Discover the remarkable whales, dolphins, porpoises and seals that inhabit — or occasionally visit — one of Scotland’s most fascinating marine environments.
The Firth of Clyde supports a remarkable diversity of marine mammals, from the small and elusive harbour porpoise to dolphins, seals and some of the largest animals on Earth.
Stretching from the upper Clyde Estuary through its sheltered sea lochs to the waters surrounding Arran, Ailsa Craig and the Kintyre Peninsula, the Clyde encompasses a complex network of marine habitats.
Its deep basins, tidal channels, rocky coastlines and productive feeding areas provide opportunities for a wide variety of marine wildlife.
Although the Clyde has experienced substantial environmental change, it remains an important habitat for cetaceans, and recent years have produced some extraordinary encounters.
Historical assessments have recorded at least 15 species of whales, dolphins and porpoises in Clyde waters since 1980. Some are encountered regularly, while others are occasional visitors whose appearances provide fascinating insights into the wider marine environment.
Here we introduce the marine mammals of the Clyde, including some of the remarkable and occasionally tragic events that have brought these animals to public attention.
Harbour Porpoise
Phocoena phocoena
The harbour porpoise is the principal focus of Clyde Porpoise’s research and one of the most frequently encountered cetaceans in the region.
Despite their widespread occurrence, harbour porpoises can be surprisingly difficult to observe.
They are small animals, generally measuring between 1.5 and 1.9 metres in length, and usually surface briefly with a gentle rolling motion.
Unlike dolphins, porpoises rarely leap clear of the water. Their small triangular dorsal fin, rounded body and lack of a prominent beak are useful identification features.
Life Beneath the Surface
Harbour porpoises are highly specialised marine predators, feeding principally on small fish and occasionally squid.
They rely on an extraordinary ability known as echolocation, producing high-frequency clicks and interpreting the returning echoes to locate prey and navigate underwater.
Their echolocation signals are typically concentrated around 130 kHz, far above the range of human hearing.
These sounds are fundamental to how porpoises experience their underwater environment.
Porpoises in the Clyde
Harbour porpoises occur throughout the Clyde, including its sea lochs, coastal waters and deeper offshore areas.
Their distribution is influenced by prey availability, water movement, seabed topography and other environmental conditions.
Through long-term passive acoustic surveys, Clyde Porpoise is investigating where these animals occur, identifying areas of repeated activity and developing methods to improve our understanding of their distribution and abundance.
Our research also examines how underwater noise and human activities may influence porpoise behaviour and habitat use.
Did you know? During the final moments of a feeding attempt, harbour porpoises can dramatically increase their echolocation click rate, producing rapid sequences known as feeding buzzes.
Common Dolphin
Delphinus delphis
Common dolphins are among the most energetic and recognisable cetaceans encountered in Scottish waters.
They have slender bodies, prominent beaks and distinctive pale markings along their flanks, often forming an hourglass-shaped pattern.
Unlike harbour porpoises, common dolphins frequently travel in social groups and may leap clear of the water or ride the bow waves of vessels.
They feed on schooling fish and squid, using echolocation and coordinated behaviour to locate prey.
Common dolphins occur in Clyde waters, although their distribution and patterns of occurrence differ from those of harbour porpoises.
Kylie — The Clyde’s Remarkable Dolphin
One of the Clyde’s most unusual marine mammals was Kylie, a solitary common dolphin that spent many years associating with harbour porpoises around the Cumbraes and surrounding waters.
Her behaviour attracted international scientific interest because dolphins and porpoises are different species with distinct acoustic characteristics.
Working with Dr Mel Cosentino and researchers at the University of Strathclyde, Clyde Porpoise contributed acoustic recordings that helped investigate Kylie’s interactions with harbour porpoises.
The research revealed unusual high-frequency clicks resembling those of harbour porpoises, raising questions about acoustic adaptation, vocal learning and communication between species.
The resulting scientific paper, published in Bioacoustics in 2022, attracted international media attention, including coverage by National Geographic and the BBC.
Kylie’s story demonstrates how long-term local observation and collaborative research can reveal extraordinary aspects of marine mammal behaviour.
Bottlenose Dolphin
Tursiops truncatus
Bottlenose dolphins are considerably larger and more robust than harbour porpoises, with adults often reaching three metres or more in length.
They can be recognised by their curved dorsal fin, relatively short beak and powerful swimming behaviour.
Bottlenose dolphins are intelligent, highly social animals, capable of maintaining complex relationships and long-term associations with other individuals.
They communicate through whistles, clicks and other vocalisations, while also using echolocation to locate prey.
Bottlenose dolphins are regularly reported in parts of the Firth of Clyde, with some groups repeatedly observed over successive years and becoming established residents.
