How do animals "know" when to get a winter-coat?

[Realitycrash]

I've been searching the interwebz, but I can't find the answer I'm looking for, so maybe one of you guys know; How does an animal "know" when they need to grow a winter-coat?
How do they know that they need thicker fur, and how do they know that they need that special kind of winter-camouflage that comes with having a white coat during the winter, but not during the summer?
(And by "know" I mean how does the body know to stimulate growth or change in the hair-production)

 

[Quaxar]

<url=http://www.enature.com/articles/detail.asp?storyID=552>This is a nice article. Also check out the links at the bottom.
Hope I didn't just do your homework...


Changing Wardrobes
The seasonal molt, when the coat of an animal changes color, is a photoperiodic phenomenon governed by lengthening or shortening periods of daylight. As daylight diminishes in autumn, many northern animals will begin to grow thicker and lighter-colored coats that eventually become completely white. Likewise, as the days lengthen in spring, the winter coat is gradually shed (in mammals) or molted (in birds) and replaced with a darker color.

As a whole, which animals change to a white coat in winter and which do not seems to be determined mainly by the climate and latitude of the area in which they live. However, studies of the Long-tailed Weasel suggest that among individuals, the propensity to molt to a white winter coat may be influenced by other factors. In the northern part of their range, most Long-tailed Weasels turn white in winter; in the central part some individuals molt to white while others remain brown all year; and in the southernmost part no individuals change color for winter. But if a northern weasel is captured and taken south, it will still turn white in winter, no matter whether snow falls or not!

 

[Realitycrash]

<url=http://www.enature.com/articles/detail.asp?storyID=552>This is a nice article. Also check out the links at the bottom.
Hope I didn't just do your homework...


Changing Wardrobes
The seasonal molt, when the coat of an animal changes color, is a photoperiodic phenomenon governed by lengthening or shortening periods of daylight. As daylight diminishes in autumn, many northern animals will begin to grow thicker and lighter-colored coats that eventually become completely white. Likewise, as the days lengthen in spring, the winter coat is gradually shed (in mammals) or molted (in birds) and replaced with a darker color.

As a whole, which animals change to a white coat in winter and which do not seems to be determined mainly by the climate and latitude of the area in which they live. However, studies of the Long-tailed Weasel suggest that among individuals, the propensity to molt to a white winter coat may be influenced by other factors. In the northern part of their range, most Long-tailed Weasels turn white in winter; in the central part some individuals molt to white while others remain brown all year; and in the southernmost part no individuals change color for winter. But if a northern weasel is captured and taken south, it will still turn white in winter, no matter whether snow falls or not!

Yes, my sister linked me the same article (and I'm 26, I don't have any homework!), but the question isn't answered. Why does the northern weasel turn white even at southen latitudes, where there is in fact more light amd warmth than there would be during the summer in northern latitudes?

 

[Suicidejim]

As soon as they see the sales being advertised.

 

[Quaxar]

<url=http://www.enature.com/articles/detail.asp?storyID=552>This is a nice article. Also check out the links at the bottom.
Hope I didn't just do your homework...


Changing Wardrobes
The seasonal molt, when the coat of an animal changes color, is a photoperiodic phenomenon governed by lengthening or shortening periods of daylight. As daylight diminishes in autumn, many northern animals will begin to grow thicker and lighter-colored coats that eventually become completely white. Likewise, as the days lengthen in spring, the winter coat is gradually shed (in mammals) or molted (in birds) and replaced with a darker color.

As a whole, which animals change to a white coat in winter and which do not seems to be determined mainly by the climate and latitude of the area in which they live. However, studies of the Long-tailed Weasel suggest that among individuals, the propensity to molt to a white winter coat may be influenced by other factors. In the northern part of their range, most Long-tailed Weasels turn white in winter; in the central part some individuals molt to white while others remain brown all year; and in the southernmost part no individuals change color for winter. But if a northern weasel is captured and taken south, it will still turn white in winter, no matter whether snow falls or not!

