La Plata dolphin

La Plata dolphin
Skeleton in the collection of Museo di storia naturale e del territorio dell'Università di Pisa
Size compared to an average human
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Eutheria
Order: Cetacea
Suborder: Odontoceti
Superfamily: Inioidea
Family: Pontoporiidae
Gray, 1870
Genus: Pontoporia
Gray, 1846
Species: P. blainvillei
Binomial name
Pontoporia blainvillei
Gervais & d'Orbigny, 1844
La Plata dolphin range

The La Plata dolphin or Franciscana (Pontoporia blainvillei) is found in coastal Atlantic waters of southeastern South America. It is a member of the river dolphin group and the only one that actually lives in the ocean and saltwater estuaries, rather than inhabiting exclusively freshwater systems.

Taxonomy

The La Plata dolphin is the only species in its genus, and is often placed in its own family, the Pontoporiidae. It was first described by Paul Gervais and Alcide d'Orbigny in 1844 (the species epithet blainvillei commemorates the French zoologist Henri Marie Ducrotay de Blainville). The La Plata dolphin is also widely known as the Franciscana - the Argentine and Uruguayan name that has been adopted internationally. Other common names are the toninha (the Brazilian name) and cachimbo.

Description

The La Plata dolphin has the longest beak (as a proportion of body size) of any cetacean — as much as 15% in older adults. Males grow to 1.6 m (5 ft, 3 in) and females to 1.8 m (5 ft, 10 in). The body is a greyish brown colour, with a lighter underside. The flippers are also very large in comparison with body size and are very broad, but narrow on joining the body, so are almost triangular in shape. The trailing edges are serrated. The crescent-shaped blowhole lies just in front of a crease in the neck, giving the impression that dolphin forever has its head cricked upwards. The dorsal fin has a long base and a rounded tip.

The La Plata dolphin weighs up to 50 kg (110 lb), and lives for up to 20 years. The gestation period is around 10–11 months and juveniles take just a few years to mature. Females may be giving birth by the age of five.

Behavior and feeding

The animal is very inconspicuous—it moves very smoothly and slowly—and can be difficult to spot unless estuary conditions are very calm. They will commonly swim alone or in small groups. Exceptional groups as large as 15 have been seen. La Plata dolphins are bottom feeders and gut inspections have revealed they eat at least 24 different species of fish, depending on which species are most common. They will also take octopus, squid and shrimp. They are, in turn, hunted by killer whales (orcas) and several species of sharks.

Range and habitat

The La Plata dolphin is found in the coastal Atlantic waters of southeastern South America, including the Río de la Plata estuary. Its distribution ranges from the Tropic of Capricorn near Ubatuba, Brazil, south to Península Valdés, Argentina. It is the only member of the river dolphin group that actually lives in the ocean and saltwater estuaries, rather than freshwater. Although some members of the species do spend portions of their lives outside of river systems, many individuals live their entire lives within rivers, never venturing into the ocean proper.

Conservation

The La Plata dolphin is listed as "Vulnerable" in the IUCN Red List of Threatened Species. However, the Franciscana is a particular conservation concern because of its restricted distribution and vulnerability to incidental capture in fishing gear. Large numbers are killed in gillnets. Although the largest documented catches in the 1970s were in Uruguay, catches in recent decades have also been high in southern Brazil and Argentina. Scientists from all three countries have voiced their concerns, and asked for international assistance in highlighting the plight of the dolphin (see Reeves et al., pg. 53).

The species is listed on Appendix I[2] and Appendix II[2] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix I[2] as this species has been categorized as being in danger of extinction throughout all or a significant proportion of its range, and CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them. It is listed on Appendix II[2] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.

A young La Plata dolphin was rescued in 2011 off Montevideo, Uruguay,[3] and in February 2016 a young dolphin died on the beach of Santa Teresita, Argentina, after being passed around by a crowd who where posing for selfies with it.[4][5]

See also

References

  1. ↑ Reeves, R., Dalebout, M., Jefferson, T.A., Karkzmarski, L., Laidre, K., O’Corry-Crowe, G., Rojas-Bracho, L., Secchi, E., Slooten, E., Smith, B.D., Wang, J.Y. , Zerbini, A.N. & Zhou, K. (2012). "Pontoporia blainvillei". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 18 January 2013. Database entry includes a brief justification of why this species is of vulnerable.
  2. 1 2 3 4 "Appendix I and Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5 March 2009.
  3. ↑ Stopera, Matt (19 October 2011). "Insanely Cute Pictures Of A Man Taking Care Of An Orphaned Baby Dolphin". Buzzfeed. Reuters. Retrieved 20 February 2016.
  4. ↑ Carma Hassan, Lynn Franco (18 February 2016). "Outrage after dolphin beach death". CNN.
  5. ↑ Brice, Chloe (19 February 2016). "Tiny dolphin killed by crowd of beachgoers for selfie in Argentina". ABC News. Retrieved 20 February 2016.

External links

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