards.

A human can push more than 2000 grams of sweat through the skin in an hour after several days of heat acclimatisation. Desert-adapted populations do not solve the problem by refusing; they solve it by starting earlier and producing less for the same load.

Many desert mammals have no sweat glands at all. They vent by panting instead, or by spreading saliva on the skin and letting it dry off. That costs the same water and works where panting would not.

Some do nothing at all until they have to. Burchell's sandgrouse holds a normal body temperature below 39 degrees. At an air temperature of 56 degrees, its body temperature climbed to 43.6 before panting began.

For scale, conventional exercise guidance treats a loss of 2 percent of body weight as the point to intervene. No desert mammal spends its life near there.

Refuse to evaporate at all

Underground is the cheapest refuge there is, and the reason is not mainly temperature. A burrow is humid, and evaporation into air that already holds water is slower.

Nighttime is the same idea outdoors. Once the air is cooler than the animal, heat leaves through radiation and convection, and neither route costs a gram.

This is why burrowing, nocturnal activity and dusk-and-dawn foraging are one strategy described three ways, not three strategies.

Tolerate a lower water content in the blood

The last resort is to change what your blood looks like when it dries out, so that you can keep going while the rest of the body is running low.

Camel red blood cells are built for exactly this. About 65 percent of the water inside a camel red cell is bound to protein and cannot be pulled out, against about 20 percent in a human red cell.

That is why a camel can dehydrate to the point where its blood is thick and still function. The cells hold their shape because there is less free water for the salt to chase.

When water does arrive, it arrives fast. Experiments with labeled water show a rehydrating camel absorbing and diluting its blood within about four hours, then spending two to four days excreting the excess.

Tolerance is not the same as harmlessness. Twenty days of water restriction in camels raised two inflammatory signals in the kidney cortex and caused oxidative stress there. The organ was coping and still being damaged.

Way to pay less	An animal that does it	What it still costs
Let body temperature rise	Arabian oryx	A smaller margin for work, and less heat left over for the night.
Dump heat without evaporating	Fennec fox, oryx with a carotid rete	Blood flow to a surface, and body size to make that surface worth having.
Exhale cooler and drier	Camel	A nasal heat exchanger, and a bigger medulla to match it.
Sweat early and less	Desert-adapted people	Water, at a rate the animal can actually replace.
Refuse to evaporate	Burrowing rodents, nocturnal hunters	Hours of the day the animal cannot use for feeding.
Hold water inside the cells	Camel	Kidney inflammation, measured after about 20 dry days.

Six routes out of the payment. The last column is the point: none of them is free, and the price is paid in energy, in feeding time, or in tissue damage.

Keeping What Is Left, and Making More

A desert kidney is a different organ

Concentrating urine is not a filter setting. It is anatomy.

In a study of 21 mammal species, the maximum a kidney could concentrate its urine tracked the thickness of the medulla. It also tracked how that medulla was divided into inner and outer zones, and the size of the vasa recta.

Desert species sit at the far end of that scale. A desert rodent can reach a maximum urine concentration nearly three times that of a laboratory rat.

The South American desert mouse opossum reached 9015 milliosmoles per liter, the highest ever recorded for a marsupial. That figure is worth keeping in mind, because it shows how species-specific the whole thing is.

Wagner Souza e Silva. A camel kidney cut open. The pale inner medulla is the machinery that lets it concentrate urine, and it costs energy to run. CC BY-SA 4.0, via Wikimedia Commons.

The saving is not free

Urea is the most abundant solute in mammalian urine, and it only gets that concentrated by being carried back and forth inside the kidney.

Urea cycles among the collecting ducts, the vasa recta and the thin limbs of the loops, using dedicated transporters. Take those away and concentrating ability falls.

So a five-fold saving in water is bought with nitrogen that has to be shuttled and energy that has to be spent. The companion post on this site covers what different nitrogenous wastes cost; this is the other half of the trade.

A reservoir is not a tank

The earlier version of this post said that desert tortoises store water in their bladder. That is right, and it is more interesting than it sounds.

Both the urinary bladder and the cloaca act as reservoirs, and water is reabsorbed out of them. The bladder is a buffer, not a one-way store that gets emptied.

The idea is old. Robert Townson proposed it in 1799, working from Galapagos giant tortoises, and it went untested for most of the century after.