Yes, my sister linked me the same article (and I'm 26, I don't have any homework!), but the question isn't answered. Why does the northern weasel turn white even at southen latitudes, where there is in fact more light amd warmth than there would be during the summer in northern latitudes?

Well, although I do study biology I can't give you a certain answer at the moment. I can give you guesses though.
As stated in the article, shorter daylight periods may be one cause since less daylight means less warmth and as such would mean that getting thicker and possibly differently coloured fur is a favourable trait.
I don't think it's too absurd to say that dropping of average day temperatures could be possibly triggers. It might also help to have a look at triggering reasons for hibernation as it's merely a different approach to the changing climate of the winter months. Hibernating animals have something in their blood called <url=http://en.wikipedia.org/wiki/Hibernation_induction_trigger#Hibernation_induction_trigger>HIT (hibernation induction trigger), so maybe change of fur is started by similar triggers.

And the weasel part of the article is kind of vague as there's not really much information, I can "take it south" 5 kms and I'm pretty sure it'll still change into its winter coat. And of course there's a chance its annual rhythm isn't even related to the daylight directly, maybe it has its own internal calendar.

 

[DoPo]

I don't think it's too absurd to say that dropping of average day temperatures could be possibly triggers.

Now, I'm far away from the biology field, but I do remember that when I did that in school, there was a bit on Himalayan rabbits - they are normally...white I think, and their winter fur is black, or at least dark in colour. Or vice versa, point being, the two are different and distinct. You can take one and if you keep an ice pack to its skin, the rabbit would actually change just that patch of fur. So I believe you may be correct.

EDIT: Actually I googled it, and I was surprised I did remember it. It's from, like 7-8 years ago when I did that in school. Here is what I talked about

And here [http://regentsprep.org/regents/biology/2011%20Web%20Pages/Genetics-%20DNA-RNA%20page.htm] is the page that image was on.

 

[Esotera]

Fur colour is generally changed by sunlight, large quantities of it will tend to break down the pigments (which is why humans get blonder hair in summer).

I'm not too certain on fur, but I'd say that temperature, the amount of daylight, and possibly diet are the regulators for how long a coat is.

 

[Quaxar]

I don't think it's too absurd to say that dropping of average day temperatures could be possibly triggers.

Now, I'm far away from the biology field, but I do remember that when I did that in school, there was a bit on Himalayan rabbits - they are normally...white I think, and their winter fur is black, or at least dark in colour. Or vice versa, point being, the two are different and distinct. You can take one and if you keep an ice pack to its skin, the rabbit would actually change just that patch of fur. So I believe you may be correct.

EDIT: Actually I googled it, and I was surprised I did remember it. It's from, like 7-8 years ago when I did that in school. Here is what I talked about

And here [http://regentsprep.org/regents/biology/2011%20Web%20Pages/Genetics-%20DNA-RNA%20page.htm] is the page that image was on.

Neat, I only knew that effect on siam cats.
<spoiler=because cat pics are always relevant and maybe someone doesn't know what a siamese cat looks like>http://petcaregt.com/blog/wp-content/uploads/2008/11/siamese-cat1.jpg
They actually have this black face, paw and tail fur because that are areas of their body which are cooler and in theory you could turn the whole cat black temporarily like your rabbit.

 

[DoPo]

Neat, I only knew that effect on siam cats.

Yay, I know something more than a biology student! I feel so proud with myself now, I'll go and tell mom

They actually have this black face, paw and tail fur because that are areas of their body which are cooler and in theory you could turn the whole cat black temporarily like your rabbit.

So, we just need to leave them in the fridge, yes? Seems straightforward enough. I assume we just need to remove the giraffe or the elephant first.

 

[Kinguendo]

Know? Its not a concious decision. Its not like they pop-out of the doors go "BRRR! Tis cold... what say you wife?" to which she replies "Verily Husband, tis cold indeed." and then they go to the shops to buy coats.

