Editing Amazon river dolphin (section)

==Biology and ecology==
The Amazon river dolphin are commonly seen singly or in twos, but may also occur in pods that rarely contain more than eight individuals.<ref name=Salazar2011>{{cite journal |author1=Gomez-Salazar, C. |author2=F. Trujillo |author3=H. Whitehead | year=2011 | title=Ecological factors influencing group sizes of river dolphins (Inia geoffrensis and Sotalia fluviatilis) | journal=Marine Mammal Science | volume=28 | issue=2 | pages=E124–E142 | doi=10.1111/j.1748-7692.2011.00496.x | url=http://babel.banrepcultural.org/cdm/ref/collection/p17054coll23/id/588 }}</ref> Pods as large as 37 individuals have been seen in the Amazon, but the average is three. In the Orinoco, the largest observed groups number 30, but the average is just above five.<ref name=Salazar2011/> During prey time, as many as 35 pink dolphins work together to obtain their prey.<ref name=":02">{{Cite web|url=http://www.wildernessclassroom.com/wilderness-library/pink-river-dolphin/|title=Pink River Dolphin|last=Hansel|first=Eric|date=2013-12-30|website=Wilderness Classroom|language=en-US|access-date=2019-10-22}}</ref> Typically, social bonds occur between mother and child, but may also been seen in heterogeneous groups or bachelor groups. The largest congregations are seen in areas with abundant food, and at the mouths of rivers. There is significant segregation during the rainy season, with males occupying the river channels, while females and their offspring are located in flooded areas. However, in the dry season, there is no such separation.<ref name=Cooke/><ref name="da Silva 2004">{{cite journal|last1=Martin|first1=A.|first2=V.|last2=da Silva|year=2004|title=River dolphins and flooded forest: seasonal habitat use and sexual segregation of Botos (''Inia geoffrensis'') cetacean in an extreme environment|journal=Journal of Zoology|volume=263|issue=3|pages=295–305|doi=10.1017/s095283690400528x}}<!--|access-date=22 November 2015--></ref> Due to the high level of prey fish, larger group-sizes are seen in large sections that are directly influenced by [[Whitewater river (river type)|whitewater]] (such as main rivers and lakes, especially during low water season) than in smaller sections influenced by [[Blackwater river|blackwater]] (such as channels and smaller tributaries).<ref name=Salazar2011/> In their freshwater habitat they are [[apex predator]]s and gatherings depend more on food sources and habitat availability than in oceanic dolphins where protection from larger predators is necessary.<ref name=Salazar2011/>

Captive studies have shown that the Amazon river dolphin is less shy than the [[bottlenose dolphin]], but also less sociable. It is very curious and has a remarkable lack of fear of foreign objects. However, dolphins in captivity may not show the same behavior that they do in their natural environment, where they have been reported to hold the oars of fishermen, rub against boats, pluck underwater plants, and play with sticks, logs, clay, turtles, snakes, and fish.<ref name=deeAnn/>

They are slow swimmers; they commonly travel at speeds of {{convert|1.5|to|3.2|kph|mph}} but have been recorded to swim at speeds up to {{convert|14|to|22|kph|mph}}. When they surface, the tips of the snout, melon and dorsal fins appear simultaneously, the tail rarely showing before diving. They can also shake their fins, and pull their tail fin and head above the water to observe the environment. They occasionally jump out of the water, sometimes as high as a meter (3.14&nbsp;ft). They are harder to train than most other species of dolphin.<ref name=deeAnn/>

