Dolphins
Delphinidae

Dolphins belong to the order of cetaceans and the suborder of odontocetes (toothed whales), alongside sperm whales, porpoises, and belugas. The mysticetes (baleen whales) constitute the other major suborder: no dolphin belongs to it. Within the odontocetes, the Delphinidae family groups the species commonly called oceanic dolphins.

Delphinidae vs. River Dolphins

The term "dolphin" actually covers several families. River dolphins, like the boto (Inia geoffrensis) from the Amazon or the Ganges river dolphin (Platanista gangetica), belong to distinct families (Iniidae, Platanistidae). The Delphinidae in the strict sense are all marine or estuarine, never strictly riverine.

Why the Orca is Technically a Dolphin

The orca (Orcinus orca) is the largest member of the Delphinidae: males exceed 9 meters and reach 6 tons. Its common English name "killer whale" causes confusion, but its classification is undisputed. The long-finned pilot whale (Globicephala melas) and the false killer whale (Pseudorca crassidens) also belong to this family, showing the morphological extent of the group.

What Unites the Family

Despite this diversity, all Delphinidae share several characteristics: conical teeth, melon (frontal adipose organ involved in echolocation), dorsal fin present in nearly all species, and conscious breathing requiring regular surfacing. Size varies from 1.2 m for Heaviside's dolphin (Cephalorhynchus heavisidii) to over 9 m for the orca.

At sea, identification relies on four quick criteria: general silhouette, color pattern, surface behavior, and relative size. A summary table follows the species portraits.

Bottlenose Dolphin (Tursiops truncatus)

The bottlenose dolphin (Tursiops truncatus) is the best-known species off European coasts. Its short, robust beak, uniform gray-brown color, and size of 1.9 to 3.8 m distinguish it at a distance. It frequently practices bow-riding (swimming in the bow wave) and approaches boats willingly. The sickle-shaped dorsal fin, often notched, is the central criterion for individual photo-ID.

Common Dolphin (Delphinus delphis)

The common dolphin (Delphinus delphis) is immediately recognizable by its ochre-and-gray hourglass pattern on the flanks and slender, elongated beak. It travels in often large groups, sometimes hundreds of individuals, and swims at high speed producing water sprays. It is the most frequently observed species in the Bay of Biscay and off Brittany.

Risso's Dolphin (Grampus griseus)

The Risso's dolphin (Grampus griseus) is unmistakable: light gray body covered in white scars left by conspecific teeth, bulging forehead without a beak, size of 2.6 to 3.8 m. Adults appear almost white. It frequents deep waters and feeds mainly on cephalopods.

Striped Dolphin (Stenella coeruleoalba)

The striped dolphin (Stenella coeruleoalba) has two contrasting lateral bands, blue and white, on very slender flanks. Very fast, it is common in the Mediterranean and northeast Atlantic. Its modest size (1.7 to 2.4 m) and high swimming speed aid identification.

Long-Finned Pilot Whale (Globicephala melas)

The long-finned pilot whale (Globicephala melas) is often confused with the orca due to its large sickle-shaped dorsal fin. Its bulbous forehead (highly developed melon), uniform black color with a light ventral patch, and size of 4 to 6 m allow distinction. It travels in tight groups and often remains at the surface during rest periods.

A group of dolphins observed from a boat provides precise information about its state and activities, provided you know how to read the signals.

Echolocation and Signature Whistles

Dolphins produce two distinct types of sounds: echolocation clicks at high frequency, used for navigation and hunting, and signature whistles, unique to each individual, which serve to maintain social contact. These whistles are learned in the first months of life and remain stable throughout life, according to Janik and Slater (1998). At the surface, they cannot be heard directly, but associated behaviors can be observed.

