Introduced mammals such as wild boar and the small Asian mongoose are also common. Jamaica is also home to about 50 species of reptiles, the largest of which is the American crocodile; however, it is only present within the Black River and a few other areas. Lizards such as anoles, iguanas and snakes such as racers and the Jamaican boa (the largest snake on the island), are common in areas such as the Cockpit Country. None of Jamaica's eight species of native snakes is venomous. Jamaica is home to about 289 species of birds of which 27 are endemic including the endangered black-Billed parrots and the Jamaican blackbird, both of which are only found in Cockpit Country. It is also the indigenous home to four species of hummingbirds (three of which are found nowhere else in the world): the black-billed streamertail, the Jamaican mango, the Vervain hummingbird, and red-billed streamertails. The red-billed streamertail, known locally as the "doctor bird", is Jamaica's National Symbol. Other notable species include the Jamaican tody and the Greater flamingo,  One species of freshwater turtle is native to Jamaica, the Jamaican slider. It is found only on Jamaica and on a few islands in the Bahamas. In addition, many types of frogs are common on the island, especially treefrogs. Beautiful and exotic birds, such as the can be found among a large number of others. Jamaican waters contain considerable resources of fresh-and saltwater fish. The chief varieties of saltwater fish are kingfish, jack, mackerel, whiting, bonito, and tuna. Fish that occasionally enter freshwater and estuarine environments include snook, jewfish, mangrove snapper, and mullets. Fish that spend the majority of their lives in Jamaica's fresh waters include many species of livebearers, killifish, freshwater gobies, the mountain mullet, and the American eel. Tilapia have been introduced from Africa for aquaculture, and are very common. Also visible in the waters surrounding Jamaica are dolphins, parrotfish, and the endangered manatee. Insects and other invertebrates are abundant, including the world's largest centipede, the Amazonian giant centipede. Jamaica is the home to about 150 species of butterflies and moths, including 35 indigenous species and 22 subspecies.