The common bottlenose dolphin, known scientifically as Tursiops truncatus, is also called the Atlantic bottlenose, or just the bottlenose dolphin. This marine mammal is the largest of beaked dolphins and the best-known member of the Delphinidae (oceanic dolphin) family. Bottlenose dolphins are the most common dolphin species found in captivity.
Characteristics & Appearance
Weight & Length
Adult male bottlenose dolphins are often heavier and larger than females. The length of an adult bottlenose dolphin can range from 8.2 ft to 11.5 ft., although some only reach 6.6 ft. in size, while others grow to 13.1 ft. A bottlenose dolphin’s weight also varies, from 330 lb. up to nearly 1,500 lb.
Physical Characteristics & Color
Bottlenose dolphins are primarily gray, although their color ranges from light to dark depending on their habitat. Their distinctive snout resembles the neck of a bottle, so they were named bottlenose. But their snout is not a nose. Bottlenose dolphins breathe through a blowhole on top of their heads.
The bottlenose communicates in a similar way to most dolphins. Their language includes a series of whistles, squeaks, and other sounds produced by their bodies as they leap gracefully from the water or playfully slap their tails.
As dolphins don’t have vocal cords, they squeak through their blowholes and whistle through nasal sacs underneath their blowholes. Dolphins also make clicking sounds underwater, called echolocating. They listen for echoes bouncing back at them, allowing them to determine the size and proximity of creatures, especially prey, nearby.
The bottlenose dolphin has a different neck from other dolphins. This species evolved with five of their seven vertebrae remaining unfused, giving their necks greater flexibility.
Lifespan & Reproduction
On average, a bottlenose dolphin lives to age 40 in the wild. Some wild females have lived to age 60 or more, and there are records of bottlenose dolphins surviving over 50 years in captivity.
The bottlenose dolphin are a polygamous species, which means they don’t mate for life. They breed year-round, but they usually mate in the spring. Male bottlenose dolphins mature and can mate from age 8 to 13, and females between 5 to 10 years old.
Males travel in small packs, called pods, to find females in heat. If a male successfully mates with a female, she is pregnant for approximately 12 months with a single calf. At birth, the calf weighs between 30 to 70 lb. and measures from under 3 ft. to nearly 5 ft. in length. The calf nurses on its mother for approximately 20 months and stays with her for several years. Females typically mate every 3 to 6 years.
Where do Bottlenose Dolphins live?
The bottlenose dolphin has adapted to thrive in various marine habitats, including the Atlantic and Pacific Oceans, the Indian Ocean, and the Mediterranean and Black seas. The only habitat they don’t tolerate is the frigid polar waters around the Arctic and Antarctic.
Inshore or coastal populations of the common bottlenose dolphin have smaller bodies and larger flippers suited for maneuvering through busy waterways like harbors, bays, estuaries, and warmer waters close to shore.
Offshore populations of the common bottlenose dolphin are often larger and a darker gray, with shorter fins and beaks. Their bigger size helps them to retain heat in colder, deeper ocean waters. Offshore populations have migrated close to 2,600 miles in one season.
Food & Diet
What do Bottlenose Dolphins eat?
Bottlenose dolphins can hunt for and feed on various prey species, depending on their marine habitat. Their diets generally include crustaceans like shrimp and crabs, squid, and small fish like herring, cod, or mackerel.
Common bottlenose dolphins also employ different hunting techniques according to habitat, and they can search for prey individually or in a pod. One group hunting technique is called herding. The pod surrounds a school of fish, taking turns to charge through the school and feed. They also use their echolocation ability to track down food, alone or in pods.
Typically, adult common bottlenose dolphins have between 80 to 100 teeth. But they don’t use their teeth to chew their food. They use their teeth to capture prey, and they swallow their prey whole. If their catch is a spiny fish, the dolphin swallows the fish headfirst, so the spine doesn’t cut their throat.
Threats & Predators
Unfortunately, human activities–or human interference–pose numerous threats to common bottlenose dolphin species in the wild.
When the dolphins feed or populate inshore or offshore waters heavily trafficked by commercial fisheries, the chance of a dolphin getting entangled in a fishing net rises significantly. Some dolphins unwittingly swim into wide-ranging nets, and they can’t escape.
In tropical hotspots, some tourism operators offer boat tours to swim with wild dolphins. While a chance to interact with wild dolphins can be a spectacular, memorable tourist experience, marine specialists are concerned that this can harass the dolphin pods, disturbing their natural rest periods.
Other threats to both inshore and offshore populations of the common bottlenose dolphin are boat collisions, noise disturbances, or oil and chemical spills polluting the marine environment. Marine biotoxins, including “red tide” toxin events, can prove deadly to bottlenose dolphin populations.
Climate Change & Global Warming
The common bottlenose dolphin is a highly adaptable species, but it could become a species at risk if global warming and climate change worsen.
Scientists found evidence of this off the west coast of Australia. In 2011, a significant heatwave gripped Australia, and scientists noted warmer than usual waters off the west coast. For the following six years, they studied the effects on the coastal dolphin population. The dolphin birth rates had dropped significantly, and their survival rates also dropped by 12%.
To the casual observer, the common bottlenose dolphin may seem as popular in the ocean as they are in captivity–adults are typically not preyed upon by other species, and they’re top predators in the wild. There are incidents of bottlenose dolphins attacked by orcas or sharks, but this is uncommon.
Marine-borne viruses and bacterial or fungal infections can affect the health and longevity of the common bottlenose dolphin. The species can suffer from stomach ulcers, heart disease, respiratory illness, tumors, and parasites like roundworms or tapeworms.
Another strange and sad situation occurring in common bottlenose dolphin populations is called an Unusual Mortality Event (UME). This event is declared by the NOAA Fisheries Office of Protected Resources after locating a large group of marine mammals stranded together in an onshore die-off.
According to NOAA Fisheries, common bottlenose dolphin populations in US waters are not currently threatened or endangered, and the species is covered by the Marine Mammal Protection Act.
NOAA places marine species like common bottlenose dolphin populations into geographical groups, called stocks, for monitoring purposes. Recent reports show that five stocks along the Atlantic Coast are considered depleted. Forty-six stocks along the Atlantic Coast and into the Gulf of Mexico are considered strategic and could be deemed to be threatened in the foreseeable future.
Through the Marine Mammal Protection Act, NOAA is working to protect, conserve, and recover all species of marine mammals found in US waters.
Fun Facts About Common Bottlenose Dolphins
- Dolphin calves are born tail first–the only animals born that way. Adult dolphins can drown if just a tablespoon of water gets in their lungs, and a calf would drown if it came out face first.
- In studying dolphin fins, scientists found a genetic resemblance to legs and toes. It’s believed that dolphins are “re-entrants,” descended from prehistoric land-dwellers who adapted to life in the water.
- An Adult bottlenose eats 5% of their body weight every day, and their stomachs have three chambers.
- The bottlenose dolphin brain is larger than a human brain, and some philosophers have suggested that they be considered “non-human” persons due to their significant intelligence.
- Dolphins are born with hair. A calf has whiskers on its upper jaw that fall out soon after its birth.
- On average, adult bottlenose dolphins can hold their breath underwater for up to seven minutes.