Boto (Inia geoffrensis)
|Also known as:||Amazon River dolphin, boutu, pink river dolphin|
|French:||Dauphin De L'Amazone, Inia|
|Size||Female length: 2.3 m (2)|
Male length: 2.7 m (2)
|Weight||85 – 160 kg (2)|
Classified as Data Deficient (DD) on the IUCN Red List (1), and listed on Appendix II of the Convention on Migratory Species (CMS or Bonn Convention) (3).
The boto is probably the best known of the five river dolphins. It has an extremely distinctive shape with a long, plump body, paddle-shaped fins and a ridge along the back rather than a dorsal fin (4). The head consists of a bulging forehead (known as the 'melon'), small eyes, chubby cheeks and an extremely long beak, which may hold up to 140 teeth (2). Probably the most striking feature of the boto, however, is its colour, which varies from bluish grey to white (5), and even pink (2). Botos have extremely flexible necks, as some of the vertebrae are unfused; they are able to move their head in most directions (4). Local people have often regarded the boto with suspicion and there are a number of myths surrounding the species, such as one in which dolphins turn into handsome men in order to seduce young girls (6).
The boto is found in the drainage basins of the Amazon and Orinoco Rivers in South America (7). It is known from Peru, Ecuador, Brazil, Bolivia, Venezuela and Columbia and Guyana (1); botos can be found as far as 3,000 kilometres from the coast (2). Some experts recognise different subspecies within the range of the boto; Inia geoffrensis humboldtiana in the Orinoco basin, I. g. boliviensis in the upper Madeira River and I. g. geoffrensis in the remainder of the Amazon basin (1).
These freshwater dolphins are found in slow-moving rivers and streams. During the wet season when waters rise and flood nearby forests, botos will also leave the deeper channels and are agile enough to swim through the trees (8).
Botos are usually observed either singly or in pairs although groups of up to 15 animals have been recorded (5). They appear to be most active during the early morning and late evening (5); slow swimmers they generally travel at around two kilometres per hour (2). Botos are reported to be playful and curious creatures, approaching boats and pulling on paddles as well as interacting with each other (2). Their flexible bodies allow botos to swim in shallow areas and to weave in and out of the trees in floodwaters; they are also known to swim upside down, possibly because their chubby cheeks make downwards vision difficult (2). Botos feed on a variety of fish and crab species (4); using echolocation to locate prey in the murky waters of the rainforest rivers (2).
Females reach sexual maturity at between six and ten years of age and the gestation period is around 11 months (7). A single calf is born in July just as the water levels are beginning to drop, thus forcing fish back into the major waterways (7). The interval between births may be as much as five years, and botos are thought to live for as long as 30 years (7).
Although the most widespread of the river dolphins, botos are threatened by the continued development of the river systems in which they are found (8). Hydroelectric or irrigation schemes that dam rivers act to isolate dolphins in smaller sections of their habitat. These dolphins were previously associated with bad spirits which has perhaps protected them from persecution (7). However, they are now coming into increased conflict with local fisherman who may view the species as competition (8). Dolphins are also caught or injured accidentally during the fishing process; either as bycatch in nets or through collisions with boats and motors (8).
The boto is fully protected by law in both Brazil and Bolivia and is partially protected in areas of Peru, Venezuela and Colombia (4). It is found within the Amazon River Global 200 Ecoregion, which is receiving some degree of international protection and recognition (7). These bizarre-looking pink dolphins have attracted a lot of attention and now support a tourist trade (5); perhaps this interest will be sufficient to preserve the future of this mysterious river dweller.
For more information on the boto see:
The Whale and Dolphin Conservation Society (WDCS):
CMS species page:
Authenticated (9/6/03) by WDCS, The Whale and Dolphin Conservation Society.
- Beak: the bill of a bird. In cetacea (whales and dolphins): the elongated forward part of the head, comprising the lower jaw and upper jaw or ‘rostrum’.
- Bycatch: in the fishing industry, the part of the catch made up of non-target species.
- Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
- Echolocation: detecting objects by reflected sound. Used for orientation and detecting and locating prey by bats and cetacea (whales and dolphins).
- Gestation: the state of being pregnant; the period from conception to birth.
- Melon: in cetaceans, the bulging forehead belonging to a number of species, which contains oil, muscles and nasal passages and is though to focus sound during echolocation.
- Subspecies: a different race of a species, which is geographically separated from other populations of that species.
IUCN Red List (July, 2009)
WDCS, The Whale and Dolphin Conservation Society (February, 2003)
Global Register of Migratory Species (March, 2008)
MarineBio.org (March, 2008)
- Carwardine, M. (1995) Whales, dolphins and porpoises. Dorling Kindersley, London.
Animal Diversity Web (February, 2003)
Animal Info (February, 2003)
CMS species page (March, 2008)