Photographic identification of distinctive dorsal-fin markings can help researchers establish whether the same individuals are returning and how they move around the region.
Minke Whale
Balaenoptera acutorostrata
The minke whale is the smallest of the baleen whales commonly encountered in Scottish waters.
Adults typically measure around seven to nine metres and can be recognised by their pointed head, curved dorsal fin and characteristic white bands across their pectoral flippers.
Unlike dolphins and porpoises, minke whales do not use echolocation.
Instead, they feed by engulfing prey-rich seawater and filtering small fish and other organisms through specialised baleen plates.
Minke whales are associated with productive feeding grounds around Scotland’s western coastline and are recorded in the Clyde, particularly where suitable prey is available.
Their presence reminds us of the importance of maintaining productive marine food webs.
Humpback Whale
Megaptera novaeangliae
Few marine encounters are as memorable as seeing a humpback whale.
Reaching approximately 12–16 metres in length, humpbacks are among the most spectacular visitors to Scottish waters.
They are recognised by their enormous pectoral flippers, distinctive body shape and the powerful tail flukes they sometimes raise above the surface before diving.
Humpback whales are well known for their energetic surface behaviour, including breaching, tail-slapping and pectoral-fin displays.
Like minke whales, they are baleen whales, feeding on fish and other small marine organisms.
Humpbacks in the Clyde
Humpback whales have become an increasingly familiar subject of wildlife reports from the Firth of Clyde.
Rather than simply passing through on brief visits, some animals have remained in the region for extended periods, with sightings separated by intervals when they temporarily disappear from view.
During summer 2026, humpback whales were repeatedly reported around Arran, Millport and surrounding waters.
The Clyde Cetacean Sightings and Arran Cetacean Sightings groups have reported multiple sigjtings over several weeks, including feeding and breaching behaviour. Photographic evidence established that at least two individuals were present during the season.
These prolonged encounters are particularly interesting because they suggest that parts of the Clyde can provide attractive feeding opportunities for these large whales.
However, repeated sightings do not automatically establish that the same individual has returned. Photographic identification, particularly of distinctive tail-fluke markings, is needed to determine which whales are involved.
Understanding their movements, feeding behaviour and the factors attracting them to the Clyde could become an important area of future research.
Protecting Visiting Humpbacks
The presence of large whales also creates conservation challenges.
In November 2024, a humpback whale became entangled in fishing gear in Loch Fyne. Following a complex rescue operation, it was successfully freed.
The incident highlighted the risks that ropes and static fishing equipment can pose to large whales.
As humpback sightings become more frequent, responsible vessel behaviour, reporting of entanglements and cooperation with fishing communities will be increasingly important.
Read about the Loch Fyne humpback rescue
Killer Whale or Orca
Orcinus orca
The killer whale, commonly known as the orca, is the largest member of the dolphin family.
Its distinctive black-and-white colouration, tall dorsal fin and powerful body make it one of the most recognisable animals in the ocean.
Orcas are intelligent and highly social predators, living in groups with complex relationships and, in some populations, specialised hunting strategies.
Although uncommon in the Clyde, occasional visits have attracted considerable public attention.
In April 2018, a group of orcas travelled into the upper Firth of Clyde, providing an extraordinary wildlife spectacle.
Depending on their population and feeding specialisation, orcas may hunt fish or marine mammals.
Their occasional appearance highlights the Clyde’s ecological connections with the wider waters of Scotland’s west coast and the North Atlantic.
Northern Bottlenose Whale
Hyperoodon ampullatus
Northern bottlenose whales are among the most remarkable and least frequently encountered cetaceans in Scottish coastal waters.
Despite their name, they are not closely related to bottlenose dolphins.
They belong to the beaked whale family, a group of highly specialised deep-diving animals that spend much of their lives far offshore.
Northern bottlenose whales can reach approximately seven to nine metres in length and are recognised by their prominent, bulbous forehead and short protruding beak.
They normally inhabit deep Atlantic waters, often beyond the continental shelf, where they dive to considerable depths in search of squid and other prey.
Their appearance in shallow coastal waters is therefore unusual and can present serious challenges to their survival.
The Clyde Bottlenose Whale Strandings of 2020
During late summer and autumn 2020, several northern bottlenose whales entered the Clyde and its adjoining sea lochs.
The animals were observed in locations including Greenock, Loch Goil, Loch Long, Gare Loch, Millport and the upper Clyde Estuary.
For several weeks, members of the public were able to observe these extraordinary deep-diving whales in waters where they would not normally be expected.
Their presence attracted significant public and media attention, while marine mammal groups, local residents and other agencies worked to monitor their movements and welfare.
