Pontoporia blainvillei (Gervais & d'Orbigny, 1844)

Russell A. Mittermeier & Don E. Wilson, 2014, Pontoporiidae, Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona: Lynx Edicions, pp. 386-393 : 393

Franciscana

Pontoporia blainvillei

French: Franciscain / German: La-Plata-Delfin / Spanish: Franciscana

Other common names: Franciscana Dolphin, La Plata Dolphin, La Plata River Dolphin

Taxonomy. Delphinus blainvillei Gervais & d’Orbigny, 1844 ,

“qui été pris a Montevideo,” Uruguay. The holotype, supposedly housed at the Muséum National d’Histoire Naturelle, Paris, has not been located .

This species is monotypic.

Distribution. SW Atlantic in SE Brazil (N to Espirito Santo State), Uruguay, and N Argentina (S to Golfo San Matias in N Patagonia); relatively common on both Uruguayan and Argentinian sides of La Plata River Estuary. The species is not continuously distributed, and there are two areas in its N distribution where it is extremely rare or absent.

Descriptive notes. Total length 117-136 cm (males) and 148-162 cm (females); weight 20-40 kg. Size variation of Franciscanas is not clinal. Sexualsize dimorphism is ¢.15%. The Franciscana has a bulky head and relatively small eyes; skull is symmetrical. Rostrum is long and slender in adults and relatively short in juveniles. Teeth are small, conical, and sharp: 53-58 in upperjaw and 51-56 in lowerjaw. Flippers of the Franciscana are broad, paddle-shaped, and visibly fingered. Dorsalfin is moderately tall and triangular to slightly falcate. Fluke span is slightly more than one-fourth of the body length. Adult skin coloration is ocher or brownish on the back, turning gradually paler toward flanks and belly; newborns can be slightly darker.

Habitat. Turbid marine coastal shallow waters and estuaries of the tropical and temperate western South Atlantic. Franciscanas are found mostly in shallow waters less than 40 m deep, and they avoid deep, clear, and cold waters.

Food and Feeding. Franciscanas are opportunistic feeders. They eat a large variety of small marine fish, mollusks, and crustaceans. Most prey is bottom-dwelling fish; some are pelagic. Prey includesfish of the families Sciaenidae , Phycidae , Trichiuridae , Batrachoididae , Stromateidae , Ophidiidae , Engraulidae, Carangiade , and Clupeidae . Among the cephalopods, coastal squid of the family Loliginidae are the most common in diets of Franciscanas. Juveniles feed on shrimps in the families Solenoceridae , Penaeidae , and Palaenomidae.

Breeding. The Franciscana has one of the shortest reproductive cycles of any cetacean. Sexual maturity is attained at c.2—4 years of age. Mean length at sexual maturity is c.115-130 cm (males) and 125-140 cm (females). Females can reproduce annually or biannually. Testes are small (0-12% of body mass). Sperm competition is unlikely. A non-promiscuous, single male breeding system with guarding strategy is suspected. Reproduction is markedly seasonal in the southern part of the distribution; births occur in the austral spring and summer in October-February. In the northernmost part of the distribution, births occur throughout the year. Gestation lasts 10-2-11-2 months. Litter size is limited to one. Newborns are ¢.60-80 cm in length. Weaning is gradual and occurs 6-9 months after birth. There is no evidence of female reproductive senescence. Longevity of the Franciscana is up to 15 years; the oldest known record is a 23year-old female.

Activity patterns. Franciscanas are shy and averse to vessels. Aerial display is a rare event. Interactions with coexisting species of ocean dolphins are rare or non-existent. There are no comprehensive studies on activity patterns. In Argentina, Franciscanas spend up to 75% of their time diving and foraging. Cooperative feeding behavior has been recorded. Average swimming speed is 1-3 m/s, with speeds not exceeding 1-8 m/s. During travel, speed is c.1-5 m/s, and individuals in the same group exhibit synchronous breathing. Foraging seems to increase and travel decrease during flood tides.

