AMAZON RIVER DOLPHIN | THE WORLD LARGEST DOLPHIN
The Amazon River dolphin (Inia geoffrensis), commonly known as the boto, bufeo, or pink river dolphin, belongs to the Iniidae family of toothed whales. The Amazon basin, the upper Madeira River in Bolivia, and the Orinoco basin, respectively, are home to the three subspecies. The Amazon River dolphin is the largest river dolphin species, with adult males weighing up to 185 kilograms (408 lb) and measuring 2.5 meters (8.2 feet) in length. Adults develop a pink coloration, which is more noticeable in males, earning them the moniker “pink river dolphin.” Males are 16 percent longer and weigh 55 percent more than females, demonstrating clear sexual dimorphism. They have a melon, like other toothed whales, which is used for bio sonar. The dorsal fin, despite its small size, is considered lengthy, and the pectoral fins are likewise enormous. When crossing flooded forests and obtaining prey, the fin size, unfused vertebrae, and relative size enable for enhanced maneuverability.
They eat up to 53 different types of fish, including croakers, catfish, tetras, and piranhas, making them one of the most diverse toothed whale diets. Other species that they eat include river turtles and freshwater crabs.
The International Union for Conservation of Nature (IUCN) designated this species as data poor in 2008 due to ambiguity about population trends and the impact of threats. While hunting is a significant danger, habitat loss and incidental entanglement in fishing lines have had bigger effects on population in recent decades. It is the only river dolphin species kept in captivity, mostly in Venezuela and Europe; nonetheless, it is difficult to teach, and captive individuals have a high mortality rate.
Biology and Ecology
The Amazon River dolphin is the world’s largest. Adult males reach a maximum length and weight of 2.55 meters (8.4 ft) (average 2.32 meters (7.6 ft) and 185 kilograms (408 lb.) (average 154 kilograms (340 lb.), while females reach a maximum length and weight of 2.15 meters (7.1 ft) (mean 2 meters (6.6 ft)) and 150 kilograms (330 lb.) (average 100 kilograms (220 lb.) and 185 kilograms. Males measure and weigh between 16 percent and 55 percent more than females, making it uncommon among cetaceans, where females are normally larger than males. The body has a sturdy and strong texture, but it is also flexible. The cervical vertebrae are not fused in oceanic dolphins, allowing the head to turn 90 degrees. The flukes are broad and triangular, and the dorsal fin, which is keel-shaped and extends from the middle of the body to the caudal region, is small in height but very long. The pectoral fins are paddle-shaped and massive. The length of the animal’s fins helps it to move in a circular motion, allowing it to swim through the flooded forest with amazing maneuverability but at a slower speed.
The color of one’s skin changes with age. As a result of frequent abrasion of the skin surface, newborns and children have a dark grey tint that fades to light grey in adolescence and turns pink in adults. Due of more frequent injuries from intra-species violence, males are pinker than females. Adults range in color from solid to mottled pink, with the dorsal surface of certain adults being darker. Temperature, water clarity, and geographical location are thought to influence color differences. There is only one albino on record, which is housed in a German aquarium.
In comparison to other toothed whales, the species’ head is slightly asymmetrical. It has a long, narrow snout and 25 to 28 pairs of long, slender teeth on both jaws. The dentition is heterodont, which means that the teeth have different shapes and lengths, as well as different functions for capturing and smashing prey. The anterior teeth are conical, with ridges on the inside of the crown later on. Despite its small eyes, the species appears to have excellent vision both in and out of water. When used for biosonar, it has a melon on its head, the shape of which may be changed by muscle control. Every 30 to 110 seconds, you will breathe.
The Amazon River dolphin’s life expectancy in the wild is unknown, however healthy animals have been reported to live between 10 and 30 years in captivity. In captivity, however, the average lifespan is only 33 months. Baby, a zoo animal in Duisburg, Germany, lived for at least 46 years, spending 45 years and 9 months there.
The Amazon River dolphin is generally observed alone or in pairs but can also be found in pods of up to eight individuals. The Amazon has seen pods as large as 37 individuals, although the average is three. The largest observed groups in the Orinoco number 30, although the average is just over five. During prey season, up to 35 pink dolphins collaborate to catch their prey.
Social ties are most commonly found between mothers and children, although they can also be present in heterogeneous groups or bachelor groups. The greatest gatherings occur in regions where there is plenty of food and along river mouths. During the rainy season, there is significant segregation, with males utilizing river channels and females and their progeny residing in flooded areas. During the dry season, however, there is no such distinction. Larger group sizes are seen in large parts directly influenced by whitewater than in smaller sections influenced by blackwater, owing to the abundance of prey fish. They are apex predators in their freshwater home, and their gatherings are more dependent on food sources and habitat availability than in marine dolphins, where protection from larger predators is required.
The Amazon River dolphin is less shy, but also less gregarious, than the bottlenose dolphin, according to captive research. It is extremely interested and exhibits a remarkable lack of apprehension towards foreign objects. Dolphins in captivity, on the other hand, may not behave the same way they do in the wild, where they have been observed holding fishermen’s oars, rubbing against the boat, plucking underwater plants, and playing with twigs, logs, clay, turtles, snakes, and fish. They are slow swimmers, averaging 1.5 to 3.2 kilometers per hour, yet they have been reported swimming at speeds of 14 to 22 kilometers per hour. The tips of the snout, melon, and dorsal fins all appear at the same time as they surface, with the tail rarely seen before diving. They may also study the environment by shaking their fins and pulling their tail fin and head above the water. They may jump up to a meter out of the water on occasion (3.14 ft). Training them is more difficult than training most other dolphin species.
Migration and habitat
River basins, main river courses, canals, river tributaries, lakes, and the ends of rapids and waterfalls are among the aquatic habitats where the Amazon River dolphin can be found. The water levels of rivers fluctuate cyclically throughout the year. Males and females appear to have selective habitat preferences, with males returning to main river channels when water levels are still high, while females and their offspring stay as long as possible in flooded areas, presumably to reduce the risk of male aggression toward the young and predation by other species.
Photo-identification is utilized at the Pacaya-Samiria National Reserve in Peru to identify individuals based on coloring patterns, scars, and deformities in the beak. Between 1991 and 2000, 72 persons were identified, with 25 of them being seen again. The time between sightings varied between one day and 7.5 years. With an average range of motion of 60.8 kilometers, the greatest range of motion was 220 kilometers. The longest distance covered in a single day was 120 km, with an average of 14.5 km. A dolphin was recorded moving only a few dozen kilometers between the dry and rainy seasons in a prior investigation done in the Amazon River’s heart. Three of the 160 animals examined were found more than 100 kilometers (62 miles) from where they were first reported. Photo-identification by competent operatives utilizing high-quality digital equipment, according to a 2011 study, could be a beneficial tool for tracking population growth, migrations, and social tendencies.