They need and eat a lot of protein. Many studies have shown that wolves can affect herd numbers, but the situation is usually self-regulating. When prey numbers decline, wolf numbers do too. When forage conditions improve, the cycle reverses itself. Wolves will keep increasing until there's no game in the country.
Wolves can breed prolifically, but normally only the alpha female and alpha male of a pack mate.
Unlike domestic canines, they only do so once a year. There is also a high death rate amongst pups and juveniles. As roads and access increase, wolves and other wildlife become more vulnerable to human actions. The chance of wolves greatly increasing anywhere in their natural range is low. Even in Montana, where they are protected by law, the population has hovered between 70 and 90 for several years.