Research On Behaviour

Research by the MWP on dwarf minke whale behaviour has included a major focus on identifying potential impacts from interactions with humans in the GBR. We are particularly concerned with the potential for cumulative impacts on the behaviour of individual whales that are interacting repeatedly with vessels and swimmers. Long-term behaviour changes are difficult to establish, and require photo-identification data as well as detailed behavioural studies.

The PhD study by Dr Arnold Mangott investigated several aspects of dwarf minke whale behaviours during their interactions with vessels and swimmers in the Great Barrier Reef, including:

1. Establishing a detailed repertoire of the non-acoustic behaviour of dwarf minke whales around tourism vessels and their swimmers, and providing context and indications for potential functions of the observed behaviours
2. The distribution of dwarf minke whales around vessels and swimmers and whether interacting whales change their behaviour during interactions with humans over time
3. The direct and indirect risks of harm associated with swimming with dwarf minke whales for the swimmers and the whales, and
4. The validity and effectiveness of dwarf minke whale behavioural records reported via the Whale Sighting Sheets and to provide details on the perceptions of passengers to help in effective risk management.

This study provided the first comprehensive assessment of the behaviour of a baleen whale associated with a tourism industry, and it provides a useful basis for future research on dwarf minke whales and other baleen whales that interact with humans. This study also provided specific recommendations to improve the future management of the swim-with dwarf minke whale industry and to ensure the protection of this species.

Some key findings (from Mangott, 2010)

Factors influencing dwarf minke whale behaviour

Mangott (2010) described over 30 distinctive dwarf minke behaviours and provided evidence for the presence of behaviours with potential social and investigative functions. Behaviours with likely social attributes such as belly presentations and bubble releases, were significantly influenced by a large group size (>6 animals), while investigatory behaviours such as close and very close approaches, motorboating, and headrises were positively influenced by the presence of resighted animals.

Changes in dwarf minke whale behaviour

The investigative nature of dwarf minke whales was further explored by quantifying the distribution of interacting whales around vessels and swimmers and examining if their behaviour changes in interactions with humans over time. Dwarf minke whales voluntarily approached dive tourism vessels and maintained contact for prolonged periods. The whales showed a highly clumped distribution around the vessel, surfacing more often within a 60 metres radius of the boat than expected and aggregating around swimmers.

Mangott’s (2010) results also suggest that dwarf minke whales change their behaviour over time in interactions with humans. Individual whales repeatedly passed very close to the swimmers and significantly decreased their passing distance over the course of an interaction. In both cases, closeness was significantly influenced by group size; i.e. the larger the group of whales, the closer individuals approached the observers. Individual dwarf minke whales significantly decreased their passing distance in subsequent interactions and resighted animals approached swimmers significantly closer than unknown individual whales.

The voluntary initiation of contact with humans, the whales’ close and prolonged association with the vessel and swimmers, the closeness of their approaches and the increased familiarity to the stimuli, all suggest a strong exploratory drive of dwarf minke whales. Indeed, the inquisitive behaviour of dwarf minke whales contrasts with the behaviour of most free-ranging marine mammals interacting with humans.

Risks associated with the swim-with-whales activity

Mangott (2010) assessed the risk of harm associated with swimming with dwarf minke whales for both the swimmers and the whales using observational data and the perceptions of Key Informants (marine mammal experts, and members of management and non-governmental organisations). This assessment revealed that most dwarf minke whale behaviours displayed during interactions are of low risk of harm to the swimmers and the whales. On rare occasions, the risk is elevated when whales perform behaviours in very close proximity to swimmers or objects in the water. The Code of Practice recommends that “if any behaviours of concern are observed, crew must carefully assess the level of risk and should consider recalling swimmers and removing ropes from the water” (Section 4.8).

Mangott’s (2010) Key Informants also expressed concern for the wellbeing of the whales in the medium to longer term, i.e. the potential of such interactions to change the behaviour of the whales and impact on their behavioural budget and fitness. Most Key Informants evaluated the current swim-with dwarf minke whale industry positively; however, they considered that this industry needs continuous monitoring and further research to identify such long-term impacts and to address knowledge gaps for adequate management.