Unfortunately, the events ended tragically.
In October 2020, a northern bottlenose whale stranded and died at Blairmore in Loch Long. Another stranded at Portavadie in Loch Fyne, and a third died after stranding in the upper Clyde near Glasgow Airport.
A scientific account subsequently published in The Glasgow Naturalist concluded that at least three whales had stranded and died. The exact number of individuals involved, and the fate of every whale, could not be established with certainty.
The event raised important questions about why deep-diving cetaceans enter shallow coastal waters and why they sometimes struggle to find their way back to suitable offshore habitat.
Possible influences include navigation, prey availability, environmental conditions and disturbance, but determining the causes of individual stranding events requires careful scientific investigation.
These events should not automatically be attributed to any particular human activity without supporting evidence.
A Longer History in the Clyde
Although the events of 2020 attracted widespread attention, northern bottlenose whales have a much longer history in Clyde waters.
Historical records document visits and strandings extending back more than two centuries, including incidents in Gare Loch, the Clyde Estuary and other coastal locations.
This makes their history in the Clyde an important subject for further investigation.
Further reading: O’Reilly, M. & Payne, A.P. (2021). Bottlenose whales in the Clyde Sea Area, Scotland in 2020. The Glasgow Naturalist, 27(3), 108–111.
Other Deep-Diving Beaked Whales
Northern bottlenose whales are members of the beaked whale family, Ziphiidae.
These animals are among the least understood marine mammals in the world.
Most inhabit deep offshore waters, where they undertake prolonged dives to feed on squid and deep-water fish.
They typically spend relatively little time at the surface, making them exceptionally difficult to study.
Several species occur in the wider North Atlantic and waters around Scotland.
Sowerby’s Beaked Whale
Mesoplodon bidens
Sowerby’s beaked whales are relatively small members of the beaked whale family, usually measuring around four to five metres.
They possess a slender body, narrow beak and a small dorsal fin positioned towards the rear of the body.
They are rarely observed alive in coastal waters, and much of our knowledge comes from stranded animals.
The Clyde region has its own documented history of Sowerby’s beaked whale strandings.
In September 2019, two juvenile Sowerby’s beaked whales stranded at Kames, near Tighnabruaich, in the Kyles of Bute.
Despite attempts to refloat them, both animals repeatedly stranded and were eventually euthanased on welfare grounds.
Historical records also include a Sowerby’s beaked whale stranding at Minard in Loch Fyne in 1987.
These incidents demonstrate that the Clyde’s association with deep-diving cetaceans extends beyond northern bottlenose whales.
Cuvier’s Beaked Whale
Ziphius cavirostris
Cuvier’s beaked whales are extraordinary deep-diving mammals capable of reaching depths of several thousand metres.
They are among the most accomplished diving mammals known to science.
Their normal habitat is deep offshore water, particularly around continental slopes and submarine canyons.
Although Cuvier’s beaked whales are recorded in Scottish and neighbouring Atlantic waters, they should not be regarded as regular inhabitants of the Clyde.
Other Rare Species
Other beaked whales recorded in the wider North Atlantic include True’s beaked whale and several species that are exceptionally rarely encountered around Britain and Ireland.
Records of these animals are important because they help scientists understand the distribution of species that are otherwise difficult to observe.
Why Are Beaked Whales Vulnerable?
The deep-diving behaviour of beaked whales makes them particularly interesting from a conservation perspective.
Research has demonstrated that certain beaked whale species can show strong behavioural responses to underwater noise, particularly some types of active sonar.
Concern has also arisen over associations between naval sonar activity and unusual beaked whale stranding events in different parts of the world.
However, strandings can have multiple causes, and establishing whether underwater noise contributed to a particular event requires detailed investigation.
For the Clyde, where naval activity, shipping and other underwater sound sources overlap with marine mammal habitat, understanding these relationships is an important scientific consideration.
Seals of the Clyde
Although Clyde Porpoise’s principal research interest is cetaceans, seals are another important component of the region’s marine mammal community.
Two species are regularly encountered: the harbour seal and the grey seal.
Harbour Seal
Phoca vitulina
The harbour seal, also known as the common seal, is the smaller of the two species.
It can be recognised by its rounded head, short muzzle and large forward-facing eyes.
Harbour seals are associated with sheltered coastal waters, sea lochs and estuaries.
They feed on fish and other marine prey and regularly haul out on rocks, sandbanks and sheltered shorelines to rest.
Grey Seal
Halichoerus grypus
Grey seals are generally larger and can be distinguished by their longer, more elongated head and sloping muzzle.
Adult males can become particularly large and powerful animals.
Grey seals occur around the Clyde’s coastline and islands, using suitable habitats for feeding and resting.
