The young stallion then seeks out other young stallions for company. Poor fertility in Hanoverian stallions and mares is not very common. The weight range for Campolina stallions and geldings is and for mares. Also, remaining wild stallions could steal domestic mares. Mares are considered easier to handle than stallions. This information is used to match stallions and mares for breeding. Stallions and mares stay with their preferred partners for years. In order to be incorporated into the studbook, stallions and mares must pass rigorous testing. In 1774 there were 50 English stallions and 30 mares imported into Virginia. The Russians closed the studbook in 1932 which included 287 stallions and 468 mares. Stallions assemble groups of mares or challenge the leader of another group for dominance. Storm Cat is also a noted sire of other successful stallions. Stallions (male horses) have a vascular penis. The largest and heaviest stallions were selected for breeding. They discovered 300 POWs, as well as 670 horses, including the famous Lipizzaner stallions.