sentences:  Reptiles include Nile crocodile ("Crocodylus niloticus"), Nile monitor lizard ("Varanus niloticus") and African rock python ("Python sebae"), the endemic Pungwe worm snake ("Leptotyphlops pungwensis") and three other snakes that are nearly endemic; floodplain water snake ("Lycodonomorphus whytei obscuriventris"), dwarf wolf snake ("Lycophidion nanus") and swamp viper ("Proatheris").There are a number of endemic butterflies.The north of the Zambezi basin has mean annual rainfall of 1100 to 1400 mm which declines towards the south, reaching about half that figure in the south-west.