Little is known of the reproductive habits of the tucuxi dolphin. The freshwater subspecies calves during the low water period of October and November (2), after an 11 to 12 month gestation. It is thought to be polyandrous (where each female has more than one male partner), and aggression between males is seen during courtship (5). The seasonal fluctuation in river water levels has a great influence on the freshwater subspecies. It enters lakes during high water but leaves as the waters begin to fall to avoid being trapped (2). A shy dolphin, the tucuxi tends to be most active during the early morning and late afternoon, but is usually a slow swimmer that jumps infrequently (5). It dives for around 30 seconds (4), and uses echolocation to communicate as well as to catch fish and shrimp (5). Group size varies, but can be up to 20 in freshwater or 50 in the marine subspecies (3).

The tucuxi dolphin (pronounced 'too-koo-shee') quite closely resembles the bottlenose dolphin, but smaller. It is blue to light grey on the back, and fades to white or whitish-pink on the belly. There is a dark bar between the mouth and the flipper. The beak is slender and long, and the dorsal fin is triangular and slightly hooked at the tip (2). Both the beak and the dorsal fin may be tipped with white (5). Some marine populations have yellow-orange sides with a bright patch on the dorsal fin (5).

Habitat dolpin mostly in both fresh and saltwater(sea), but for species Sotalia fluviatilis they are live in saltwater and near to the surface and we can found around the world it can be found nearly everywhere including the Indian ,Atlantic, & Pacific Oceans, the Mediterrean, Red & Black Seas. Dolpin always make a group ,that is these lifestyle and this group so important becouse these need each other example for looking a food ,hunting and to protect these self from predators. These will make same noise for protect self, guide they child also group. It is the way they to communication. The sound of dolphins can be grouped into three types, that is (1) click for echolocation, (2) bursering described as a screech or bark, (3) whistle usually used for communication. Dolpin also life at depths greater than 200 meters but they will depend to the noise than a light.Dolpin life is more rely to sound rather than sight and hearing. Dolphins cannot breathe under water. They breathe out of their blowhole. This is why we can’t put anything in their blowhole, because this is their route to breathe and make sounds. But they can hold their breath for amazing amounts of time seven minutes. So they do need to come up for a breath . That make doplin including in active swimmer, because they speeds of swiming is 60 km / h or 37 mph . They always swim like activity jumps to the air with the head first and fell back into the water.Some reviewer called this activity is breaching. Dolpin also do not sleep well under water for a long time because they will could drown. Therefore, when they sleep only was half asleep a few moments in a day. They also do migrate if the water gets so cold the temperature in minimum stage. Also they may migrate if the fish supply and feeding habits change and looking for food. They can even travel hundreds of miles just to follow their food supply. Some like cold and deeper water than others. But if there is enough food available then they may just stick to a local area.

Tucuxis are found in the Amazon drainage as far inland as southern Peru, eastern Ecuador, and southeastern Colombia. They occur in the main tributaries of the Amazon/Solimões River basin and they cross international boundaries in areas such as Leticia, between Brazil and Colombia. The species does not occur in the Beni/Mamoré river basin in Bolivia nor in the upper Rio Negro. Its putative presence in the Orinoco is controversial because of a stretch of rapids and waterfalls that are suspected to block the species movements to this area (Flores and da Silva 2009). During the flood season, Tucuxis may move into smaller tributaries, but apparently they do not move into the inundated forest to feed (as botos, Inia geoffrensis, often do), staying mainly in the main river channels, tributaries and lakes (da Silva and Best 1996). Tucuxis are largely sympatric with the Boto in the Amazon and Orinoco systems but generally do not interact with that species.

Tucuxis, also known as gray dolphins and Guianian River dolphins, are neotropical dolphins that live exclusively in the Amazon and Orinoco basins and are thought to be endemic to this region of South America. The closest living relatives of Tucuxis are Costeros, dolphins that live in the shallow waters along the Atlantic Coast of South America. However, Tucuxis are sympatric with Amazon River dolphins of the family Iniidae.

Biogeographic Regions: neotropical (Native )

Amazon River

Occurring in the river systems of the Amazon and the Orinoco, as well as along the coasts from Brazil to Nicaragua, the tucuxi dolphin is split into two subspecies. The freshwater subspecies, Sotalia fluviatilis fluviatilis, inhabits only fresh water and is found as much as 250 km up the Orinoco River system and as much as 2,500 km up the Amazon River system. The marine subspecies, Sotalia fluviatilis guianensis, is found in the coastal estuaries and bays of the east coast of South America as far south as the Brazilian city of Florianópolis (2).

