Common dolphin
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Common dolphin are oceanic dolphin that consist of two species: the long-beaked common dolphin and the short-beaked common dolphin. Even though these dolphins live in the water, they are considered mammals since they breathe air. They are only one of the few mammals that live in the ocean. These dolphins are very complex creatures and are also quite intelligent with the use of echolocation and different behavioral tactics. They have distinct differences but, as you will read in body design, the two dolphins are somewhat hard to distinguish from one another. Their interaction with other dolphins in their families is intriguing. The short-beaked dolphin is the most common dolphin and up until 1994, the long-beaked common dolphin was grouped in with the short-beaked, but due to genetic and anatomical differences, they created the long-beaked common dolphin species. [2][3]
Body Design
Common dolphins can range in weight anywhere from 160-500 pounds. The short-beaked common dolphin weighs on average about 440 pounds while the long-beaked common dolphin can weigh anywhere from 160-500 pounds. The short and long-beaked common dolphins span in length, 8.5-9 feet at the most, which is the average length of the short-beaked common dolphin, and the long-beaked common dolphin can span from 6-8.5 feet which makes it one of the smallest dolphins.[4] As in most species of dolphins, the female is slightly smaller than the male.[5][6]These dolphins also have about 57 pairs of teeth on their upper and lower jaws that aid them in catching and holding prey. Even though they have all of these teeth, they don't chew their food.[7] Their dorsal fin is curved backwards, tall and has a triangular shape. They usually swim at about 5-7 miles per hour but have been able to reach speeds up to 29 miles an hour. They can travel over a span of 150-200 miles in a two day time period.[8][4] These dolphins have bilateral symmetry, meaning they are essentially the same if cut in two vertical halves. They are also classified as endothermic, or warm-blooded.[4]
Another aspect of body design is what the dolphins actually look like. They have an hourglass-shaped, slender figure, which separates the two colors, and with a dark grey color on their backs which creates what looks like a cape in a V-shape. Common dolphins have a yellowish tan color on the thoracic panel (the panel on their thorax) of their bodies.[5]Both species of common dolphins look quite similar, but the short-beaked dolphins have larger dorsal fins and flippers when compared to the long-beaked dolphin. The long-beaked dolphin, as read in their name, has a slightly longer beak then the short-beaked dolphin. Calves, or baby dolphins, tend to have a paler color than the fully matured adult.[9] They can be easily differentiated from other dolphin species due to their crisscrossed pattern on the dolphins' back.[8] The flippers and flukes (the two lobes of the dolphin's tail) are black or dark brown, as well as the back. Their eyes have black rings surround the eye with markings that go all they way to the beak.[4]
Life Cycle
When common dolphins turn three or four years old or when they grow to about six or seven feet, they are sexually mature and can start to reproduce. The length is believed to have more influence than the age. Females tend to mature earlier than males do, but it sometimes depends on the location. The time of mating takes places from about June to September. Common dolphins are viviparous, meaning they reproduce sexually and give birth to live young. Normally the whole gestation period last anywhere from 10-11 months, female common dolphins can reproduce once every 1-3 years and give birth to one calf on average. The calves are born tail first and are 30-34 inches in length. The calves are nursed for about a year to 19 months. The calves don't suck on the mother's teats, because if they did they wouldn't be able to breathe and they don't have lips to suck with. To solve this problem the mother, through muscle contractions can eject the milk into the calf's mouth.[10] [11][7][4]
Once the dolphins are born, they become part of the pod immediately. The calves adapt quickly and learn to breathe and swim like their mothers. As the babies mature and grow they showcase noticeable differences. For instance, the calves will stop swimming in the 'echelon swimming' pattern, or swimming right next to their mothers, to the 'infant-positioning' swimming, which is swimming underneath their mother. After a month of the dolphin's life, the calf will 'practice forage' meaning the baby will become more independent and leave the mother's side more frequently to play with other dolphins and explore the surrounding ocean.[12] The lifespan of the common dolphin can go to about 35-40 years, but most are known to die at the age of 22.[5]
Ecology