Tigerhawkvok. A desert tortoise. Its bladder and cloaca act as reservoirs that water is reabsorbed from, not one-way tanks. CC BY-SA 3.0, via Wikimedia Commons.

Making water out of food

Metabolic water is the one source a desert animal can increase without finding anything. It is also the one the earlier version of this post left as a slogan.

It is a stoichiometry, and anyone can do it. Oxidising glucose gives carbon dioxide and water, in fixed proportions.

The same is true of fat. The interesting part is that the two substrates are not equally good at it.

Substrate	The oxidation	Water per gram
Glucose	C6H12O6 + 6 O2 gives 6 CO2 and 6 H2O	180 g makes 108 g, so 0.60 g
Palmitic acid	C16H32O2 + 23 O2 gives 16 CO2 and 16 H2O	256 g makes 288 g, so 1.13 g
Protein	Oxidation, with nitrogen leaving as urea	Roughly 0.4 g, because water carries the nitrogen out

Fat returns nearly twice the water per gram that carbohydrate does. That is the whole reason a fat store is also a water store, and it is the reason a hump works.

Fat is better than carbohydrate because it carries less oxygen per carbon, so more of the oxygen it takes in ends up as water rather than as carbon dioxide.

So a camel's hump is not a canteen. It is a fat store, and fat happens to be the best drinking-water source the animal carries with it. The same store is food as well, so a camel that is not hunting for forage is not hunting for water either.

National Park Service. A kangaroo rat. It never drinks. Nearly all of its water is made by oxidising the seeds it eats. Public domain, via Wikimedia Commons.

The animal that never drinks

Kangaroo rats live on seeds, and seeds are dry. Almost everything that ends up as water in one was made inside it.

This is the animal that "survives without drinking" most often means. And the honest version is that it never drinks because its food arrives already packaged with the water it needs.

It is a trade rather than a free win. Given a choice of body temperature, Merriam's kangaroo rats choose the one that conserves energy rather than the one that conserves water.

The two cannot be optimized together. Below the comfortable temperature range they generate more metabolic water and lose less, but they also burn more energy staying warm.

Collecting water that is already in the air

The other route is to take water out of the air itself, and this is more common than most people expect.

A review of the field counted more than 39 species in 24 genera that collect water passively through their skin or their scales.

It reduces them to six mechanisms, and no animal needs all six. Some make a surface wettable. Some increase the area water spreads across. Some carry it a long way. Some accumulate and hold it. Some make it by condensation. And some simply use gravity.

KeresH. A thorny devil. Channels between its scales carry dew across the body by capillary action, to the mouth. CC BY-SA 4.0, via Wikimedia Commons.

The Australian thorny devil does several of those at once. Channels between its overlapping scales pulled a 7 microlitre drop of water radially across more than 9.2 millimeters of skin.

The channel volume works out at 5.76 microliters per square centimeter on its back, and filling the whole system costs 3.19 percent of body mass.

That is worth pausing on. The lizard spends about three percent of its body weight filling a plumbing system, then walks that water to its mouth.

The beetle that does not do what the textbooks say

The most famous story in this whole subject is about a Namib beetle that stands in fog on a dune crest. Its back is covered in bumps, and the story goes that the bumps catch droplets and funnel them down into its mouth.

The literature does not support that, and this post checked it directly.

The beetles actually observed fog-basking on the ridges are the Onymacris, and they have smooth wing cases. The beetle with the bumpy back had not been seen fog-basking at all when researchers went looking for it.

Trip Lamb, Rachel Pollard, and Jason E. Bond. An Onymacris from above. This is the beetle that fog-basks, and its wing cases are smooth, not bumpy. CC BY 3.0, via Wikimedia Commons.

More recent work does not rescue the funnel either. It treats surface shape as a problem of droplet impact and drainage at the millimeter scale, where texture helps droplets slip toward targets.

These animals also stand head-down into the fog, in a pose that no design for delivering water to a mouth would produce.

Hans Hillewaert. A Stenocara gracilipes, the bumpy-backed beetle the textbook story tells you channels fog into its mouth. CC BY-SA 3.0, via Wikimedia Commons.

What is true, and better, is that these animals wet their whole bodies in the fog and take the water across the cuticle. There is no chute. The body is the collector.

On the Atlantic coast of the Namib, much of what the desert life drinks is fog that forms over cold water and blows inland.

