The intelligence of the sea
1.The first cetacean was Pakicetus, which lived 55 million years ago. It was a shore animal with well-developed four limbs. The first dolphins (and toothed whales) are considered the Squalodontidae, which lived 33 to 15 MA years ago. They were 3 m (10 ft) long and had large teeth.
2.Dolphins live in bands, which can be large in the case of the pelagic species (up to 1,000 individuals, the record being of 8,696 dolphins in a group), while coastal dolphins live in small groups. Females stay in the center, to be protected against sharks and killer whales. In all species there are solitary individuals.
Coastal dolphins hunt isolated and have a more varied menu. The pelagic dolphins hunt in teams that communicate through sounds. They detect fish shoals using the sonar and circle them.
Sometimes groups of two different dolphin species (but which do not compete for the same food, like a fish eating one and a squid eating one) can unite to defend themselves against sharks. Dolphins defend against sharks with blows applied with the rostrum into their abdomen.
Tunas and frigate birds accompany the dolphins to take advantage of their sonar. Fish eating species of dolphins have 80-150 sharp, curbed teeth; squid eating species have few teeth.
3.To display superiority, a dolphin snaps its teeth and blows the water with the tail. Males are polygamous and the female is fecundated by several males during the breeding season. In the case of large species, sexual maturity is reached at the age of 10, but mating occurs first time by the age of 15. The nuptial parade includes acrobatic breaching. The underwater mating lasts for 15-20 seconds.
The gestation last 10-12 months (depending on species) and the newborn is 0.7-1.1 m (2.3-3.6 ft) long. A "midwife" helps at the birth and protect the newborn. The nipples are found in two ventral grooves lateral to the genital groove. They have a muscle that retracts them or ejects the milk.
The offspring do not have lips, they cannot suckle, they hit with their rostrum the nipple area and the milk is ejected into their mouth. Offspring can be milk-fed for 19 months. The offspring is protected by the whole group.
4.Smaller dolphins reach 35-40 km (22-25 mi) per hour but the orca or killer whale, which is in fact the world’s largest dolphin, reaches 50 km (31 mi) per hour, which is a lot in the water. Due to their speeds, they can execute jumps outside the water which can be 5-6 m (16-20 ft) high and 11 m (36 ft) long in the case of the bottlenosed dolphin, the most common dolphin species.
The secret of the dolphin speed is not only connected to its hydrodynamic shape, but also to the structure of its skin, which presents an elasticity that decreases friction between its body and water. The epiderm is elastic, while the derma is sinuous, with papillae and grooves which at high speeds deform themselves, absorbing turbulence. Through the decrease of the resistance, a more rapid advance is achieved for the same muscle power and energy waste. But the bubbler is also extremely elastic, similar to rubber. The acceleration achieved by the elastic return of the bubbler, which is compressed and stretched with every fluke beat, can save 20 % of the energy wasted during the period of continuous swimming. This can be possible because half of the bubbler's volume is represented by a complex collagen web, wrapping the dolphin's body.
The dorsal and pectoral fins have the role of stabilizers.
Inside the dolphin skin, there are numerous tactile receptors which inform the brain about the "whirls" in the surrounding water, which transmit signals to the elastic cells that modify their shape so that they prevent and impede whirls’ formation that would slow down the dolphin.
But dolphins are also excellent divers. They can dive down to 300 m (1000 ft) with ease but their ability goes down to 900 m (3,000 ft). (Beaked whales, cetaceans related to the true dolphins, can dive to 1,900 m (6,300 ft)). Their lungs, muscle and blood present adaptations that enable them to retain much more oxygen from one breath than the human being does.
Between two respirations, a dolphin’s heartbeat slows down to the half, blood vessels from the muscle contract decreasing significantly the oxygen consumed by muscles, ensuring this way a reserve for the brain, which cannot miss it.
Other complex adaptations enable the dolphins to return to the surface from a deep dive without the need of taking decompression pauses, as people do for avoiding sudden nitrogen embolia that would cause death.
