Poster presentation 12th International Mammalogical Congress

'Spot' call: an unknown great whale sound (#611)

Rhianne Ward 1 , Alexander Gavrilov 1 , Robert D McCauley 1
  1. Centre for Marine Science and Technology, Curtin University, Bentley, Western Australia, Australia

Underwater passive acoustic recordings in the Southern and Indian Oceans off Australia have regularly recorded a short duration (8–10 s), low frequency (22–28 Hz) tonal sound with a symmetrical bell-shaped envelope. When recorded nearby at high level the sound is often accompanied by higher frequency down sweeps (40–100 Hz) and is repeated at irregular intervals varying from 120-200 s. It is termed the ‘spot’ call due to its spot-like appearance on spectrograms of long time averaging. Recordings made in some parts of the Southern Ocean display a spot call chorus almost year round, with a peak in individual high intensity calls detected during the austral winter-spring. The spot call displays a decrease in fundamental frequency over years. Additionally, an almost instantaneous intra-seasonal jump in frequency from around 22 to 28 Hz was also observed in 2006. Although similar in appearance to the first unit of the Antarctic blue whale z-call, significant differences in fundamental frequency, the rate of decrease in fundamental frequency spatial and seasonal presence are seen. We present evidence to suggest the spot call is produced by another great whale species.