This couldn't happen to a nicer group of guys.

If you're searching for a reason not to have sex with animals, add this to the list: It could give you penis cancer, according to a new study published in the Journal of Sexual Medicine.

The authors found that men who have had sex with animals were twice as likely to develop penile cancer as those who stick with their own kind.

Lead author Stenio de Cassio Zequi, a urologist in Sao Paulo, gave Live Science his theory explaining the increased risk.

"We think that the intense and long-term SWA [sex with animals] practice could produce micro-traumas in the human penile tissue," Zequi said. "The genital mucus membranes of animals could have different characteristics from human genitalia, and the animals' secretions are probably different from human fluids. Perhaps animal tissues are less soft than ours, and non-human secretions would be toxic for us."

A member of a pro-zoophilia group told The Huffington Post by email that the results of the study should prompt people to take precautions, like using a condom, when having sex with animals. She added that it was unlikely to deter diehard zoophiles. "They might become more cautious," she said, "but they wouldn't change their nature."

One thing that did change recently was the law in Florida, where a measure banning bestiality received unanimous support in both chambers of the state's legislature earlier this year (well before Zequi's study was published). The sentiment was overwhelming but the political process was muddled, requiring three attempts to pass the bill.

That would make Florida the thirty seventh state with such a measure on the books, according to information on the Animal Legal Defense Fund website. The group, which advocates for animal protection laws, said that (prior to the Florida bill), "Thirty-six states (and three U.S. territories) have laws which expressly criminalize the sexual assault of an animal, though these provisions are often poorly equipped to accomplish meaningful convictions. Those states without such statutes are left to consider charges via their anti-cruelty laws, laws which, due to both the nature of the criminal conduct itself and the often lengthy lapses between the assaults and any investigation or examination of the animals, are often ill-fitting for successful prosecutions."

Zequi's study is based on a questionnaire about personal and sexual habits completed by 118 penile cancer patients and 374 healthy men recruited between 2009 and 2010.

Additionally, the research found that people who said they have had sex with animals also reported more venereal diseases.

This story has been updated to include information on laws addressing bestiality in the United States. Information from a pro-zoophilia group has also been redacted.