Humberto L. Cappozzo

Natural and anthropogenic factors associated with the distribution of South American sea lion along the Atlantic coast

The aim of this work was to analyse those characteristics of the Atlantic coast that are associated with distribution, abundance and breeding activity of Otaria flavescens at three ecological scales. We followed a research strategy that consists in looking at the variables that are associated with the pattern of distribution at regional and landscape scales, instead of following local population in time. We used bibliographic data of censuses carried out between 1946 and 1997 and a Geographic Information System (GIS) to integrate information proceeding from censuses and different environmental variables. At a regional scale, we found that the distribution of breeding colonies did not vary in the period of time analysed and was associated with the pattern of occupation of the coast and the tide width. There was a significant decrease in abundance between 1946 and 1997. In ‘north-central Patagonia’, the segment of coast with the highest number of sea lions in Argentina, distribution of colonies was associated with islands availability and negatively correlated with places were anthropogenic disturbance was high. At a local scale, breeding colonies were positive associated with slight slope coasts and negatively associated to rocky beaches. We identify those characteristics of the coast associated with distribution of breeding colonies of O. flavescens, which operate at different ecological and temporal scales.

Sexual harassment and female gregariousness in the South American sea lion, Otaria flavescens

Most colonial pinnipeds form extreme clusters of breeding females that cannot be entirely explained by the distribution of sites for reproduction. Avoidance of male harassment has been postulated as an important determinant of reproductive aggregation in this group of mammals. Female gregariousness can reduce harassment by resident males by two mechanisms; directly by the ‘dilution effect’ or indirectly because resident males that defend large female groups are less harassing. In order to investigate the relationship between male harassment and female gregariousness in relation to the size of breeding groups, we analysed the behaviour of dominant males and their females in a breeding colony of Otaria flavescens. Females in large breeding groups received less harassment by resident males due to dilution effects and because males that defended a large group interacted less frequently with females than males with small groups.

Ontogenetic development and sexual dimorphism of franciscana dolphin skull: A 3D geometric morphometric approach

The aim of this work was to study the postnatal ontogenetic development of Pontoporia blainvillei skull, identifying major changes on shape, and relating them to relevant factors in the life history of the species. We analyzed a complete ontogenetic series (73♂, 83♀) with three‐dimensional geometric morphometric techniques. Immature dolphins showed a very well‐developed braincase and a poorly developed rostrum, and the principal postnatal changes affected the rostrum and the temporal fossa, both structures implied functionally to the feeding apparatus, thus suggesting a specialized mode for catch fast prey in P. blainvillei. Osseous elements associated with sound production were already well developed on immature dolphins, suggesting the importance of this apparatus since the beginning of postnatal life. Sexual dimorphism was detected on both shape and size variables. Females were bigger than males, in accordance with previous studies. Shape differences between sexes were found on the posterior part of premaxillaries and external bony nares (P < 0.01), suggesting that this sexual dimorphism is related to differences on vocalization capabilities. J. Morphol. 275:1366–1375, 2014.

Age and growth of franciscana dolphins, Pontoporia blainvillei (Cetacea: Pontoporiidae) incidentally caught off southern Brazil and northern Argentina

Age and length data of 291 franciscana dolphins (Pontoporia blainvillei) incidentally captured on the coast of Rio Grande do Sul State (RS), southern Brazil, were used to fit growth curves using Gompertz and Von Bertalanffy growth models. A small sample of franciscanas (N ¼ 35) from Buenos Aires Province (BA), Argentina, were used to see if there are apparent growth differences between the populations. Male and female franciscana samples from both areas were primarily (78–85%) ,4 years of age. The Von Bertalanffy growth model with a data set that excluded animals ,1 year of age provided the best fit to data. Based on this model, dolphins from the RS population reached asymptotic length at 136.0 cm and 158.4 cm, for males and females, respectively. No remarkable differences were observed in the growth trajectories of males and females between the RS and BA populations.

The role of Pleistocene glaciations in shaping the genetic structure of South American fur seals (Arctocephalus australis)

Abstract Analysing a 529 bp segment of the mitochondrial control region, we evaluated the role that Pleistocene glaciations may have had in shaping the genetic structure currently found in the two southernmost breeding areas of the South American fur seal, Arctocephalus australis. Additionally, we analysed if these two breeding areas correspond to different conservation units. We found 26 haplotypes in 54 individuals. Colonies from the Uruguayan breeding area did not show significant differences in haplotype frequencies, which suggest that they are remnants of a single ancient gene pool. The genealogical relationship between haplotypes revealed a pattern of phylogeographic structure with two main haplogroups corresponding to the different breeding areas. The analysis of molecular variance and the estimate of population divergence time also indicated significant genetic differences and a long period of isolation between Atlantic and Pacific colonies, suggesting that these breeding areas would correspond to different conservation units.

