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WHAT IS THE COLOUR OF THE FRANCISCANA (PONTOPORIA BLAINVILLEI)?: A REVIEW AND A PROPOSED ASSESSMENT METHOD MICAELA TRIMBLE1,* AND RICARDO PRADERI 2 ABSTRACT: Colouration pattern is suggested as a potentially useful characteristic to identify populations of franciscana (Pontoporia blainvillei). Such information is needed for the creation of management and conservation plans for the species. The existence of geographic variation in the colour of the franciscana has been hypothesized; it is suggested that Brazilian and Uruguayan individuals are greyish, while the Argentinean are brownish. We examined individuals from Uruguay using an objective method (Villalobos and Villalobos, 1947) to determine colour patterns. We also reviewed the variation of the colour pattern of the franciscana throughout this species' distribution as noted in the published literature. In the original description of the species in 1844 and in several subsequent papers during the 19 th century, the colour pattern of the franciscana was erroneously described (e.g. as black and white). Only since the 20 th century have the colouration descriptions approximately matched the actual specimens observed. These descriptions can be typically divided into two basic classes: greyish and ochre/brown. However, within these two general colour groups there is great variation. Several descriptions provided by Brazilian, Uruguayan, and Argentinean authors agree with the above hypothesis. The great variation within the modern descriptions of the franciscana´s colour suggests that a variety of factors must be involved; therefore, we conclude that on the basis of the literature alone, it is very difficult to decide whether differences really exist in the franciscana´s colour along its distribution. According to Villalobos and Villalobos (1947), the colour pattern of Uruguayan specimens could be interpreted as 'greyish dorsally and yellowish-grey laterally'. Due to some limitations found in this technique, we propose a new method based on the RGB ("red, green, blue") system that may fulfill our expectations for an objective procedure to determine colouration patterns. This standardized method would allow for a reliable comparison of colour patterns among franciscana populations. RESUMEN:El patrón de coloración es sugerido como un carácter potencialmente útil para identificar poblaciones de franciscana (Pontoporia blainvillei). Esta información es necesaria para la creación de planes de manejo y conservación de la especie. La existencia de variación geográfica en la coloración de esta especie ha sido hipotetizada; se sugiere que los ejemplares de Brasil y Uruguay son grisáceos y los de Argentina amarronados. Se examinaron ejemplares de Uruguay mediante una técnica objetiva (Villalobos y Villalobos, 1947) para determinar patrones de coloración. También se hizo una revisión de la variación del patrón de coloración de la franciscana a lo largo de su distribución, basada en la literatura publicada. Según la descripción original de la especie en 1844, y varios trabajos ...