To describe the diving and surfacing characteristics of blue whales in Sri Lankan waters, it was necessary to first distinguish between different dive types.
Previous studies have shown that blue whale dives can be separated into relatively shorter surface dives and relatively longer deep dives.
A ‘fluke up’ dive constituted of the whale lifting its tail flukes out of the water before a deep dive and a non-fluke up dive comprised of a ‘high arch’ dive where the whale arched its back steeply before sinking below the surface prior or a ‘lazy fluke’ where the whale skimmed the surface of the water with its tail fluke prior to the deep dive.
Time series of Inter-Breath Intervals (IBI) were estimated as the time between two surfacings in a focal follow. Based on this, all dives preceded by a high arch, lazy fluke or fluke were classified as deep dives and all other dives classified as surface dives.