In humans and dogs, hair goes white with age. Why? And why, on dogs, is it only around the muzzle - why not all over? and does it happen with other mammals?
Male gorillas develop silver hair on their backs at the age of 11-12, though with a life span of 30-50, it is not associated with old age.
I have wondered about that myself - especially since I am getting white hairs in my eyebrows! These are almost transparent they are so white.
And some cats get greyer as they get older - my Gwen has gotten a lot greyer around her nose/mouth in the last few years.
This site says that hair is colored because of cells at the root that produce melanin. With age they stop producing so much, or sometime any, but it doesn’t say why.
I checked the SD archive and found nothing. Either Cecil has never addressed this (almost unthinkable) or my search skills are lousy.
One of the odd notions is that hair goes white from fright.
Supposedly, many who faced the guilletine went white waiting in jail.
Of course, these where usually noblemen who used dyed their hair. (In those days, the dye would just wash out, but they didn’t wash their hair much.)
Cecil does address that one in Can hair turn white overnight from fright?
I’ve known elderly dark-furred dogs that went salt-and-pepper grey all over. Apparently the muzzle fur goes first, by a couple of years, though.
My hunch is that we rarely see senectudinal animals. (Yeah, it’s a weird word, but it’s the proper one for “showing physical signs of old age.”) “Old” dogs, cats, horses, etc., are actually in later middle age as far as potential lifespan is concerned, and are often put down due to chronic ailments before they actually arrive at the equivalent of old age in a human. And wild animals rarely survive to elderliness.
so it’s the equivalent of grey temples in humans?
Or a gray beard.
The pigmentation cells wear out, as does everything else, with age.
As for hair going gray with fright I am still young enough that I can count my gray hairs. While not having actually made a log of the appearance of gray hairs I would swear the ones I do possess each have a story attached to them. That is, one gray hair is a fight with my wife (now ex) or another is from work when a server crashed and so on. Again, nothing scientific about it but I really would say they seem to have appeared (or I have bothered to notice them) shortly after some intense period in my life.
I am not getting enough of them that applying a story to each one is stretching my abilities but I offer this for whatever it is worth.
I’ve had two lovebirds that lived long enough that some of their head feathers started losing their color. Just another datapoint. Parrots that live long enough will also sometimes start going bald, poor things.
Age is the most apparent cause.
I knew a lady whose hair turned white at about 20-22 years of age. Lasted all her life.!
No apparent cause. :rolleyes:
And why does the white/ grey hair tend to be thicker than normal hair?
My hair started turning grey when I was around 26 and now that I am 32 it is at least 50/50. I used to have naturally spiral-curled hair, and now it’s more wavy than anything. I think it is partly the texture of the grey hair, and partly the fact that I keep it dyed.
It would seem that stress can be a factor as well.
I recall a number of Presidents that looked pretty young going into the White House and came out looking as if they had aged 20 years, white hair and all.
The issue was addressed in this article:
Nishimura EK, Granter SR, Fisher DE., Mechanisms of hair graying: incomplete melanocyte stem cell maintenance in the niche.
Science. 2005 Feb 4;307(5710):720-4.
In case the title doesn’t say it all, here’s the abstract (email me if you want full text)
Aren’t there “white” horses that are born black and fade through grey to white?
Do roans do the same thing?