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The cheetah is really fast, and the primary reason it has such little stamina is getting too hot. Ive looked into having more efficient metabolism to produce less body heat and I didnt get anywhere with it. Is it biologically possible through evolution, genetic engineering, or even artificial life to have the analog of an instant cold pack to increase the stamina of animals by selectively lowering their body heat? Urea for example mixed with water is endothermic and lowers the temperature of the water.

Any ideas on how an animal like the cheetah could increase stamina by limiting its body temperature? Please only mention ways of cooling down that is not already in use by animals on Earth. Thanks in advance.

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  • $\begingroup$ Why the limit of using a cooling down method that isn't in use by any other animal? $\endgroup$ – Trioxidane Jun 3 at 17:12
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    $\begingroup$ Because I like to write short stories that are unique, and if I write sci-fi I only write hard sci-fi. I can't just say "this animal runs fastest and has more stamina then any other" without a scientifically plausible reason. $\endgroup$ – Vladimir Silver Jun 3 at 19:44
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As you described, certain compounds endothermically dissolve in water.

You could have a network of tubes (similar to blood vessels) that can be cooled by dissolving urea or ammonium nitrate in the network, cooling the animal. Urea's main advantage is that it is already a biological waste product in humans and other animals, and it can easily be produced from ammonia and carbon dioxide.

Ammonium nitrate, while not produced via any common biological process, is also a powerful oxidizer, possibly providing an extended source of oxygen for your animal, allowing it to increase its stamina even further. Although these oxidation reactions are exothermic, they could replace the "usual" reactions that generate heat in the animal, allowing it to even possibly stop breathing briefly. The animal could "recharge" by filling up a specialized organ with AN synthesized from air and water, if your alien planet has similar air composition as ours.

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  • $\begingroup$ This is excellent thank you. I didnt even consider the oxidizing effects of ammonium nitrate. $\endgroup$ – Vladimir Silver Jun 3 at 17:07
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Blood fur

Cold packs can be a good way to cool down, but there's two downsides. Many cold packs start a chemical process that is hard to stop, meaning it'll continue until it's finished. The second is that it might cool down too fast, chilling the creature and reducing the muscles and brains effectiveness. This could even be dangerous.

You need a well controlled way to cool down. For that the cheetah can use blood fur.

Blood fur are tiny but tough hair follicles that have two hollow tubes inside them. They are connected to the blood vessels on the skin, allowing blood to flow to and from the hair follicles. In the skin each blood vessel to a follicle can be constricted individually, which is triggered by damage to the follicle. When it gets damaged it'll release a tiny hormone that shuts it down. In addition, the nervous system can autonomously change tiny regions in the skin on or off. This way the blood flow to the follicles is controlled, making sure blood only goes there when cooling is needed. It'll also allow only parts of the body to cool down, controlling how much heat is expelled. This os much like the sweating system of humans, only with blood through hairs.

Using blood in hairs will increase the surface area a thousandfold. As blood is the main transporter of heat, the closeness to the air inside a hair will allow heat exchange at a great level. Cooling down can be done at a very precise level, preventing over or undercooling. The fur can also become very thick for further protection, as cooling is now not a problem anymore.

In addition, when the cheetah attacks and starts using the blood fur to cool, it'll change to a blood red colour in places.

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  • $\begingroup$ Won't that make the cheetah (or equivalent) extremely vulnerable to blood loss? No need to penetrate the skin, damaging the hair would be really bad $\endgroup$ – KerrAvon2055 Jun 4 at 2:57
  • $\begingroup$ @KerrAvon2055 there is a danger, but I think it isn't as large as you might think. Each hair is meant to be quite durable, so it'll be difficult to damage a huge amount at once. The hairs you damage need to have blood running through at that moment. Each hair damaged will release a chemical that'll be noticed by the skin, shutting off all blood to the damaged hair(s). Each hair doesn't have a lot of blood running through it. If the damage to hair is so catastrophic it'll die from blood loss, it's justifiably a huge attack. Most creatures it'll hunt won't be able to do it I think. $\endgroup$ – Trioxidane Jun 4 at 4:37
  • $\begingroup$ This is a rather unique answer. I considered hydrophobic fur with sweat, where the sweat is actually pushed away from the skin by the fur, but I like this a lot better. Thanks! $\endgroup$ – Vladimir Silver Jun 4 at 21:34
  • $\begingroup$ ++ for plausible physiology! But I know you got the name "Bloodfur" from your D&D character who is an expatriate flind. $\endgroup$ – Willk Jun 5 at 17:36
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What desert animals sometime do, in order to not overheat, is to increase their base body temperature: since spontaneous heat exchange always go from the high temperature to the low temperature and is proportional to the temperature gradient, by increasing the term on their side on the equation they can lower the unwanted heat exchange.

What you want to do is getting rid of the larger amount of waste heat produced under effort.

Another way to increase the heat exchange is to use evaporation, if the organism can afford wasting some water and the atmosphere is not saturated with humidity. That's what we human do with sweating.

Alternatively, or jointly, it is impossible to increase the surface temperature by increasing the blood flow in the surface layers. That's also why our skin becomes more red when we are under exercise.

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