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| Subspecies: | Unknown |
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| Est. World Population: | |
| CITES Status: | NOT LISTED |
| IUCN Status: | Least Concern |
| U.S. ESA Status: | NOT LISTED |
| Body Length: | |
| Tail Length: | |
| Shoulder Height: | |
| Weight: | |
| Top Speed: | |
| Jumping Ability: | (Horizontal) |
| Life Span: | in the Wild |
| Life Span: | in Captivity |
| Sexual Maturity: | (Females) |
| Sexual Maturity: | (Males) |
| Litter Size: | |
| Gestation Period: | |
Habitat:
The Risso’s Dolphin primarily occurs over continental slope, but can also be found in oceanic and continental shelf waters, and is often found around offshore islands (Azzellino et al. 2008, Hartman et al. 2008, Bearzi et al. 2011, Chen et al. 2013, Jefferson et al. 2014, Azzellino et al. 2017, Rogan et al. 2018, Mistic Seas II 2019, Waggitt et al. 2020). It appears to prefer waters 200–1000 m deep, warmer than 12°C (Hartman 2018).
Risso’s dolphins are social, typically in groups of 10–30, but can also be found in much larger groups (Bearzi et al. 2011, Hartman 2018).
Risso’s Dolphins appear to feed predominantly at night (Praca and Gannier 2008, Soldevilla et al. 2010, Hartman 2018). Their diet is predominantly composed of cephalopods (Öztürk et al. 2007, Praca and Gannier 2008), with families Argonautidae, Eledonidae, Ommastrephidae, Histioteuthidae and Onychoteuthidae apparently predominant (Blanco et al. 2006, Luna et al. 2022). Eledone cirrhosa, Argonauta argo, Sepia officinalis, Todarodes sagittatus, Loligo forbesi, Loligo vulgaris, Gonatus spp., Histioteuthis reversa, Histioteuthis bonnellii, Ancistroteuthis lichtensteinii, Sepiola oweniana and Illex coindetii appear to be among the commonly taken species (Evans 2013). Praca and Gannier (2007) suggested that the Risso’s Dolphin in the western Mediterranean Sea may be a specialist in relation to habitat use (highly dependent on the upper slope) but a generalist in relation to diet.
In some areas, Risso’s Dolphins occasionally display aggressive behavior toward larger cephalopod eating species such as Sperm Whales (Physeter macrocephalus), Pilot Whales (Globicephala spp.), and False Killer Whales (Pseudorca crassidens) (Hartman 2018). In the Gulf of Corinth, Mediterranean Sea, two Risso’s Dolphin individuals have been repeatedly observed in mixed-species groups with Striped Dolphins (Stenella coeruleoalba) and Common Dolphins (Delphinus delphis), but never on their own (Frantzis and Herzing 2002, Bearzi et al. 2016). In Scottish waters, Risso’s Dolphins x Common Bottlenose Dolphin hybrids have been observed (Hodgins et al. 2014, Van Geel et al. 2022).
Risso’s dolphins are social, typically in groups of 10–30, but can also be found in much larger groups (Bearzi et al. 2011, Hartman 2018).
Risso’s Dolphins appear to feed predominantly at night (Praca and Gannier 2008, Soldevilla et al. 2010, Hartman 2018). Their diet is predominantly composed of cephalopods (Öztürk et al. 2007, Praca and Gannier 2008), with families Argonautidae, Eledonidae, Ommastrephidae, Histioteuthidae and Onychoteuthidae apparently predominant (Blanco et al. 2006, Luna et al. 2022). Eledone cirrhosa, Argonauta argo, Sepia officinalis, Todarodes sagittatus, Loligo forbesi, Loligo vulgaris, Gonatus spp., Histioteuthis reversa, Histioteuthis bonnellii, Ancistroteuthis lichtensteinii, Sepiola oweniana and Illex coindetii appear to be among the commonly taken species (Evans 2013). Praca and Gannier (2007) suggested that the Risso’s Dolphin in the western Mediterranean Sea may be a specialist in relation to habitat use (highly dependent on the upper slope) but a generalist in relation to diet.
