Guyana Dolphin

The Guiana dolphin is frequently described as similar to the bottlenose dolphin in appearance, but it is typically smaller, at only up to 2.1 m (6.9 ft) in length. Individuals are light to bluish grey in coloration on their back and sides. The ventral region is light grey. The dorsal fin is typically slightly hooked, with a triangular shape. The beak is well-defined and of moderate length.

The Guiana dolphin is very similar in appearance to the closely related tucuxi (Sotalia fluviatilis) with most differences only apparent in skull shape and body size. The Guiana dolphin is the larger of two at a maximum mass of 121 kilograms versus 53 kilograms for the tucuxi.

Researchers have recently shown that the Guiana dolphin has an electroreceptive sense, and speculate this may also be the case for other odontocetes.

The Guiana dolphin is seen to practice site fidelity with staying in the same area for a long time or returning back to previous sites. In addition to site fidelity the Guiana dolphin is also seen to not travel far to forage and generally stays in the same area. Though seen to practice site fidelity this species is seen to have patterns of movement that correlate with the seasons. The Guiana dolphin is found close to estuaries, inlets and other protected shallow-water areas around the eastern and northern South American coast. It has been reported as far south as southern Brazil and north as far as Nicaragua and possibly Honduras. This species has been observed to tolerate a wide range of temperatures and salinities

Guiana dolphins feed mainly on a wide variety of bony fish and occasionally on shrimps, cephalopods, and crabs. Studies of growth layers suggest the species can live more than 40 years. Diet for the Guiana dolphins range dramatically depending on where said dolphins are located at due to their opportunistic feeding habits. Feeding often occurs in more shallow waters where there is a more concentrated amount of prey.

Behavior regarding social interaction between individuals is commonly seen for the purpose of foraging and traveling. Group size and behavior in general is seen to differ within the seasons. Along with tending to forage in pods the Guiana Dolphin is also seen to be an opportunistic feeder.

This species generally forms small groups averaging about 2-6 individuals, but does occasionally form larger aggregations of up to several hundred animals. They are quite active and may jump clear of the water (a behaviour known as breaching), somersault, spy-hop or tail-splash. They are unlikely, however, to approach boats.

A study of a population off the coast of southern Brazil in the late 1990s found that females matured at 5–8 years of age and males where mature at 7 years of age. The gestation period was found to be approximately 12 month gestation period. The Guiana Dolphin is not seen to have a defined breeding season though the reproductive cycle is 2 years long. After age 25, the researchers found that the reproductive cycle had increased to 2.5 years a possible indication of reproductive senescence, or aging. The Guiana dolphin practices polyandry causing correlation to males competing for access to females.

The Guiana dolphin is listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements. As with all coastal cetaceans, the Guiana dolphin suffers from negative interactions with humans. Entanglement in gill nets, seine nets, and shrimp traps is responsible for the death of many animals each year. There is very limited gene flow between concentrations of this dolphin, and large stretches of coast contain no animals at all, so recovery from depletion of a local population may take time.