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Alithographica — Inktober Day 4: Seasonal x Freeze
#arctic #arcticfox #fox #freeze #lineart #micronpen #nature #sciart #seasonal #inktober #inktoberday4 #inktober2019
Published: 2019-11-04 17:03:11 +0000 UTC; Views: 352; Favourites: 60; Downloads: 3
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Inktober day 4, sciart x official prompts: Seasonal x freeze.
“Who are you?” “I’m you but it’s fucking cold outside.”
Bite-sized science fact: Arctic foxes change between their famous dense white winter coat and a darker, thinner summer coat. The summer coat’s lower critical temperature (the temp at which the animal needs to increase its metabolism to stay warm) is 5°C (41°F), but its winter coat keeps it protected until -7°C (19°F). It does not start to shiver until -70°C (-94°F).
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Comments: 5
"It does not start to shiver until -70 °C (-94 °F)." I seriously wonder (1) if that is actually true, and (2) if it is, how and why that insulative ability developed. The study that reported that (written in 1950) had a very small sample size, and also reported a lower critical temperature of ≤-40 °C, massively lower than that newer value, which paper critiqued the poor instrumentation of the earlier study. Also, almost nowhere in their natural range due to temperatures ever get that cold, and I highly doubt they often make voyages through the only areas of the Northern Hemisphere that record such temperatures (the high slopes of Denali and possibly Mount Logan, an isolated British Columbian valley between Steamboat Mountain and Summit Lake, and possibly some uninhabited valleys in Yakutia.) This means a lack of selective pressure. It also means their insulation would be overkill for their environment, much more so than many other species (potentially indirectly reducing reproductive fitness)—for example, modern humans are currently thought to have originated on the plateaus of Botswana, which occasionally, when the winter nights are clear and the Southern wind blows, record frost, and can in exceptional instances get below -5 °C. There are very few humans who would not start shivering naked at 0 °C.
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I'm super late to replying to this, but thank you for the extra information! I don't often dig directly into the methodology of a paper to make sure it's sound (and I don't always have the knowledge to make that assessment) so I appreciate when someone shares their knowledge with me.
(In a general sense of "why such dramatic insulation would develop" though—shivering costs a lot of energy because your muscles are constantly contracting. It keeps you warm, but it isn't sustainable. If you could rely on pure insulation you could save resources, which is critical in the dead of winter...but like you mentioned, that cost-benefit fitness balance does tip back at a certain point.)
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Amazing - do you know how warm it can stand with its summer coat?
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Nope, sorry! But a quick search says the average arctic summer temp is ~40F so certainly at least that.
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Good to know - thanks! (Yeah -94°F - I can't even imagine!)
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