About Bottlenose Dolphins

The playful and sociable bottlenose is familiar to humans, thanks to TV celebrity bottlenoses like Flipper, and their frequent confinement in marine theme parks and aquariums. People are impressed by dolphins’ ability as swimmers, jumpers, and divers, and charmed by the upturned corners of the dolphin’s mouth, which makes it appear to be wearing a permanent smile. However, our interactions with dolphins occur in unnatural settings and the behaviour we tend to see in parks and Hollywood films is actually abnormal. Real dolphin life under the sea is still something of a mystery to us.

There are two different species of Bottlenose Dolphin, the Common and the Indo-Pacific. Subspecies may also exist, but scientists do not currently have sufficient data to clearly distinguish them. Dolphins are a type of whale, and though they are considered to be small compared to some of their relatives, they can be as long as 20 feet.

The social lives of dolphins

Bottlenose Dolphins are highly social animals. In the wild, they live in long-term social groups called pods with as many as 12 other dolphins. The pod will be either a group of females and their young or a mixed group of juveniles. At times, several pods will join together to form larger groups of a hundred dolphins or more. Males live mostly alone or in groups of two or three, joining the females occasionally for mating.

Researchers were very interested to discover that there are specific individual dolphins who play central social networking roles in what seems to be a complex community. In a seven year study, scientists saw that pods seemed to be socially connected by common members, allowing the whole community to socialize. When an individual who had brought groups together left, the groups would break apart again, only reuniting if the socialite returned.

Human friends

Dolphins are sensitive animals that care deeply for their family members. They have been known to extend their caring to other species as well. Humans have been deeply moved by the compassion dolphins have sometimes shown them. Bottlenose Dolphins have occasionally rescued injured divers by pushing them up to surface, which is how they usually help other injured dolphins. In November 2004, there was a very dramatic report of dolphin intervention in New Zealand. Three lifeguards swimming 100m off the coast were approached by a Great White Shark. A group of Bottlenose Dolphins, apparently aware of the danger to the swimmers, herded them together and surrounded them tightly for forty minutes, preventing an attack from the shark, as they returned to shore.

Some dolphins have been known to pay visits to humans. Male dolphins that travel alone sometimes enjoy the company or attention of humans. Young males are especially likely to hang around marinas near people, swim with them, and follow their fishing boats.

Behaviour

Dolphins are not only aggressive toward sharks; they have been known to attack smaller species of dolphin and porpoise when they find themselves competing for food. Male dolphins also compete very aggressively for females, engaging in behaviour that proves their toughness, like head butting.

Though males are not involved in raising the young dolphins, mating is an intimate affair for Bottlenoses. It is always preceded by lengthy foreplay, which involves caressing, nudging, nuzzling, rubbing, clapping, and yelping.

Dolphin culture?

A 2005 study singled out Bottlenose Dolphins as the first and, so far, the only marine mammals observed to have any material culture. The scientists watched Bottlenose Dolphins breaking sponges off the ocean floor then using them to cover their noses while searching for fish along the bottom. Almost all the dolphins seen sponging were female and the researchers believed that they learned to do so from their mother. Despite the sponge example, researchers have observed that dolphins learn behaviour more from peers than from their mothers. Experts of mimicry, dolphins gradually figure things out for themselves and copy each other.

Dolphin Intelligence

Dolphins have one of the highest mammal brain-to-body ratios, but it is not definitely known that this makes them smarter than other animals. Their behaviour has certainly lead people to believe as much.

Dolphins seem to be self-aware and have demonstrated that they are conscious of their own actions and interactions with their surroundings and with others. Captive dolphins at the Institute for Marine Mammal Studies in Mississippi had been trained to give any litter that landed in their pool to a trainer, who would reward them with a fish. One dolphin learned to cheat the system by hiding the litter she found at the bottom, then tearing off and returning pieces gradually in order to maximize the number of fish she would get for it. This particular dolphin seemed to be capable of planning for the future and delaying gratification, which are rather sophisticated characteristics.

Researchers have not figured out if dolphins have an actual language, but dolphins at Kewalo Basin Marine Laboratory in Hawaii have learned to understand a sign language that was developed by a team of scientists. The scientists believe the dolphins’ responses to the language show a deep understanding and capability for abstraction because the animals recognize the significance of the order of words in a sentence and not just of the words themselves. They were also able to learn the meaning of the sign “create” and would respond to the sign by doing something they had not been taught.

The sad truth about marine theme parks

Dolphins are very popular at marine theme parks because they can be trained to do impressive tricks and aquatic acrobatics and, to the ignorant eye, seem to be enjoying themselves. However, dolphin shows are the unfortunate result of a cruel and unnatural domination. In the wild, dolphins hunt the fish they eat, while in captivity they have no means of fending for themselves and must rely on their trainers for all food. Trainers take advantage of the dolphins’ hunger to force them to perform in return for food. In fact, former trainers have revealed that, when they’re not hungry, dolphins are completely unwilling to perform any of the tricks the crowd believes the animals enjoy.

Dolphins are also trained by the US and Russian militaries to help with wartime tasks, such as planting mines on enemy ships, finding underwater mines, or attacking divers. Using animals for war, let alone any human purpose, is not fair, but people are nonetheless impressed by the challenging work dolphins have sometimes done for humans.

Did you know?

• The elongated upper and lower jaws of the bottlenose dolphin look a bit like an old-fashioned bottle, which gives them their name. However, the bottlenose’s true nose is the blowhole on top of its head.
• Male dolphins are a bit longer and a lot heavier than the females.
• The dolphins that live in shallower water closer to shore tend to be smaller – as much as 1.5 m shorter in length.
• Dolphins have cone-shaped teeth that allow them to eat fish and other sea creatures.
• Dolphins propel themselves through the water using their powerful tails.
• Dolphins have very smooth skin that helps them move through water faster. They replace the outermost layer of their hairless skin every two hours. No other mammal regenerates skin this quickly.
• Because their skin is smooth, dolphins scar very easily. All dolphins have scars so researchers often rely on these markings to identify individuals.
• Dolphins cannot breathe underwater as fish can. Like other whales, dolphins need to breathe air through their blowholes. They usually come up for a breath every 3 or 4 minutes but it seems that offshore dolphins may be able to dive for up to 15 minutes.
• Dolphins need to be awake or semi-conscious to breathe, so an unconscious dolphin will drown. Therefore, they sleep in a semi-conscious state at the surface with their blowhole exposed and only a few minutes at a time. They have the remarkable ability to rest one half of their brain while the other half remains alert for approaching danger, and then are able to switch which side they are resting.
• A dolphin can move each of its eyes independently of the other.
• Dolphins are able to find their food and navigate by using not only eyesight and hearing, but also echolocation. This involves producing intense, short, broadband pulses of ultrasonic sound, which sound like clicks to humans. The dolphin judges its surroundings based on how long it takes the sound to return to them. This method of finding their way is one of the reasons why life in a relatively small pool at a marine theme park is so stressful for the animals. Their sound pulses end up bouncing off the walls to bombard them with constant jumbled and meaningless reverberations. Indeed, many dolphins seem to go crazy after a few months in captivity.
• Male bottlenoses seem to have a more stressful life than females and rarely live past 30 years, while the female lifespan averages around 40 years.
• Some bottlenose dolphin populations have declined due to pollution and habitat alteration. Dolphins also accumulate contaminants in their tissues, which may affect their ability to reproduce and contribute to higher infant mortality. Because many dolphin populations frequent near-shore areas, they are particularly vulnerable to entanglement in fishing gear and boat collisions.