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I have a race of lizard people who live in an arctic climate (tundra/taiga). I just realized that this might be a problem, assuming they're cold-blooded, and I refuse to change the fact that they're lizards, because the language I've designed for them is all about reptilian hissing.

I could rig up some kind of elemental magic thing, which wouldn't be going too much out of my way, but before I do: in a not-very-advanced (medieval-ish) fantasy world, are there any non-magical ways for them to survive?

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    $\begingroup$ just becasue they are reptiles does not mean they have to be cold blooded, there are plenty of warmblooded lizard like things in history. $\endgroup$ – John May 3 '17 at 0:46
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    $\begingroup$ Lots of good answers. I'll add: geothermal hot springs! $\endgroup$ – Grimm The Opiner May 3 '17 at 7:15
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    $\begingroup$ @GrimmTheOpiner why don't you post that as an answer instead of a comment? $\endgroup$ – PJvG May 3 '17 at 13:14
  • $\begingroup$ It's more a useful addition to an existing answer than an answer in itself. $\endgroup$ – Grimm The Opiner May 3 '17 at 13:37
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    $\begingroup$ lizards squeak youtu.be/prU6lbRjabM?t=1m38s and geese hiss youtu.be/ygTa1mOTSo0?t=50s so why would vocalisation make a difference here? $\endgroup$ – Pete Kirkham May 3 '17 at 16:04

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There are a number of options.

Firstly, the distinction between 'cold-' or 'warm-blooded' is, primarily, a set of internal thermoregulatory differences that is a subset of normal homeostasis. An outsider wouldn't see them at face value. Thermoregulation isn't just two separate bins of either 'ectothermy' or 'endothermy'. A further distinction can be made between homeotherms which maintain a constant internal body temperature within a narrow range of temperatures, and poikilotherms whose internal temperatures vary significantly. Dinosaurs likely had a thermoregulatory strategy in between both extremes, called mesothermy. The primary evidence for which has been extrapolated from their intermediate growth rates.

Ectotherms use external sources to regulate their body temperatures and are colloquially referred to as "cold-blooded" even though their body temperatures often stay within the same temperature ranges as warm-blooded animals. Endotherms create most of their heat via metabolic processes, and many have a larger number of mitochondria per cell than ectotherms (which enables them to generate heat by increasing the rate at which they metabolize fats and sugars). However, endothermic animals must sustain their higher metabolism by eating more food more often. For example, an endothermic mouse must consume food every day to sustain high its metabolism, while an ectothermic snake may only eat once a month because its metabolism is much lower.

You could:

  • Give them a natural antifreeze glycoprotein circulating in their bloodstream, like some fish.

  • Channel your inner feathered dinosaur and give them all a thick coat of downy feathers.

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  • Give them all a thick insulating layer of fat, and/or large brown fat deposits (a specialized type of adipose tissue that specializes in generating heat).

  • Make them huge. Many animals found in colder environments are proportionally larger than their more temperate cousins (Bergmann's rule), no doubt due to lessened heat dissipation due to the Square-Cube law.

  • They eat far more than you would think a reptile would, and their metabolisms are specialized for using this fuel (more mitochondria etc) to generate energy.

  • Make them huddle together in huge packs

enter image description here

  • Allow them to make clothes if they're intelligent and dextrous enough. Their ancestors would likely have been temperate animals that didn't 'need' clothes to survive.
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Fire

Your Lizards could live/have settled in an area of naturally occurring methane seeps. There could be a large deposit that is slowly seeping out nad had been lit on fire like Darvaza Crater. Also, Artic Climates are known to contribute to atmospheric methane so these seeps may be tapped as well.

Also equally viable is an area with volcanic activity like Iceland, plenty of hot vents and hydrothermal springs.

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Have them originally evolve somewhere else and move there. After all humans evolved for the savannah and use technology to live in the arctic.

If they are intelligent they should be using fire and clothing anyway, and tech can make up for a lot of shortcomings. maybe they live in the arctic NOW because other fast breeding races pushed them out of more hospitable areas, like how we used to think humans had done to Neanderthals.

There is also no reason your lizard people cannot be endothermic there are plenty of lizard looking things in history that were endothermic, archosaurs and early mammals are good examples.

If you need them to be ectotherms then you have some problems. They are going to be inactive most of the year and hibernate the rest, this is rather unlikely for an intelligent creature, brains eat a lot of calories (1/3 of all our calories) and need them all the time and an ectoderm may not be able to support this.

