It has been said that the black, or ship, rat carrying such diseases as bubonic plague, typhus, rabies, and trichinosis, has altered human destiny more than any individual in recorded history. Wherever man has gone, and in all his activities, his unchosen companion has been the black rat. The success of this species is due to its extremely wide-ranging diet and its rapid rate of reproduction. Litters of up to 10 young are born every 6 weeks or so throughout the year.