Aarnieu river dolphin

The Aarnieu river dolphin is a species of toothed whale that lives in the Aarnieu and related rivers in East Alutra, namely in the countries of Ordrey, Ecoralia, and Lathadu. It is also known colloquially by the name Slaíde (The Charming One) in Ordrey. Two subspecies are currently recognized, the Upper Aarnieu river dolphin, native to Ordrey and Ecoralia, and the Lower Aarnieu river dolphin, found primarily in Lathadu and parts of southern Ordrey. The Aarnieu river dolphin is the largest species of river dolphin ever recorded, with adult males reaching 180 kilograms in weight and 2.5 meters in length. Sexual dimorphism is very evident, with males measuring 16% longer and weighing 55% more than females. Like other toothed whales, they have a melon, an organ that is used for bio sonar. The dorsal fin, although short in height, is regarded as long, and the pectoral fins are also large. The fin size, unfused vertebrae, and its relative size allow for improved maneuverability when navigating flooded forests and capturing prey.

They have one of the widest ranging diets among toothed whales, and feed on up to 53 different species of fish, including the infamous Aarnieu catfish/ They also consume other animals such as river turtles and freshwater crabs.

The Aarnieu river dolphin population declined drastically in the late decades of the 19th century as the region's nations industrialized and made heavy use of the river for fishing, transportation, and hydroelectricity. In 1988, the species was declared by a World Forum commission to be "data deficient" due to uncertainty regarding its population trends and the impact of said threats. It is believed that only through great effort and mutual cooperation between the three home nations was extinction avoided, with populations slowly rebounding in the modern day. It is the only species of river dolphin kept in captivity, mainly in East Alutra. It is difficult to train and a high mortality rate is seen among captive individuals, meaning that they are generally only kept for conservation purposes.

Taxonomy
There is ongoing debate about the classification of species and subspecies. Today, two main subspecies are recognized: the Upper and Lower Aarnieu river dolphins. A third proposed subspecies, the Tretuish river dolphin, was described in 1987. Molecular analysis suggests that the Tretuish dolphins are derived from the Upper Aarnieu population and are not genetically distinct. In 2004, it was proposed that the Upper and Lower subspecies were different species entirely based on skull morphology. In 2012, following the analysis of mitochondrial DNA from specimens of both groups, biologists found that the two groups did not possess significantly unique mtDNA. As such the species level distinction once held is not supported by current results.

Description
The Aarnieu river dolphin is the largest known river dolphin in the world. Adult males reach a maximum length and weight of 2.55 meters and 185 kilograms on average, while females reach a length and weight of 2.15 meters and 150 kilograms. Their bodies are robust and strong but also flexible. Unlike in oceanic dolphins, the cervical vertebrae are not fused, allowing the head to turn 90 degrees. The flukes are broad and triangular, and the dorsal fin, which is keel-shaped, is short in height but very long, extending from the middle of the body to the caudal region. The pectoral fins are large and paddle-shaped. The length of its fins allows the animal to perform a circular movement, allowing for exceptional maneuverability to swim through marshes and flooded forests but decreasing its speed.

Specimens range from gray to brownish on the dorsal (back) side, and white on the ventral (belly) side. The skull of the species is slightly asymmetrical compared to other toothed whales. It has a long, thin snout, with 25 to 28 pairs of long and slender teeth to each side of both jaws. Dentition is heterodont, meaning that the teeth differ in shape and length, with differing functions for both grabbing and crushing prey. Anterior teeth are conical and later have ridges on the inside of the crown. Because of its poor vision, the Aarnieu river dolphin relies primarily on sonar for navigation. The sonar system also plays an important role in socializing, predator avoidance, group coordination, and expressing emotions. Because of its poor vision, the baiji relies primarily on sonar for navigation. The sonar system also plays an important role in socializing, predator avoidance, group coordination, and expressing emotions. Sound emission is focused and highly directed by the shape of the skull and melon. Peak frequencies of echolocation clicks are between 70 kHz and 100 kHz. It has a melon on the head, the shape of which can be modified by muscular control when used for biosonar. Breathing takes place every 30 to 110 seconds.

Longevity
Life expectancy of the Aarnieu river dolphin in the wild is unknown, but in captivity, the longevity of healthy individuals has been recorded between 10 and 30 years. However, an individual named Colm at the Porth Grai Zoo and Aquarium in Salia lived at least 46 years, spending 45 years and 9 months in captivity.

