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SC/69A/CMP/10/Rev1
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Resource ID
19975
Access
Open
Document Number
SC/69A/CMP/10/Rev1
Full Title
Variation in songs of Arabian Sea humpback whales indicates continued isolation, stability of singing behaviour, and connectivity between Oman and India
Author
Salvatore Cerchio, Andrew Willson, Meredith Sackett, Suaad Al Harthi, Karthik Ashok, Robert Baldwin, Tim Collins, Howard Gray, G. Latha, Darryl Macdonald, Shyam Madhusudhana, Gianna Minton, Charles Muirhead, Maia Sarrouf Willson
Authors Summary
Paper SC/69A/CMP/XXX reports on the use of humpback whale song recorded off the coast of Oman between 2011 and 2020, and the coast of India in 2011 and 2017, to assess the degree of change over a ten year period, whether there was indication of novel song introduction that would imply connectivity with SH populations, and the connectivity of whales on either side of the Arabian Sea. During the first eight years of the study period (2011-2018), Oman song maintained an atypically slow and gradual change compared to other populations of humpback whales, with more substantial change observed at the end of the study in 2020. There were no large-scale introductions of new phrase-types, or replacement of phrases across the ten years, that would be indicative of cultural diffusion events as has been described in SH populations, in which the entire song is replaced by the song of immigrant whales. Thus these results reinforce the current understanding that the ASHW population is isolated from other populations. Comparison of the Oman songs with a small sample of songs recorded off western India indicated that all phrases in the India sample (two in 2011, and six in 2017) were also present in the Oman songs, indicating a close connection between whales found in both the western and eastern Arabian Sea. Variation in the shared phrases provided a preliminary suggestion that song changes may have been transmitted from India to Oman across seasons (as opposed to within a breeding season), raising the potential for the existence of population substructure within the Arabian Sea. These results reinforce the understanding that the Arabian Sea humpback whale population is isolated as indicated by population genetic studies and the lack of photographic matches to date, and unique on multiple levels of its behaviour and life history patterns.
Publisher
IWC
Publication Year
2023
Abstract
Humpback whale song recorded off the coast of Oman between 2011 and 2020 was used to assess the degree of change over a ten year period, and whether there was indication of novel song introduction that would imply connectivity with Southern Hemisphere populations. During the first eight years of the study period (2011-2018), Oman song maintained an atypically slow and gradual change compared to other populations of humpback whales, with only a few exceptions in three phrase lineages. Between 2018 and 2020 (noting that there no samples from 2019), there was a complete shift from long complex phrases to short simple phrases; however, in all cases the new, short phrase variants represented elements of the previous, parent phrases from 2018. There were no large-scale introductions of new phrase-types, or replacement of phrases across the ten years. In all but one instance, new phrases resulted from the splitting of existing lineages and formation of new variants of an existing phrase-type. There was only one example of a potentially novel phrase-type being introduced during 2017. Therefore, we observed no cultural diffusion events as has been described in Southern Hemisphere populations, in which the entire song is replaced by the song of immigrant whales. Comparison of a small sample of songs recorded off western India in 2011 and 2017 indicated that all phrases diagnosed in the India sample (2 phrases in 2011 and 6 phrases in the 2017 sample) were also present in the Oman songs, indicating a close connection between whales found in both the western and eastern Arabian Sea. These results reinforce the understanding that the Arabian Sea humpback whale population is isolated as indicated by population genetic studies and the lack of photographic matches to date, and unique on multiple levels of its behaviour and life history patterns.