5 – Bullmastiff
Bullmastiffs are large and intimidating dogs, and males can reach weights as much as 130 pounds. Bred by English gamekeepers in the 19th century to assist English wardens or gamekeepers guard estates and capture poachers. The foundation breeding was 60 percent Mastiff and 40 percent Bulldog.
The powerful Bullmastiff is also serious and self-assured. He is afraid of nothing, and once aroused will seldom back down. Bullmastiffs are guard dogs and will protect their family and property. They require a fenced yard and should never be allowed to roam.Though sensible with strangers, the Bullmastiff does have well-established protective and territorial instincts.
Bullmastiffs also have a high prey drive, and many Bullmastiffs cannot live withcats for that reason.