Behavior
Aarnieu river dolphins are commonly seen in pods as large as 40 individuals, but on average contain closer to 10-13. However, they are also regularly seen singly or in twos. When pursuing prey, the entire pod works together to obtain their next meal. Typically, social bonds occur between mother and child, but may also be 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. Due to the high level of prey fish, larger group-sizes are seen in large sections that are directly influenced by whitewater (such as main rivers and lakes, especially during low water season) than in smaller sections influenced by blackwater (such as channels and smaller tributaries). In their freshwater habitat they are apex predators and gatherings depend more on food sources and habitat availability than in oceanic dolphins where protection from larger predators is necessary.

Captive studies have shown that the Aarnieu river dolphin is less shy than oceangoing varieties, but also tends to be less sociable. It is very curious and has a profound 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 the fishermen, rub against the boat, pluck underwater plants, and play with sticks, logs, clay, turtles, snakes, and fish. They are slow swimmers; they commonly travel at speeds of 1.5 to 3.2 kilometers per hour but have been recorded to swim at speeds up to 14 to 22 kilometers per hour. 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. They are harder to train than most other species of dolphin.

Courtship and reproduction
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. 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 polygynous mating system, though polyandry and promiscuity cannot be ruled out. In captivity, courtship and mating foreplay have been documented. The male takes the initiative by nibbling the fins of the female.

Breeding is seasonal, and births generally occur between late Spring and early Summer. The period of birthing coincides with the Aarnieu's flood season, which provides 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 80 centimeters long and in captivity have registered a growth of 0.21 meters 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. The relatively long duration of breastfeeding and parenting suggests a strong mother-child bond. 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.

Diet
The diet of the Aarnieu river dolphin is the most diverse of the toothed whales. It consists of at least 53 different species of fish across the river's basin. The dolphin's dentition allows it access to shells of river turtles and freshwater crabs. 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 dolphin's dentition allows it to access shells of river turtles and freshwater crabs and shrimp. 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. Usually, the dolphins are active and feeding throughout the day and night. However, they are predominantly active during twilight hours. They consume about five percent of their body weight per day. They are known to take advantage of the disturbances made by boats to catch disoriented prey. Sometimes, they associate with Sedic otters 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.

Echolocation and communication
The waters of the Aarnieu river and its various tributaries are often very murky, meaning that the Aarnieu river dolphin is forced to depend on its sense of echolocation 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 Aarnieu river dolphin produces less powerful clicks compared to other similar sized toothed whales. 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, so if detectable echoes are only reflected back from nearby objects, the echoes will quickly return, and the Aarnieu river dolphin is then able to click at a high rate. This in turn allows the animals to have a high acoustic update rate on their surroundings which may aid prey tracking when echolocating in rivers, flooded forests, and swamps with plenty of hiding places for the prey. While hunting in murky water, they emit a series of clicking noises, 30 to 80 per second, which they use by listening to the bouncing sonar which bounces off their prey.

Like other dolphins, Aarnieu 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 vocalizations are different in structure from the typical whistles of other species of dolphins.

Distribution and population
Aarnieu river dolphins are among the most widespread river dolphins in the world, present across the Aarnieu river basin and its various tributaries. Boundaries are set by waterfalls as well as very shallow water. Studies to estimate the population are difficult to analyze due to the difference in the methodology used. In a study conducted in a stretch of the Sostynagh River in Lathadu, a total of over 300 individuals were sighted. Density was estimated at 0.08-0.33 animals per square kilometer in the main channels, and 0.49-0.93 per square kilometer in the branches. In another study, on a stretch of 120 kilometers at the confluence of Ordrey, Ecoralia, and Lathadu, 345 individuals with a density of 4.8 per square km in the tributaries. 2.7 and 2.0 were observed along the banks. As a result of the studies conducted, it was found that the density is higher in the riverbanks, decreasing towards the center of the river. In studies conducted during the rainy season, the density observed in the floodplain was 18 animals per square km, while on the banks of rivers and lakes ranged from 1.8 to 5.8 individuals per square km. These observations suggest that the Aarnieu river dolphin is found in higher density than any other cetaceans.

Habitat and migration
The Aarnieu river dolphin is located in most of the area's aquatic habitats, including river basins, major courses of rivers, canals, river tributaries, lakes, and at the ends of rapids and waterfalls. Cyclical changes in the water levels of rivers take place throughout the year. During the dry season, dolphins occupy the main river channels, and during the rainy season, they can move easily to smaller tributaries, to the forest, and to floodplains. Males and females appear to have selective habitat preferences, with the males returning to the main river channels when water levels are still high, while the females and their offspring remain in the marshes and flooded areas as long as possible; probably because it decreases the risk of aggression by males toward the young and predation by other species.