5.The high intelligence of the dolphins is regarded as a reaction to the complex marine environment. The dolphin’s brain has the same size of a human one and displays the same complicated grooves pattern. Archaeological data show they have been having these big brains for millions of years. But there are differences between a dolphin and a human brain: in the case of the dolphin, the auditory areas are more developed than in humans (due to their complicated ultrasound sonar used for mapping the environment).
The QE (encephalization coefficient) (volume of the brain versus body surface) is about 2. In lower mammals (like mice) this value falls under 1; in humans is 7.4, in chimpanzee 2.5, in primitive river dolphins 1.5 while large dolphins display a value of 5.6, explaining their developed mental and imprinting abilities.
Their visual areas are less developed than in people`s case, while olfactory areas are completely absent (in humans, they are greatly reduced, but existent). But their cortex, the brain part of mental and cognitive processes, has the same size like in humans and its surface is even more complicated and grooved than in humans. Anyhow, their intelligence and the way they perceive the world are different from ours; their world is a more acoustic one.
6.These cetaceans are famous for their sonar, so that they can make acoustic mental "images" of the environment. This way they can detect in murky waters fish shoals located hundreds of meters away. The sonar employs sounds from 250 Hz to 220 kHz. Sounds under 20 kHz can be heard by humans, the others are ultrasounds.
The basal frequency is emitted by melon (the swollen front) localizing remote objects, while high frequencies locate close objects. The echoes are captured not only by the ears, but also by the fatty sinuses of the lower jaw and carried to the auditory bulla. When the sonar is impaired by parasites (like the Nasitrema, a parasite trematode worm, affecting the brain and inner ear, so that the animal cannot avoid obstacles), toxins eliminated by microorganisms during red tides or electromagnetic interferences, the dolphins can strand. In the case of pilot whale (a large dolphin), if the dominant individual strands, the other members of the group will follow it.
Dolphins are devoid of olfaction and they see well in the air, as the lens changes shape easily when passing from the watery to aerial environment. The touch sense is extremely fine.
7.Dolphins can communicate, transmitting and receiving much more complex information than other animals. Some are inaudible ultrasounds, other sounds can be heard by humans, too. In captivity, the variety of the sounds can grow and they even try to imitate the sounds of the human speech. The male emits calls during breeding season or at the appearance of a danger. Females emit calls to accustom the offspring with their voice.
Attitudes have their meaning. The head pulled out of the water with the vertical body means a floating object has been observed.
These marine mammals touch one another with their rostrum, or hug one another with the pectorals, a type of behavior that has the role to increase cohesion in the group.
8. There were cases of dolphins which defended shipwrecked people swimming in the water from shark attacks till rescue ships appeared. And real cases of people saved from drowning by dolphins are known; this behavior is mentioned in many tales, from ancient Greek stories to the legends of the Polynesians and Maori of the New Zealand.
Sometimes they carried people more than 20 mi (32 km) to the shore. In other cases, dolphins guided fishermen lost in the mist or shipwrecked people found in boats to the shore. But dolphins do not save only people. Sometimes their behavior can seem curious: in a Florida aquarium, dolphins helped a sick shark to breathe, by pushing it to the water surface: this way they killed the shark, even if this would have helped a sick dolphin (or a shipwrecked human). The friendly relationship in some cases between dolphins and fishermen is well-known: the dolphins urge the fish to the fishermen’s nets and this eases their own hunting.
The case of the "Pelorus Jack" is a famous one: between 1887 and 1912, a dolphin helped ships cross safely the Cook Strait, between the two main islands of the New Zealand, which are dangerous due to submarine rocks and currents.
It is curious that the dolphins never attack humans, even if just a fluke blow or bite would be enough. They can even attach to some humans. But their excessive hunting (like the infamous Japanese dolphin hunt), overfishing and massive development of the navigation deplete many populations.