Both seal species are important marine predators and form part of the wider ecological relationships within the Clyde ecosystem.
Like cetaceans, they can be affected by changes in prey availability, disturbance, fishing interactions and environmental conditions.
Why Marine Mammals Matter
Marine mammals occupy important positions within marine food webs.
As predators, their feeding ecology is linked to fish populations, prey distribution and the productivity of the waters they inhabit.
Changes in their distribution, behaviour, health and reproductive success can therefore provide useful clues about environmental change.
However, the presence of marine mammals does not automatically mean that an environment is healthy.
Animals may continue to use important feeding areas despite exposure to underwater noise, pollution, fishing interactions and other pressures.
The increasing public interest in humpback whales, the unusual interactions involving Kylie and the tragic northern bottlenose whale strandings each illustrate different aspects of the relationship between marine mammals and the Clyde.
Understanding these relationships is essential to effective conservation.
For Clyde Porpoise, the aim is not simply to document where animals occur, but to understand why they use particular habitats, how those habitats are changing and what environmental pressures may influence their survival.
Watching Marine Mammals Responsibly
Encountering a wild whale, dolphin, porpoise or seal can be an unforgettable experience.
However, the welfare of the animals must always come first.
Marine mammals can be disturbed by repeated vessel approaches, excessive speed, sudden changes of direction or attempts to encourage interactions.
Wildlife watchers should maintain a respectful distance, avoid chasing or surrounding animals and allow them to continue feeding, travelling or resting without interference.
When watching from a vessel, movements should remain slow and predictable, and animals should never be deliberately obstructed.
Particular care is needed around mothers with young, feeding animals and whales that appear distressed or entangled.
NatureScot’s Scottish Marine Wildlife Watching Code provides practical guidance for responsible wildlife encounters.
Read the Scottish Marine Wildlife Watching Code
Helping Us Understand the Clyde’s Marine Mammals
Public observations can provide valuable information about marine mammal occurrence, particularly for species that are difficult to monitor through conventional surveys.
Useful sighting information includes the date, time, location, number of animals, direction of travel and any distinctive behaviour.
Photographs can be especially valuable for identifying dolphins and humpback whales, where natural markings may allow researchers to recognise individuals across repeated encounters.
Observations made from shore or during ordinary vessel journeys can complement dedicated scientific surveys.
Clyde Porpoise welcomes information about marine mammal sightings and unusual observations from throughout the region.
Research and sighting enquiries: david@clydeporpoise.org
Reporting Stranded Marine Mammals
If you encounter a live stranded or injured whale, dolphin, porpoise or seal requiring assistance, contact British Divers Marine Life Rescue on 01825 765546.
Do not attempt to return a stranded whale or dolphin to the sea without specialist advice.
Dead marine mammal strandings in Scotland should be reported to the Scottish Marine Animal Stranding Scheme (SMASS), which collects valuable information about causes of death, disease, pollution and other environmental pressures.
Learning More About the Clyde
The marine mammals of the Clyde are part of a complex and continually changing ecosystem.
From harbour porpoises feeding in sheltered sea lochs to humpback whales exploiting seasonal food resources and rare deep-diving species entering coastal waters, their lives reveal the remarkable ecological connections between the Clyde and the wider Atlantic Ocean.
Understanding these animals requires long-term observation, scientific research, public engagement and careful consideration of the activities taking place around them.
Through our acoustic monitoring, collaborative research and conservation advocacy, Clyde Porpoise aims to contribute to that understanding.
Protecting the Clyde’s marine mammals begins with recognising the extraordinary lives unfolding beneath its surface — and understanding the habitats on which they depend.
Further Reading
Scottish Government — Clyde Ecosystem Review
An assessment of the Clyde’s marine environment, including historical records of cetaceans and changes affecting its ecology.
Read the Clyde Ecosystem Review
Hebridean Whale and Dolphin Trust — Whale Track Summer 2026
Reports of humpback whales, dolphins and other marine wildlife, including prolonged sightings in the Clyde.
Read the summer sightings report
O’Reilly & Payne (2021) — Bottlenose Whales in the Clyde Sea Area, Scotland in 2020
A scientific account of the northern bottlenose whales observed in the Clyde and the subsequent strandings.
Scottish Marine Animal Stranding Scheme — Annual Report 2019
Includes an account of two Sowerby’s beaked whales stranded near Tighnabruaich.
National Museums Scotland — Collecting Marine Mammals
An accessible introduction to marine mammal research, including beaked whales and the scientific importance of studying stranded animals.
British Divers Marine Life Rescue — Northern Bottlenose Whales in the Clyde
A contemporary account of the monitoring and attempted relocation of northern bottlenose whales in 2020.