SC/69A/NH/07rev1  

Document Number

SC/69A/NH/07rev1

Full Title

Documenting humpback whale presence off Senegal, West Africa, using passive acoustic monitoring

Author

Meredith Sackett, Danielle Cholewiak, Robert L. Brownell Jr, Lucy Keith-Diagne, Salvatore Cerchio

Authors Summary

Passive acoustic monitoring was conducted off Dakar, Senegal, from June 2021 to January 2023, to evaluate the temporal occurrence of humpback whale song and the potential utilization of this habitat as a breeding area for both Northern and Southern Hemisphere humpback whale populations. No song was detected during the single boreal winter period. However, humpback song was detected during two austral winter periods, in September 2021 and from July – November 2022, corresponding to the Southern Hemisphere breeding season. Song structure was compared to a sample recorded in August 2022 from Conkouati, Republic of Congo, and was found to match all phrase types. While there were relatively few days with detections of song in 2021, humpback song was much more consistently present during the austral winter of 2022, with a peak daily occurrence of 17hr/day in August. The lack of humpback song presence during the boreal winter does not necessarily indicate a lack of animal presence, and strandings data do indicate the presence of humpback whales in Senegal in boreal winter months. However, the results reinforce previous reports of Southern Hemisphere humpback whales occurring in the North Atlantic, off West Africa and Cape Verde Islands. Acoustic monitoring effort is ongoing, and additional studies are needed to determine whether this region may ultimately serve as a breeding area for populations from both hemispheres.

Publisher

IWC

Keywords

Publication Year

2023

Abstract

Passive acoustic monitoring was conducted off Dakar, Senegal (14.6° N, 17.6° W), from June 2021 to January 2023, to evaluate the temporal occurrence of humpback whale song and the potential utilization of this habitat as a breeding area for both Northern and Southern Hemisphere humpback whale populations. No song was detected during the single boreal winter period. However, humpback song was detected during two austral winter periods, in September 2021 and from July – November 2022, corresponding to the Southern Hemisphere breeding season. Song structure was compared to a sample recorded in August 2022 from Conkouati, Republic of Congo, and was found to match all phrase types. While there were relatively few days with detections of song in 2021, humpback song was much more consistently present during the austral winter of 2022, with a peak daily occurrence of 17hr/day in August. The lack of humpback song presence during the boreal winter does not necessarily indicate a lack of animal presence, and strandings data do indicate the presence of humpback whales in Senegal in boreal winter months. However, the results reinforce previous reports of Southern Hemisphere humpback whales occurring in the North Atlantic, off West Africa and Cape Verde Islands. Acoustic monitoring effort is ongoing, and additional studies are needed to determine whether this region may ultimately serve as a breeding area for populations from both hemispheres.