Distribución espacial y estructura de unidades reproductivas de Lobo Marino Sudamericano, Otaria byronia( de Blainville, 1820) durante la temporada reproductiva en la lobería de Punta Chaiguaco, Isla de Chiloé
Fecha
2017
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Profesor Guía
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Universidad de Valparaíso
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Facultad
Facultad de Ciencias
Departamento o Escuela
Programa de Licenciatura en Ciencias Mención Biología.
Determinador
Recolector
Especie
Nota general
Licenciado en Ciencias mención Biología. Universidad de Valparaíso. 2017.
Resumen
The southern sea lion (SSL) Otaria byronia has a wide distribution in South America with an estimated abundance of 500,000 animals. In the Pacific coast, the rookery of Punta Chaiguaco, located in the south west coast of Chiloé Island, is one of the main breeding colonies in austral Chile as well as Isla Doña Sebastiana, Isla Metalqui, Isla Guafo and Isla Guamblin. The aim of this study was to analyze the population structure of Punta Chaiguaco colony during the reproductive season, to assess the distribution and structure of polygynous reproductive units (PRU). We hypothesized that larger males will use the most suitable area in the rookery with a higher number of estrous females and newborn pups. Aerial surveys were conducted in April 2012, February 2013 and February 2016; and three independent observers counted the animals from digital photographs defining 28, 31 and 28 PRU, respectively. PRU occurred in four main habitats and different measurements (Image J) and population counts were made in each unit.
A Principal Component Analysis (PCA) was performed considering ten variables, the first five components explained 92.1% of cumulative variance. The first component explained the 35.6% of the variance and accounts for male and female standard length, sea surface temperature, and the total number of animals in the colony. The variables which are inversely related were terrain categories (habitat), level of PRU and tide level. The population structure of PRU differ significantly per habitats in 2012 and 2016 (Goodness of fit test), and a t-test suggested that the size of males and females varied across habitats in the same years. Our study shows that the distribution in the rookery, the structure of the PRU and the size of the breeding animals vary according to environmental conditions, such as tide level and habitat suitability. Differences in male length among seasons could be explained by daily and annual circarhythms and related too with overfly during April, completely delayed from reproductive season. Additionally we suggest that reproductive units with large males include a high number of robust females and newborn pups.
Finally, from 2013 data of totals of animals by functional age category, we determine that the population structure of the study area is representative of the main reproductive colonies of Southern Chile (Test of Independence using G-Test). Reaching the conclusion, from data of population structure, that Isla Metalqui, Isla Guamblin and Punta Chaiguaco are the main areas in austral Chile where the conservation of the specie should be focused.
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Lugar de Publicación
Valparaíso
Auspiciador
Palabras clave
Lobos Marinos, Distribucion del habitat, Reproducción, Chile