Moongateclimber. Fog rolling in off the Atlantic. This is where much of the Namib desert's drinkable water actually comes from. Public domain, via Wikimedia Commons.

Flying thirty kilometers for a drink

The sandgrouse case is worth finishing with, because it is the one that refuses the whole framing.

The earlier version of this post opened a section called "Desert Birds: Surviving on Metabolic Water" and then said that sandgrouse carry water-soaked feathers to their chicks. Those two sentences cannot both be true.

Namaqua sandgrouse nest up to 30 kilometers from a watering hole. The male flies to water, soaks himself, flies home, and the chicks drink from his feathers.

Recent work on the feather itself found that holding water through flight depends on differences in how stiff the different parts of the feather are. It is a structure, not a soak.

Snowmanradio. A Namaqua sandgrouse. Males nest up to 30 km from water and fly it home in soaked belly feathers. CC BY 2.0, via Wikimedia Commons.

So these birds do not go without, and they do not make their own. They run an air service to the nearest hole.

It is also worth saying what desert birds are not. They are not desert animals by default, and the reason birds excrete uric acid has little to do with deserts. Sandgrouse are a measured special case within a larger group, and the earlier version of this post turned a special case into a rule.

And the ones that just wait for rain

Snakes drink too. Prairie rattlesnakes were recorded pressing their bodies against wet ground to route water to their mouths, in 72 separate events across 94 free-ranging animals.

Nobody knows how much of an insect's water loss goes out through its tracheal system rather than across its cuticle. The argument is still running, and it matters, because the answer decides what the breathing system is for.

What the Earlier Version Got Wrong

The sidewinder is gripping, not lifting

The earlier version said that sidewinder snakes move so as to minimize ground contact and reduce heat absorption.

Both halves of that are backwards. As a sandy slope gets steeper, a sidewinder increases the length of its body held in contact with the sand.

On level sand it also lifts about 40 percent higher off the ground than it does on a hard floor, and uses a shorter wave in its body.

So the gait is not avoiding the desert. It is gripping it. Sidewinding is a solution to loose granular substrate, and heat avoidance is at best a side effect.

Bloopityboop. A sidewinder moving over loose sand. The gait controls how much of the body grips the substrate. CC BY-SA 4.0, via Wikimedia Commons.

Nobody solved this by not sweating, or by staying still

Sweating was dealt with above. The other instinct, simply sitting out the bad season, is what large desert animals tend to refuse.

For large animals the answer has usually been to move. Blue wildebeest survive the gaps between water by traveling when conditions are right, not by sitting out a drought. The cost of transport over land falls as body size rises, so the biggest animals can cross the biggest gaps.

For people, the exchange rate is explicit in the archaeology. Modeling Kalahari persistence hunts, researchers found that water loss rather than heat was what limited how long an early hominin could run down prey.

Skin is part of this too, and it is not a fixed barrier. Lizard skin water loss has been measured rising and falling within seconds of a body temperature change.

Which surface is in the sun, and what posture an animal is holding, are both decisions inside the budget.

Every desert animal turns out to be managing the same exchange rate. They differ only in which part of it they chose to attack, and what they gave up to pay for it.

Key Terms in Plain English

These are the words in this article that would send you to a dictionary. Each one is given here the way it is actually used above.

Term	What it means
Evaporation	Liquid water becoming vapor. The only way an animal can dump heat into open air, and the reason desert life is a water problem.
Evaporative cooling	Losing heat by turning water into vapor. Cheap in energy, expensive in water.
Heat acclimatisation	Days of exposure that raise sweating capacity and move the temperature at which sweating starts.
Heterothermy	Letting body temperature move instead of holding it fixed. Waste heat is stored in the day and shed at night.
Countercurrent heat exchanger	Blood vessels running beside an airway in opposite directions, so warm leaving blood heats cool entering air.
Rete mirabile	A braid of arteries that cools blood on its way to the brain, saving the rest of the body from the cost.
Urinary osmolality	How concentrated urine is, in milliosmoles per liter. Higher means less water spent.
Medulla	The inner part of the kidney. Long, thick medullae are what make concentrated urine physically possible.
Vasa recta	Hairpin capillaries that run alongside the kidney tubules. Their size tracks how well a species concentrates urine.
Cloaca	The common chamber at the end of the digestive and urinary tract. In tortoises it stores water alongside the bladder.
Metabolic water	Water produced inside the body by oxidising food. Fat returns about twice as much per gram as carbohydrate.
Urea	The nitrogenous waste mammals excrete. Recycling it inside the kidney is what makes very concentrated urine possible.
Vapor pressure deficit	How much more water the air could hold than it does now. This is what drives evaporation, and it rises steeply with heat.

