The bottlenose dolphin, like the one who played Flipper, is by far the most common species of dolphins and one of the most loved marine mammals, especially by children, thanks to their high intelligence and altruism and their beautiful, affectionate and gentle nature. The animal star of 1964 and 1995 TV series “Flipper”, as well as of the movie “Flipper” (1993) was a bottlenose dolphin. More precisely, the 1964 series featured 5 different female bottlenose dolphins, because females are generally less aggressive than males and easier and quicker to train. The 1993 film, a remake after the movie with the same name from 1963 was an acknowledgement of the fact that it was still safe for humans to go back into the ocean, considering the scary saga “Jaws”.
The bottlenose dolphin is a marine mammal belonging to the order “Cetacea”, the suborder “Odontocetae” (all whale species), the family “Delphinidae”( oceanic dolphin) and the genus “Tursiops”. This genus consists of three species : the common bottlenose dolphin, the Indo-Pacific bottlenose dolphin and the recently discovered (2011) the Burrunan dolphin, divided into two sub-species: the Pacific bottlenose dolphin and the Black Sea bottlenose dolphin. Although they are often referred to as porpoises, the latter marine group also includes whales such as the beluga whale and the orca.
These majestic creatures live in pods, which represent social groups typically comprised of 10 to 30 dolphins, but the pods can even reach up to 1000 members. They are encountered in tropical oceans and warm temperate waters around the globe. These dolphins are highly adaptable and they can thrive in captivity as well ; the bottlenose dolphins are the consummate stars of acquariums worldwide because they are very interactive with humans and enjoy the close contact. This marine species is one of the most researched in marine biology, in particular their behaviour, communicative skills and cognitive function.
In terms of general appearance, the bottlenose dolphin s average size is 7 to 14 feet and its average weight is 350 pounds to 1,200 pounds. Their size varies according to their habitat; Those who live in waters near the shore, close to the bottom or in cooler, northern waters (like Moray Firth in Scotland) are heavier and longer than those which live in shallower and warmer, southern waters( like the Florida coast). Also, males are heavier and somewhat longer than females. One very interesting fact is its jumping ability – it can breach out of the water up to 16 feet, just for fun, and it typically lands with a splash on one side or on its back. The color of the common bottlenose dolphin varies between different shades of grey, darker near the dorsal fin; the color of the Indo-Pacific bottlenose dolphin is dark grey on its back and light grey or white on its belly; the Pacific bottlenose dolphin also has a black line running from its forehead to its eye.
Its name is given by its elongated lower and upper jaw, known as a rostrum, which makes its face loo like it is smiling. Its nose is the blowhole found on top of the head. In order to breath, they must surface two to three times per minute and get air into their blowholes. A very interesting fact is that they can store twice the amount of oxygen that a human can and as such, they can stay submerged for up to 20 minutes. They sleep near the surface and they can breath because one brain hemisphere is active during sleep. It has between 18 to 28 teeth on each side of the upper and lower jaw as well. The pectoral flippers on each side of its body are used for steering and they swim by moving the lobes of its tail up and down. Their life expectancy in the wild and in captivity alike is roughly 45-50 years.
Another interesting fact is that they are reported to undergo hybridization with other species of dolphins, mostly with the Risso s dolphin, which occurs both in the wild and in captivity. The most renowned hybrid is the wolphin, a hybrid between a bottlenose dolphin and a false killer whale; two of them currently live in captivity in Hawaii. In the wild, their defense mechanism against predators consists of mobbing techniques ( battling or forcing them to flee) and outswimming them. They have sharp sense of vision and of hearing, good sense of taste, but a poor sense of smell.
The bottlenose dolphin is a carnivore and it prefers mostly fish such as tuna, mackarel, drum, croaker, weakfish and grey mullet, squid and crustaceans. The most interesting fact about tracking their prey is their perfect use of echolocation. They can emit 1000 clicking sounds per second which travel underwater until the prey fish is found. Then, these encrypted sounds bounce back as echoes to the original sender, encoding information related to the location, shape, form and size of their prey, which led researchers to believe that they can form a picture or image of the target from these sounds. These marine mammals are expert users of this sonar-like technique.
In the wild, they hunt mostly in group, as a team and they use their herding abilities to the maximum; they are excellent strategists and they will herd the fish towards the shore and feed themselves at will on the washed up fish. They rarely hunt alone for bait fish or bottom-dwelling fish. This “strand feeding” technique is used in particular by this highly intelligent species around the coasts of South Carolina and Georgia. Another strategy they usually use is “fish wacking”, by trapping the school of forage fish and then hitting the fish with their flukes (lobes of the tail) in order to drive them onto a tidal flat (coastal wetland) and knock them out of the water, for the purpose of capturing the fish more easily.
The bottlenose dolphins in Florida Keys are even more resourceful, because they also feed themselves using a foraging strategy, such as mud plume feeding, by developing in the shallow water a U-shaped plume of mud used to rush through for capturing fish more efficiently. These smart mammals have been often seen following fishing boats, hoping that they can get their fins on some yummy fish they did not work to catch in the first place. This practice can also spell tragedy for these amazing creatures, because waiting for food to fall into their lap, can accidentally cause them to be trapped in fishing nets. As long as they wait for the fishing boats to leave, they are out of harm s way.
Their average speed is 5-11 km/h, but they can reach up to 35 km/h. Only dolphins which live in cooler waters can dive deeper for bottom-dwelling fish.
Their amazing communicative skills are fascinating to humans. They make use of a complex system of whistles, burst pulsed sounds and squeaks to communicate between them and with people as well. Another interesting fact is that they lack vocal chords, so they use six air sacs found near the blowhole to make sounds. Each dolphin has its unique signature whistle and that is how marine biologists recognize them in the wild. The melodious whistle tones are used between mother and offspring and for hunting ; the strident burst pulsed sounds are used to avoid aggression when food is found. Researchers have distinguished 30 different sounds.
Ongoing research related to their cognitive abilities includes mimicry, body language, pointing gestures, gaze, self-recognition in the mirror and extensive memory. A very interesting fact about them is that bottlenose dolphins and sea otter are the only marine mammals to use tools, such as marine sponges placed on their rostrum for protection.
Due to their high intelligence (they have 5.8 billion cortical neurons), they can be trained to perform high-end tricks in captivity , such as tail-walking. Studies have shown that mothers can teach the behavior to their offsprings. In Mauritania and Brazil, untrained dolphins have been observed to cooperate with fishmen in foraging a school of fish. They are altruistic towards are marine creatures; one dolphin helped two stranded sperm whales back into the sea, using vocalization.
This species is not an endangered species yet, but it is threatened by climate changes and mostly by humans. Thousands of bottlenose dolphins end up entangled in fishing nets ( tuna nets in particular) each year, where they suffer a cruel death. The legislation has recently regulated the commercial fishing industry and it requires “dolphin-safe” fishing methods.
They are not only used for entertainment, but as therapy animals as well, in particular for disabled children. Military dolphins are also trained in the US for detecting sea mines and divers.