===Courtship===
Adult males have been observed carrying objects in their mouths such as branches or other floating vegetation, or balls of hardened clay. The males appear to carry these objects as a socio-sexual display which is part of their mating system. The behavior is "triggered by an unusually large number of adult males and/or adult females in a group, or perhaps it attracts such into the group. A plausible explanation of the results is that object-carrying is aimed at females and is stimulated by the number of females in the group, while aggression is aimed at other adult males and is stimulated by object-carrying in the group."<ref name="171.66.127.192">{{cite journal|last1=Martin|first1=A.R.|last2=Da Silva|first2=V.M.F.|last3=Rothery|first3=P.|year=2008|title=Object carrying as social–sexual display in an aquatic mammal|journal=Biology Letters|volume=4|issue=3|pages=243–245|doi=10.1098/rsbl.2008.0067 |pmid=18364306|pmc=2610054}}</ref>
Before determining that the species had an evident [[sexual dimorphism]], it was postulated that the river dolphins were monogamous. Later, it was shown that males were larger than females and are documented wielding an aggressive sexual behavior in the wild and in captivity. Males often have a significant degree of damage in the dorsal, caudal, and pectoral fins, as well as the blowhole, due to bites and abrasions. They also commonly have numerous secondary teeth-raking scars. This suggests fierce competition for access to females, with a [[Polygyny in animals|polygynous]] mating system, though [[Polyandry in animals|polyandry]] and [[Promiscuity#Other animals|promiscuity]] cannot be excluded.<ref>{{cite journal|last1=Best| first1=R.|first2=V.|last2=da Silva|year=1984|title=Preliminary Analysis of Reproductive Parameters of the boutu, ''Inia geoffrensis'', and the Tucuxi, tucuxi, in the Amazon River System|journal=Report of the International Whaling Commission |issue=Special Issue|volume=6|pages=361–369}}</ref>

In captivity, courtship and mating foreplay have been documented. The male takes the initiative by nibbling the fins of the female, but reacts aggressively if the female is not receptive. A high frequency of copulations in a couple was observed; they used three different positions: contacting the womb at right angles, lying head to head, or head to tail.<ref name=bebej/>

===Reproduction===
Breeding is seasonal, and births occur between May and June. The period of birthing coincides with the flood season, and this may provide an advantage because the females and their offspring remain in flooded areas longer than males. As the water level begins to decrease, the density of food sources in flooded areas increases due to loss of space, providing enough energy for infants to meet the high demands required for growth. Gestation is estimated to be around eleven months and captive births take 4 to 5 hours. At birth, calves are {{convert|80|cm|in}} long and in captivity have registered a growth of {{convert|0.21|m|ft}} per year. Lactation takes about a year. The interval between births is estimated between 15 and 36 months, and the young dolphins are thought to become independent within two to three years.<ref name=bebej/>

The relatively long duration of breastfeeding and parenting suggests a high level of parental care. Most couples observed in their natural environment consist of a female and her calf. This suggests that long periods of parental care contribute to learning and development of the young.<ref name=bebej/>

===Diet===
[[File:Amazon dolphin eating fish.jpg|thumb|Amazon river dolphin feeding]]
The diet of the Amazon river dolphin is the most diverse of the toothed whales. It consists of at least 53 different species of fish, grouped in 19 families. The prey size is between {{convert|5|and|80|cm|in}}, with an average of {{convert|20|cm|in}}. The most frequently consumed fish belong to the families [[Sciaenidae]] (croakers), [[Cichlidae]] (cichlids), [[Characidae]] (characins and tetras), and [[Serrasalmidae]] (pacus, piranhas and silver dollars).<ref name="animaldiversity.org">{{cite web | url=https://animaldiversity.org/accounts/Inia_geoffrensis/ | title=Inia geoffrensis (Amazon river dolphin) | website=[[Animal Diversity Web]] }}</ref> The dolphin's dentition allows it to access shells of river turtles (such as ''[[Podocnemis sextuberculata]]'') and [[freshwater crabs]] (such as ''Poppiana argentiniana'').<ref name=acs/><ref name=deeAnn/><ref name="animaldiversity.org"/> The diet is more diverse during the wet season, when fish are spread in flooded areas outside riverbeds, thus becoming more difficult to catch. The diet becomes more selective during the dry season when prey density is greater.<ref name=best/>

Usually, these dolphins are active and feeding throughout the day and night. However, they are predominantly [[crepuscular]]. They consume about 5.5% of their body weight per day. They sometimes take advantage of the disturbances made by boats to catch disoriented prey. Sometimes, they associate with the distantly related [[tucuxi]] (''[[Tucuxi|Sotalia fluviatilis]]''), and [[giant otters]] (''[[Giant otter|Pteronura brasiliensis]]'') to hunt in a coordinated manner, by gathering and attacking fish stocks at the same time. Apparently, there is little competition for food between these species, as each prefers different prey. It has also been observed that captive dolphins share food.<ref name=acs/><ref name=deeAnn/>

