University of Miami Rosenstiel School of Marine and Atmospheric Science
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Dolphin Information

Dolphins are marine mammals belonging to the infraorder Cetacea.  These cetaceans are part of the family of toothed whales that also includes orcas and pilot whales.  Dolphins can be found worldwide in the shallow seas of continental shelves.  The oceanic dolphins belong to the Delphinidae family, but there are species of brackish and freshwater dolphins that live in rivers and streams like the Amazon and South Asian river dolphins.  There are at least 43 species of dolphin, 38 of which are oceanic and 5 being river dolphins.  Dolphins are characterized by their streamlined bodies, two limbs modified into flippers and small conical shaped teeth.  Colorations will vary, but they are usually gray underneath with a darker back.  Their curved mouths give the appearance of a permanent “smile” on the dolphin’s face.  Size varies greatly by species with the smallest dolphin, the Maui’s dolphin, growing to around 5 feet in length, and the largest dolphin, the orca, growing up to around 30 feet in length. 

They are carnivores and do consume mostly fish and squid.  They will use echolocation to track their prey.  Echolocation is a built-in sonar that bounces sound waves off of prey and other objects, revealing information to the dolphin like its location, size and shape.  Dolphins are commonly known for their playful demeanor and extremely social lifestyle.  Dolphins live in pods and can sometimes be spotted by tourists leaping out of the water and even behind boat waves.  When it comes to mating, dolphins have more than one mate.  It takes a while for a dolphin to reach sexual maturity.  Bottlenose dolphins will start reproducing anywhere between 5 to 15 years old.  Bottlenose dolphins also have 12 month pregnancy periods, only a single offspring at a time and the propensity of giving birth every 3-6 years.  Luckily, bottlenose dolphins live to be anywhere between 40-60 years to compensate for the delayed reproduction and lower fecundity rate.  With any species, a baby dolphin will stay with its mother until up to 6 years of age.  Being warm-blooded mammals, dolphins nurse their young.

While some species of dolphin may not necessarily be considering endangered or vulnerable, dolphins are naturally protected by the Marine Mammal Protection Act.  Dolphins face many threats today due to climate change, fisheries bycatch, plastic pollution and offshore oil and gas development.  Seismic blasting is a concern for dolphins of their own echolocation abilities.  The greatest threats though appear to be climate changing pushing dolphins into colder waters to follow after their prey source, and dolphins getting caught accidentally by fishermen.  Many organizations are making sure that at the very least, the Marine Mammal Protection Act is not weakened in anyway.

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