Largest Pod of Bottlenose Dolphins Recorded in Irish Waters

3rd Sep 2009 During a rare respite in the weather (during dinner time, of course!) the Cetaceans on the Frontier research team (see http://www.iwdg.ie/ShipSurveys/?id=68) witnessed something that none had thought possible. Hopes were high that we would encounter some of the infamously elusive offshore bottlenose dolphins during the Cetaceans on the Frontier research cruise. We had had a distant and fleeting glimpse of a small pod breaching through the large swell on day three of the voyage.

However, we were completely taken by surprise on day 9, when about 50 miles west of Erris Head, Co. Mayo, a pod of bottlenose dolphins, possibly numbering up to 250 animals powered into view from our port side. These dolphins were on a mission and showed no interest in our ship. Bottlenose dolphins in offshore waters appear to be less inquisitive than those in inshore waters. It still remains unclear whether we have separate offshore and inshore 'ecotypes' as is the case in the western Atlantic.


The dolphins charged past us at speed and the R.V. Celtic Explorer had to increase her speed just to keep up. The pod eventually slowed down upon encountering around 10 pilot whales, which were logging on the surface.



During this encounter we obtained a lot of images of individual dolphins but only about 10% of the 250 or so bottlenose dolphins in this pod were photographed successfully, as most avoided the ship. All identified animals were all new dolphins, previously unidentified in Irish waters. they have all been photo-id catalogue photo ID catalogue. This begs the question: is there a distinct offshore ecotype in Irish waters that does not venture inshore where most of our photo ID work is carried out?

The IWDG photo-id catalogue of bottlenose dolphins has now reached an impressive 125 well-marked individual dolphins. We are still very interested in any images of bottlenose dolphins that our members might wish to share to further enhance our knowledge of the movements and social structure of this species in our waters. Please send any images to sightings@iwdg.ie where they will be added to the Irish catalogue with due credit to the photographer.

Conor Ryan

IWDG