Tucuxi

## Description

Tucuxi is a species of dolphin, which is quite similar to the bottlenose dolphin, but smaller. A dark stripe runs between the animal's mouth and flipper. The back is blue to light grey, while the belly is white or whitish-pink. The animal has long and slender beak. The triangular-shaped dorsal fin is slightly hooked at the tip. The beak and the dorsal fin can be white at the tip. In addition, some marine populations of this species exhibit yellow-orange sides and a bright marking on their dorsal fin.

## Distribution

There are two subspecies of the Tucuxi dolphin: the freshwater subspecies, occurring in the Amazon River system and the Orinoco River system; and the marine subspecies, found along the east coast of South America, from Brazil to Nicaragua, in the Caribbean Sea and Atlantic Ocean.

## Behavior

The Tucuxi dolphins can be observed in very small groups, consisting of a female and her calf, as well as large groups of 50 - 60 animals. However, they are most commonly found in groups of 10 - 15 individuals. Calves typically live in larger groups in order to learn various social behaviors from members of the group. When diving, these animals typically remain submerged for about 30 seconds. The Tucuxis are shy dolphins, which do not tend to jump and usually swim slowly. The periods of increased activity occur in the early morning and late afternoon. The Tucuxi dolphins are known to use echolocation when hunting as well as a form of communication. They also communicate with conspecifics through a wide variety of clicks and whistles, by which they inform other of threats, location of food and different desires including mating desire.

## Diet

These carnivorous (piscivorous and molluscivorous) animals mainly feed upon marine ray-finned fishes, supplementing their diet with squids and octopuses.

## Reproduction

Very little is known about the mating habits and system of this animal. The Tucuxi dolphins are thought to have polyandrous mating system, where one female mates with multiple males. During courtship, males are known to display aggressive behavior towards each other. Breeding season occurs in late summer and early fall, lasting from August to October. Calves are usually born in the autumn, during the low-water season. Gestation period lasts for 10 - 11.6 months, yielding a single calf. There's very little information on parental behavior of this species. It is known that mother dolphins whistle at their offspring when finding food. Both sexes reach sexual maturity at 6 years old, when males are 180 cm long and females are 160 cm long.

## Population

### Threats

Currently, large numbers of these animals are accidentally being caught in gillnets of large fishing boats. In the south Caribbean Sea, Tucuxi is the most common cetacean to be caught by coastal fisheries. Tucuxi is hunted (although in small numbers) in many areas of its range for meat as well as blubber, which is used as shark bait. The animal suffers from loss of its natural habitat due to heavy metal pollution, noise and use of banned pesticides. Potential threats to this species include a proposal for the construction of hydroelectric dams, which may cause population fragmentation across the area of Tucuxis' range, and as a result, higher degree of inbreeding. Construction of hydroelectric dams may also lead to extinction of the migratory fish, which are the main food source of these dolphins.

### Number

According to the IUCN Red List, the total population size of the Tucuxi is unknown for today, but it seems to be common across its range. However, there are estimates of specific populations in following areas: the Samiria River system in Peru - 350 dolphins; and the Amazon River, bordering Colombia, Peru and Brazil - 409 dolphins. Currently, Tucuxis are classified as Data Deficient (DD) on the IUCN Red List.

## Fun Facts

The word 'Tucuxi' is pronounced as 'too-koo-shee'.

These dolphins are capable of making high leaps of up to 120 cm out of the water. They come to the surface to breathe every 5 - 85 seconds.

While fish typically swim by moving their tails from side to side, dolphins move their tails up and down.

Dolphins are more efficient swimmers than fish, since they have more oxygen in their blood and are able to swim longer than fish.

These animals are known to play with both members of their pods and these of other pods. They have also been observed playing with seaweed, turtles and even humans.

Tucuxis have good eyesight both above and under the surface.

All species of dolphin evolved from land mammals. Their ancestor lived around 50 million years ago and slightly resembled a wolf. Hunting in shallow waters, these animals gradually adapted themselves to the aquatic lifestyle. In course of time, their forelegs turned to flippers while hind legs disappeared; then they developed their fluke; the fur gradually disappeared; the nostrils moved to the top of the head.

Dolphins, along with porpoises and whales, belong to the group of cetaceans - aquatic mammals, lacking hind limbs as well as blowhole for breathing.