Bob Of Burleson wrote:I think mixed-blood pit bulls do tend to be less stable and more aggressive than most dogs. It's genes plus upbringing. The people who want big dogs for protection or other not-so-admirable purposes are going to seek out pits crossed with Rottweilers, Dobermans, Mastiffs, etc. You've got hundreds of years of mixed aggression traits swirling around in the progeny and sometimes that doesn't work out so well.
This is long but has some good info:
A 9-year (1979–88) review of fatal dog attacks in the United States determined that, of the 101 attacks in which breed was recorded, pit bulls were implicated in 42 of those attacks (42%).[24] A 1991 study found that 94% of attacks on children by pit bulls were unprovoked, compared to 43% for other breeds.[25] A 5-year (1989–94) review of fatal dog attacks in the U.S. determined that pit bulls and pit bull mixed breeds were implicated in 24 (29%) of the 84 deaths in which breed was recorded.[26]
A 20-year (1979-1998) study by the American Veterinary Medical Association into fatal dog attacks on humans[27] concluded that "fatal attacks on humans appear to be a breed-specific problem (pit bull-type dogs and Rottweilers)," and that "pit bull-type dogs and Rottweilers were involved in more than half" (67%) of all the 238 recorded dog bite-related fatalities (DBRF) in the United States during that period, with pit bulls accounting for 66 deaths. They also wrote that:
"It is extremely unlikely that they accounted for anywhere near 60% of dogs in the United States during that same period and, thus, there appears to be a breed-specific problem with fatalities."[27]
A 15-year (1991–2005) review of dog attack fatalities investigated by the Kentucky Medical Examiner determined that pit bulls were implicated in 5 of the 11 fatal attacks (45%).[28] Another 15-year (1994–2009) review of patients admitted to a Level I Trauma Center with dog bites determined that pit bulls were most often involved in these attacks: of the 228 patients treated, the breed of dog was recorded in 82 attacks, and of these, 29 (35%) of the attacks were by pit bulls.[29] In 45% of the attacks, the dog belonged to the victim's family.[29]
A 5-year (2001–05) review of dog attack victims admitted to the Children's Hospital of Philadelphia determined that pit bull terriers were implicated in more than half of the bites where breed was identified. Of the 269 patients where breed was identified, 137 (51%) were attacked by pit bulls.[30] The authors wrote:
"...the overwhelming number of bites involving pit bull terriers in this study and others certainly has some degree of validity when it comes to identifying bite-prone breeds. Pit bull terriers, German shepherds, and Rottweilers were the offending breeds implicated in our study, and have accounted for the majority of dog bites according to other investigators."[30]
A review of the medical literature found that pit bulls and pit bull cross-breeds were involved in 42–45% of dog attacks.[31] Fatalities were most often reported when children were attacked, with 70% of victims being under the age of 10.[31
http://en.wikipedia.org/wiki/Pit_bull