The West Indian manatee or "sea cow", also known as the North American manatee, is the largest surviving member of aquatic mammals. It is further divided into two subspecies, the Florida manatee and the Antillean or Caribbean manatee, based on genetic and morphological studies. Manatees are obligate herbivores, have developed vocal communication abilities, and are covered in highly sensitive vibrissae that are used for feeding and navigation. During inbreeding season, several males form mating herds around an individual female; on average, one calf is born to a female manatee every two to three years.