From August 25,2006 to August 15,2007 in the open water of Tongling Freshwater Porpoise National Nature Reserve,the diurnal behavior and time budget of a pregnant Yangtze finless female porpoise(Neophocaena phocaenoides asiaeorientalis)was observed using focal-animal and continuous sampling methods.The results indicated that:1)the female predominantly invested its time in feeding(66.0±1.1%,Mean±SE),followed by traveling(11.5±0.3%),resting(10.5±0.5%),socializing(9.8±1.1%)and other(2.1±0.1%),2)among different months,it showed significant differences for each of the above behaviors except traveling,3)each of the five behaviors was significantly different among the 11 periods of the day,and 4)significant differences were observed for each of the five behaviors across the five zones of the water.