 

[deathzero021]

hmm.. maybe when it gets cold? they say "wow it's cold! i could use some more fur!" and thus grow their hair out long.

 

[FEichinger]

hmm.. maybe when it gets cold? they say "wow it's cold! i could use some more fur!" and thus grow their hair out long.

That sounds neat in theory. In practice, though, "sensing temperature" is a complicated beast - also: The question quite directly included that the animals in question don't simply sense "it's cold" but "it's environmentally getting colder than about a month ago", which turns it into an even more complicated beast.

 

[deathzero021]

hmm.. maybe when it gets cold? they say "wow it's cold! i could use some more fur!" and thus grow their hair out long.

That sounds neat in theory. In practice, though, "sensing temperature" is a complicated beast - also: The question quite directly included that the animals in question don't simply sense "it's cold" but "it's environmentally getting colder than about a month ago", which turns it into an even more complicated beast.

i dont understand why feeling cold is a "complicated" thing. I touch some ice, it feels cold. my cat knows when something is cold, it doesnt like it. it reacts to it instantly. i don't think animals are as senseless and stupid as people think they are. they've been surviving for longer than we have anyway. they must know a few things.

 

[disgruntledgamer]

hmm.. maybe when it gets cold? they say "wow it's cold! i could use some more fur!" and thus grow their hair out long.

No it's shorter days also for coat colour change.

 

[RedDeadFred]

I don't think it's too absurd to say that dropping of average day temperatures could be possibly triggers.

Now, I'm far away from the biology field, but I do remember that when I did that in school, there was a bit on Himalayan rabbits - they are normally...white I think, and their winter fur is black, or at least dark in colour. Or vice versa, point being, the two are different and distinct. You can take one and if you keep an ice pack to its skin, the rabbit would actually change just that patch of fur. So I believe you may be correct.

EDIT: Actually I googled it, and I was surprised I did remember it. It's from, like 7-8 years ago when I did that in school. Here is what I talked about

And here [http://regentsprep.org/regents/biology/2011%20Web%20Pages/Genetics-%20DNA-RNA%20page.htm] is the page that image was on.

Wow. That is actually really cool. Science FTW!

Also, props to remembering something from biology class 7 years ago. My last biology class wasn't even 4 years ago and I've already forgotten everything I learned.

 

[FEichinger]

hmm.. maybe when it gets cold? they say "wow it's cold! i could use some more fur!" and thus grow their hair out long.

That sounds neat in theory. In practice, though, "sensing temperature" is a complicated beast - also: The question quite directly included that the animals in question don't simply sense "it's cold" but "it's environmentally getting colder than about a month ago", which turns it into an even more complicated beast.

i dont understand why feeling cold is a "complicated" thing. I touch some ice, it feels cold. my cat knows when something is cold, it doesnt like it. it reacts to it instantly. i don't think animals are as senseless and stupid as people think they are. they've been surviving for longer than we have anyway. they must know a few things.

It's not about momentarily knowing "it's cold". It's about knowing "the current average temperature is below X, where X is the temperature at which I should probably get some warmer clothes on".
Humans found the need to have people tell them how cold it is, and depict that with numbers. Seriously, humans are much more stupid than most animals when it comes to this.
The biology behind sensing warmth is very interesting - and very complicated. And, again: Humans aren't nearly as capable as animals when it comes to sensing these nuances. Most of us usually put on warmer clothing either a) when a fellow human tells them (Today: 5°C!), or b) when their experience tells them (It's October, dipshit!) or c) when their body tells them (I c-c-c-an't t-t-t-alk ... t-t-t-oo c-c-old).

Humans, however, can't just magically induce their skin, like "it's getting cold, grow some more hair or ... something, come on, do something!". We only have a physical reaction of our muscles - not anything deep on biology. Various animals, on the other hand, do have some way of doing that - darker fur, thicker fur, all that shizzle. The question is: What triggers it - when do they start doing that?

 

[Hammartroll]

<url=http://www.enature.com/articles/detail.asp?storyID=552>This is a nice article. Also check out the links at the bottom.
Hope I didn't just do your homework...