Source:
http://news.softpedia.com/news/8-Amazing-Facts-About-Dolphins-71147.shtml
1.The first cetacean was Pakicetus, which lived 55 million years ago. It was a shore animal with well-developed four limbs. The first dolphins (and toothed whales) are considered the Squalodontidae, which lived 33 to 15 MA years ago. They were 3 m (10 ft) long and had large teeth.
2.Dolphins live in bands, which can be large in the case of the pelagic species (up to 1,000 individuals, the record being of 8,696 dolphins in a group), while coastal dolphins live in small groups. Females stay in the center, to be protected against sharks and killer whales. In all species there are solitary individuals.
Coastal dolphins hunt isolated and have a more varied menu. The pelagic dolphins hunt in teams that communicate through sounds. They detect fish shoals using the sonar and circle them.
Sometimes groups of two different dolphin species (but which do not compete for the same food, like a fish eating one and a squid eating one) can unite to defend themselves against sharks. Dolphins defend against sharks with blows applied with the rostrum into their abdomen.
Tunas and frigate birds accompany the dolphins to take advantage of their sonar. Fish eating species of dolphins have 80-150 sharp, curbed teeth; squid eating species have few teeth.
3.To display superiority, a dolphin snaps its teeth and blows the water with the tail. Males are polygamous and the female is fecundated by several males during the breeding season. In the case of large species, sexual maturity is reached at the age of 10, but mating occurs first time by the age of 15. The nuptial parade includes acrobatic breaching. The underwater mating lasts for 15-20 seconds.
The gestation last 10-12 months (depending on species) and the newborn is 0.7-1.1 m (2.3-3.6 ft) long. A "midwife" helps at the birth and protect the newborn. The nipples are found in two ventral grooves lateral to the genital groove. They have a muscle that retracts them or ejects the milk.
The offspring do not have lips, they cannot suckle, they hit with their rostrum the nipple area and the milk is ejected into their mouth. Offspring can be milk-fed for 19 months. The offspring is protected by the whole group.
4.Smaller dolphins reach 35-40 km (22-25 mi) per hour but the orca or killer whale, which is in fact the world’s largest dolphin, reaches 50 km (31 mi) per hour, which is a lot in the water. Due to their speeds, they can execute jumps outside the water which can be 5-6 m (16-20 ft) high and 11 m (36 ft) long in the case of the bottlenosed dolphin, the most common dolphin species.
The secret of the dolphin speed is not only connected to its hydrodynamic shape, but also to the structure of its skin, which presents an elasticity that decreases friction between its body and water. The epiderm is elastic, while the derma is sinuous, with papillae and grooves which at high speeds deform themselves, absorbing turbulence. Through the decrease of the resistance, a more rapid advance is achieved for the same muscle power and energy waste. But the bubbler is also extremely elastic, similar to rubber. The acceleration achieved by the elastic return of the bubbler, which is compressed and stretched with every fluke beat, can save 20 % of the energy wasted during the period of continuous swimming. This can be possible because half of the bubbler's volume is represented by a complex collagen web, wrapping the dolphin's body.
The dorsal and pectoral fins have the role of stabilizers.
Inside the dolphin skin, there are numerous tactile receptors which inform the brain about the "whirls" in the surrounding water, which transmit signals to the elastic cells that modify their shape so that they prevent and impede whirls’ formation that would slow down the dolphin.
But dolphins are also excellent divers. They can dive down to 300 m (1000 ft) with ease but their ability goes down to 900 m (3,000 ft). (Beaked whales, cetaceans related to the true dolphins, can dive to 1,900 m (6,300 ft)). Their lungs, muscle and blood present adaptations that enable them to retain much more oxygen from one breath than the human being does.
Between two respirations, a dolphin’s heartbeat slows down to the half, blood vessels from the muscle contract decreasing significantly the oxygen consumed by muscles, ensuring this way a reserve for the brain, which cannot miss it.
Other complex adaptations enable the dolphins to return to the surface from a deep dive without the need of taking decompression pauses, as people do for avoiding sudden nitrogen embolia that would cause death.
