Using Unmanned Aerial Vehicles (UAVs) to assess humpback whale behavioral responses to swim-with interactions in Vava’u, Kingdom of Tonga

Abstract

The Kingdom of Tonga is a one of the few countries worldwide that allow swim-with-whales tourism activities. Most of the tour operators are based in Vava’u archipelago which represents an important breeding ground for Oceania humpback whales (Megaptera novaeangliae). This study represents an assessment of the effects of swimmer approaches on humpback whales’ behaviour using Unmanned Aerial Vehicles (UAVs). UAV flights took place during the 2016 and 2017 whale breeding seasons from onboard research and swim-with-whales vessels. Whales’ behavioural states (resting, travelling, surface-active, socialising, nurturing) were assessed from aerial videos and the proportions of time spent in each state in the presence and absence of swimmers were compared. Whale agonistic behaviours directed towards swimmers and the injury of a swimmer caused by a whale were documented. Results indicate that in-water tourism activities significantly altered the time spent in each behavioural state by humpback whale in Vava’u. Mother-calf pairs decreased the proportion of time spent nurturing, while the time spent travelling increased two-fold when approached by swimmers. These findings indicate a potential energy expenditure increase for humpback whale mothers and their calves in response to swim-with tourism activities in Vava’u. Moreover, whales’ behavioural responses can pose danger of injury to swimmers.