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Dolphin Questions
Frequently asked questions about dolphin biology, behavior, conservation, and species — answered with scientific accuracy.
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Frequently asked questions about dolphin biology, behavior, conservation, and species — answered with scientific accuracy.
What is the difference between dolphins and porpoises?
→Dolphins have conical (cone-shaped) pointed teeth. Porpoises have spade-shaped teeth with flat, chisel edges. This difference is the original basis for separating the two groups taxonomically.
Most dolphins have a pronounced, elongated beak (rostrum). Porpoises have a much shorter, rounded snout with no distinct beak. Exceptions exist — Risso's Dolphins have very short beaks.
Dolphins typically have a curved (falcate) dorsal fin — hooked backward like a wave. Porpoises generally have a triangular, shark-like dorsal fin that points straight up.
Dolphins are highly social and vocal, forming large pods. Porpoises tend to be shyer, less social, and quieter — typically seen alone or in small groups.
What is the largest dolphin species?
→The orca (Orcinus orca) is the largest member of the dolphin family. Adult males reach up to 32 feet and weigh up to 6 metric tons. Despite the name "killer whale," orcas are true dolphins.
Hector's Dolphin and Commerson's Dolphin are both around 4–5 feet long and under 130 lbs — competing for the world's smallest marine dolphin.
What species of dolphin are endangered?
→The Baiji (Chinese River Dolphin) of China's Yangtze River is considered critically endangered and possibly extinct. No confirmed sightings since 2004.
Fewer than 8,000 Hector's Dolphins remain off New Zealand. Maui's Dolphin, the North Island subspecies, has fewer than 50 adults.
The Ganges River Dolphin has an estimated 3,500–5,000 individuals remaining. Threats include bycatch and habitat fragmentation.
The Amazon River Dolphin was reclassified as Endangered in 2018 after population declines exceeding 50% were documented.
How do dolphins sleep?
→Dolphins must breathe air, but they are voluntary breathers — every breath requires a conscious decision. This means falling completely unconscious would be fatal.
Dolphins sleep with only one hemisphere of the brain at a time. While one half rests, the other remains alert, keeping one eye open and monitoring the environment.
One common dolphin sleep behavior is 'logging' — floating motionless at the surface, body horizontal, like a log. Pods often log together.
Where do dolphins live?
→Dolphins are found in every ocean on Earth — from the tropics to sub-polar waters. The Orca is the most widely distributed dolphin, found from pole to pole.
Four dolphin species live permanently in rivers. The Amazon River Dolphin (Boto) inhabits the Amazon and Orinoco river systems. The Ganges River Dolphin lives in the Ganges, Brahmaputra, and Indus.
What do dolphins eat?
→Dolphins are carnivores. Most species primarily eat fish and squid. Orcas eat everything from salmon to great white sharks depending on which cultural population they belong to.
Dolphins eat approximately 4–5% of their body weight per day. A 440-lb bottlenose dolphin consumes about 18–22 lbs of fish daily.
Many dolphin species hunt cooperatively. Bottlenose dolphins in South Carolina use 'strand feeding' — chasing fish onto muddy banks, then sliding briefly onto land to catch them.
What is the average lifespan of dolphins?
→Dolphin lifespan varies enormously. Orcas are the longest-lived, with females recorded up to 90+ years. Most medium-sized dolphins live 30–45 years; smaller dolphins typically 15–25 years.
Approximate maximum lifespans: Orca 60–90+ yrs · Bottlenose 40–50 yrs · Common Dolphin 35–40 yrs · Spinner 20–25 yrs · Striped Dolphin 58 yrs · Amazon River Dolphin 30+ yrs.
What is being done to protect endangered dolphins?
→The US Marine Mammal Protection Act (1972) and the 'dolphin-safe' label introduced in 1990 dramatically reduced dolphin deaths in tuna purse seine nets.
Acoustic pingers — underwater sound emitters attached to nets — significantly reduce dolphin bycatch. Mandatory pinger programs exist in New Zealand, the EU, and parts of the US.
New Zealand has established the Hector's Dolphin Sanctuary prohibiting set nets and trawling in the most critical habitat areas.
