March is Dolphin Awareness Month, and there's no better way to observe the occasion than by learning more about these beautiful aquatic mammals. Whether you have been an avid dolphin enthusiast for years or are just starting to investigate the subject, there is no end to surprising facts about these fascinating animals. So in honor of Dolphin Awareness Month, let's examine some important and interesting dolphin facts.
Dolphins are marine mammals that can be distinguished by a few common physical traits.
Dolphins are warm-blooded, breathe air, give birth to live young, nurse their young, and have tiny little hairs on their rostrum when they are born. While a dolphin is born with a few hairs around the tip of their rostrum, these follicles fall out shortly after birth, leaving the dolphin smooth and hairless. The one exception is the Amazon River dolphin, which retains these hairs on its rostrum. Dolphins have a very thick outer (epidermal) skin layer. The surface of their epidermis is replaced up to once every 2 hours to promote a smooth hydrodynamic surface (decreases drag when swimming) and to prevent the colonization of fouling organisms on their skin.
The overall shape of a dolphin's body is also unique. Streamlined and fusiform, dolphins are capable of swimming at top speeds of up to 20 – 25 miles per hour. They use their flukes (or tail fins) for propulsion via the up and down strokes, while the pectoral fins are used to control steering and turning. A dolphin’s dorsal fin has two main functions: stability and thermoregulation. The fin acts similarly to the keel of a sailboat, helping the dolphin swim through the water in a straight line.
The word "bottlenose" in the term Atlantic Bottlenose dolphin is a misnomer for this marine mammal because the bottle-shaped body part on the front of their face is actually their mouth, not their nose. Dolphins don’t have noses, and they don’t have a sense of smell. The closest thing to a “nose” would be their blowhole, located on the top of their head, but they cannot smell out of this hole.
Dolphins use sound to navigate and possibly communicate with each other.
Though there is some debate regarding the use of structures that resemble vocal chords in their larynx, many of their sounds are produced by nasal sacs and bones in their blowholes. Dolphins can make squeaks, buzzes, whistles, clicks, and a wide array of other crazy noises. Acoustic signals are essential for bottlenose dolphins to maintain contact with other conspecifics. These signals, comprised of whistles, clicks, and burst-pulses, are suggested to relay information about the individual’s locations and motivations to reunite. Although we know that dolphins communicate, we are just scratching the surface in understanding the components of each different sound type and what they are used for (e.g., behavioral context).
Echolocation works similarly to an ultrasound. It gives a dolphin the capacity to explore their environment 3-dimensionally and aids in navigation and hunting in low light and low visibility environments. They emit sounds, or clicks, from their nasal passages, which are then passed through their melon (forehead). The melon is filled with fatty tissue and fluid and acts like an acoustic lens to focus the sounds in different directions. The sound waves then bounce off of objects of interest and are received by the dolphin’s lower jaw as an echo. This information is then passed to the brain via the inner ear. Echolocation is very efficient. Bottlenose dolphins are capable of distinguishing an object the size of a ping-pong ball from a football field away.
While their exact diet varies depending on habitat, all dolphins are predators that feed on a wide variety of fish, cephalopods and crustaceans.
Don't let their beautiful, graceful appearances fool you: dolphins are adept predators. In the wild, dolphins eat predominantly fish (piscivorous), but they also consume significant amounts of squid and crustaceans. However, diet varies by region, season, sex, age, and reproductive status. For example, researchers discovered over 40 different types of prey in the stomachs of stranded bottlenose dolphins, but a few species were most abundant. Similarly, resident bottlenose dolphins in Sarasota, Florida, exhibited a variety of prey in their stomach, but pinfish accounted for approximately 70% of their diet. Despite having 80 – 100 cone-shaped teeth (homodonts), dolphins do not chew their food but rather swallow their prey whole.
Although it's Dolphin Awareness Month, many species of dolphins still face widespread threats in the wild.
Unfortunately, one of the characteristics marine mammals share is that most are, or have been, exploited by humans. Whales, sea otters, sea cows, and seals have been historically overexploited, which has resulted in the extinction of some species (e.g. Stellar sea cow, Caribbean monk seal, and the Atlantic gray whale) and the endangered status of many. Though there are laws that protect marine mammals, not all countries abide by these laws. So, the direct harvesting of whales, seals, walruses, dugongs, and dolphins still occurs today in various places throughout the world.
How can you help fight the growing risks facing these beautiful aquatic mammals? Use this March awareness month to educate yourself about the plight many dolphin species face and get involved with conservation efforts through organizations such as the National Marine Mammal Foundation and Dolphins Plus Marine Mammal Responder.
