Dolphins, Delphinidae (family)

Detailed introduction

The Delphinidae family is the most diverse and widely distributed family of toothed whales in the order Cetacea, encompassing over 30 genera and more than 90 extant species, including true dolphins, killer whales (orcas), false killer whales, spinner dolphins, and bottlenose dolphins . They are renowned for their high sociality, echolocation , and complex behaviors, and are apex or secondary predators in the ocean, playing a crucial role in food web structure and energy flow.

Ecology and Behavior

• Diet: Primarily feeds on mid-to-upper-level fish and cephalopods , with some larger species (such as killer whales) also preying on other marine mammals and seabirds.

• Social structure: ranging from small groups to large "supergroups", with special matrilineal or mixed kinship networks; exhibiting cooperative hunting, inheritance and learning, and dialectal calls.

• Echolocation: Utilizes the melon to focus a sound beam to detect the environment and prey; interspecific acoustic libraries and signal diversity.

• Migration and residence: Some populations migrate seasonally, while there are also resident populations and offshore/nearshore lineages.

Morphology and Identification (Common Characteristics at the Departmental Level)

Sizes range from 1.2 meters (small spinner dolphins) to 8–9 meters (killers); streamlined body shape with a distinct dorsal fin and rostrum (killers and others have short rostrums); multiple conical teeth; single blowhole; subcutaneous fat layer and muscles adapted for high-speed, long-distance swimming.

Body type and lifespan (at the departmental level)

• Body length: approximately 1.2–9.0 meters (depending on the species).

• Weight: Approximately 40 kg to 6,000+ kg (orca).

• Lifespan: Small true dolphins live 20–40 years, while large species (such as orcas) can live 60–90 years or even longer.

Distribution and Habitat

Except for some enclosed polar regions, they can be found in almost all oceans around the world , with different species distributed from the coast and continental shelf to the high seas and deep sea. Nearshore types are often associated with estuaries, upwellings and continental shelf fronts, while pelagic types are associated with warm pools, eddies and leading edge systems.

Threats and Protection

• Secondary catches and entanglement: drift gillnets, longline fishing, purse seines, etc.; sonar deterrents, weak breaks, and release regulations can mitigate these issues.

• Noise and Vessels: Shipping, military sonar, and seismic exploration affect communication and foraging; vessel collision risk.

• Pollution and food web changes: Persistent pollutants, plastics, and climate variability alter baitfield patterns.

• Unhealthy tourism and harassment: close-range chasing, feeding, and stalking lead to impaired energy budgets and behavior.

IUCN: This page provides a family-level overview and is "unassessed" overall; there is significant variation in species/population levels (LC–CR). Key measures include: improved and avoidance of fishing gear, noise management, speed/route optimization, spatiotemporal protection of key habitats and migration routes, and long-term acoustic-photographic identification monitoring and citizen science data.