Many dogs have a splotchy coat pattern called “merle”. This coat is due to the lightening of random patches of black pigment, creating a look with white, grey, and black areas (or brown, depending on a dog’s coat genetics).
We hear from a lot of people whose dogs were suspected to be Catahoula Leopard Dog or Australian Shepherd mixes due to this pattern! While those breeds do frequently have merle coats, it can come from a variety of other breeds. Collies, Great Danes, Dachshunds, and Shetland Sheepdogs are just a few possibilities. Merle has also been introduced into other breeds such as Poodles, Pomeranians, Chihuahuas, and French Bulldogs. A dog only needs one merle-patterned parent to be merle themself, so this characteristic can come from many generations back.
To learn a little more about the genetics of the merle pattern, you can check out this blog post: https://embarkvet.com/resources/blog/embark-introduces-merle-coat-color-testing/