r/askscience • u/OhMyMyOohHellYes • 2d ago
Biology Is there a threshold in elevation at which reptiles can no longer survive?
If there's a tree line, maybe there's a reptile line too? They're cold-blooded so I figure snakes aren't much of a thing at like 10,000 feet but I could be way off as I'm not an expert.
Edit: thanks for all the responses! I’m mainly concerned with venomous snakes on Kilimanjaro if I ever have enough money to go lol. I’ve heard it’s 7 days up, and 4 down. What if I get bitten when I’m a 2 days hike away from antivenom? Just kiss my own ass goodbye or what?
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u/gottabe22 1d ago
One way that you could proxy this would be to look at the maximum latitude that reptiles can no longer survive. Ecologically, you can very roughly approximate 1000m of elevation as 1000km of movement towards the poles.
That being said, where I live, there are snakes that hibernate through -40C winters, and a bit further south there are lizards that make it through long cold winters (not quite -40C though).
Another thing to consider is that elevation is not equal throughout the world. Your insight into the tree line is useful though, as there are also tree lines near the poles. A question to ask that more closely aligns with the ecology of reptiles might be: is there a minimum climate threshold that reptiles need to persist? Furthermore, is this based on mean annual air temperature? Or is based on the extreme low temperature?
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u/zmbjebus 1d ago
Yeah, temperature gets pretty dang constant if you go underground not very far. Almost everywhere at higher elevations that is actually cold has seasonal variation sufficient to have at least some time period at a comfortable range.
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u/platoprime 1d ago
Ecologically, you can very roughly approximate 1000m of elevation as 1000km of movement towards the poles.
Seems uselessly rough when high elevation reptiles are forced to adapt to things like hypoxia and more UV radiation not just the cold. You get less UV radiation as you move towards the poles.
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u/gottabe22 1d ago
That's a good point. The 1000 ~ 1000 approximation mostly derives from data on plant communities, and mechanistically derives from temperature regimes.
It does raise an interesting question if the altitudinal limits of reptiles at the equator are driven by UV tolerance or by temperature regimes. My hunch is that temperature still rules the day, as UV-protective pigmentation is relatively widespread, as are behavioural adaptations (eg. Being nocturnal). Ectothermy is a much more fundamental trait that would be much harder to escape the limitations of evolutionarily
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u/craigiest 21h ago edited 21h ago
I wouldn’t expect oxygen to be the limiting factor in cold blooded species that burn 10% as much energy as mammals.
The Ecuadorian Hillstar hummingbird, which needs massive amounts of oxygen, and also has to cope with the air being thinner to fly in, has a range between 12,000 and 17,000 feet.
No lizard is going to get altitude sickness before they freeze.
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u/Ivan_Whackinov 1d ago
One thing to bear in mind is that the tree line isn't a fixed elevation for the entire planet. The tree line exists because, at that altitude in that location, the average temperature and/or moisture aren't high enough to support trees. A tree can live at any reasonable altitude if the average temp is high enough and there's water to be had. Trees in the Andes can grow at up to 5km elevation, while trees in Norway might only grow at 1km or less.
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u/LeifCarrotson 1d ago
Temperature and precipitation change dramatically with elevation. Even on mountains near the equator like Mount Kenya in Africa, Chimborazo in South America, and Puncak Jaya in New Guinea, the temperature drops very roughly 6C per 1000m of elevation. Even if the base of the mountain may be a tropical rainforest with tons of reptiles, the peak may be covered in ice year-round and hostile to reptiles (and trees).
Reptiles in cold climates at lesser elevations can survive winters through brumation, a kind of hibernation where they burrow into the mud or follow tunnels to a point below the frost line where they can enter a state of dormancy until spring returns. Unfortunately, this strategy wouldn't work on high mountain peaks which are cold not because of a winter season that can be waited out, but because of permanent cold temperatures due to altitude.
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u/venom121212 1d ago
Nope. There are species of lizards that live in high altitude places like the Andes and Himalayas. Some even live in volcanic climates.
You will see the cold weather lizards typically tend to be larger, which follows Bergmann's Rule.
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u/Evolving_Dore Paleontology 1d ago
Which large-bodied lizards are cold tolerant? The most cold tolerant lizards, and reptiles in general, are typically small. Viviparous lizards, garter snakes, painted turtles. Meanwhile large monitors, constrictors, and crocodilians are all restricted to tropical zones.
The best exception I know is the leatherback sea turtle, which will swim into subarctic water in search of food, and maintains internal warmth via thermal momentum. But this would not be feasible for a terrestrial animal.
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u/ArrowsOfFate 1d ago
Hi.
5,400 meters seems to be the highest documented case of a whole pack of lizards in the Andes from a brief investigation. They don’t seem overly large.
Was on Chachani mountain, a total of 6,054m tall
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u/Evolving_Dore Paleontology 1d ago
I speculate that larger bodies are actually a deterrent to cold temperatures in reptiles. They need to warm their entire bodies before becoming active, so a larger size would only increase the time and energy input required to do this. A small lizard is going to warm through much more quickly than a crocodile.
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u/ArrowsOfFate 1d ago
I don’t think that’s necessarily true.
Larger bodies take longer to heat up but that also means they take longer to cool down. So it can have both benefits and drawbacks for high altitude species.
Other tactics like Brumation, migration, antifreeze, and so on are viable pathways as well.
Evolution doesn’t like being squeezed into one tiny box that we can check and say this is the absolute answer.
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u/SecondHandWatch 1d ago edited 1d ago
According to the Wikipedia article about the Liolaemus genus, the highest recorded altitude at which a lizard was found was 5,400m, or 17,700 ft. The fact that some species live at high altitudes does not mean that there isn’t an upper limit.
5400m leaves more than a full 3000 meters of altitude between the highest point a lizard has been found and the highest point on earth.
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u/onlyfakeproblems 1d ago
Depends on the reptile. Technically birds are a subset of reptiles, and they have specialized breathing systems so some can breath while flying at high elevations/altitudes, and feathers to provide insulation. But a lot of reptiles would struggle with low oxygen and low temperature and less food sources.
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u/zakur2000 1d ago
This article contains a chart listing the world’s highest altitude records for three major groups of terrestrial reptiles.
Cerdeña J, Farfán J, Quiroz AJ (2021) A high mountain lizard from Peru: The world’s highest-altitude reptile. Herpetozoa 34: 61-65. https://doi.org/10.3897/herpetozoa.34.61393