The Greater Swiss Mountain Dog is devoted to family. They can be suspicious of strangers and prefer to be properly introduced. They are active, calm, and dignified, and love being part of daily household life. Among the four Sennenhunden, or Swiss mountain dogs, this breed is considered the oldest, and is also the largest. The breed nearly died out in the early 1900s but has since recovered in popularity. They are still considered a relatively rare breed in the US.