A case study from the Gold Coast Queensland, Australia.
Authors:
Torre-Williams, Laura1,2 and Hou, Wen 2
Affiliation:
1 Griffith Centre for Coastal Management, Griffith University, Queensland, Australia
2 Gold Coast Newborn Calf Study, Queensland, Australia
*Corresponding Author: Laura Torre Email: l.torre@griffith.edu.au or whalecalfstudy@gmail.com
Abstract:
Little is known about what happens when whales approach whale-watching vessels, as most studies have focused on these vessels approaching whales. We investigated intentional approaches by humpback whales (Megaptera novaeangliae) to tourism vessels during their migrations from 2018 to 2023. This behaviour is known as “Mugging”, for this study, we defined mugging as “the occurrence of a whale or whales intentionally making a very close approach to the vessel, often remaining less than one body length (10 to 15 m) away from the vessel and staying with the vessel for a period of time”. 127 mugging events were recorded involving 320 whales, with the most common pod size being two (48%). Observations totaled 2407 minutes of mugging, with the length of encounters ranging from short duration (one to five minutes) 44.6%, medium duration (six to ten minutes) 24.0%, up to very long duration (36 to 50+ minutes) 4.3%.
This phenomenon occurred most often in August (55.9%), followed by September (20.5%). Associated species were recorded on a small number of encounters (16.5%) and were usually groups of Indo-Pacific bottlenose dolphins (Tursiops aduncus) (71.4%) or various seabirds (23.8%).
The most common group composition engaged in mugging vessels were mixed subadult/adult groups (60.6%), followed by juvenile/adult (20.5%), and then juvenile groups (18.9%). Mother calf pods engaged in a few muggings (4.0%), including mother-calf-escort groups.
Initial behaviours just prior to mugging encounters included surface activity (pec slapping, breaching, tail slapping) (29.9%) and swimming by the vessel at (26.8%). Of all whale pods observed, 26 mixed-age groups were present, most commonly comprising juveniles and adults (80.8%). Discrete behaviours occurring during the mugging (logging, rolling, spy-hopping, diving under the vessel, etc.) were also recorded. Mugging behaviour places the whales close to vessels. Recommendations for boaters are suggested to reduce any possible negative impacts on these animals.