Dall's porpoise reactions to tagging attempts using a remotely-deployed suction-cup tag

Remotely-deployable non-invasive (suction-cup attached) tags to record underwater behavior of cetaceans have recently been developed. How useful these tags are for applications on a broad range of species has yet to be documented. However, we attempted to use such tags to study the diving behavior of Dall's porpoise (Phocoenoides dalli) in the trans-boundary area of British Columbia and Washington state, and report here on the feasibility of the technique, including the reactions of Dall's porpoise to tagging attempts. Tagging activities were undertaken in August 1996, while porpoises were bow-riding on a small vessel. We made 15 tagging attempts and 13 resulted in tag contact with a porpoise. No reactions were observed for the 2 misses, nor for 2 of the 13 hits. Of the 11 cases when tag reactions were observed, porpoises returned to continue bow-riding almost immediately in 7 cases, suggesting no long-term effect. Short-term reactions observed included a flinch (9 of 13 hits), tail-slap (1 of 13 hits) and high speed swimming away from the vessel (4 of 13 hits), with some hits resulting in more than one type of reaction. Three of 13 hits resulted in successful tag attachment. One tag remained attached for 41 minutes, providing the first diving behavior data for this species. Rates of descent and ascent, as well as swimming velocity, were relatively high only for the first 6-8 minutes after tag attachment, suggesting a reaction to tagging that lasted approximately 8 minutes.