===Echolocation===
Amazonian rivers are often very murky, and the Amazon river dolphin is therefore likely to depend much more on its sense of echolocation than vision when navigating and finding prey. However, echolocation in shallow waters and flooded forests may result in many echoes to keep track of. For each click produced a multitude of echoes are likely to return to the echolocating animal almost on top of each other which makes object discrimination difficult. This may be why the Amazon river dolphin produces less powerful clicks compared to other similar sized toothed whales.<ref name=Ladegaard2015>{{cite journal|first1=Michael|last1=Ladegaard|first2=Frants Havmand|last2=Jensen|first3=Mafalda|last3=de Freitas|first4=da Silva|last4=Vera M.F.|first5=Peter Teglberg|last5=Madsen|year=2015|title=Amazon river dolphins (Inia geoffrensis) use a high-frequency short-range biosonar|journal=Journal of Experimental Biology|volume=218|issue=Pt 19|pages=3091–3101|doi=10.1242/jeb.120501|pmid=26447198|doi-access=free|bibcode=2015JExpB.218.3091L |hdl=1912/7584|hdl-access=free}}<!--|access-date=1 October 2015--></ref> By sending out clicks of lower amplitude only nearby objects will cast back detectable echoes, and hence fewer echoes need to be sorted out, but the cost is a reduced biosonar range. Toothed whales generally do not produce a new echolocation click until all relevant echoes from the previous click have been received,<ref name=Au1993>{{cite book |last=Au |first=Whitlow W.L. |date=1993 |title=The Sonar of Dolphins |url=https://www.springer.com/us/book/9780387978352 |location=New York |publisher=Springer-Verlag |pages=115–118 |isbn=978-0-387-97835-2}}</ref> so if detectable echoes are only reflected back from nearby objects, the echoes will quickly return, and the Amazon river dolphin is then able to click at a high rate.<ref name=Ladegaard2015 /> This in turn allow these animals to have a high acoustic update rate on their surroundings which may aid prey tracking when echolocating in shallow rivers and flooded forests with plenty of hiding places for the prey. While preying in murky water, they emit series of clicking noises, 30 to 80 per second, which they use by listening to the bouncing sonar which bounces off their prey.<ref name=":02"/>

===Communication===
Like other [[dolphin]]s, river dolphins use whistling tones to communicate. The issuance of these sounds is related to the time they return to the surface before diving, suggesting a link to food. Acoustic analysis revealed that the vocalisations are different in structure from the typical whistles of other species of dolphins.<ref>{{cite journal|first1=Jeffrey|last1=Podos|first2=MF|last2=Vera da Silva|first3=R.|last3=Marcos Rossi-Santos|year=2002|title=Vocalizations of Amazon River Dolphins: Insights into the Evolutionary Origins of delphinid Whistles|journal=Ethology|volume=108|issue=7|pages=601–612|doi=10.1046/j.1439-0310.2002.00800.x}}<!--|access-date=22 November 2015--></ref>

Male Amazon river dolphins have been observed to exhibit an unusual aerial [[urination]] behavior, predominantly in social contexts involving other males. During these events, a urinating male positions itself upside down, ejecting a urine stream into the air, while a receiving male actively seeks the stream with its [[Rostrum (anatomy)|rostrum]], possibly detecting chemical signals through specialized bristles. Researchers speculate that this behavior likely serves a social or communicative function beyond waste elimination, potentially facilitating [[Semiochemical|chemical communication]] in a species with limited olfactory capabilities.<ref>{{Cite journal |last1=Araújo-Wang |first1=Claryana |last2=Cantor |first2=Mauricio |last3=Wang |first3=John Y. |date=2025-02-01 |title=Aerial urination suggests undescribed sensory modality and social function in river dolphins |url=https://www.sciencedirect.com/science/article/abs/pii/S0376635725000117 |journal=Behavioural Processes |volume=225 |pages=105149 |doi=10.1016/j.beproc.2025.105149 |pmid=39864636 |issn=0376-6357}}</ref>