Most any isle has wild horses except for cloud isles (HI 1) and main isles with arenas (HI 2).
On HI 1, you can go to the Horse Whisperer which is located up the path from the equestrian park (there is another on saddle isle). He can tell you the location of a wild horse of your breed choice for a fee.
isle 2
only on the snowy isles
All isles! all isles can be great! like my luck is icelandics, try to find out your easiest breed to catch
You can get horses almost anywhere. Like if you go to non-main isles you can capture wild horses, you can also get some at the barn/livery, and at the auction house. You can get supplies at the tack store.
To find horses on HorseIsle, simply wander around on the terrain outside of towns and not on Cloud Isle. Wild horses can be found on every terrain (except for cloud), including desert, grass, lava, and beach.
There is no great place or bad place to catch wild horses. All 30 horses that are out roam around on all isles except for Cloud Isle. Sometimes there aren't horses on all isles. -BouncingBalloons ~ Chestnut Server
You can find a horse almost anywhere on the isles on Horse Isle. You can't find horses on Cloud Isle or in towns or in water, and only a few are found on beaches. But wild horses are nearly anywhere! FACT: There are 30 horses that are randomly placed on the isles at one time. Only certain horses can be found in certain places sometimes. If you open a horse description in the library, some of them will say where they could be found. Remeber to always have a horse opening for this reason. :)
Wild horses roam around on all the isles except for Prison and Cloud Isle. There is really no ONE certain place to catch wild horses. Or in this case, thoroughbreds. ~ShinyUnicorn~ PINTO SERVER
Wild horses can be found anywhere on any of the isles except Cloud isle and in towns. Some wild horses can only be found on a specific isle like llamas can only be found on Jungle isle and Zebras can only be found on Lava isle
Apart from animals in zoos, I think that it would probably be heavy horses - Shires, Clydesdales, Suffolk Punches, Percherons etc.
Sasha Alexander plays Maura Isles on Rizzoli and Isles. Hope this helped :)
Shetland ponies originated in the Shetland Isles, located northeast of mainland Scotland. Small horses have been kept on the Shetland Isles since the Bronze Age. People who lived on the islands probably later crossed the native stock with ponies imported by Norse settlers.