Population Genetics of Franciscana Dolphins (Pontoporia blainvillei): Introducing a New Population from the Southern Edge of Their Distribution

Due to anthropogenic factors, the franciscana dolphin, Pontoporia blainvillei, is the most threatened small cetacean on the Atlantic coast of South America. Four Franciscana Management Areas have been proposed: Espiritu Santo to Rio de Janeiro (FMA I), São Paulo to Santa Catarina (FMA II), Rio Grande do Sul to Uruguay (FMA III), and Argentina (FMA IV). Further genetic studies distinguished additional populations within these FMAs. We analyzed the population structure, phylogeography, and demographic history in the southernmost portion of the species range. From the analysis of mitochondrial DNA control region sequences, 5 novel haplotypes were found, totalizing 60 haplotypes for the entire distribution range. The haplotype network did not show an apparent phylogeographical signal for the southern FMAs. Two populations were identified: Monte Hermoso (MH) and Necochea (NC)+Claromecó (CL)+Río Negro (RN). The low levels of genetic variability, the relative constant size over time, and the low levels of gene flow may indicate that MH has been colonized by a few maternal lineages and became isolated from geographically close populations. The apparent increase in NC+CL+RN size would be consistent with the higher genetic variability found, since genetic diversity is generally higher in older and expanding populations. Additionally, RN may have experienced a recent split from CL and NC; current high levels of gene flow may be occurring between the latter ones. FMA IV would comprise four franciscana dolphin populations: Samborombón West+Samborombón South, Cabo San Antonio+Buenos Aires East, NC+CL+Buenos Aires Southwest+RN and MH. Results achieved in this study need to be taken into account in order to ensure the long-term survival of the species.

Biological parameters of franciscana dolphins, Pontoporia blainvillei , by-caught in artisanal fisheries off southern Buenos Aires, Argentina

Fil: Negri, Maria Fernanda. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Austral de Investigaciones Cientificas; Argentina

Genetic diversity and population structure of the franciscana dolphin, Pontoporia blainvillei, in Southern Buenos Aires, Argentina

ABSTRACT The franciscana dolphin, Pontoporia blainvillei, is endemic to the coastal waters of the southwestern Atlantic Ocean and the most endangered dolphin in the area. Four Franciscana Management Areas (FMAs) are currently recognised; however, results of genetic studies suggest the requirement for additional FMAs and highlight the need for more detailed studies in the southern extreme of the species distribution. With this aim, we studied the genetic diversity and population structure of the species analysing an mtDNA control region fragment (434 bp) in 44 individuals collected in four sampling sites located in Southern Buenos Aires. Haplotype diversity (H = 0.75 ± 0.05) was mostly higher than the observed in endangered or near threatened odontocetes. Population structure analyses suggest that three different genetic populations should be recognised within FMA IV: Northern, Eastern and Southern Buenos Aires. Altogether, these results should be taken into account in future conservation plans for the species.

Cranial development and directional asymmetry in Commerson’s dolphin, Cephalorhynchus commersonii commersonii : 3D geometric morphometric approach

Commersons dolphin, Cephalorhynchus commersonii, is one of the smallest species of odontocete cetaceans. We aimed to study the postnatal cranial ontogeny of C. commersonii through geometric morphometric technique, analyzing the postnatal ontogeny of the symmetric and asymmetric components of shape and providing information about sexual dimorphism affecting cranial shape and size. We digitized 57 landmarks in a sample of 139 crania of an ontogenetic series. Our results indicate that C. commersonii presents sexual size dimorphism of cranium in adults, but not shape dimorphism. Major changes between juveniles and adults were associated with lengthening of the rostrum and accentuation of telescoping, as observed in other odontocetes. We found that the degree of asymmetry has a very subtle but still significant change during ontogeny, which may have functional implications. We also observed little general variation in skull shape during postnatal development, supporting the idea of the conservatism of young-like characters in adults of C. commersonii. In accordance with this, we detect a very early attainment of stability of shape and size, being statistically similar in males and females. Differences in overall cranial shape and growth patterns in C. commersonii and Pontoporia blainvillei can be functionally associated to specific modes of feeding, suggesting also differences in the melon morphology.

Morphological Analysis of the Flippers in the Franciscana Dolphin, Pontoporia blainvillei, Applying X-Ray Technique

Pectoral flippers of cetaceans function to provide stability and maneuverability during locomotion. Directional asymmetry (DA) is a common feature among odontocete cetaceans, as well as sexual dimorphism (SD). For the first time DA, allometry, physical maturity, and SD of the flipper skeleton—by X‐ray technique—of Pontoporia blainvillei were analyzed. The number of carpals, metacarpals, phalanges, and morphometric characters from the humerus, radius, ulna, and digit two were studied in franciscana dolphins from Buenos Aires, Argentina. The number of visible epiphyses and their degree of fusion at the proximal and distal ends of the humerus, radius, and ulna were also analyzed. The flipper skeleton was symmetrical, showing a negative allometric trend, with similar growth patterns in both sexes with the exception of the width of the radius (P ≤ 0.01). SD was found on the number of phalanges of digit two (P ≤ 0.01), ulna and digit two lengths. Females showed a higher relative ulna length and shorter relative digit two length, and the opposite occurred in males (P ≤ 0.01). Epiphyseal fusion pattern proved to be a tool to determine dolphins age; franciscana dolphins with a mature flipper were, at least, four years old. This study indicates that the flippers of franciscana dolphins are symmetrical; both sexes show a negative allometric trend; SD is observed in radius, ulna, and digit two; and flipper skeleton allows determine the age class of the dolphins. Anat Rec, 297:1181–1188, 2014.