Movements, Home range and Social organization. Franciscanas live in small groups of 2-3 individuals, but aggregations of up to 30 individuals occur, probably for foraging and breeding purposes. Franciscanas perform short-distance movements and have small home ranges of a few tens of kilometers. They seem to be organized in matrilineal small units, although the level of stability is unknown. Some groups are first-order related individuals, consisting of a mature female and more than one immature individual, indicating natal philopatry. Half-sibling (second-order) relationships are also observed within groups. A group composed of a mother, two male offspring, and the putative father of one of them has been observed. These family groups and evidence of natal philopatry suggest lack of dispersal by males and females.

Status and Conservation. CITES Appendix II. Classified as Vulnerable on The IUCN Red List. This classification was warranted because a decline of more than 30% over three generations was projected based on population viability analyses. The cause of the projected decline was high levels of fishing-related mortality. Rate of decline was probably underestimated because a period of only 25 years was considered and other sources of non-natural mortality such as habitat degradation (pollution and overfishing) were not incorporated into the analyses. Four Franciscana Management Units were identified: coastal waters of Spirito Santo and Rio deJaneiro states (Brazil); Sao Paulo, Parana, and Santa Catarina states (Brazil); coastal waters of Rio Grande do Sul State (Brazil) and Uruguay; and coastal waters of Argentina. Abundance of Franciscanas in all of these units is small, and causes of decline have not ceased and,in fact, are increasing because of fishery expansion and lack of enforcement or mitigation actions.

Bibliography. Alonso, Eljarrat et al. (2012), Alonso, Feo et al. (2012), Ameghino (1918), Barbato et al. (2012), Barreto & Rosas (2006), Bordino, Thompson & Iniguez (1999), Bordino, Wells & Stamper (2008), Botta et al. (2010), Brownell (1989), Cassens et al. (2000), Costa-Urrutia et al. (2012), Cowx et al. (1998), Cozzuol (1985, 2010), Cremer & Simobes-Lopes (2005), Crespo, Harris & Gonzalez (1998), Crespo, Pedraza et al. (2010), Danilewicz (2003), Danilewicz, Claver et al. (2004), Danilewicz, Moreno et al. (2010), Danilewicz, Rosas et al. (2002), Danilewicz, Secchi, Ott & Moreno (2000), Danilewicz, Secchi, Ott, Moreno, Bassoi & Borges-Martins (2009), Danilewicz, Zerbini et al. (2012), Di Beneditto & Ramos (2001), Dorneles et al. (2007), Haimovici et al. (1996), Hamilton et al. (2001), Leonel et al. (2010), Melcon et al. (2012), Mendez, Rosenbaum & Bordino (2008), Mendez, Rosenbaum, Subramaniam et al. (2010), de Muizon (1983, 1984, 1988), Ott & Danilewicz (1998), Pilleri (1971), Praderi (1985, 1997, 2000), Prado et al. (2013), Ramos, Di Beneditto & Lima (2000), Ramos, Di Beneditto, Siciliano et al. (2002), Reeves, Dalebout et al. (2008a), Reilly & Barlow (1986), Ribeiro et al. (1998), Rodriguez et al. (2002), Rosas & Monteiro-Filho (2001), Ruffino & Castello (1992), Santos & Netto (2005), Secchi (2006, 2010a, 2010b), Secchi, Danilewicz & Ott (2003), Secchi, Kinas & Muelbert (2004), Secchi, Ott & Danilewicz (2003), Secchi, Wang et al. (1998), Secchi, Zerbini et al. (1997), Seixas, Kehrig, Costa et al. (2008), Seixas, Kehrig, Fillmann et al. (2007), Siciliano et al. (2002), Zerbini et al. (2010), Zhou Kaiya (1982).

Figures

Distribution. SW Atlantic in SE Brazil (N to Espirito Santo State), Uruguay, and N Argentina (S to Golfo San Matias in N Patagonia); relatively common on both Uruguayan and Argentinian sides of La Plata River Estuary. The species is not continuously distributed, and there are two areas in its N distribution where it is extremely rare or absent.