In culture
In traditional Sedic folklore, at night, the Aarnieu river dolphin becomes a handsome young man who seduces humans, impregnating women, and then returning to the river before morning to return to dolphin form. Similarly, females become beautiful young women, often luring men into the water to their doom. The myth has been suggested to have arisen because it serves as a way of hiding illegitimate children in Sedic society, said to have been 'born under the sign of the Slaíde' or similar romantic notions. In the area, tales relate that it is very bad luck to kill a dolphin, and even worse luck to eat its flesh. Legend also states that if a person makes eye contact with an Aarnieu river dolphin, they will have good luck for life. Associated with these legends is the use of various fetishes, such as dried eyeballs and genitalia. These are often accompanied with the intervention of a bag witch or shaman. A recent study has shown, despite the claim of the seller and the belief of the buyers, few to none of these fetishes are derived from Aarnieu river dolphins. They are often derived from sea-going dolphins harvested along the coast, or even from domestic animals such as sheep or pigs.

Per Sedic folklore, a beautiful young woman named Mona is said to have lived with her mother and father on the banks of the Aarnieu. When Mona was 16 years old, her mother died. Her father loved his wife deeply, and went mad following her death. The local Bann's counselors pressed for him to remarry. Her father agreed, but only on the condition that his bride be as beautiful as his deceased wife. After searching fruitlessly, he began to desire his daughter because of her strong resemblance to her mother. He lured her onto the river in a boat and attempted to force himself on her, but she freed herself by plunging into the river. The spirit of the river, named Teighchloaie, pitied her and turned her into a dolphin to escape her father's insanity. She was thereafter declared a Saint, declared to be a patron figure for those afflicted with mental illness, as well as victims of incest.

Conservation
As the region developed economically, pressure on the river dolphin grew significantly. Industrial and residential waste flowed into the Aarnieu. The riverbed was dredged and reinforced with concrete in many locations. Ship traffic multiplied, boats grew in size, and fishermen employed wider and more lethal nets. Noise pollution caused the nearly blind animal to collide with propellers. However, the primary factor was likely unsustainable by-catch in local fisheries, which used rolling hooks, gill nets, and electrofishing. At least half of all known dolphin deaths in the 1950s and 1960s were caused by rolling hooks and other fishing gear. Unlike most historical-era endangerments of large-bodied animals, the Aarnieu river dolphin was the victim not of active persecution but of incidental mortality resulting from massive-scale human environmental impacts, primarily uncontrolled fishing. There are some scientists who have found that pollution has resulted in emerging diseases caused by parasitic infection in the dolphin population. The Aarnieu river dolphin's reliance on aquatic environments could have resulted in interaction with both terrestrial and marine pathogen risks. Since it has a limited distribution endemic to the Aarnieu River and its tributaries, the freshwater environment may have a higher pathogen level than marine waters. The pathogens in these waters could lead to viral infections that can result in epizootics, which has caused the deaths of thousands of marine mammals over the last twenty years. There have also been captured/killed individuals that have had helminth infestations in the stomach which leads scientists to believe that parasitic infections could be another cause of decline amongst the species.

In the 1970s, the population was estimated at around 6,000 animals. Realizing the urgency of the situation, the governments of Ordrey, Ecoralia, and Lathadu signed the Aarnieu Ecological Compact in 1976, enacting strict measures to promote the conservation of unique species endemic to the Aarnieu. In conjunction with these efforts, several breeding programs were established in Ordrey and across East Alutra, most notably in Salia, Edury, and Gladomyr. These breeding programs allowed the species to recover and be reintroduced to the Aarnieu while conditions steadily improved. Since 1982, five protected areas of the Aarnieu have been designated as aquatic reserves. Four were built in the main Aarnieu channel where the dolphins are actively protected and fishing is banned. The fifth protected area is an isolated oxbow lake located in northern Lathadu. As well as these five protected areas, there are also numerous "Protection Stations" along the Aarnieu. These stations consist of two observers and a motorized boat with the aim of conducting daily patrons, making observations and investigating reports of illegal fishing. Although recovery was not as rapid as first hoped, populations of Aarnieu river dolphins have steadily increased following the 1976 treaty and its accompanying regulations, and today that are considered to be only Endangered rather than critically so. In 2017, the government of Lathadu propagated select Ayekist texts in hopes of raising the community support to aid in the conservation of the dolphins. In the Summer of 2013, Ordrey's Federal Assembly passed a resolution declaring dolphins "nonhuman persons," and as such has forbidden their captivity for entertainment purposes; keeping dolphins in captivity must be for the purpose of conservation and satisfy certain legal requirements. Lathadu's National Diet adopted a similar resolution in 2015.