Sotalia fluviatilis and Sotalia guianensis are very similar in appearance and were once classified as a single species. However, phylogenetic evidence indicates that they diverged approximately 1.5 to 2 million years ago during the Pliocene or early Pleistocene. Despite their many similarities, three major differences help distinguish between these 2 species. First, S. fluviatilis largely prefers fresh water habitat, whereas S. guianensis prefers saline coastal habitat. Second S. fluviatilis is much smaller in size than S. guianensis. Finally, the haplotype and nucleotide sequences of S. fluviatilis are as diversified from S. guianensis as they are from other delphinids. In general, S. fluviatilis is smaller and has a shorter beak than most other members of the family Delphinidae. It ranges from blue to pearl-grey along the dorsal surface and from white to pale-pink along the ventral surface. Most individuals have a white tipped beak. The dorsal fin has a prominent triangular shape that sometimes hooks toward the caudal fin. Adults have between 28 and 35 teeth. Sotalia fluviatilis is not sexually dimorphic and ranges from 86 to 206 cm long and weighs 55 kg on average.

Average mass: 55 kg.

Range length: 86 to 206 cm.

Average length: 152 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

Average mass: 46666.7 g.

Habitat and Ecology

Systems

• Freshwater

Tucuxis are found throughout the Amazon and Orinoco River basins and are commonly found near low current confluences and river junctions where food is abundant and less energy has to be expended during foraging bouts. They avoid mud banks and flooded forest areas. The mouth of the Amazon River occurs at its junction with the Atlantic ocean, thus making the first 2 km of the river relatively saline. Although some Tucuxi can be found within this area, they prefer the freshwater habitat found further inland.

Habitat Regions: tropical ; freshwater

Aquatic Biomes: rivers and streams; brackish water

Other Habitat Features: estuarine

In freshwater in Amazon and Orinoco drainage basins.

The freshwater subspecies inhabits rivers and lakes, but is not found in flooded forests and avoids rapids, whereas the marine subspecies inhabits shallow, protected estuaries and bays (2).

Tecuxis are carnivorous, and primary prey includes marine ray-finned fishes, along with squids and octopuses. Confluence areas result in favorable pH levels for plankton growth, which attracts many species of ray-finned fish. As a result, Tucuxis are often seen travelling to confluences, likely in search of prey.

Animal Foods: fish; mollusks

Primary Diet: carnivore (Piscivore , Molluscivore )

Although barnacles are commonly found Tucuxis, they are not considered parasitic, as they have no known negative impact on their host. Limited information exists regarding parasites of Tucuxis; however, stomach flukes and two species of nematode (Anisakis typica and Halocercus brasiliensis) are known to infect the gastrointestinal tissues of this species at various stages throughout their complex life cycle.

Commensal/Parasitic Species:

• stomach flukes, (Braunina cordiformis)
• parasitic nematode, (Anisakis typica)
• parasitic nematode, (Halocercus brasiliensis)
• barnacles, (Xenobalanus globicipitis)

Other than illegal hunting by humans, Tucuxis have no known predators.

Known Predators:

• humans, (Homo sapiens)

Like most dolphins, Tucuxis use a variety of whistles and clicks to communicate with conspecifics. Among delphinids, evidence suggests that species' size has a linear effect on whistle pitch, with smaller species having higher pitched whistles and larger species having lower pitched whistles. Tucuxis align with this relationship, and as one of the smallest extant dolphin species, they are known to have some of the highest pitched whistles when compared to other dolphins (e.g., 16% of whistles exceed 24Hz). Whistle frequency tends to ascend rather than descend during a single whistle. Whistling increases while foraging, and is thought to attract conspecifics to where food is abundant; suggesting a co-operative rather than competitive attitude between conspecifics. Like other delphinids, Tucuxis use echolocation to help them find prey.