In some areas, Risso’s Dolphins occasionally display aggressive behavior toward larger cephalopod eating species such as Sperm Whales (Physeter macrocephalus), Pilot Whales (Globicephala spp.), and False Killer Whales (Pseudorca crassidens) (Hartman 2018). In the Gulf of Corinth, Mediterranean Sea, two Risso’s Dolphin individuals have been repeatedly observed in mixed-species groups with Striped Dolphins (Stenella coeruleoalba) and Common Dolphins (Delphinus delphis), but never on their own (Frantzis and Herzing 2002, Bearzi et al. 2016). In Scottish waters, Risso’s Dolphins x Common Bottlenose Dolphin hybrids have been observed (Hodgins et al. 2014, Van Geel et al. 2022).
Range:
The Risso’s Dolphin is relatively widespread across European waters, but not particularly abundant anywhere across this range. It is present throughout the Mediterranean Sea, along the Iberian peninsula, in the Bay of Biscay, around UK and Ireland, in Macaronesian archipelagos and around the Faroe Islands (Bearzi et al. 2011, Bloch et al. 2012, Chen et al. 2013, Jefferson et al. 2014, Rogan et al. 2018, Mistic Seas II 2019, Waggitt et al. 2020, ACCOBAMS 2021, Hammond et al. 2021).
It primarily occurs over continental slope, but can also be found in oceanic and continental shelf waters, and is often found around offshore islands (Azzellino et al. 2008, Hartman et al. 2008, Bearzi et al. 2011, Chen et al. 2013, Azzellino et al. 2017, Rogan et al. 2018, Mistic Seas II 2019, Waggitt et al. 2020).
Resident or semi-resident populations have been documented in some areas, such as in the Ligurian Sea (Bearzi et al. 2011, Azzellino et al. 2016), around the Azores (Hartman et al. 2008, Hartman et al. 2015), in the Hebrides, Scotland (Weir et al. 2019), and in Cardigan Bay, Wales (de Boer et al. 2013).
It primarily occurs over continental slope, but can also be found in oceanic and continental shelf waters, and is often found around offshore islands (Azzellino et al. 2008, Hartman et al. 2008, Bearzi et al. 2011, Chen et al. 2013, Azzellino et al. 2017, Rogan et al. 2018, Mistic Seas II 2019, Waggitt et al. 2020).
Resident or semi-resident populations have been documented in some areas, such as in the Ligurian Sea (Bearzi et al. 2011, Azzellino et al. 2016), around the Azores (Hartman et al. 2008, Hartman et al. 2015), in the Hebrides, Scotland (Weir et al. 2019), and in Cardigan Bay, Wales (de Boer et al. 2013).
Conservation:
Existing conservation actions
The Risso’s Dolphin in Europe is protected under a number of treaties, including the EU Habitats Directive (Annex IV), ACCOBAMS, ASCOBANS, CITES Appendix II, CMS Appendix II and Barcelona Convention SPA/BD protocol Annex II. Important Marine Mammal Areas (IMMAs) have been identified in the Mediterranean Sea.
Conservation actions needed to mitigate major threats
The species is still insufficiently known, so a better understanding of their distribution, important habitats and potential hotspots is needed, together with robust estimates of abundance. Both large-scale line-transect surveys and local mark-recapture studies are needed to better understand patterns of abundance and trends. Moreover, more information on population structure across Europe is needed, ideally through both genetic, photo-ID and ecological markers, and potentially acoustics. A better understanding of bycatch and contaminants levels, and their effects on individual and population health, is also needed. Finally, in places where Risso’s Dolphins are subject to whale-watching, an assessment of the potential impacts of such activities on vital rates should be carried out.
The Risso’s Dolphin in Europe is protected under a number of treaties, including the EU Habitats Directive (Annex IV), ACCOBAMS, ASCOBANS, CITES Appendix II, CMS Appendix II and Barcelona Convention SPA/BD protocol Annex II. Important Marine Mammal Areas (IMMAs) have been identified in the Mediterranean Sea.
Conservation actions needed to mitigate major threats
The species is still insufficiently known, so a better understanding of their distribution, important habitats and potential hotspots is needed, together with robust estimates of abundance. Both large-scale line-transect surveys and local mark-recapture studies are needed to better understand patterns of abundance and trends. Moreover, more information on population structure across Europe is needed, ideally through both genetic, photo-ID and ecological markers, and potentially acoustics. A better understanding of bycatch and contaminants levels, and their effects on individual and population health, is also needed. Finally, in places where Risso’s Dolphins are subject to whale-watching, an assessment of the potential impacts of such activities on vital rates should be carried out.