Men who have sex with animals are twice as likely to develop cancer of the penis, a new study has found. A team of urologists from centres around Brazil looked at risk factors for penile cancer in men and conducted a study on 492 men ranging in age from 18 to 80 years old. They found that men who had sex with animals during their lifetimes were twice as likely to develop cancer of the penis as others. Those who had engaged in bestiality also reported a higher incidence of sexually transmitted diseases and of 492 volunteers, 118 were oenile cancer patients. Stjnio de Cassio Zequi, the lead author of the study said that if a man has sex with an animal it could produce micro-traumas in the human penile tissue. "The genital mucus membranes of animals could have different characteristics from human genitalia, and the animals' secretions are probably different from human fluids," the Daily Mail quoted him as saying. "Perhaps animal tissues are less soft than ours, and non-human secretions would be toxic for us," he added.