5.The high intelligence of the dolphins is regarded as a reaction to the complex marine environment. The dolphin’s brain has the same size of a human one and displays the same complicated grooves pattern. Archaeological data show they have been having these big brains for millions of years. But there are differences between a dolphin and a human brain: in the case of the dolphin, the auditory areas are more developed than in humans (due to their complicated ultrasound sonar used for mapping the environment).
The QE (encephalization coefficient) (volume of the brain versus body surface) is about 2. In lower mammals (like mice) this value falls under 1; in humans is 7.4, in chimpanzee 2.5, in primitive river dolphins 1.5 while large dolphins display a value of 5.6, explaining their developed mental and imprinting abilities.
Their visual areas are less developed than in people`s case, while olfactory areas are completely absent (in humans, they are greatly reduced, but existent). But their cortex, the brain part of mental and cognitive processes, has the same size like in humans and its surface is even more complicated and grooved than in humans. Anyhow, their intelligence and the way they perceive the world are different from ours; their world is a more acoustic one.
6.These cetaceans are famous for their sonar, so that they can make acoustic mental "images" of the environment. This way they can detect in murky waters fish shoals located hundreds of meters away. The sonar employs sounds from 250 Hz to 220 kHz. Sounds under 20 kHz can be heard by humans, the others are ultrasounds.
The basal frequency is emitted by melon (the swollen front) localizing remote objects, while high frequencies locate close objects. The echoes are captured not only by the ears, but also by the fatty sinuses of the lower jaw and carried to the auditory bulla. When the sonar is impaired by parasites (like the Nasitrema, a parasite trematode worm, affecting the brain and inner ear, so that the animal cannot avoid obstacles), toxins eliminated by microorganisms during red tides or electromagnetic interferences, the dolphins can strand. In the case of pilot whale (a large dolphin), if the dominant individual strands, the other members of the group will follow it.
Dolphins are devoid of olfaction and they see well in the air, as the lens changes shape easily when passing from the watery to aerial environment. The touch sense is extremely fine.
7.Dolphins can communicate, transmitting and receiving much more complex information than other animals. Some are inaudible ultrasounds, other sounds can be heard by humans, too. In captivity, the variety of the sounds can grow and they even try to imitate the sounds of the human speech. The male emits calls during breeding season or at the appearance of a danger. Females emit calls to accustom the offspring with their voice.
Attitudes have their meaning. The head pulled out of the water with the vertical body means a floating object has been observed.
These marine mammals touch one another with their rostrum, or hug one another with the pectorals, a type of behavior that has the role to increase cohesion in the group.
8. There were cases of dolphins which defended shipwrecked people swimming in the water from shark attacks till rescue ships appeared. And real cases of people saved from drowning by dolphins are known; this behavior is mentioned in many tales, from ancient Greek stories to the legends of the Polynesians and Maori of the New Zealand.
Sometimes they carried people more than 20 mi (32 km) to the shore. In other cases, dolphins guided fishermen lost in the mist or shipwrecked people found in boats to the shore. But dolphins do not save only people. Sometimes their behavior can seem curious: in a Florida aquarium, dolphins helped a sick shark to breathe, by pushing it to the water surface: this way they killed the shark, even if this would have helped a sick dolphin (or a shipwrecked human). The friendly relationship in some cases between dolphins and fishermen is well-known: the dolphins urge the fish to the fishermen’s nets and this eases their own hunting.
The case of the "Pelorus Jack" is a famous one: between 1887 and 1912, a dolphin helped ships cross safely the Cook Strait, between the two main islands of the New Zealand, which are dangerous due to submarine rocks and currents.
It is curious that the dolphins never attack humans, even if just a fluke blow or bite would be enough. They can even attach to some humans. But their excessive hunting (like the infamous Japanese dolphin hunt), overfishing and massive development of the navigation deplete many populations.
Source:
http://news.softpedia.com/news/8-Amazing-Facts-About-Dolphins-71147.shtml
This world is a weird place. :lol:
