The Amazon dolphin, also called the inia or bouto, is the largest river dolphin. Inia geoffrensis, as scientists call it, reaches 2.5 meters in length and weighs 2 centners. Light gray juveniles become lighter with age. The Amazonian dolphin has a full body, with a thin tail and a narrow muzzle. A round forehead, a slightly curved beak and small eyes are the characteristics of this species of dolphin.
The Amazonian dolphin is found in rivers and lakes Latin America. According to its distribution area, scientists divide the species into three subspecies: Inia geoffrensis geoffrensis, Inia geoffrensis boliviensis and Inia geoffrensis humboldtiana.
Amazonian dolphins live throughout the Amazon River basin, even in small rivers and lakes. They usually do not change their place of residence, except for seasonal migration. When the water level in the river drops, ini look for a deeper channel. If the river floods, the dolphins can move to the flooded plains. During the rainy season, Amazonian dolphins have the opportunity to swim from the bed of one river to the basin of another.
These dolphins do not form groups. It is quite rare to see a school of several dolphins; this happens only during breeding. Since they do not form groups, they do not have a hierarchy. Inias lead an active lifestyle both day and night. Compared to other dolphins, these swim at a slower speed, up to 3 km/h on average. The maximum speed of the Amazonian dolphin is 22 km/h. They can dive and stay underwater for up to 2 minutes. When swimming, inias maneuver perfectly.
Amazonian dolphins feed on small fish and can eat up to 12 kg of food per day. They eat different types fish, and the structural features of the jaw allow them to feast on turtles and crabs.
Amazonian dolphins hunt near the shore, near river mouths or near waterfalls. In these places the water is quite cloudy, and the fish does not have time to escape from the hunter. In addition, dolphins obtain food from the bottom, digging it out of the silt, and steal fish from fishing nets. Sometimes the Amazon dolphin goes hunting together with a giant otter or a tukashi dolphin. Although dolphins have good eyesight, they rely on hearing to hunt, as well as touch using the method of echolocation.
Living in the wild, Amazonian dolphins love to play and are curious about their surroundings. They do not abandon their relatives who are in trouble, for example, wounded. They are not afraid to approach boats. These dolphins can be tamed, but cannot be trained. In captivity they become aggressive, which is why they are not kept in oceanariums.
Scientists have not fully explored the nature of ini reproduction. There are only assumptions that males engage in battle for the female. After the birth of the calf, the female stays with him for a long time in shallow water, where it is easier for him to float to the surface to breathe. In addition, it is easier to get food here and there is no dangerous predators. The cub feeds on its mother's milk for up to one year, but remains with her longer, up to approximately three years. The Amazonian dolphin reaches sexual maturity at five years of age. The total lifespan of Indians is unknown; in captivity they do not survive more than 33 months.
Amazonian dolphin playing important role in the ecosystem. It is a hunter of a number of fish species, and also serves as food for black caimans, blunt-nosed sharks, and.
Man doesn't hunt Amazonian dolphins. However, some fishermen kill these animals due to damage to their fishing nets. The laws of Latin American countries prohibit or restrict the capture of the Amazon dolphin. Despite environmental degradation, the number of Amazonian dolphins is not decreasing.
Bright pink spots flash among the trees, slide between the branches, and gracefully bend around trunks swollen with water. These are Amazonian river dolphins, also known as boutos (for the locals) or inii (Inia geoffrensis), frolicking in the flooded jungle. The Amazon, having overflowed during the rainy season, flooded the jungle in its upper reaches, thus giving the dolphins a chance for real forest hunting. Why do dolphins, the original inhabitants of the salty sea waters, moved to fresh water bodies? Healy Hamilton, a biologist at the California Academy of Sciences, explains that about 15 million years ago, during the Miocene era, sea levels were higher, leaving large parts of what is now South America under saltwater. Hamilton's hypothesis is that over time, the sea gradually retreated to modern boundaries, and some of the dolphins remained in their former territories. And over millions of years in the Amazon basin they turned into completely amazing creatures, not much like everyone’s favorite movie hero Flipper.
Pink color is not the only way to attract a female. Sometimes the bowto takes a bunch of plants or a piece of wood in its beak, begins to circle and hit the water with its prey. Local residents thought for a long time that this was just a game, until Martin discovered: only males hold objects in their mouths - and only in the presence of females.Bouto reaches almost two and a half meters in length and weighs about 200 kilograms. His distinctive feature- a long, leathery snout, similar to a beak or sting, which is so convenient for digging out crustaceans from the bottom silt and catching fish rushing about in a tangle of branches. The cervical vertebrae of Amazonian dolphins do not fuse together, and therefore their heads can rotate at an angle of 90 degrees to the body - a very useful ability for navigating among trees. Another distinctive feature river dolphins– small eyes: in muddy water Sight is of little use anyway, and it’s easier to find prey using echolocation. River dolphins are not only found in the Amazon; they can also be found in the Indian Ganges, the Pakistani Indus and in the waters of the Rio de La Plata between Argentina and Uruguay. There are four species of river dolphins, and the bouto is the largest of them. Until recently, there were five species of river dolphins. However, already at the beginning of this century, dolphins from the Chinese Yangtze River were completely destroyed - since 2002, scientists have not been able to detect them. According to Hamilton, at first glance everything freshwater dolphins appear identical, but their four genera belong to three different families. Judging by DNA tests, river dolphins diverged earlier than sea dolphins from their common ancestors, the ancestors of cetaceans, in at least three cases - first in India, then in China and South America. The evolution of each of the families proceeded independently and in parallel - geographically isolated and genetically different kinds, adapting to similar conditions, eventually acquired similar characteristics. Every spring gives Amazonian dolphins a chance to escape their narrow borders. river bed and remember the ancient boundless homeland. Tony Martin from the University of Kent in England studies dolphins in nature reserve Mamirahua has been in western Brazil for 16 years. Here, two tributaries of the Amazon flood thousands of square kilometers of jungle for six months, turning it into a huge lake under tree cover. Martin and his Brazilian colleague Vera da Silva discovered that female dolphins were swimming deeper into the forest, perhaps to hide from the aggressive bright pink males. Females are mostly gray in color; But the males, Martin and da Silva believe, acquired their cute pink color as a result of multiple wounds. “On large males there is no living space from scars,” says Martin. “They fight furiously for life and death: they bite off each other’s jaws, tails, fins, and tear apart each other’s blowholes.” There are few bright pink males, but they are the ones who have the greatest success with females - at least during mating season, when the water returns to the river bed and the females are forced to swim back from the deep jungle. Pink color is not the only way to attract a female. Sometimes the bowto takes a bunch of plants or a piece of wood in its beak, begins to circle and hit the water with its prey. Local residents thought for a long time that this was just a game, until Martin discovered: only males hold objects in their mouths - and only in the presence of females. In addition, during this demonstration, the likelihood of a fight among males increases 40 times. It turns out that both, trying to impress their friends, show off items that they generally don’t need. “It’s like some guy showing off his Ferrari,” Martin explains. By the way, besides dolphins, only monkeys and humans use objects to show off. Martin believes that there are only about 100 thousand Amazon dolphins left in the wild, and they are great danger. In seven years, the population from the Mamiraua reserve has halved. Fishermen use dolphin meat as bait for catfish, and often the bouto accidentally gets caught in the net and suffocates, unable to surface. According to ancient local beliefs, buto is magical creature, capable of changing its appearance. Sometimes it comes out of the river in the form of a person to lure gullible men and women into a fabulous underwater kingdom. They even say that dolphins wear hats so that their blowholes and onion-like heads are not visible. But, alas, no less rich Chinese myths did not help the white dolphins of the Yangtze. How to save the buto from the fate of their relatives?
The Amazonian dolphin is the most major representatives river dolphins. These dolphins are also known as bouto or inia.
The body length of these dolphins reaches 2.5 meters. Juveniles are light gray in color, which becomes lighter with age.
They have a full body, while the tail and muzzle are narrow. The eyes are small, the forehead is round, the beak is slightly curved - this is character traits Amazonian dolphins.
Representatives of the species live in water bodies of Latin America. Depending on their habitat, 3 subspecies are distinguished: Inia geoffrensis boliviensis, Inia geoffrensis geoffrensis and Inia geoffrensis humboldtiana.
The habitat extends to the entire Amazon River basin, these live even in small lakes and rivers. Most often, they live in one place all their lives, only moving during seasonal migration. But if the water level in the river drops, dolphins have to find new channels. When the river floods, they can settle in flooded flat areas. During the rainy season, dolphins often move from one river bed to another.
Amazonian dolphins do not live in groups; only during the breeding season do they occasionally unite in small groups. Because they don't have social life, then there is no hierarchy. These dolphins are active both day and night.
Compared to other dolphins, the ini does not have such a high speed - about 3 kilometers per hour. But if necessary they can swim with maximum speed 22 kilometers per hour. They can stay under water for up to 2 minutes. Amazonian dolphins can maneuver perfectly while swimming.
The diet of Amazonian dolphins consists of small fish. A dolphin consumes about 12 kilograms of food per day. They feed not only on fish, but also on crabs and turtles.
Dolphins get food from the banks of rivers or near waterfalls, since in these places the water is not clear and the fish do not have time to hide from the predator. In addition, Amazonian dolphins look for food in the mud. They also steal fishing nets. They sometimes hunt alongside dolphins and giant otters. Although Amazonian dolphins have good eyesight, they use touch, hearing and echolocation when hunting.
Amazonian dolphins living in nature are very curious and playful, they show interest in everything around them. They never leave their loved ones who are in trouble. Amazonian dolphins do not shy away from people and approach boats without fear. They can get used to humans, but they cannot be trained. In captivity they begin to show aggression, which is why they do not live in oceanariums.
Scientists probably do not know how reproduction occurs in Amazonian dolphins. There is an opinion that males fight for females. After the female gives birth to a baby, she lives with him for a long time in shallow water, because there it is easier for him to emerge to breathe. In addition, they do not live in shallow water large predators, and it’s easier to find food here.
The mother feeds the baby with milk for a year, but he does not leave her longer, remaining with her until he is 3 years old. Representatives of the species experience puberty at the age of 5 years. It is unknown how long Amazonian dolphins live in the wild, but they do not survive in aquariums for more than 33 months.
Bouto reaches almost two and a half meters in length and weighs about 200 kilograms. Its distinctive feature is a long, leathery snout, similar to a beak or sting, which is so convenient for digging out crustaceans from the bottom silt and catching fish rushing about in the tangle of branches.
Why did dolphins, the original inhabitants of salty sea waters, move to fresh water bodies? Healy Hamilton, a biologist at the California Academy of Sciences, explains that about 15 million years ago, during the Miocene era, sea levels were higher, so large parts of what is now South America were under thick salt water. Hamilton's hypothesis is that over time, the sea gradually retreated to modern boundaries, and some of the dolphins remained in their former territories. And over millions of years in the Amazon, they turned into absolutely amazing creatures, not much like everyone’s favorite movie character Flipper.
River dolphins are not only found in the Amazon - they can also be found in the Indian Ganges, in the Pakistani Indus and in the waters of the Rio de La Plata between Argentina and Uruguay. There are four species of river dolphins, and the bouto is the largest of them.
Until recently, there were five species of river dolphins. However, already at the beginning of this century, dolphins from the Chinese Yangtze River were completely destroyed - since 2002, scientists have not been able to detect them.
According to Hamilton, at first glance, all freshwater dolphins appear to be the same - but their four genera belong to three different families. Judging by DNA tests, river dolphins diverged earlier than sea dolphins from their common ancestors, the ancestors of cetaceans, in at least three cases - first in India, then in China and South America. The evolution of each of the families proceeded independently and in parallel - geographically isolated and genetically different species, adapting to similar conditions, eventually acquired similar characteristics.