Terms used above, in roughly the order they first appear.

Key Takeaways

• The binding constraint in a desert is not how much water exists. It is the exchange rate at which heat can leave a body, and heat only leaves into air by evaporating water.
• Storing heat beats spending water. Arabian oryx let body temperature swing about 4 degrees across a summer day and shed it overnight, at almost no water cost.
• Camels save about 60 percent of respiratory water by exhaling air that is both cooler and less saturated, and their nasal heat exchanger is the reason they can.
• Concentrating urine is anatomy, not a setting. Medullary thickness, vasa recta dimensions and urea recycling all scale with it, so the water saved is paid for in energy and nitrogen handling.
• Fat returns about 1.13 grams of water per gram, against 0.60 for glucose, which is why a camel hump is a water store and not a canteen.
• A kangaroo rat never drinks because it manufactures water from dry seeds, and it trades water against energy rather than optimizing either one.
• More than 39 species in 24 genera collect water from air through their skin, using six distinct mechanisms, and a thorny devil's skin fills to 3.19 percent of body mass.
• The Namib beetle textbook story is wrong. The beetles that fog-bask have smooth wing cases, not bumpy ones.
• Sandgrouse are not an example of surviving without water. They fly up to 30 kilometers to fetch it and carry it home in a feather.
• No desert animal avoids sweating, and most large ones would rather travel than wait, because the cost of crossing ground falls as animals get bigger.

Frequently Asked Questions

Do desert animals never drink?

Some genuinely do not. A kangaroo rat lives on seeds and makes almost all of its water internally, so it never needs to find any.

Many others drink, just rarely. Camels can go roughly two weeks between drinks, and when they do they take enough to matter and then spend days excreting the excess.

So "survives without water" covers two quite different lives. One animal is a closed system. The other is a commuter.

Where does a desert animal get water when there is no rain?

From more places than most lists suggest. Dew and fog, the water inside grasses and succulents, and the water inside whatever prey it eats.

Arabian oryx never drink standing water. They get essentially all of theirs as preformed water from the grasses they graze.

Is it true that desert animals do not sweat?

No, and it is the most common error in popular writing on this. Many desert animals sweat, and human beings who live in deserts are among the best sweaters on record.

What desert-adapted animals do is start sweating earlier and produce less for the same load.

Many small mammals cannot sweat at all, so they vent by panting or by spreading saliva on their skin.

Why do desert animals come out at night?

Because night is when heat can leave for free. Once the air is cooler than the animal, heat moves out through radiation and convection, and neither route uses water.

Does a camel hump actually store water?

No, and this is worth correcting because the number sticks. The hump stores fat.

Oxidizing that fat produces about 1.13 grams of water per gram, against 0.60 grams from glucose. So a hump is an excellent water store in the only sense that matters: burning it generates water, and lots of energy besides.

What happens to a desert animal when it rains?

Most of them drink within hours. Desert animals are not adapted to go without indefinitely; they are adapted to survive long dry spells and then take full advantage of a short wet one.

