Behavioural responses of juvenile Steller sea lions to hot-iron branding

Here we present the first data showing the post-branding behavioural responses in a marine mammal. Eleven captive juvenile Steller sea lions (Eumetopias jubatus) were observed for 3 days before and 3 days after hot-iron branding. Four of six monitored behaviours changed significantly after branding. The proportion of time sea lions spent in locomotion decreased from 0.07 before branding to 0.03 during the first 24 h following branding. Wound-directed behaviour (scratching, biting and head rubbing the branded area) increased from 0.0 before branding to 0.01–0.02 during the first 48 h after branding and returned to baseline thereafter. Time in the pool declined from 0.17 before branding to 0.05 during the first 24 h after branding and approached baseline by the second 24-h period. The time spent with pressure on the branded side showed little change from the 0.08 before branding to 0.10 during the first 24 h after branding; however, this behaviour decreased to 0.02 and 0.01 on following two days. These results show that Steller sea lion behaviour changes for up to 72 h after hot-iron branding. Changes in these behaviours may be useful in assessing alternative effective analgesic protocols for this procedure.