Australian Humpback Dolphin
Australian Humpback Dolphin (Sousa sahulensis)
Humpback dolphins are found in tropical to temperate, coastal waters of the eastern Atlantic, Indian, and western Pacific oceans. All humpback dolphins belong to the genus Sousa. The taxonomy of this genus was unclear, however morphological and genetic analysis has led to the recognition of four humpback dolphin species: S. teuszii, Atlantic humpback dolphin; S. plumbea, Indian Ocean humpback dolphin; S. chinensis, Indo-Pacific humpback dolphin; and S. sahulensis, Australian humpback dolphin.
Australian humpback dolphins (Sousa sahulensis) are found in shallow nearshore waters of northern Australia and in the southern waters of New Guinea. They range in size from 1-3 m (3.3- 9.8 ft). They occur individually or in groups up to 12 but are mostly seen in smaller groups of 3–4 animals. The dolphins live in a “fission-fusion society” in which individuals associate in groups that change in size and composition according to their behavior. However, mothers and calves maintain associations that can last for up to four years. Cumulative impacts of coastal development and its associated activities (e.g., seismic surveys, dredging, blasting, pile driving, and shipping) is recognized as one of the most serious anthropogenic threats to Australian humpback dolphins.
Australian humpback dolphins produce different underwater sounds described as broadband clicks, barks, quacks, grunts, and whistles. Broadband clicks span 8 kHz to at least 22 kHz. They are directly associated with foraging behavior but may also be used in social interactions. Barks and quacks are burst pulse sounds (0.6 kHz to > 22 kHz, with a duration of 0.1-8 s) and are associated with both foraging and social activities. Grunts are low frequency, narrow band sounds (0.5-2.6 kHz) produced during social activities. Whistles range widely in frequency (0.9-22 kHz) and occur during social and foraging activities. The number of whistles recorded in a group increase significantly as mother-calf pairs increase, suggesting whistles may be used as contact calls.
Like other odontocetes, Australian humpback dolphins also use biosonar, producing echolocation clicks for orientation, navigation, and foraging. These clicks have a mean source level of 199 underwater dB, center frequency of 106 kHz, and interclick intervals of 79 ms. These parameters are similar to those of other similar-sized delphinids.
Additional Links on DOSITS
- Animals and Sound > Use of Sound > Marine Mammals > Individual Specific Vocalizations
- Animals and Sound > Use of Sound > Marine Mammals > Navigation
- Animals and Sound > Use of Sound > Marine Mammals > Feeding
- Animals and Sound > Sound Sources > Seismics
- Animals and Sound > Sound Sources > Shipping
- Animals and Sound > Sound Sources > Pile Driving
- Audio Gallery > Airgun
- Audio Gallery > Pile Driving
- Audio Gallery > Ship
- Audio Gallery > Dredging
- Audio Gallery > Explosive Sound Sources
- Audio Gallery > IndoPacific Humpback Dolphin
- de Freitas, M., Jensen, F. H., Tyne, J., Bejder, L., & Madsen, P. T. (2015). Echolocation parameters of Australian humpback dolphins ( Sousa sahulensis ) and Indo-Pacific bottlenose dolphins ( Tursiops aduncus ) in the wild. The Journal of the Acoustical Society of America, 137(6), 3033–3041. https://doi.org/10.1121/1.4921277
- Jefferson, T. A., & Rosenbaum, H. C. (2014). Taxonomic revision of the humpback dolphins ( Sousa spp.), and description of a new species from Australia. Marine Mammal Science, 30(4), 1494–1541. https://doi.org/10.1111/mms.12152
- Parra, G. J., & Cagnazzi, D. (2016). Conservation Status of the Australian Humpback Dolphin (Sousa sahulensis) Using the IUCN Red List Criteria. In Advances in Marine Biology (Vol. 73, pp. 157–192). Elsevier. https://doi.org/10.1016/bs.amb.2015.07.006
- Parra, G. J., & Jefferson, T. A. (2018). Humpback Dolphins. In Encyclopedia of Marine Mammals (pp. 483–489). Elsevier. https://doi.org/10.1016/B978-0-12-804327-1.00153-9
- Van Parijs, S. M., & Corkeron, P. J. (2001). Vocalizations and Behaviour of Pacific Humpback Dolphins Sousa chinensis. Ethology, 107(8), 701–716. https://doi.org/10.1046/j.1439-0310.2001.00714.x