Key references
• Proc R Soc B 1981, desaturation of exhaled air in camels, 211(1184):305-319 -- exhaling cooler and drier air, a saving of about 60 percent
• Proc R Soc B 1981, respiratory water loss in camels, 211(1184):291-303 -- body temperature swinging up to 7 C, and 0.06 to 1.2 g of water a minute
• J Exp Biol 2003, heterothermy and the water economy of free-living Arabian oryx, 206(9):1471-1478 -- 4.1 C of daily body temperature swing in summer
• J Comp Physiol B 2010, does water limitation drive heterothermy in oryx, 180(7):1111-1119 -- amplitude rises to 5.0 C while the mean barely moves
• J Exp Biol 2012, selective brain cooling in Arabian oryx, 215(22):3917-3924 -- the brain held 0.24 C below carotid blood, and more so than in gemsbok
• J Exp Biol 2016, evaporative cooling capacity in Burchell's sandgrouse, 219(14):2137-2144 -- body temperature up to 43.6 C before panting starts
• J R Soc Interface 2023, water-holding feathers of Namaqua sandgrouse, 20(201):20220878 -- nesting 30 km from water and flying it home in a feather
• Front Zool 2010, fog-basking behavior and water collection efficiency in Namib darkling beetles, 7:23 -- the beetles that fog-bask have smooth backs
• PNAS Nexus 2024, geometry for low-inertia aerosol capture in fog-basking beetles, 3(2):pgae077 -- impaction and drainage, not a funnel
• R Soc Open Sci 2017, adsorption and movement of water by the skin of the thorny devil, 4(9):170591 -- 5.76 microlitres per square centimeter
• J Exp Biol 2016, cutaneous water collection by the thorny devil, 219(21):3473-3479 -- filling the capillary system costs 3.19 percent of body mass
• J Exp Biol 2018, passive water collection with the integument, 221(Pt 10) -- 39 species in 24 genera, and six distinct mechanisms
• Science 2014, sidewinding with minimal slip, 346(6206):224-229 -- contact length INCREASES as a sandy slope steepens
• Biol Open 2023, locomotor kinematics of the sidewinder on sand versus vinyl, 12(11) -- lifting about 40 percent higher with a shorter body wave
• Physiol Biochem Zool 2003, Merriam's kangaroo rats select temperatures that conserve energy rather than water, 76(4):522-532 -- a trade, not a free win
• Biol Bull 2015, aquaporins in desert rodent physiology, 229(1):120-128 -- urine nearly three times as concentrated as the laboratory rat
• Acta Anat 1977, kidneys and vasa recta in relation to urine concentrating capacity, 98(4):456-468 -- 21 species, and the medulla does the work
• Comp Biochem Physiol A 2001, water conservation in the South American desert mouse opossum, 130(2):323-330 -- 9015 mOsm/L, the highest recorded for a marsupial
• Biol Rev 1998, urinary and cloacal bladders in chelonian water economy, 73(4):347-366 -- a reservoir water is reabsorbed from, proposed in 1799
• Cell Biol Int 2005, osmotic and diffusive properties of intracellular water in camel red cells, 29(9):731-736 -- 65 percent bound water against 20
• J Appl Physiol 1984, tritiated water metabolism during dehydration and rehydration in the camel, 56(1):217-220 -- absorbed within about four hours
• Front Vet Sci 2023, long-term dehydration in the dromedary camel, 10:1236425 -- body temperature raised to cut evaporative cooling
• BMC Vet Res 2020, long-term dehydration and the camel kidney, 16(1):458 -- tolerance has a cost, in inflammation and oxidative stress
• Curr Zool 2025, rain-harvesting behavior in free-ranging prairie rattlesnakes, 71(1):1-13 -- 72 events in 94 snakes
• J Exp Biol 2001, seasonal variation in energy expenditure and water flux in the Arabian oryx, 204(13):2301-2311 -- living on preformed water in grass
• Comp Biochem Physiol A 2002, respiratory water loss in insects, 133(3):791-804 -- how much of it is respiratory is still argued over
• J Therm Biol 2020, evaporative water loss in seven species of fossorial rodents, 89:102564 -- a humid burrow is what closes the budget
• Ecol Evol Physiol 2024, cutaneous evaporative water loss in lizards changes immediately with temperature, 97(2):118-128 -- within seconds
• J Hum Ergol (Tokyo) 1995, maximal sweating rate in humans, 24(2):137-152 -- over 2000 g an hour after acclimatisation
• Clin Sports Med 1999, water and electrolyte requirements for exercise, 18(3):513-524 -- 2 percent of body weight as the usual ceiling
• Am J Hum Biol 2020, water turnover among human populations, 32(1):e23365 -- across mammals, turnover tracks body mass with r squared of 0.90
• Nature 2018, remarkable muscles and locomotion in desert wildebeest, 563(7731):393-396 -- moving at the right time beats sitting it out
• J Hum Evol 2020, dehydration and persistence hunting in Homo erectus, 138:102682 -- water, not heat, was the limiting factor
• Companion post: what waste chemistry costs in water
• Companion post: why excretory organs exist at all

Figures are from Wikimedia Commons, with the author and license named in each caption. Figures and values are from the cited papers.