A long-term study on the dynamics of the elephant ( Elephas maximus) population in Ruhuna National Park, Sri Lanka

Abstract

The population of elephant ( Elephas maximus) in Block I of Ruhuna National Park, Sri Lanka was monitored through visual observations between 1960 and 1991. This represents perhaps the longest study of monitoring a single population of elephants in the world. Elephants were observed opportunistically for 23 years during the study period. In 166 days, a total of 579 observations were made during which 2246 sightings of elephants were recorded. There were 354 bull groupings and 225 family units or herds. The adults (males and females) make up 65% of the population. In general the proportions of the adult tuskers, makhnas (tuskless males), adult females, subadults and young have not changed much over the study period. But the proportion of tuskers among adult bulls shows wide fluctuation. Tuskers make up about 9.1% of the bulls in the park. The observed adult male:adult female ratio is 1:1.86. Almost all the solitary animals that were observed were males. Solitary bulls were encountered throughout each year, but their numbers reached a peak following the rains. The largest bull group consisted of seven animals. The most frequently encountered herd consisted of 3–10 animals. About 80% of the herds showed no association with adult males. The diurnal activity patterns of the bull groups and family units were largely similar but the bull groups were slightly more active in the mornings compared to the family units. The herds may be less tolerant of vehicles and people than the males and hence shift their activity towards the late evening hours. Although breeding may go on throughout the year, the calving intensity was found to vary. 85% of the young were seen during the rainy season. Despite its small size (140 km 2), Block I of Ruhuna National Park is one of the best areas that support viable elephant populations. This shows that in poor countries, simple measures such as protection and monitoring of elephants are easier, cheaper, and more likely to be successful than high-tech methods such as translocations or reintroductions which are difficult, expensive and likely to fail. ©