Social Structure: Pods, Alliances, and Cultural Transmission

Dolphins live in pods whose composition varies by species. In bottlenose dolphins, stable male alliances lasting several years have been documented, particularly in Australia (Connor et al., 1992). Cultural transmission is confirmed: the use of marine sponges as hunting tools, observed at Shark Bay, is passed from mother to daughter (Krützen et al., 2005). At sea, group cohesion and surface synchronizations indicate the pod's social state.

Cooperative Hunting Strategies

Herding (encircling fish schools) is visible from a boat: dolphins dive in formation, resurface quickly, and seabirds often join the activity. Carousel hunting behaviors have been documented in common dolphins in the northeast Atlantic (Souffleurs d'Écume reports). A group swimming fast and changing direction frequently is likely hunting.

Unhemispheric Sleep

Dolphins sleep by keeping one cerebral hemisphere active to control breathing. At the surface, a group swimming slowly in a line, unresponsive to external stimuli, is likely in logging (surface rest) phase. This is a particularly sensitive moment to disturbances: approaching a resting group is one of the most common mistakes of inexperienced observers.

Dolphins are present in all oceans, from the Arctic to tropical waters. Species distribution depends on water temperature, depth, and prey availability.

Northeast Atlantic and Brittany

From Camaret-sur-Mer, I regularly observe the common dolphin and bottlenose dolphin from April to October, with peaks in summer linked to fish concentrations. Obs-MAM data and Souffleurs d'Écume reports confirm year-round bottlenose dolphin presence off Brittany coasts, with photo-ID identified residents. The Bay of Biscay is one of Europe's richest areas for cetacean diversity.

Mediterranean

The Mediterranean hosts populations of striped dolphin, coastal bottlenose dolphin, and, more rarely, Risso's dolphin. Anthropogenic pressures are strong: dense maritime traffic, intensive fishing, chemical pollution. The Pelagos Sanctuary (France, Italy, Monaco) offers partial protection to pelagic populations (Pelagos Agreement, 1999).

Azores and Canary Islands

Deep waters around the Azores and Canary Islands allow exceptional diversity: Risso's dolphin, Atlantic spotted dolphin (Stenella frontalis), bottlenose dolphin, and sometimes rare species like the Fraser's dolphin (Lagenodelphis hosei). Local operators report near-daily sightings of multiple species on the same trip, thanks to favorable bathymetry.

New Zealand, Australia, South Africa

Southern waters host endemic species: the Hector's dolphin (Cephalorhynchus hectori), the world's smallest marine dolphin (1.2 to 1.6 m), is strictly coastal in New Zealand and listed Endangered by the IUCN (2020). In South Africa, the long-beaked common dolphin (Delphinus capensis) forms superpods documented by east coast operators.

River Dolphins

River dolphins deserve separate mention. The boto (Inia geoffrensis) from the Amazon is listed Endangered (IUCN, 2018). The Ganges river dolphin (Platanista gangetica) is Endangered (IUCN, 2022). The baiji (Lipotes vexillifer) from the Yangtze is considered functionally extinct since the 2000s (IUCN, 2017): no confirmed sightings since 2002.

Observing dolphins without disturbing them is not a matter of vague goodwill. There are precise, verifiable rules and objective criteria for choosing a reputable operator.

Minimum Legal Distances in France and Europe

In France, regulations from the July 1, 2011 decree recommend not approaching cetaceans closer than 100 meters. In Natura 2000 zones or certain marine protected areas, additional restrictions apply. Approach must be in the axis of swim direction, never head-on or cutting across the animals' path. Engine must be reduced to slow speed from 300 meters.

High Quality Whale Watching Charter Criteria

The High Quality Whale Watching (HQWW) charter, developed by the NGO WDC (Whale and Dolphin Conservation), defines precise standards for operators: observation time limited to 30 minutes per group, no encircling, mandatory training for naturalist guides, and commitment to sharing data with scientific databases. A certified HQWW operator displays this label and can justify its practices.

