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Isle of Lewis Risso’s dolphin project

The waters off the Isle of Lewis, in the north-west of Scotland provide important habitat for Risso’s dolphins.

Although predominantly thought to be an offshore species, the coastal waters off of Lewis are used extensively by this little-known species including mothers and calves, with WDCs own data showing that some of the same individuals return here year after year. Our ultimate goal is to better understand the habitat needs of Risso’s dolphins (as well as other whales, dolphins and porpoises that use this area) and to get better protection for them through a marine protected area.

Every year since 2010, WDC has ventured to the Isle of Lewis to collect effort-based observations, photographic identifications and acoustic data. Every individual Risso’s dolphin that we’ve encountered has a unique entry in our catalogue and over time this information will help us to build a clearer picture of Risso’s dolphins presence and absence patterns (do they use the area all year round?), habitat use (are they feeding here?), population trends (are there less of them, as the fishermen suggest?), behaviour and social structure in this particular area. Year after year we see some of the same animals return to the area, and engage in feeding, socialising and breeding – with several newborn calves sighted in the summer months.

From a UK perspective, very little is known about Risso’s dolphin populations and therefore it’s difficult to promote specific management recommendations until we know much more. What we do know is that they face numerous threats, from bycatch to habitat degradation, wildlife watching to noise. To help us help them we need to answer a number of questions – which is exactly what our research is trying to do.

By working with other WDC colleagues who run a similar project in Wales, and other Risso’s dolphin researchers around the UK, we hope to answer some of these questions and ensure these charismatic dolphins get the protection that they so badly need.

Adding to the importance of the research, since 2011, we have been documenting a rare phenomenon, that of potential hybridisation between Risso’s dolphins and bottlenose dolphins. Hybridisation between species of whale and dolphin is known to happen between a few species, however, it is still considered relatively rare and predominantly a ‘chance’ mating event as opposed to something more evolutionary or a result of the impact of other threats. Our discovery of at least four possible individuals (the first ever recorded event in UK waters) and their subsequent resighting over the years is undoubtedly of scientific interest but more importantly it should be a major conservation concern.

Scientific papers

Risso’s dolphins (Grampus griseus) in a proposed Marine Protected Area off east Lewis (Scotland, UK), 2010–2017

Potential hybridism between free-ranging Risso’s dolphins (Grampus griseus) and bottlenose dolphins (Tursiops truncatus) off north-east Lewis (Hebrides, UK)

Objectives of the project

  • Is there one population of Risso’s dolphins spread out in waters around the UK? Or do they form specific, isolated populations?
  • Do they have preferred habitat?
  • Do they ‘meet up’ anywhere, mate and breed and then return to their preferred habitat?
  • To understand the extent of potential hybridisation between Risso's and bottlenose dolphins.
  • To ensure Risso's dolphins are strictly protected throughout their range, as required in law, and that specific local management is in place in the North East Lewis MPA, which dolphins use year-round to feed, calve and to interact with each other.


As a direct result of our work on the Isle of Lewis, the Scottish Government has proposed to protect a significant proportion of what we’ve identified as being incredibly important habitat for this particular ‘group’ of Risso’s dolphins.

Risso's dolphin

Find out more about Risso's dolphins

Visit our species guide to learn more about this species.

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