Every spring gives Amazonian dolphins a chance to leave the narrow confines of the river bed and remember their ancient, vast homeland.
Tony Martin from the University of Kent in England has been studying dolphins in the Mamirahua Nature Reserve in western Brazil for 16 years. Here, two tributaries of the Amazon flood thousands of square kilometers of jungle for six months, turning it into a huge lake under tree cover.
Martin and his Brazilian colleague Vera da Silva discovered that female dolphins were swimming deeper into the forest, perhaps hiding from the aggressive bright pink males. Females are mostly gray in color; But the males, Martin and da Silva believe, acquired their cute pink color as a result of multiple wounds.
Pink color is not the only way to attract a female. Sometimes the boat takes a bunch of plants or a piece of wood in its beak, begins to circle and hit the water with its prey. Local residents thought for a long time that this was just a game, until Martin discovered: only males hold objects in their mouths - and only in the presence of females.
Martin believes that there are only about 100 thousand Amazon dolphins left in the wild, and they are in great danger. In seven years, the population from the Mamiraua reserve has halved. Fishermen use dolphin meat as bait for catfish, and often the bouto accidentally gets caught in the net and suffocates, unable to surface.
: length of adults is 1.24-2.5 m with a weight of 98.5-207 kg; females are noticeably smaller than males, which is generally unusual for river dolphins. Body color changes with age. Juvenile dolphins are fawn-gray with a light belly; adults are very light-colored, with a pinkish or pale blue back and a white belly. Individuals living in lakes are usually darker than those in rivers.
The body is full, thinning towards the tail. The long and narrow snout ends in a beak, slightly curved down and covered with sparse short bristles. The forehead is steep and rounded. The eyes are very small (the horizontal diameter of the eyeball is 13 mm, and the vertical diameter is 12 mm), but well functioning.
Ini's eyes are different from those of other cetaceans. If in other species of the order the eyes are adapted to capture the weakest light, then in the Indian the cornea and lens are yellow in color, apparently protecting the eyes from sunlight. This, as well as the large protruding retina, relatively large and retracted lens, indicate that the eyes are adapted to aerial rather than underwater vision. However, the behavior of the inies does not confirm this.
The cervical fold is pronounced; the cervical vertebrae are not fused. The head is movable and can be rotated to the side by 90°. The blowhole is semilunar, slightly shifted to the left. The dorsal fin replaces a long (30-61 cm long), gently sloping, low crest (hump). Its apex accounts for 2/3 of the body length. The blades of the pectoral and caudal fins are large and wide. The edges of the fins are often frayed, with tooth marks left by other fins. The unusually long humerus increases the mobility of the pectoral fins, which increases the ini's maneuverability when swimming. Developed muscles provide movement pectoral fin in all directions, including inward and outward rotation.
Distribution and subspecies
The range covers the Amazon River system with its tributaries in Brazil, Bolivia, Northern Peru, Ecuador, Colombia, Venezuela (upper reaches of the Rio Negro), as well as the Orinoco River system, covering about 7 million km².
There are 3 subspecies of inia (1998):
- Inia geoffrensis geoffrensis- found in the Amazon basin;
- Inia geoffrensis boliviensis- in the upper reaches of the Madeira River, separated from the rest of the Amazon by impassable rapids (Bolivia); in some classifications it is considered as a separate species;
- Inia geoffrensis humboldtiana- Orinoco basin.
Lifestyle
Inias are found almost everywhere, including tributaries, small channels, river mouths, lakes; common above and below waterfalls and rapids. Limited in their distribution mainly to salty coastal waters, impassable rapids, waterfalls and the smallest sections of rivers. Mostly sedentary, but commit seasonal migrations, depending on fluctuations in water level. During the dry season, when the rivers become shallow, the ini stay in the riverbeds large rivers. During the rainy season, they move into small channels, as well as into flooded plains and forests. During river floods, Indians can swim across flooded land from one river basin to another.
