Dog filter: What are the dark patches on puppies' bellies?

July 10, 2016 11:19 AM

I've noticed that all of my dogs (and most puppies in general) have had some irregular, dark splotches on their bellies and underarms (underlegs?) that fade with age. Kind of like liver spots on older humans, but larger and darker, and generally much lighter by about one year of age. What are these called, and can they be used to estimate a dog's age? Curious because I've noticed them on all of the dogs I've ever had, but nothing turns up on google, except for pathological conditions.
posted by stillmoving to Pets & Animals (12 answers total)

My dog had a splotchy belly as a puppy and still does; you just can't see it nearly as well because the hair on his belly is so much thicker as an adult- as a puppy he was practically bald there. He had part of his chest shaved to deal with a dog bite when he was about a year and a half old and, yup, there were the spots. Any chance that is what you are experiencing?
posted by charmedimsure at 11:25 AM on July 10, 2016

My partner's long-deceased beagle had these when she was younger, and he referred to it as her "cow belly." It looks like they're just generally considered like freckles, from some dog forums I've visited.
posted by jabes at 11:52 AM on July 10, 2016

Response by poster: Won't threadsit, but I don't think that the spots just appear lighter due to covering with fur. (Although this reminds me: I've also noticed that puppies tend to have bald-er tummies and armpits, that fill in with fur as they get older. Can this also be used for estimating age?) I was recently looking at photos of our dog and he had dark, dark brown spots on his belly as a younger dog. He still has the spots but they've faded dramatically, but are still visible through his fur.
posted by stillmoving at 12:00 PM on July 10, 2016

All conjecture based on my two-toned dog: I thought the dark spots were where, if covered with hair, the hair would be a darker color. My dog is white and brown, and it seemed like the darker splotches became brown hair.
posted by bluedaisy at 12:44 PM on July 10, 2016 [4 favorites]

Anecdotes not being science, your dog's mileage may vary etc. etc.: my dog with the aforementioned blotches is totally cream-colored, so at least on him they have nothing to do with eventual fur color.
posted by charmedimsure at 4:07 PM on July 10, 2016

They are essentially dark skin like you would find on a person. Areas where the melanin content of the skin is higher than in other spots. You can tell because when your dog is out in the sun more, they get darker. If they are inside more, or if hair covers them, they get lighter.
posted by kindall at 4:42 PM on July 10, 2016

If you look at the belly of a very short-haired dog*, you can easily see that it's fairly common to have splotches of dark skin under light-colored fur, even if other dark splotches on that same belly are covered with darker fur. Dogs' fur and skin coloring don't always match up.

*If you're near the SF peninsula, you're welcome to check out Crosbie's belly sometime.
posted by tangerine at 8:50 PM on July 10, 2016

My dog had a silly, spotty belly as a puppy, and now that he's full grown it's only gotten spottier (and sillier). He now has spots not just on his belly, but also in his armpits and on top of his muzzle. They do not correspond to the spots in his fur.

I don't really know what's driving it. Some combination of genetics, early (perhaps in-utero) developmental quirks, and environment I assume. What the actual factors are that determine the spotting though, I've no idea.
posted by Anticipation Of A New Lover's Arrival, The at 4:06 AM on July 11, 2016

Sally, our white terrier of indeterminate origin, has dark splotches on her belly and armpits that have multiplied as she has gotten older. I assumed they were akin to freckles, as she has less hair in those spots and she likes to lie in the sun on the patio steps like a beached seal. She does not have dark spots in her fur in those areas.
posted by sarajane at 8:50 AM on July 11, 2016

In humans it's called a "natal spot" or "Mongolian spot."

My favourite highschool Social Sciences teacher is a 3rd generation Chinese Canadian; when he and his wife had their first daughter, decades ago, in a small town way up in Northern BC, she had a natal spot. During a routine checkup, a nurse asked them, "So... are you happy with having a daughter..." probing them on whether they were abusing their child.

It almost came to tears but another nurse overheard and resolved the situation - some First Nations people also have the marking in the small of their backs that goes away with age."
posted by porpoise at 11:53 AM on July 11, 2016

Development of splotchy patterns in the coat which resemble these belly splotches is one of the milestones on the road to domestication (see Fig. 5 in the linked article), but the Wikipedia page on piebald animals seems to imply that those are unrelated to the ones on the belly:

A piebald or pied animal is one that has a pattern of pigmented spots on an unpigmented (white) background of hair, feathers or scales. The spots are pigmented in shades of black and/or yellow as determined by the genotype controlling the color of the animal. The animal's skin underneath its coat may or may not be pigmented under the spots but the skin in the white background is not pigmented.

in that the skin under white fur is not pigmented.

It would be nice to be able to look at an entire litter and compare their bellies, because if I had to guess at a possible function for these spots, I'd say they might help particularly the mother distinguish among littermates, and both mother and father distinguish their offspring from others, a view which is somewhat encouraged by the frequency with which puppies seem to roll over and show their bellies when faced with anything that even hints at aggression.
posted by jamjam at 2:40 PM on July 11, 2016

I have a particoloured poodle puppy. Under his black areas his skin is blue, under the white bits it's pink. When we were waiting for him (on a breeder's waiting list) i read a lot about colouring in poodles (i'm in the UK where particoloured poodles have to be registered with the KC as "colour not recognised" because it doesn't adhere to the breed standard, even though it was one of the foundation coat types of the breed, so i was interested in how, if we've been drowning "mismarked" puppies for hundreds of years, parti's still existed). In many dogs the way the hair/fur expresses colour is not directly related to the skin colour, but how the genes express in the hair. So a completely white poodle can have dark patches of skin, but they grow white hair on them.

My puppy has a bald and spotty tummy and i'm hoping it thickens up as he grows because it seems like every time i walk him in longer grass every biting insect in a 5 mile radius hops on under for a snack :/
posted by intergalacticvelvet at 2:00 AM on July 20, 2016