Although it may not seem like it, there are 5 species of dolphins that live in rivers. The most famous of them all is the pink dolphinIt is also known by the local names boto, bufeo, tonina, or Amazon River dolphin. With this name, we know where it lives and the areas where it ranges. Its scientific name is Inia geoffrensis and belongs to the genus Inia, within the superfamily Platanistoidea and the family Iniidae.
In this article we are going to talk about the pink dolphin in depth, since it is not the same type of dolphin that we are used to seeing in the sea and it presents unique adaptations to the Amazon and Orinoco rivers.
Key features
These types of dolphins are not the same as the ones we usually see in the sea. They have developed specific adaptations to live in rivers, with murky waters, flooded forests, and narrow channels. In fact, these dolphins are very distantly related parentally to marine dolphins, as they belong to different families.
Among the existing species of river dolphins, pink dolphins are among the most striking due to their anatomy and size. It is the largest river dolphin, with males that can reach about 2,5 m in length and weights exceeding 150 kg, and smaller females. It presents a marked sexual dimorphism, with males between 16% and 55% larger than females.
Coloration varies with age: newborns are dark gray, turning to light gray, and adults may become pink or mottledThe pinkish hue is associated with an abundance of capillaries in the skin and superficial microabrasions; in addition, the color intensifies with excitement, a phenomenon comparable to blushing in humans.
Their bodies are robust and very flexible. Unlike oceanic dolphins, the cervical vertebrae are not fused, allowing them to turn their heads almost 180 degrees and maneuver between roots and branches in the flooded forest. The dorsal fin is low and elongated like a keel, and the pectoral fins are large and wide, ideal for tight turns although they reduce speed.
Like other odontocetes, they have an organ of fatty tissue on their forehead called melon, which they use for echolocationIn turbid waters, their vision is limited but functional; echolocation allows them to orient, communicate and hunt with precision.
The idea that their brain capacity is 40% greater than that of humans has become popular. It should be noted that this is a large and complex brain with high social and cognitive skills, although these comparisons do not directly equate to greater than human intelligence.
Threats of the pink dolphin
These dolphins are social and curious creatures (as other reports on dolphins interacting with puffer fish), historically abundant in the Amazon and its tributaries. However, the deterioration of their habitat has accelerated. The species is classified by the IUCN as Endangered, and their populations face multiple anthropogenic pressures.
Among the main threats is the mercury contamination associated with gold mining. This metal bioaccumulates in the food chain and can cause neurological and reproductive effects. In areas near gold mines, cases have been documented. higher mortality rates and health problems.
Another threat is the river trafficBeing curious, dolphins approach boats and can suffer collisions with propellers. The noise pollution of engines and machinery interferes with their echolocation, disorienting them and reducing their hunting success.
La bycatch in nylon nets and trammel nets has increased. In some places, the deliberate killing of botos to use their meat as bait in fisheries de peces scavengers, a particularly harmful practice.
La dam construction and dams alters flows, fragments populations and hinders the migration of their prey. deforestation floodplains reduces fishery productivity and refuge availability. Flooding events extreme heat and droughts associated with climate variability have also caused occasional mortalities in lakes and shallow areas.
Meals
These cetaceans have one of the the broadest diet of all odontocetesThey feed mainly on de peces river, with dozens of species identified among their usual prey, including corvinas, cichlids, characins such as tetras and piranhas, and various catfish. They complement their diet with crabs y river turtles small in size.
Since crabs and turtles tend to be bottom-dwellers, botos swim with their heads pointing downwards to explore. heterodont dentition allows them to both hold slippery prey and crush shells: the front teeth are more conical and the later ones have edges internal
Among their hunting techniques is the grazing, in which banks surround de peces to concentrate them and capture them in turnsThey are located near confluences and mouths, where the currents break up schools of fish. They also take advantage disturbances created by boats to catch disoriented prey. Sometimes they hunt in coordination with tucuxis y giant otters, with low competition for food because each species selects different prey.
They are active day and night, with frequent feeding peaks in the early morning and mid-afternoon. An individual may consume around 5% of your body weight daily, varying according to the season and the availability of prey.
Anatomy and behavior
Although the predominant colors are pink, light gray, or brown, there is no single accepted cause to explain their hue. It is likely due to abundant superficial capillaries, abrasions from the environment and environmental factors such as water temperature and transparency. Adult males are usually pinker due to intraspecific aggressive interactions.
Compared to marine dolphins, their dorsal fin is low, the pectorals are wide and the neck vertebrae are not fused. These characteristics give them a extraordinary maneuverability in flooded forests, at the cost of lower average velocity. Its surface emergence pattern simultaneously shows snout, melon and dorsal, and rarely perform steep acrobatic jumps, although young ones may do so.
In captivity, they have been observed to have curious personality traits and a low degree of shyness around new objects. In the wild, they can playing with branches, leaves or logs, and even hold fishermen's oars, although their behavior in controlled environments does not always reflect natural behavior. relatively slow swimmers in regular motion, capable of faster bursts when necessary.
They breathe at variable intervals depending on their activity and perform powerful exhalations with moist air visible through the blowhole. variable melon in shape through muscular control optimizes the emission of echolocation clicks and vocalizations They show structures that are different from those of many marine dolphins.
