Highway Route 116, the nearest principal road, heads west toward Lajas and east toward Ponce, passing through the island of Puerto Rico's driest area. The largely intact forest of the Guánica Dry Forest reserve hosts the greatest number of bird species found on the island, including several bird species seldom found anywhere else: the Puerto Rican lizard cuckoo, Puerto Rican woodpecker, the Puerto Rican nightjar, and the Puerto Rican emerald hummingbird. Other animals thought to be extinct in Puerto Rico have turned up in this forest. Many different types of cactus grow here, a stunning contrast to the lush Caribbean National Forest in the northeast part of the island, which is a tropical rainforest. The contrast is due to the mountain ridge Cordillera Central which separates Guánica from the northeast part of the island; while the northeast receives over of precipitation each year, Guánica receives less than 30, and some regions of the forest reserve are said to receive only six inches.