Risso’s dolphins – photo-identification and distribution

During 2016 and 2017, Caroline has been working with Whale and Dolphin Conservation (WDC) on their long-running project on Risso’s dolphins (Grampus griseus) in UK waters. The Risso’s dolphin is a large and distinctive species, with a blunt head and extensive scarring over the body and flanks that accumulates with age and causes older animals to appear almost white. Despite their characteristic appearance, Risso’s dolphins are not a well-studied species due to their preference for deep, pelagic habitat in most parts of their range. The UK is relatively unusual in having Risso’s dolphin populations in nearshore, shallow habitats as well as offshore along the continental shelf edge.

The waters around the Eye Peninsula near Stornoway in the Hebrides are a well-documented hotspot of occurrence for Risso’s dolphins in UK waters, and this area is now being considered for a proposed Marine Protected Area (MPA) for the species. Currently we are compiling and assessing the photo-identification data that has been collected by WDC around Lewis for the past six years, to determine the number of animals using the region and their site fidelity. Follow-on work may include comparisons of photo-identification data from other areas of the UK, in order to understand whether movements of animals occur between areas or whether separate populations exist. This information will all help to clarify what management measures might be most appropriate to protect Risso’s dolphins in the UK and will feed into the MPA designation process.

Selected publications from Risso's dolphin research:

Weir, C.R., Hodgins, N.K., Dolman, S.J. and Walters, A.E.M. (2019). Risso’s dolphins (Grampus griseus) in a proposed Marine Protected Area off east Lewis (Scotland, UK), 2010–2017. Journal of the Marine Biological Association of the United Kingdom, 99: 703–714.

Hodgins, N.K., Dolman, S.J. and Weir, C.R. (2014). Potential hybridism between free-ranging Risso’s dolphins (Grampus griseus) and bottlenose dolphins (Tursiops truncatus) off north-east lewis (Hebrides, UK). Marine Biodiversity Records, 7: e97. DOI:10.1017/S175526721400089X

Jefferson, T.A., Weir, C.R., Anderson, R.C., Ballance, L.T., Kenney, R.D. and Kiszka, J.J. (2013). Global distribution of Risso’s dolphin Grampus griseus: a review and critical evaluation. Mammal Review, 44: 56–68. doi: 10.1111/mam.12008.

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