Like most dolphins, common dolphins live in the oceans; the Atlantic, Pacific and Indian Oceans. The long-beaked common dolphins live in shallow, tropical or subtropical, warmer climates by coasts and the continental shelf. The long-beaked common dolphins usually live in the Atlantic, Indian and Pacific Oceans. They tend to be found around Baja California up to central California. They have also been found around South America by the coasts of Peru, Venezuela, Chile, Argentina and Brazil. Short-beaked dolphins are found in deeper waters, that are also warm and in tropical or subtropical climates.[13] Unlike most dolphins, the common dolphin doesn't migrate. Although, they will move if their food supply becomes scarce or the water becomes too cold. [7][4]
Commons dolphins have a pretty basic diet consisting mostly of squid and schools of fish, but they do eat a variety of other crustaceans.[13] Oddly, these dolphins don't chew their food, meaning the food they eat needs to be small enough for them to swallow. Despite this, they are still quite picky about the fish that they eat, but the fish available to them depends on their location. Most of their feeding occurs at night, due to the fact they rest during the day. During the feeding times, the dolphins eat about 5% of their body weight.[7] They catch the fish by forcing the school of fish to the surface and as they fish become confused the dolphins prey.[14]
The common dolphin's main threat is man. They are hunted for their oils meat in Russia and Japan. Despite this, they are not considered endangered. Their numbers are not by any means small or looking like they would be endangered at about 3 million dolphins in the Eastern Pacific, 100,000 in the waters of Northwestern Europe and more than 300,000 off of the western coast of North America .[5]
Behavior
Common dolphins have an interesting behavior tactic that enables them to communicate with other dolphins and hunt efficiently. This behavior is called echolocation. So what exactly is echolocation? Echolocation is the act of dolphin sending out sound waves. The sound waves will eventually bounce off an object and then the sound waves come back to the dolphin. The sound waves tell the dolphin how far away the object is, the size of the object, the shape of the object and the texture. Echolocation helps dolphins to find how far away their food is.[11] Common dolphins like to communicate with other dolphins and have community with one another. Echolocation can play a fundamental role in this.
Common dolphins are very social mammals. They live in large groups of dolphins called pods ranging in number anywhere from a few hundred to several thousand. The pods show the dolphin's intelligence. They create a hierarchy within the pod to keep order and often create subgroups based on the dolphins age or different aspects of the dolphin. They are also quite active animals and have been known to take part in activities such as somersaults and bow riding. Some smaller dolphins have been known to jump vertically out of the water. Common dolphins also eat, swim and breathe together almost never being alone. [7] Not only are these dolphins playful and social, they are quite affectionate creatures as well. When one dolphin is sick, another will help the sick dolphin to breathe by using the dolphins' fins to keep the sick afloat. They show sadness when a member of their pod dies, and show happiness when reunited with another dolphin.
Video
Common dolphins swimming
References
- ↑ Delphinus Delphis Wikispecies. Web. Last accessed 22 November 2015. Unknown Author.
- ↑ Long-beaked common dolphin (Delphinus capensis) Widescreen Arkive. Web. Accessed 9 February 2016. Unknown Author.
- ↑ Short-beaked common dolphin fact file Widescreen Arkive. Web. Accessed 9 February 2016 Unknown Author.
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Alspaugh, Maria. Delphinus delphis Animal Diversity Web. Web. Accessed 9 February 2016
- ↑ 5.0 5.1 5.2 5.3 Long-Beaked Common Dolphin (Delphinus capensis) National Oceanic and Atmospheric Administration. Web. Last Accessed 12 December 2012. Unknown Author.
- ↑ Short-Beaked Common Dolphin (Delphinus delphis) National Oceanic and Atmospheric Administration. Web. Last Updated 12 December 2012. Unknown Author.
- ↑ 7.0 7.1 7.2 7.3 7.4 Common Dolphin Facts (Delphinus delphis) Bio Expedition. Web. Accessed 2 February 2016 Unknown Author.
- ↑ 8.0 8.1 Delphinus delphis — Common Dophin, Short-beaked Common Dolphin Australian Government Department of the Enviornment. Web. Accessed February 9 2016. Unknown Author.
- ↑ Long-Beaked Common Dolphin About Education. Web. 3 February 2016 Last Acessed. Unknown Author.
- ↑ Fertl, Dagmar. Common Dolphin Delphinus Delphis (Short-Beaked) Delphinus Capensis (Long-Beaked) American Cetacean Society. Web. Accessed 17 January 2016.
- ↑ 11.0 11.1 Common Dolphin Breeding and Reproduction Kids do Ecology. Web. Published 2002. Unknown Author.
- ↑ Life History and Reproduction Bioweb. Web. Accessed 9 February 2016. Unknown Author.
- ↑ 13.0 13.1 Common Dolphin Delphinus Delphis (Short-Beaked) Delphinus Capensis (Long-Beaked) American Cetacean Society. Web. Published 2002.
- ↑ Common Dolphin Australian Museum . Web. Last Updated 4 November 2013. Unknown Author.
