It’s the end of January. Here in New England we have a couple of months of bitter cold weather yet to come, but the horses are shedding. That’s because the trigger that tells their bodies to start to lose their worn-out old hair and grow new is not temperature. It’s the amount of daylight. We’ve passed the solstice and days are getting longer. Sunshine hits the the light receptors in the eyes which conveys that information to the pineal gland which sends out chemical messages to the body. When there’s 16 hours of sunlight you’re full into shedding season. Electric lights can trigger this process, too, so if your barn, like mine, has a busy schedule late into the afternoon and into the evening, and if the aisle and arena lights are on, your horse is going to shed in the middle of winter.
Temperature does not usually determine the shedding schedule! However, body temperature does effect how long your horse’s winter hairs grow. Coddle them with thick blankets early in the season and keep your barn warm, and they’ll grow shorter coats. That said, there has been some research on Shetland ponies. When it’s a particularly wet and cold winter, they shed later than the sunlight dictates.
Meanwhile, here in Maine, Tonka’s been absorbing that sunshine and he’s been under electric lights until about 8 pm. A minute with the curry yields this:
BUT… move the curry over to his black markings and this is what I get:
This made me ask: why the difference between white and dark hair? In a review of the scientific literature on horse coats, shedding and thermoregulation I learned a few things. It turns out that what we observe – that our horses don’t shed evenly out – is true. They start the process at their hindquarters. Then the belly and chest join in. Then the shoulders and back. Finally the loin loses it’s winter coat. This makes sense. The long hair persists where it’s needed the most.
The butt, where a horse sheds first, is where Tonka is white, which explains why the curry was filled with white hairs but not black.
BUT… I’m not entirely satisfied with that answer. The line between where he’s shedding and where he’s not, follows his markings exactly. I wonder if coat color is also a factor in how horses lose and grow hair. That led me to research on how human hair color is linked to traits like thickness of each strand, but I couldn’t find comparable studies on horse hair. I didn’t come across anything on how coat color affects the equine’s hair growth cycle. If you can shed some light on this (pun intended!) please direct me to the research. Anecdotal accounts are not a substitute for research, but they’re interesting, and they are what inspire the questions that lead to the science. Is your horse’s butt shedding? Do you have a multicolored horse? What have you observed?
No research just observations. I’ve noticed this on my multicolored horse. Of course you know that black or darker hair absorbs more of the photoelectric spectrum of sunlight, white absorbs almost none. This will apply to the skin underneath as it is pigmented to match the hair color. Black hairs are also more coarse- maybe that has something to do with it? Sorry I don’t have concrete research to help you. I’m enjoying your articles. Thank you.
Yes, his black areas do get warmer in the sun… hmmm…. There’s certainly a difference in the mane thickness between his black and white patches. The white areas have way more hair strands and are very challenging to braid. Doesn’t matter how much I try to thin it.
My grey mare presents her Appaloosa colours. She was born black with a white blanket and black spots on the blanket and is now completely grey with black spots on her rear end. The black spots shed later and the hair is longer. The grey hairs, although shorter, are so dense that it’s difficult to find her skin through the hairs. She has only worn a blanket for the last three winters and I do find that her hair is shorter under the blanket. Her legs are just as hairy (rivals my own, truth be told!) as she is part Percheron. I don’t clip her at all. She lives outside, comes into a heated barn to be quickly tacked, and is not exposed to artificial light at odd times of the day. And she is carefully ridden in a heated arena. I don’t let her get overheated in winter because she has to go back outside.
We’ve been together for 19 years. She begins to shed around 15 Feb, which I suspect would correlate with the similar angle of the sun that you experience in Maine. We are in Edmonton Alberta Canada. The angle of the sun in Maine today is 25-ish degrees and in Edmonton, AB on 15 Feb last year (when Dancer starts to noticeably start shedding) is 24-ish degrees at solar noon. Hmmmm…
https://www.timeanddate.com/sun/canada/edmonton?month=2&year=2019
Appaloosa coloring has so many interesting aspects to it. How coats change colors over the seasons and through the years is also fascinating! It sounds like your mare has been visually gorgeous – and varied – her entire life. February, by the way, is also when my hens would resume laying.
I have a black/white pinto saddlebred/mft. There is no question in my mind after grooming him 26 years now. His white hair gets much thicker than the black and sheds heavier and earlier than his black areas, regardless of where it is on his body. My other horse is solid black and his coat gets quite thick but not long like by pinto. He also sheds later than the pinto.
First of all, I LOVE hearing about people who have had their older horses for so many years. I hope I’ll be saying that about Tonka in a decade! I agree that the white is thicker than the black, even on a horse like Tonka who barely grows a coat.
I find this oddly fascinating! Please keep us posted on what you learn.
Don’t you just love these weird nature details? 🙂
I agree with Regina’s post, my black/white horse sheds the white first regardless of where it is on his body. My blaze faced solid color horses always started shedding the white on their faces long before anywhere else started shedding. I couldn’t find and research articles that were very good either.
Friends at my barn report that the blazes are shedding.
It’s been decades since I had a multi-colored horse so I don’t remember. But Stella is shedding out on her butt and back pretty substantially, which surprised me. Lance and Russell before him were slow to shed, and Lance starts on his face, then his neck; his butt is last!
There are always exceptions to the rule and it doesn’t surprise me that your Lance is one of them! 🙂
Great research adventure on this one! Very interesting.