UK waters provide important habitat for Risso’s dolphins with a critical area having been identified (and designated as a Marine Protected Area) off the Isle of Lewis, in the north-west of Scotland.
Although predominantly thought to be an offshore species, there are many places around the UK where Risso’s dolphins can be seen close to land. One such place is the coastal waters off Lewis in the Outer Hebrides, Scotland, which 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 goal is to better understand the habitat needs of Risso’s dolphins (as well as other whales, dolphins and porpoises that use the same areas) and to get better protection for them.
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. Year after year we see some of the same individuals return to the area, engaging in feeding, socialising and breeding – with several new-born calves sighted in the summer months.
Together with other groups such as the Hebridean Whale and Dolphin Trust, we submitted an application for the waters around the north-east coast of the Isle of Lewis, to be designated as a Marine Protected Area (MPA) for Risso’s dolphins (and sand-eels, because they’re important too) and in December 2020, the Scottish government gave the official seal of approval and the site and the dolphins and other marine wildlife within it, are theoretically ‘protected’. However, there is no management plan for the site yet and so it’s important that we continue to gather data to ensure the resulting plan is evidence-based, robust and fit for purpose.
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 extended research is trying to do.
To unravel some of the mysteries that surround this species and initially help us get a better understanding of how they use the wider Scottish waters, we collected photos of Risso’s dolphins from around Orkney, Shetland and the north-east of Scotland. Thanks to other researchers, members of the public, wildlife enthusiasts and tour operators sending in their photos, even historical ones dating as far back as 2001, we were able to publish two Photo-ID catalogues for Risso’s dolphins - one identifying 91 individual dolphins seen in the waters of Orkney and north-east Scotland and the other detailing 42 individuals who have been spotted around Shetland and Fair Isle. Our initial analysis is also showing, that similar to what we have documented on the west coast of Scotland, there may be long-term associations between individual dolphins and evidence of site fidelity.
In 2023 we will be undertaking a similar ‘citizen science’ based photo-id project in association with the University of Exeter, local wildlife watching operators and members of the public. Elsewhere in the UK, WDC also curates a Risso’s dolphin photo-id catalogue dating back to 1999, from the waters around the Llŷn Peninsula and Bardsey Island, north-west Wales.
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.
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? Is UK legislation/management unit fit for purpose?
- 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 for example 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 designated the North East Lewis MPA. This comprises a significant proportion of what we’ve identified as being incredibly important habitat for this particular ‘group’ of Risso’s dolphins.
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