• gray whale;
  • Eschrichtius robustus;
  • DTAG;
  • tagging;
  • feeding behavior;
  • diving;
  • lateralized behavior


A digital acoustic recording tag was used to examine the 3-D orientation of gray whales feeding along the central British Columbia coast. A total of 96 feeding dives were recorded from six different whales. More than half (53.1%) of the whales' bottom time was spent rolled at an angle greater than 45°. Whales rolled an average of 2.9 times per feeding dive, and rolling behavior was often accompanied by a negative pitch angle. Out of 282 recorded rolls, 274 (97.2%) were to the right. Likewise, 98.5% of the total time spent rolled at an angle greater than 45° was spent rolled to the right. The gray whales in this study showed a significant right-side bias on both an individual (P≤ 0.009) and group level (P < 0.001). Based on the findings of this study and previous reports of uneven baleen wear (Kasuya and Rice 1970), it is proposed that gray whales exhibit a population-wide right-side rolling bias similar in character to the 90/10 split of right handedness in humans.