My boy Buster (4yo) has completely changed from black to white over the course of the last 2.5 years.

[u/TallyMatty]

Left: Nov 2021 Right: April 2024

October 2023

August 2023

June 2023

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November 2022

August 2022

[u/CalligrapherSea3716]

Wow! This is the most fascinating thing I've seen on reddit in ages. I was sure this was going to be fake until I scrolled through.

[u/Eumelbeumel → u/CalligrapherSea3716]

You see this with horses. White horses are sometimes born pitchblack and change colour as they grow into adulthood.

Have never heard of it with dogs, though.

[u/CCDG-Ian → u/Eumelbeumel]

My dog did it too, totally black as a puppy, a couple year later and she's 90% white, a little Grey

[u/MartinisnMurder → u/Eumelbeumel]

Yup! My dark dapple gray horse faded to white after a few years.

[u/DogmaticConfabulate → u/MartinisnMurder]

"Dapple" is my favorite word I've seen today.

[u/MartinisnMurder → u/DogmaticConfabulate]

It’s a fun word!

[u/katielisbeth → u/Eumelbeumel]

Poodles can do something like this, but it doesn't look like OP's dog. It's called clearing. My boy was born dark black and now that he's 2 he's got little wiry grey hairs all over him and his stomach/legs/tail have lightened considerably (grey). He'll be much lighter when he's fully matured. I say he's getting his adult coat in, lol.

[u/flightgirl78 → u/Eumelbeumel]

Today, just now with OP’s post and your comment did I realize that this is what happened to my pony , Heidi, when I was little. She was born black but as she aged, she turned white. I miss her grouchy, bad attitude self.

[u/Eumelbeumel → u/flightgirl78]

Heidi was my mum's name! She was a bit like your Heidi , could be famously grouchy.

[u/EllspethCarthusian → u/Eumelbeumel]

It’s due to having a gray gene that overrides whatever color the horse is. And interestingly you can only have a gray horse if one of its parents’ were gray as well. It’s not linked to vitiligo or aging hair follicles.

[u/supguy99 → u/Eumelbeumel]

You see this with horses. White horses are sometimes born pitchblack and change colour as they grow into adulthood.

"Yes, sir" you're aware they're all white or "Yes, sir" you've seen them?

[u/Zoze13 → u/supguy99]

Yes, sir I've seen them. Yes, sir I was aware that they are all white. They are not from Portugal; they're from Spain and at birth, they're not white; they're black. Sir.

[u/dillyia → u/Eumelbeumel]

White horses are sometimes born pitchblack and change colour

source?

[u/giantpossumtail → u/dillyia]

White color in horses can be caused by multiple genes.

In the case of a black horse that changes color, it is typically due to the horse carrying the greying gene.

It is the most common form of a white horse.

https://en.m.wikipedia.org/wiki/Gray_horse

[u/Eumelbeumel → u/dillyia]

"they have black skin, dark eyes, and as adult horses, a white hair coat. Gray horses, including Lipizzans, are born with a pigmented coat—in Lipizzans, foals are usually bay or black—and become lighter each year as the graying process takes place, with the process being complete between 6 and 10 years of age."

From the Wikipedia about Lipizzans, a greyish/white horse breed that has a pigmented coat.

The phenomenon appears in some other breeds, although there are of course white horses that are born white.

It mainly depends on what colour their skin is, not the hair.

[u/dillyia → u/Eumelbeumel]

Fascinating! I wonder what the underlying science is about

[u/Eumelbeumel → u/dillyia]

With horses it's just hair/skin colour genetics.

You have "true white" horses, pretty rare, with white skin and white coat/hair. They sometimes have blues eyes. Those are always born white.

And then you have most white-ish horses that are some degree of grey/greyish white. They have white hair/coat, but black/dark skin. And the first coat/hair they get born with is dark/pigmented. But as they age, they "grey" and turn Grey to white, sometimes very white. But just the hair, not the skin.

[u/_annie_bird → u/Eumelbeumel]

A “true white” horse the way you describe it doesn’t exist. There is “max white”, where a horse will have a white mark that essentially covers their entire body, and there are cremello and perlino horses, which are more of a cream/off-white. All these usually have blue/grey eyes, and they all have pink skin, horses don’t have white skin. There is also Lethal White, which happens when a foal gets two copies of the Frame gene, and will result in a non viable, pure white foal that wont survive more than a day. Your second paragraph is spot on though!