Low energy expenditure and resting behaviour of humpback whale mother-calf pairs highlights conservation importance of sheltered breeding areas

• Published in: Scientific Reports
• Main Authors: Bejder, L., Videsen, S., Hermannsen, L., Simon, M., Hanf, D., Madsen, P. T.
• Format: Text
• Language: English
• Published: Nature Publishing Group UK 2019
• Subjects: Article; Humpback Whale
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6347592/; http://www.ncbi.nlm.nih.gov/pubmed/30683890; https://doi.org/10.1038/s41598-018-36870-7

Understanding the behaviour of humpback whale mother-calf pairs and the acoustic environment on their breeding grounds is fundamental to assessing the biological and ecological requirements needed to ensure a successful migration and survival of calves. Therefore, on a breeding/resting ground, Exmouth Gulf, Western Australia, we used animal-borne DTAGs to quantify the fine-scale behaviour and energetic expenditure of humpback whale mothers and calves, while sound recorders measured the acoustic environment. We show that: (i) lactating humpback whales keep their energy expenditure low by devoting a significant amount of time to rest, and their use of energy, inferred from respiration rates, is ~half than that of adults on their foraging grounds; (ii) lactating females mainly rest while stationary at shallow depths within reach of the hull of commercial ships, thus increasing the potential for ship strike collisions; (iii) the soundscape is dominated by biological sources; and (iv) even moderate increases of noise from vessels will decrease the communication range of humpback whales. Planned commercial infrastructure in Exmouth Gulf will cause a substantial increase in shipping traffic with the risk of ship strikes and acoustic disturbance potentially compromising energy reserves for the southern migration of humpback whales.