An engineered ecosystem
The annual elephant gathering at Kaudulla National Park is a direct consequence of ancient hydraulic engineering. The centerpiece of the 6,900-hectare park is the Kaudulla Tank, a massive reservoir built in the 3rd century AD by King Mahasena. During the dry season, typically from July to December, smaller water sources in the region evaporate, drawing herds of Sri Lankan elephants (Elephas maximus maximus) to the reliable waters of the tank. As the water level recedes, it exposes vast plains of lush grasses, providing a critical food source. This combination of water and food attracts up to 400 individuals, creating one of the largest known congregations of Asian elephants.
The park is an important part of a larger "elephant corridor" that connects with Minneriya and Wasgamuwa National Parks. The elephants migrate between these areas depending on the season and water availability. The gathering peaks at Kaudulla generally between August and December, after a similar event at the nearby Minneriya reservoir. This seasonal movement shows the elephants' deep spatial memory and their reliance on this network of protected habitats, a system underwritten by an irrigation project nearly two millennia old.
A temporary elephant society
The gathering is more than a large group of animals; it is a complex, temporary society that offers scientists a chance to observe elephant behavior on a large scale. The fundamental social unit is the matriarchal herd, composed of related females and their offspring. These family groups travel and forage together, cooperatively protecting the calves. Lone bulls and small bachelor herds are also drawn to the reservoir, creating a dynamic social environment.
Researchers observe a wide range of social interactions. Juvenile elephants engage in play, sparring and splashing in the shallows. Adult males, sometimes in a state of heightened testosterone known as musth, compete for mating opportunities with receptive females. Communication is constant, from low-frequency rumbles that travel through the ground to loud trumpeting calls. The sheer density of animals allows for behaviors rarely seen when herds are dispersed. This annual event is a living laboratory for understanding elephant communication, social structures, and the complex dynamics of their populations.