The ecology of the Sri Lankan elephant in the Wasgomuwa Strict Nature Reserve and its environs is reported for the first time. Seasonal changes in the availability of grazing sites influenced changes in the home range of elephants. Availability of such sites in the wet season was limited by agricultural activities. Paddylands, after the harvest of the rice crop in the late wet season, became important dry season grazing sites. In the Reserve and areas outside its southern boundary on the left bank of the Mahaweli River, (a) female herds were seen more often than solitaries (b) female herds were larger and had a higher than expected number of juveniles in the dry than in the wet season (c) about 45% of the individuals were juveniles and (d) 7.4% of adult and sub-adult females had calves. Conflict between elephants and farmers will be most intense along the southern and eastern boundaries of the Wasgomuwa National Park, established in 1984 by the addition of new areas predominantly to the northern part of the Wasgomuwa Strict Nature Reserve.