First record of orca predation on franciscana dolphins (Pontoporia blainvillei) in Argentina

PADULA, ANTONELLA DAIRA; GANA, JOAQUÍN CARLOS MARIO; GIARDINO, GISELA VANINA; DE LEÓN, MARTA CAROLINA; ELISSAMBURU, ANDREA; RODRÍGUEZ, DIEGO; DENUNCIO, PABLO

THE LATIN AMERICAN JOURNAL OF AQUATIC MAMMALS

LAJAM

Año: 2022 vol. 17 p. 68 - 72

1676-7497

Highly digested prey items were identified in the stomachcontents of an adult male orca, including beaks of four longfinnedsquids Loligo sanpaulensis (Class: Cephalopoda), a partiallydigested cetacean rib, and 14 odontocete teeth (Fig. 2B and2C). The size and the shape of the teeth found in the stomach revealed that they belonged to a franciscana dolphin. Kasuya andBrownell (1979) described decades ago that franciscana dolphinteeth range between 7 and 10 mm (length of teeth found: 8.41mm ± 1.27), with a crown antero-posteriorly compressed, and aroot of L or J-shape, and lingual-buccally flattened, characteristicparticularly notorious in older specimens. Two measurementswere taken at the external surface of each tooth, followingRamos et al. (2000): (1) tooth length (L-mm), measured fromthe apical extremity of the crown to the end of the root; and(2) cingulum width (CW-mm), measured in the maximum widthin the intersection of the crown with the root (Fig. 2D). Thesemeasurements were compared to a reference teeth collectionof P. blainvillei of known age (Table 1; Denuncio et al., 2013).Significant differences were found for cingulum width betweenthe year class 1 and 2 of the reference collection and the onesin the stomach (K-W: CW: χ2 = 40.764, d.f. = 3, p ≤ 0.01), but therewere no significant differences between the year class 0 andthe ones found in the present study (p = 0.69) (Fig. 2D). Thesefindings indicate that the teeth found seem to belong to a youngspecimen less than one year of age (up to 108 cm TL; Denuncioet al., 2013).