A high concentration of blue whales and sperm whales have been spotted in the seas off Dondra Head along the Deep South coast of Sri Lanka during the months of November to April. Alankuda beach in Kalpitiya is the best places if you are interested in seeing dolphins. November to March is the best season to go Dolphin Watching off Kalpitiya. Whale and Dolphin watching is also possible during June to September off the eastern shores such as Trincomalee. Whales like deep waters and they communicate using high frequency sounds. They use long songs and clicks and noise from ship propellers create a lot of background noise that could disrupt their communication. Off Dondra Head or Mirissa the continental shelf narrows sharply. Marine biologist Anderson believes some of the blue whales off Dondra Head could be resident whales while others could be migratory ones crossing over to the Arabian Sea from the Bay of Bengal. He suspected that in January they would be passing Sri Lanka on the way to Bay of Bengal and in April they will be passing Sri Lanka again down the south coast passing Maldives to the Arabian Sea.