Dolphin Swimming

My name is iiiuuiiiioo

// June 23rd, 2009 // View Comments // Dolphins for kids

Bottlenose dolphins identify themselves with a specific whistle. Each dolphin chooses its own whistle, usually by starting the day of its birthday. This name stays the same for at least ten more years.

Tooth fairy’s paradise

// May 27th, 2009 // View Comments // Dolphins for kids

Some dolphins have even more teeth than crocodiles. Bottlenose dolphins have between 88 to 100 teeth, and they only get one set of them for the rest of their lives. They don’t use their teeth to chew their food, they use them to catch their food and then they swallow it.

are sharks afraid of dolphins?

// April 23rd, 2009 // View Comments // Dolphins for kids

Not really, unless the shark is relatively smaller.
This is a common believe, based on the record of a bottlenose dolphin killing a leopard shark, that was publicized by Flipper TV show.

The truth is that dolphins will avoid natural predators whenever is possible. In the wild, dolphins and sharks pretty much leave each other alone, but 70% of wild dolphins show some degree of shark scarring.
In many cases, dolphins are able to elude attack by detecting through echolocation.

The huge gang of dolphins

// March 12th, 2009 // View Comments // About Dolphins

By Melissa Bañuelos

Part I

We are used to dolphin faces in waterparks and aquariums, we watched the movie “Flipper”, we know how to draw a dolphin, we know how to identify it from sharks and other marine animals, but most of the time we are just talking about one type of dolphin called “the bottle nose dolphin”.

Contributing to the awesome variety of our Planet, there are different dolphin species: 37 types of oceanic dolphins, 4 river dolphins and 6 types of porpoises. In this article we will talk about the most common species and their main characteristics that will be useful to identify them. Next time you see a dolphin you will know which one of all the cousins is greeting you, probably it won’t be Flipper.





Atlantic Spotted Dolphin: The upper body of the Atlantic spotted dolphin is a dark gray color and they develop spots as they get older. They have a chunky beak with a white spot at the end.









Hump Backed Dolphin: They are generally gray with a lighter color along their underside. When they are young they don’t have a hump, but as they grow older the hump will appear infront of the dorsal fin. Sometimes the hump can be a third of the full body length.







Atlantic White-sided Dolphin: Black on the back, with dark grey lines and a long white oval blaze below the dorsal fin, above the blaze there is an ochre band and their belly is white. They have a black ring around the eyes.






Bottlenose dolphin: As we have mentioned, this is one of the most common species. They are truly flexible in their behavior and docile with humans. Their short beak has the shape of a bottle that appears to be floating on the water.






Part II: The Huge Ganng of Dolphins

Echolocation

// February 10th, 2009 // View Comments // About Dolphins

Echolocation, also called biosonar, is the biological sonar used by several animals such as dolphins, shrews, most bats and whales. It is important to marine mammals because it allows them to navigate and feed in the dark at night and in deep or murky water where it isn’t easy to see.

Toothed whales emit a focused beam of high-frequency clicks. Sounds are generated by passing air from the bony nares through the phonic lips. These sounds are reflected by the dense concave bone of the cranium and an air sac at its base. The focused beam is modulated by a large fatty organ known as the ‘melon’. This acts like an acoustic lens because it is composed of lipids of differing densities. Most toothed whales use clicks in series, or click train, for echolocation. Toothed whale whistles do not appear to be used in echolocation. Different rates of click production in a click train result on familiar barks, squeals and growls of the bottlenose dolphin.

The major areas of sound reception are the fat-filled cavities of the lower jaw bones. Sounds are received and conducted through the lower jaw to the middle ear, inner ear, and then to hearing centers in the brain via the auditory nerve. Lateral sound may be received through fatty lobes surrounding the ears with a similar acoustic density to the bone. The brain receives the sound waves in the form of nerve impulses, which relay the messages of sound and enable the dolphin to interpret the sound’s meaning.

Bottlenose dolphins are able to learn and later recognize the echo signatures returned by preferred prey species.

Cetacean evolution

// February 10th, 2009 // View Comments // About Dolphins

The cetaceans (whales, dolphins and porpoises) are descendants of land-living mammals. There are some evidences that confirm this fact: their need to breathe air from the surface; the bones of their fins that resemble the jointed hands of land mammals; and the vertical movement of their spines, a common characteristic of a running mammal rather than the horizontal movement of fishes.

The traditional theory of cetacean evolution was that whales were related to the Mesonychids, an extinct order of carnivorous ungulates (hoofed animals), which looked rather like wolves with hooves and were a sister group of Artiodactyls.

However, since the early 1990s analysis of a wide variety of protein and DNA sequence data consistently indicated that whales should be included among Artiodactyls. Most probably they belong to a sister group of Hippopotamids. In other words, the proto-whales were former artiodactyls that kept typical features of their mesonychid ancestry (such as triangular teeth that modern artiodactyls have already lost).

The Pakicetids were hoofed-mammals that are sometimes classified as the earliest whales. They lived in the early Eocene, around 53 million years ago. They looked rather like dogs with hoofed feet and long, thick tails. They have been linked to whales by their ears: the structure of the auditory bulla is formed from the ectotympanic bone only. The shape of the ear region in Pakicetus is highly unusual and only resembles the skulls of whales.

The most remarkable of the recent discoveries has been the Ambulocetus, which looked like a three-meter long mammalian crocodile. Ambulocetus was clearly amphibious, as its back legs were better adapted for swimming than for walking on land, and it probably swam by vertically undulating its back, as otters, seals and whales do. Smaller cousins of the Ambulocetus was the Remingtonocetid family, which had longer snouts, and were slightly better adapted for underwater life. In both groups, the nasal openings were at the tip of the snout, like in land-mammals.

Known Protocetids had large fore and hindlimbs that could support their body on land, and it is likely that they lived in the sea and on land. It is unclear at present whether Protocetids had the horizontal tail fin of modern cetaceans. However, what is clear, is that they were more adapted to an aquatic life-style. The nasal openings are now halfway up the snout; a first step towards the telescoped condition in modern whales.

Basilosaurus and Dorudon lived around 38 million years ago, and were fully recognizable whales entirely living in the ocean. Basilosaurus was as big as the larger modern whales.
Although they look very much like modern whales, basilosaurids and dorudontids lacked the ‘melon organ‘ that allows their descendants to use echolocation as effectively as modern whales. They had small brains; this suggests they were solitary and didn’t have a complex social structure. Basilosaurus had two tiny but well-formed hind legs which were probably used as claspers when mating; they are a small reminder of their ancestors’ lives. Interestingly, the pelvic bones associated with these hind limbs were no longer connected to the vertebral column as it was in protocetids.

Squalodon lived from the early middle Oligocene to the middle Miocene, around 33-14 million years ago. Skulls of Squalodon show evidence of the first hypothesized appearance of echolocation.

During the early Miocene, echolocation developed in its modern form. Early dolphins including Kentriodon and Hadrodelphis, were from small to medium-sized toothed cetaceans with largely symmetrical skulls, and thought likely to include ancestors of some modern species. Kentriodontines ate small fish and other nectonic organisms; they are thought to have been active echolocators, and might have formed schools.

Today, the whale hind parts are internal and reduced, and they serve as anchor for the muscles of the genitalia. Occasionally, the genes that code for longer extremities cause a modern whale to develop miniature legs.
Modern dolphin skeletons have two small, rod-shaped pelvic bones thought to be vestigial hind limbs. In October 2006 an unusual Bottlenose Dolphin was captured in Japan; it had small fins on each side of its genital slit which scientists believe to be a more pronounced development of these vestigial hind limbs.