Animal attacks are violent attacks caused by non-human animals against humans, one of the most common being bites. These attacks are a cause of human injuries and fatalities worldwide. According to the 2012 U.S. Pet Ownership & Demographics Sourcebook, 56% of United States citizens owned a pet. In the United States in 1994, approximately 4.7 million people were bitten by dogs. The frequency of animal attacks varies with geographical location, as well as hormonal secretion. Gonad glands found on the anterior side of the pituitary gland secrete androgen and estrogen hormones. Animals with high levels of these hormones, which depending on the species can be a seasonal occurrence, such as during rutting season, tend to be more aggressive, which leads to a higher frequency of attacks not only to humans but among themselves. In the United States, a person is more likely to be killed by a domesticated dog than they are to die from being hit by lightning according to the National Safety Council.