Changing Wardrobes
The seasonal molt, when the coat of an animal changes color, is a photoperiodic phenomenon governed by lengthening or shortening periods of daylight. As daylight diminishes in autumn, many northern animals will begin to grow thicker and lighter-colored coats that eventually become completely white. Likewise, as the days lengthen in spring, the winter coat is gradually shed (in mammals) or molted (in birds) and replaced with a darker color.

As a whole, which animals change to a white coat in winter and which do not seems to be determined mainly by the climate and latitude of the area in which they live. However, studies of the Long-tailed Weasel suggest that among individuals, the propensity to molt to a white winter coat may be influenced by other factors. In the northern part of their range, most Long-tailed Weasels turn white in winter; in the central part some individuals molt to white while others remain brown all year; and in the southernmost part no individuals change color for winter. But if a northern weasel is captured and taken south, it will still turn white in winter, no matter whether snow falls or not!

Genetics intrigue me. What I'd be curious to know is if the northern weasel would continue to change to white in the winter, while living in the south it's whole life or if it would eventually "realize" that changing white was pointless (or possibly bad because being white would make you stand out) and eventually "switch off" it's color changing genes; since we have recently been discovering that the "junk DNA" actually acts like a switch board, giving animals more variety in their genes then they immediately seem to have. Also they should see that if the northern weasel never stops turning white, that his future generations also continue turning white; like they should breed two northern weasels in the south. To me it would seem like common sense for an animal to be able to alter such genes in accordance to what environment it's currently in.

 

[Hammartroll]

As a response to the OP, I think they "know" simply because outside signals tell their bodies to react in a certain way. For example when humans get a tan, their skin doesn't turn dark because it's burning, or something like that. What happens is your skin cells sense the photons bombarding them using sensors on the outside of their membrane, which sends a signal into your cells to start producing darker colored pigments as a defensive mechanism so that you don't ACTUALLY burn.

So using that example, I would assume that animals are able to pick up something from the environment (or perhaps they've developed a biological clock) that causes a chain reaction in their cells to start changing the pigment of their fur.

 

[Quaxar]

<url=http://www.enature.com/articles/detail.asp?storyID=552>This is a nice article. Also check out the links at the bottom.
Hope I didn't just do your homework...


Changing Wardrobes
The seasonal molt, when the coat of an animal changes color, is a photoperiodic phenomenon governed by lengthening or shortening periods of daylight. As daylight diminishes in autumn, many northern animals will begin to grow thicker and lighter-colored coats that eventually become completely white. Likewise, as the days lengthen in spring, the winter coat is gradually shed (in mammals) or molted (in birds) and replaced with a darker color.

As a whole, which animals change to a white coat in winter and which do not seems to be determined mainly by the climate and latitude of the area in which they live. However, studies of the Long-tailed Weasel suggest that among individuals, the propensity to molt to a white winter coat may be influenced by other factors. In the northern part of their range, most Long-tailed Weasels turn white in winter; in the central part some individuals molt to white while others remain brown all year; and in the southernmost part no individuals change color for winter. But if a northern weasel is captured and taken south, it will still turn white in winter, no matter whether snow falls or not!

Genetics intrigue me. What I'd be curious to know is if the northern weasel would continue to change to white in the winter, while living in the south it's whole life or if it would eventually "realize" that changing white was pointless (or possibly bad because being white would make you stand out) and eventually "switch off" it's color changing genes; since we have recently been discovering that the "junk DNA" actually acts like a switch board, giving animals more variety in their genes than they immediately seem to have. Also they should see that if the northern weasel never stops turning white, that his future generations also continue turning white; like they should breed two northern weasels in the south. To me it would seem like common sense for an animal to be able to alter such genes in accordance to what environment it's currently in.

You know, I am thinking of going for the genetics/microbiology part of my study and this sounds like fantastic research for a bachelor paper... damnit, if I didn't have two cats I'd probably get myself two weasels right away!