Dolphins
Dolphins are part of the family of toothed whales that includes orcas and pilot whales. They are mammals and breathe through a blowhole on the top of their head. Dolphin coloration varies, but they are generally gray in color with darker backs than the rest of their bodies.
Size The Amazonian River dolphin is the smallest of the dolphin species at five feet in length. It weighs about 100 lbs. The largest dolphin species is the orca. Male orcas grow to about 18 feet in length and weigh about 19,000 pounds!
Lifespan Most dolphin species have a long lifespan. It is estimated that some individuals may have lived for more than 100 years.
Diet
Variety including fish, squid and crustaceans.
Population
It is difficult to estimate population numbers since there are many different species spanning a large geographic area.
Range
Most species live in tropical and temperate oceans throughout the world. Five species live in rivers.
Behavior
Dolphins are well known for their agility and playful behavior, making them a favorite of wildlife watchers. Many species will leap out of the water, spy-hop (rise vertically out of the water to view their surroundings) and follow ships, often synchronizing their movements with one another. Scientists believe that dolphins conserve energy by swimming alongside ships, a practice known as bow-riding.
Dolphins live in social groups of five to several hundred. They use echolocation to find prey and often hunt together by surrounding a school of fish, trapping them and taking turns swimming through the school and catching fish. Dolphins will also follow seabirds, other whales and fishing boats to feed opportunistically on the fish they scare up or discard.
Reproduction
Mating Season Throughout the year, though in some areas there is a peak in spring and fall.
Gestation 9-17 months depending on the species. When it is time to give birth, the female will distance herself from the pod, often going near the surface of the water.
Number of offspring Usually one calf; twins are rare.
As soon as the calf is born, the mother must quickly take it to the surface so it can take its first breath. The calf will nurse from 11 months to 2 years, and after it is done nursing it will still stay with its mother until it is between 3 and 8 years old.
Threats
Marine pollution, habitat degradation, harvesting, low frequency sonar, entanglement in fishing gear, boat traffic.
Legal Status/Protection
CITES* (All species of dolphin are protected under CITES: Appendix I: snubfin dolphin, Amazonian River dolphin, Indo-pacific humpbacked dolphin and the Atlantic humpbacked dolphin; Appendix II: all other dolphins), Endangered Species Act** (the Chinese River dolphin and the Indus River dolphin are listed as endangered under the Endangered Species Act), Marine Mammal Protection Act***
*Convention on International Trade in Endangered Species of Wild Fauna and Flora, an international treaty with 172 member countries. Appendix I species cannot be traded commercially. Appendix II species can be traded commercially only if it does not harm their survival.
** The Endangered Species Act requires the US federal government to identify species threatened with extinction, identify habitat they need to survive, and help protect both. In doing so, the Act works to ensure the basic health of our natural ecosystems and protect the legacy of conservation we leave to our children and grandchildren.
*** The Marine Mammal Protection Act prohibits, with certain exceptions, the take of marine mammals in U.S. waters and by U.S. citizens on the high seas, and the importation of marine mammals and marine mammal products into the U.S.
