a b s t r a c tIn the South American sea lion (Otaria flavescens), daily fluctuations in abundance have been analyzed based on sequential counts of the number of animals hauled-out. However, no studies have analyzed haul-out activity in relation to an annual cycle or according to different age/sex classes. The objective of this study was to determine the daily and seasonal haul-out patterns of each age/sex class of South American sea lions as a function of the time of the day. A total of 222 days were analyzed in a breeding colony of Chile, from May 2008 to December 2010. During the non-breeding season (March to December) males, females, and juveniles showed a unimodal pattern, in which few sea lions are hauled-out in the morning and maximum numbers are found in the rookery during the early afternoon (1330-1630). In contrast, during the breeding season (austral summer) the proportion of individuals hauled-out shifted from a unimodal to a bimodal pattern, especially in the case of juveniles. Our results indicate that there are fine scale differences in haul-out behavior among age/sex classes, as well as larger scale seasonal differences in the proportion of sea lions ashore. These differences appear to be related to reproductive activities, food availability and thermoregulatory requirements. These patterns of seasonal variability of South American sea lion haul-out should be taken into consideration when planning surveys to estimate population abundance.

Coastal storms have increased in recent decades, affecting many species, including the South American sea lion (Otaria byronia). Reports of stranded sea lion pups are becoming common in Chile, presumably due to the increase in the frequency and intensity of coastal storms. to validate this assumption, a 10-year database was built by coupling wave generation and coastal propagation models to correlate pure wave parameters (significant wave height Hs, peak period Tp, normalized wave power Hs 2 Tp) and wave parameters including the tidal level (maximum surface elevation η, modified wave power η 2 Tp) with records of stranded pups in Cobquecura, the largest breeding colony in central chile. the correlation between the number of pups stranded per day and wave parameters in the first half of January and the last half of February is poor, while they are stronger for the second half of January and the first half of February. The higher number of stranded pups coincide with coastal storms with normalized wave power values exceeding a threshold of 100 m 2 /s. Conversely, below this threshold there is wide dispersion between the number of strandings and wave parameters. identifying wave parameter thresholds could be used to predict when newborn pups will be most affected by coastal storms, and thus help institutions to develop remediation techniques for animals at risk. Climate variability and change in the marine environment are emerging issues that have been reported to affect a wide range of species in different ways 1-4. Signs of climate change include changes in air and sea surface temperatures, a rise in the absolute mean sea level, changes in salinity, ocean acidification, and increased frequency and intensity of extreme events, among others 5. All of these signs are causing shifts in the abundance and distribution of several species, loss of habitat and changes in survival rates and breeding success. Some responses have been relatively consistent among species, such as a general advance in the timing of breeding and the migration of several bird species 6,7. However, other responses, like population size and breeding success are less consistent, and vary by species and location 8,9. Most studies on climate change in marine environments have focused on the rise in temperature and changes in the availability of resources 10,11. Other effects, such as the occurrence of coastal storms, have been overlooked, even though extreme events are expected to become more common over time, as they are associated with climate

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Resumen.-Se han descrito tácticas reproductivas para machos y hembras en sistemas reproductivos poligínicos, dentro de las cuales, una respuesta conductual sexo-específico sería esperable para maximizar el éxito reproductivo. El presente estudio da cuenta de un seguimiento conductual del lobo marino común Otaria flavescens durante la época reproductiva (ER) y no reproductiva (ENR) en el Santuario de la Naturaleza Lobería Cobquecura, Chile central. Se registraron patrones conductuales de machos, hembras, juveniles y crías entre mayo de 2008 y diciembre de 2009. Los machos presentaron más registros de conductas asociadas a agresión, desplazamiento y reconocimiento durante ER, mientras que la conducta descanso fue mayor durante ENR. Hembras y juveniles presentaron mayores registros de reconocimiento durante ENR mientras que las otras categorías conductuales no presentaron diferencias entre ER y ENR. Las conductas agresivas por parte de los machos así como las relacionadas al cuidado parental por parte de las hembras podrían ser estrategias conductuales desarrolladas por ambos sexos para asegurar la viabilidad poblacional. Este estudio contribuye al conocimiento de los patrones conductuales reproductivos de la especie y forma parte de uno de los seguimientos conductuales reproductivos más continuos desarrollados en la actualidad en el lobo marino común. Dado que el estudio se realiza en un área protegida dentro del marco legal de Santuario de la Naturaleza, los resultados expuestos serán de utilidad para futuras comparaciones con loberas reproductivas afectadas por actividad antrópica. Palabras clave: Sistema reproductivo poligínico, comportamiento reproductivo, otáridos, Otaria flavescens, ChileAbstract.-In a polygynous mating system males and females have different reproductive strategies; so it is expectable that both sexes have evolved different reproductive behavioral responses to maximize their reproductive success. We analyze the behavior of different sex/age classes of Otaria flavescens during breeding (BS) and non-breeding seasons (NBS) at a Nature Sanctuary breeding colony, central Chilean coast. From May 2008 to December 2009 data of males, females, juveniles and pups were recorded. Males performed more aggression, locomotion and recognizing behaviors during the BS, while they mostly rested during the NBS. Females and juveniles performed more recognizing behavior in the NBS, while the other behavior categories did not show differences between the NBS and the BS. As reproductive behavioral strategies, male aggression and maternal care may increase the overall population viability. This study contributed to a better understanding of the reproductive behavior patterns of this species based on what is to our knowledge the most continuous monitoring of a South American sea lion breeding colony. Since the study has been undertaken in a Nature Sanctuary, the results may be used as a baseline to compare with behavioral data from colonies perturbed by human activities.