Distribution and habitat
They inhabit the course of the main tributaries of the Amazon River and the Orinoco river, as well as the upper basin of the Madeira, mainly below 400 m asl. Its range includes several countries in South America such as Brazil, Peru, Colombia, Ecuador, Bolivia and Venezuela, among others, occupying main channels, tributaries, lakes and floodplains.
During the dry season, dolphins move towards main channels and deep areas. In the rainy season they take advantage of the flooded forest (igapó) and the várzea plain, where there is a greater supply of food. There is a seasonal segregation: At high waters, females with young remain longer in calm, flooded areas, while males concentrate earlier in the channels.
Studies with photo-identification in protected areas such as Pacaya Samiria have allowed individuals to be recognized by pigmentation patterns and scars, documenting movements of tens to hundreds of kilometers. Densities can be high near riverbanks and estuaries, decreasing towards the center of the large rivers.
Taxonomy and subspecies
Inia geoffrensis is the only member of the genus Inia. They are recognized up to three subspecies described: I. g. geoffrensis in much of the Amazon, I. g. humboldtiana in the Orinoco basin and I. g. boliviensis in the upper Madeira basin. The latter has been proposed by some authors as a full species, although genetic evidence is inconclusive and the classification remains a matter of scientific discussion.
Morphological differences include variations in cranial characters and body proportions, with populations isolated by rapids and extensive waterfalls that limit gene flow.
reproduction and life cycle
Males and females may initiate courtship, which includes acoustic signals, physical contact and exhibitions. In captivity they have been described high frequencies of copulations and various positions, although these behaviors may differ in freedom. Males show intra-male competition evident, with scars on fins and body.
Females reach maturity at around 1,75 to 1,80 m in length, and males somewhat later. Reproduction is usually seasonal and in many areas coincides with the dry season. The gestation lasts around 11 months and births occur at high water levels, when food is abundant in flooded areas.
The young at birth measure around 80cm length and weigh several kilos. The Breastfeeding usually lasts about a year, and birth intervals can range from 15 and 36 monthsThe aging process lasts from two to three years, with a mother-child bond strong that facilitates the learning of hunting and navigation skills.
Conservation, management and legal status
The species is included in CITES Appendix II and also in the CMS Appendix II. In several countries there are protected areas, closed seasons and specific regulations. Given that their maintenance in captivity presents high mortality and health problems, conservation in situ of the habitat and the threat mitigation, including proposals such as dolphin microsanctuary in Algeciras, are a priority.
Necessary actions include: control of mercury contamination; reduction of bycatch and the use of boto meat as bait; design of wildlife crossings or management measures in dams; fisheries planning that reduces the competition and conflict with fishermen; and population monitoring through photo-identification and acoustics. Working with local communities and the Responsible tourism provides conservation incentives.
Interaction with humans, culture and environmental education
The pink dolphin occupies a prominent place in the Amazonian folklore, where powers and transformations are attributed to it. These narratives can be used to promote environmental education and respect, avoiding practices that encourage harm or capture.
Supposed boto products have been sold in some markets, although analysis has revealed confusion with other species. It is essential do not acquire derivatives nor participate in activities that promote their exploitation. When sighting them, it is recommended do not feed them, do not touch them, maintain a safe distance and prioritize ecotourism operators that comply with good practices.
Predators and natural mortality
There are no frequently documented habitual predators, but occasionally they could be attacked by black caiman, bull shark in estuarine areas, anaconda or even jaguars in particular situations. Some individuals have scars attributable to catfish that could bite soft tissue. Natural mortality increases with skin diseases and respiratory, especially in altered environments, and sometimes with rescues of stranded dolphins.
Acoustic signal and communication
Like other odontocetes, they use echolocation clicks y whistlingPart of their emissions are associated with the moment of immersion and the location of prey. The structure of their vocalizations It differs from that of common marine dolphins, reflecting adaptations to the river environment.
Where to watch them responsibly?
Regions with frequent sightings include protected areas of the Peruvian Amazone such as Pacaya Samiria, sections of the Solimões/Amazonas in Brazil, and basins of the Orinoco. Opt for low-impact tours such as canoeing or kayaking, with accredited guides, reduces stress on animals and provides benefits to local communities. Maintaining distance, avoiding chases and do not offer food These are basic rules.
FAQs
Are the dolphins in southern Lake Maracaibo, in Ologa and El Congo, pink dolphins or tucuxi? In that area, brackish water coastal dolphins predominate, commonly identified as Sotalia guianensis (sometimes called lake dolphins). The pink dolphin Inia geoffrensis It is native to the Amazon and Orinoco basins and is not considered a resident of Lake Maracaibo. tucuxi Sotalia fluviatilis It is distributed in the Amazon, not in Maracaibo. Therefore, what was observed in Maracaibo does not correspond to the pink dolphin.
They make up the majority of the river dolphin population in existence, since the other river species are highly threatenedIt's a shame that whenever there's something special in nature, it suffers from human actions. Although they have been kept in aquariums, as revealed complaints in aquariums, they are difficult to train and present high mortality in captivity, which reinforces the importance of protecting them in freedom.
The pink dolphin is consecrated as a icon of Amazonian biodiversity: a large toothed whale of exceptional size, color, and maneuverability, with a varied diet, complex behavior, and an evolutionary history linked to the great South American rivers. Its future depends on reducing threats such as pollution, bycatch and habitat fragmentation, in addition to promoting research, fishery management sustainable and the responsible ecotourism.
