The Heck horse is a horse breed that is claimed to resemble the tarpan (Equus ferus ferus), an extinct wild equine. The breed was created by the German zoologist brothers Heinz Heck and Lutz Heck in an attempt to breed back the tarpan. Although unsuccessful at creating a genetic copy of the extinct species, they developed a breed with grullo coloration and primitive markings. After the Nazi invasion of Poland, they were introduced to the Bialowieza Forest, where a small herd still survives. Heck horses were subsequently exported to the United States, where a breed association was created in the 1960s.