Behaviors to Avoid

Certain behaviors are particularly harmful, even if they seem minor. Accelerating to catch up with a departing group causes measurable stress on the animals' heart rate (studies on Tursiops truncatus, Constantine et al., 2004). Encircling a group with multiple boats traps them and disrupts communication. Encouraging dolphins to swim with humans by jumping in from a boat is illegal in several countries and ethically unacceptable everywhere.

Choosing a Responsible Operator

Before boarding, three questions suffice to assess an operator: does it have a trained naturalist on board, not just a sailor? Does it share observation data with Obs-MAM or an equivalent scientific database? Does it apply a time limit for observing each group? An operator unable to answer these three questions clearly warrants caution.

Every observer, even amateur, can produce data useful for research. Tools are accessible and protocols simple.

How Photo-Identification Works

Photo-identification relies on natural marks on the dorsal fin: notches, scars, deformations. These marks are unique and stable over time, like a fingerprint. A clear photo of the right or left flank, with the full fin visible, suffices for a valid submission. I use a 400 mm minimum lens from the deck to obtain usable images at legal distances.

Submitting Observations to Obs-MAM and Happywhale

Obs-MAM, the OFB (French Office for Biodiversity) portal dedicated to marine mammals, centralizes French observations. A complete submission includes: date, time, GPS coordinates, species (or "undetermined"), number of individuals, observed behavior, and photos. Happywhale enables international dorsal fin comparisons and has linked individuals seen in Brittany to sightings off Iberian coasts.

What Citizen Science Databases Have Taught Us

Citizen science data have documented large-scale seasonal movements, unsuspected site fidelities, and stable social associations over decades. The northwestern Mediterranean bottlenose dolphin photo-ID catalog, partly fed by amateur observers, now exceeds 1,500 identified individuals (GDEGeM data, 2023).

Reporting a Stranding or Distressed Animal

In France, any stranding or injured animal must be reported to the National Stranding Network (RNE), coordinated by PELAGIS. Never attempt to return an animal to the water yourself without instructions from specialized teams: this can worsen injuries and poses risks to the handler. The regional emergency number is available on the PELAGIS website.

Dolphins face multiple documented threats. IUCN statuses vary greatly by species: no generalization is possible.

Accidental Captures (Bycatch)

Bycatch is the leading cause of unnatural dolphin mortality in the northeast Atlantic. In France, estimates report several thousands of common dolphins accidentally captured each winter in pelagic nets, mainly during bass and sole fishing (ICES report, 2022). The NGO Souffleurs d'Écume has documented bycatch-related strandings on Brittany coasts for years, with recurrent peaks from January to March.

Sound and Chemical Pollution

Sound pollution (maritime traffic, military sonars, seismic surveys) disrupts echolocation and communication. Studies on Tursiops truncatus show measurable behavioral changes at sound levels below current regulatory thresholds (Nowacek et al., 2007). Chemical pollution from PCBs and endocrine disruptors affects reproduction: critical concentrations have been measured in Mediterranean bottlenose dolphin populations (OSPAR report, 2021).

Direct Hunting: Taiji and Grindadráp

Dolphin hunting persists in two main contexts. In Taiji (Japan), hundreds of dolphins, mainly Pacific white-sided dolphins (Lagenorhynchus obliquidens) and bottlenose dolphins, are captured annually for aquatic parks or slaughtered. In the Faroe Islands, the grindadráp mainly targets long-finned pilot whales: hundreds to thousands of individuals are killed annually, depending on the year (WDC data, 2022).

IUCN Statuses by Species

The bottlenose dolphin is listed Least Concern (LC) by the IUCN (2019), but some local populations, notably in the Mediterranean, are under pressure. The common dolphin is also LC (IUCN, 2021). Hector's dolphin is Endangered (EN, IUCN, 2020). The Ganges river dolphin is Endangered (EN, IUCN, 2022). The baiji is Critically Endangered, possibly extinct (CR(PE), IUCN, 2017). The diversity of statuses reflects the diversity of situations: treating "dolphins" as a homogeneous group regarding threats is an analytical error.