Creatures with a slow metabolism are unlikely to evolve human like intelligence, they just can't spare the calories.

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  • $\begingroup$ The ancient Greeks believed the brain was an organ that cooled the blood. Perhaps the reverse might happen for a lizard people. With the energy consumption necessary for an intelligent brain warms their blood and then the rest of their bodies. Humans evolved in tropical Africa & went on to colonize the rest of the planet. So why not sapient lizards? Agree about clothing & fire. Plus one. $\endgroup$ – a4android May 3 '17 at 3:42
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    $\begingroup$ in which case they are endotherms, inefficient endotherms but endotherms. $\endgroup$ – John May 3 '17 at 20:23
  • $\begingroup$ Quite so. Poilkilotherms with an overheated organ. That was more of a biologist joke than a serious suggestion. Although I should tread carefully, evolution has a bad habit of being surprising when you least expect it. $\endgroup$ – a4android May 4 '17 at 7:10
  • $\begingroup$ the big inefficiency is the brain can't burn fat, so have your heat generator also be incapable of using the most efficient form of energy storage would be weird, but not impossible as you said. the difference between the real world and fiction, fiction has to make sense. $\endgroup$ – John May 4 '17 at 13:55
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There are a wide variety of cold-blooded creatures in Alaska. For one, there's Wood Frogs (though more associate with sub-arctic taiga aka forests), which hibernate all winter. There are also insects that either use natural antifreeze, supercooling or else hibernate in a free-dried state.
Finally, you can just have them spend time in salt water or in the water that lies under ice layers, that's where the fish stay all winter.

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Exothermic bacteria

Perhaps your race isn't inherently endothermic, but they utilize a strain of bacteria that produce heat as a metabolic byproduct to survive in cold environments. These bacteria would be consumed and take up residence in the digestive systems of your lizard people, where they would draw energy from the food their hosts consumed and produce heat.

If they aren't self-sustaining in terms of their population inside of a lizard person, they'd have to be consumed on a regular basis. Your lizard people would culture them in some form of substrate, and then prepare them in some sort of food or potion for consumption. They'd remain warm and effectively endothermic so long as they had access to a steady supply of their bacterial warming potions.

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Hibernation and reproductive adaptations

There are reptiles living in Arctic regions in reality. Check out the ranges of the viviparous lizard and European adder, for example. They survive by simply hibernating through the winter. They have pretty good tolerance of cold temperatures (sometimes you might spot an adder in the snow in the spring) though they still have to wait until summer to really be active. Typically they give birth to live young since eggs might have trouble staying warm otherwise.

So, nothing beyond what already exists is strictly needed for survival. However, since these are intelligent beings, they might be capable of functioning in the cold much better - they can use insulation, artificial heat sources, etc. Hibernation would likely still be a big deal in their society, though its importance might wane as technology develops.

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Enormous size

By the square cube law volume is going to increase faster than surface area. This means that heat capacity of a body increases by the cube of one dimension, while the surface area increases by the square. Once you scale this up large enough, a creature can shrug off the cold pretty well.

Digging in and hibernation

Cold weather climates have a permafrost layer in the soil which is, as you may guess, permanently frozen. The temperature down here never drops below around -5 C. If you creature is already enormous, when the darkest parts of winter arrive (maybe the sun goes away, as above the arctic circle), it could dig itself into the permafrost and hibernate to reduce heat loss until the spring arrives.

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Related to ckersch’s idea of bacteria that needs to be consumed, you could have a digestive process like that of the Brontosaurus: similar to a modern-day Rumen, a large fermentation vat generates a great deal of heat as it processes the rough wood that was swallowed.

Even if much smaller than the great sauropods, having this internal heat source means that warm clothing will now work.

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Does it have to be carbon based life? Borrowing from a fanfic/crossover as well as canon with a world that has trolls, a silica-based life form could/would be more efficient at colder temps.

Or just go all exo-lifeform - "it isn't what we'd call warm-blooded, and it ain't what we'd call cold-blooded... we don't know what to call it, and to the 'zards its just the way they are - they have no frame of reference"

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There are plenty of chemical reactions that give off heat:

Perhaps the lizard people inadvertently discovered some such process, even if the scientific explanation for what happens isn't understood. I imagine them bundling up and then grabbing some kind of water skin and the related reagents before heading outside. Similar to pepsi+mentos -- though hopefully less violent -- the reagents don't need to take up much space at all.

This also opens up other plot points, e.g., "but the reaction also produced a terrible smell" or maybe "but inhaling too many fumes caused you to become intoxicated" etc.

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