Tecuxis use their vision to perceive the local environment, and despite living in a freshwater environment, have a number of ocular features that are similar to those of many marine dolphins. Tucuxis have two high density ganglion areas, a feature which is common among delphinids and helps them process visual information more efficiently than Amazon River dolphins, which have only one. Being originally adapted for life in a saline environment, however, may negatively affect their ability to see objects in freshwater at high resolution. Evidence suggests that although their clarity of vision is less than that of true river dolphins, it is better than that of marine dolphins. What they lack in eye sight, however, they make up for in their ability to echolocate prey and potential predators.

Communication Channels: acoustic

Perception Channels: visual ; echolocation

Evidence suggests that wild Tucuxis can live for up to 35 years. There is no information available indicating the average lifespan of captive individuals. They are susceptible to capture stress and often tangle and suffocate themselves within netting. In addition, Tucuxi do not respond well to extended periods of transportation.

Average lifespan

Status: wild: 35 years.

Observations: Little is known about the longevity of these animals, but one wild born specimen was still living in captivity at about 31-32 years of age (Richard Weigl 2005).

There is no information available regarding the mating system of Tucuxis.

Tucuxis breed during late summer and early fall. Gestation ranges from 10 to 11.6 months and results in one calf, which is born during the fall low-water season. Newborn calves range in size from 71 to 106 cm in length. Both sexes become sexually mature by six years of age, at which point males are around 180 cm long and females are around 160 cm long. Despite their differences in length at reproductive maturity, fully grown males and females are usually equal in length and weight.

Breeding season: Tucuxis breed from August to October.

Average number of offspring: 1.

Range gestation period: 10 to 11.6 months.

Average age at sexual or reproductive maturity (female): 6 years.

Average age at sexual or reproductive maturity (male): 6 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Average number of offspring: 1.

Little is known of parental care in Tucuxis; however, mothers are known to whistle at their calves once they have found food. As mammal, mothers likely nurse their young until weaning is complete.

Parental Investment: female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 3
Species With Barcodes: 1

Tucuxis are classified as "data deficient" on the IUCN Red List of Threatened Species. Currently, population trends are unknown and thus potential conservation and management needs cannot be determined. They are the only species of fresh-water delphinid currently known. Although there has never been a commercial fishery for this species, a significant number of deaths occur due to by-catch and incidental mortality in fishing gear. Other potentially important threats include damming, overfishing of prey, boat strikes, chemical pollution and noise pollution. Without further research on the demographics of this species throughout its geographic range, the significance of these threats cannot be established and potential conservation and management actions cannot be prioritized.

US Federal List: no special status

CITES: appendix i

State of Michigan List: no special status

IUCN Red List of Threatened Species: data deficient

The tucuxi dolphin is classified as Data Deficient on the IUCN Red List 2004 (1), and is listed on Appendix I of CITES (5). It is also listed on Appendix II of the Convention on Migratory Species (2).

Population

Population Trend

Major Threats

The tucuxi dolphin is regularly caught accidentally in gillnets of large fishing trawlers, and is the most common cetacean in the by-catch of coastal fisheries in the south Caribbean Sea. Intentional hunting appears to be rare, but does take place for meat to eat, for blubber to be used as shark bait, and for the genital organs and eyes which are sold as love amulets (1). A major potential threat is a proposal for the construction of hydroelectric dams, which would cause population fragmentation and increased inbreeding, as well as the extinction of the migratory fish that constitute the diet of the freshwater tucuxi dolphin (2). Pollution from heavy metals, banned pesticides and noise are also concerns, as is habitat loss (1).

Conservation Actions

The superstition of fishermen, who believe the tucuxi dolphin to be a sacred animal that brings the bodies of drowned people back to the shore, has ensured that it has rarely been targeted as a food item (6). In 1994, the International Whaling Commission's (IWC) Scientific Committee urged member states to reduce by-catch and monitor populations (1). The IWC had previously started the Sotalia Project with the organisation 'Brasil's Biologists', which sets out to study the behaviour and habitat needs of the tucuxi dolphin, and has managed to build a significant collection of photo identifications (6).

There are no known adverse effects of Tucuxis on humans.

Indigenous South Americans hold Tucuxis in high regard as protectors that carry the drowned to shore for burial. Despite Brazilian law protecting them, Tucuxis are illegally hunted for their meat (bait), oil (emulsion to protect boats from water), and various body parts that are used in traditional medicines or religious ceremonies.

Positive Impacts: body parts are source of valuable material; source of medicine or drug

Data Deficient (DD)