Dolphins!
Appearance
Dolphins live in all of the world’s oceans and some rivers. They live in reefs, estuaries and deep water. The specific area varies for each species. Each species lives in different water temperatures. Most species prefer salt water except for the river dolphins.
Food
Dolphins are carnivores and eat fish, squid, jellyfish and other cephalopods, which are marine invertebrates. They cannot chew food so they swallow food whole and eat it headfirst. They hunt in groups, stunning the fish with sound waves and eating ten to twenty pounds of food a day. Because their diet is so simple, dolphins can be kept in captivity easily.
Breeding
A bull is a male and a cow is a female. Courtship consists of head bumping and playing. The gestation period is 9 to 12 months. The calf is born tail first, has all its senses and can swim immediately. The mother pushes it to the surface for air. It drinks rich vitamin milk form its mother and doesn’t cry. Baby stays close to mom for 2 years and is sometimes cared for by an “auntie”, another female dolphin who helps the calf’s mother. The bull takes no part in raising the young. The calf stays with its mother up to 8 years but only nurses for 2 years. Dolphins are one of the few species that can survive and breed in captivity.
Habits
Dolphins rarely dive over 30 meters deep in the water because they must surface every 5 minutes to breathe. They are very playful and love to follow boats. They can use pebbles, seaweed and wood as toys. They come to play with swimmers and divers and sometimes rescue them if the person is drowning.
They like to rub their bellies on the sand which is called beach rubbing. Leaping up and down is called porpoising. They spy-hop to see what’s happening (their head pops out of the water) and when they jump and splash it is called breaching.
Dolphins are very sociable animals. Pods are groups of 2 to 40 and schools or herds are several hundred animals. Dolphins are usually with other dolphins. They rush to help if one is injured and they socialize with other species during migration.
Dolphins are very intelligent and can learn a variety of tricks such as jumping 10 feet in the air and throwing balls through hoops. They communicate with a variety of clicks, squeaks and whistles and can make 800 clicks a second.
Threats
Dolphin’s main predators are sharks, orca whales and people. One threat from humans is all the garbage, oil and chemicals that pile up and ruin dolphin habitat. Another is tuna purse-seine nets. Dolphins usually hang around tuna so tuna fisherman chase dolphins in high-speed boats then throw a net around the dolphins and tuna when they tire. This method of fishing is called purse seining and is effective at catching many tuna. Unfortunately it also kills about 20,000 dolphins a year. Since the 1950s purse seining has killed over 6 million dolphins although it appears to be slowing down due to public outcry. Dolphins are also caught accidentally by gill nets. Driftnets were banned in 1993 but gill nets still pose a threat to dolphins.
Protection laws are in place in much of the world but in Japan and Sri Lanka thousands of dolphins are killed for meat.
Some species of dolphin are already on the verge of extinction and tougher laws must be put in place to protect them.
Interesting Facts
· They are in the genus Delphinus and suborder odenticeti.
· Sailors believe it’s good luck to see a dolphin on a voyage.
· Ancient Greeks associate dolphins with Apollo, the sun god.
· Their sounds are called phonations.
· Captive dolphins die early because of germ build-up in their tanks.
· Scientists think dolphins are descended from a furry-legged ancestor.
· Dolphins live to an average of 25 years.
· They are considered adults if old enough to breed.
· They usually swim 10 to 15 miles per hour, but can go up to 40 mph if chased.
· They are actually toothed whales.
· There are 38 species of dolphins.
· They are in the delphinadae family.
· When diving their lungs partially collapse and their heart rate slows.
