Dear colleagues, My co-authors and I are pleased to announce the following publication: Cholewiak DC, Cerchio S, Jacobsen JK, Urban J, Clark CW. 2018. Songbird dynamics under the sea: acoustic interactions between humpback whales suggest song mediates male interactions Abstract: The function of song has been well studied in numerous taxa and plays a role in mediating both intersexual and intrasexual interactions. Humpback whales are among few mammals who sing, but the role of sexual selection on song in this species is poorly understood. While one predominant hypothesis is that song mediates male–male interactions, the mechanism by which this may occur has never been explored. We applied metrics typically used to assess songbird interactions to examine song sequences and movement patterns of humpback whale singers. We found that males altered their song presentation in the presence of other singers; focal males increased the rate at which they switched between phrase types (*p* = 0.005), and tended to increase the overall evenness of their song presentation (*p* = 0.06) after a second male began singing. Two-singer dyads overlapped their song sequences significantly more than expected by chance. Spatial analyses revealed that change in distance between singers was related to whether both males kept singing (*p* = 0.012), with close approaches leading to song cessation. Overall, acoustic interactions resemble known mechanisms of mediating intrasexual interactions in songbirds. Future work should focus on more precisely resolving how changes in song presentation may be used in competition between singing males. This paper is open-access and is available here: http://rsos.royalsocietypublishing.org/content/5/2/171298 Sincerely, Danielle Cholewiak ________________________________________ Danielle Cholewiak, Ph.D. Passive Acoustic Research Group / Protected Species Branch NOAA Northeast Fisheries Science Center 166 Water Street Woods Hole, MA 02543 Tel: (508) 495-2010 Fax: (508) 495-2066 http://www.nefsc.noaa.gov/psb/acoustics/index.html