Inias, as a rule, live alone or in pairs (usually a female with a baby), rarely in groups of 3-6 individuals. Large flocks observed in areas rich in food or during the breeding season. Not territorial. Social hierarchy(in captivity) are not established, but they often show aggression towards each other, sometimes leading to death. Active both during the day and at night. They swim slower than most dolphins: their usual speed is 1.5-3.2 km/h, maximum speed is 14-22 km/h. Very maneuverable. They dive shallowly; remain under water for 0.5-2 minutes. When exhaling, small fountains are released. They can jump more than 1 m out of the water.
Inia feeds mainly on small fish, eating 9-12 kg per day (about 2.5% own weight). Their diet is very diverse, including at least 43 species of fish from 19 families; prey sizes vary from 5 to 80 cm. They prefer fish of the croaker family ( Sciaenidae), cyclide ( Cichlidae), characins ( Characidae) and piranhas ( Serrasalmidae); the structure of their teeth allows them to also eat Amazonian river turtles (Podocnemis sextuberculata) and crabs ( Poppiana argentiniana). Their diet is most varied during the wet season, when the fish move to flooded lands and become more difficult to catch, and is more selective during the dry season. Ini feed most actively between 6-9 a.m. and 3-4 p.m. They often hunt near the shore, in river mouths and under waterfalls, as well as where two rivers merge and the turbidity of the water disorients the fish, making it easier to catch. They dig through mud with their beak, taking food from the bottom. They can enter nets and steal fish from there. Sometimes they follow the boats, catching the fish they spook. They can form unique hunting groups with a giant otter ( Pteronura brasiliensis) and a tukashi dolphin ( Sotalia fluviatilis), together driving and attacking schools of fish. Vision is well developed, although the main senses are hearing and touch. For hunting and orientation under water, echolocation is used. Echolocation clicks recorded from captive dolphins typically had a frequency of 45 kHz. They communicate with each other by clicking with frequencies of 16-170 kHz. They also make screams, high-pitched squeals, barks, whimpers, but not whistles.
In nature, inies are playful and quite curious. They take care of wounded and stranded relatives. They can swim up to boats and rub against them. They are well tamed, but they are aggressive and difficult to train, so they are quite rare in aquariums and oceanariums.
Reproduction
The biology of reproduction is poorly understood. Presumably, they are polygamous (signs of this include sexual dimorphism and aggressive behavior males). Males are often covered in bite marks and abrasions received during competition for a female.
Role in the ecosystem
Population size and status
Ice has no commercial significance. Portuguese colonists had previously hunted river dolphins for lamp oil, but local residents traditionally they do not use their meat or skin. Body parts of dead frosts are used for amulets; the fat is used in traditional medicine as a remedy against asthma and rheumatism. In the folklore of the Amazon peoples, bouto appear as the reborn souls of drowned people, or as werewolves ( encantado), taking the form of beautiful boys and girls. In addition to dispersing piranhas, anglers use their presence to detect schools of fish.
Hoarfrost are usually caught by accident when they inadvertently get caught in fishing nets. They are also caught and destroyed by fishermen for damaging their nets and reducing their catch. Since 1988, the practice has been banned in Brazil and Bolivia and restricted in Peru, Venezuela and Colombia. Population increase and anthropogenic pressure on environment provide Negative influence on the ini population. Reducing the number of fish as a result of fishing is one of the problems. Hydroelectric dams both impede fish migration and separate ini populations, potentially reducing genetic diversity within subpopulations. Deforestation in flooded areas leads to a decrease in the food supply for fish that serve as food for ini. Finally, pollution of water bodies with agricultural pesticides and heavy metals (including) from gold mines has a particularly negative impact on dolphins and their food supply.
The Amazonian inia is the most prosperous species among river dolphins. However, in the International Red Book lists it has the status of “vulnerable species” ( vulnerable). Compared to the rapidly declining ranges of the lake and Gangetic dolphin, the range of the ini remains stable, and determination of the number is difficult due to the inaccessibility of its habitats. Presumably it is in the tens of thousands.
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