Daily and annual circarhythms activity in the South American sea lion Otaria flavescens (Carnivora: Otariidae) at the central zone of Chile

Abstract

Daily and annual circarhythms activity in the SouthResumen.-En otáridos se han estudiado la presencia de circaritmos de actividad sobre la base de cambios en las densidades poblacionales en las loberas. En este trabajo, se estudiaron los ritmos circadiano (24 h) y circanual (1 año) del lobo marino común Otaria flavescens en las loberas de Cochoa y Punta Curaumilla en Chile Central. El ritmo circadiano fue estudiado en ambas loberas. En cada una de ellas se realizaron censos cada 45 min durante 3 días de observación continuos (72 h). Los resultados demuestran que se produce un aumento del número de animales en tierra en horarios diurnos y una disminución en los nocturnos. Dichas fluctuaciones están asociadas a un ciclo de 24 h, y demuestran la existencia de un ritmo circadiano en estas loberas. El ritmo circanual fue estudiado en la lobera de Cochoa. Para ello se realizaron 145 observaciones durante 3 años consecutivos (1995)(1996)(1997)(1998). Los resultados muestran un aumento de la población en los meses de otoño a primavera, y una disminución brusca en el verano. Estas fluctuaciones se asocian a un ciclo de un año, y demuestran la existencia de un ritmo circanual en esta especie. Palabras clave: Lobo marino común, Otaria flavescens, Otaria byronia, ritmo circadiano, ritmo circanual.

Distribution and abundance of the South American sea lion Otaria flavescens (Carnivora: Otariidae) along the central coast off Chile

“…Within-day corrections in non-breeding colonies were made using the circadian rhythms reported by Sepúlveda et al (2001). Considering that the number of sea lions on shore is maximal at midday hours (between 1200 and 1600 h), censuses made earlier or later than this period were corrected using the adjustment curve described by these authors.…”

“…However, because juveniles do not participate in reproduction, their abundance usually shows a variation during the day. Thus, juveniles from breeding colonies were corrected in the same way as in non-breeding colonies using the adjustment curve reported by Sepúlveda et al (2001).…”

Comparison of behavioral patterns of South American sea lions between breeding and non-breeding seasons

“…Males, including satellite males, try to obtain mates by retaining females arriving to the colony from the sea, and initiating group raids into the breeding area to seize females (Campagna et al 1988). Aggressive behavior begins to decline at the end of the BS mainly due at the end of the breeding season, reproductive activity ceases (Sepúlveda et al 2001, Acevedo et al 2003. These may explain the increment of resting behavior performed by males in this study during the NBS.…”

“…Females copulate and give birth within the territories established by the males (Campagna & LeBoeuf 1988a, Sielfeld 1999, Acevedo et al 2003. At the end of the breeding season, reproductive activity ceases and the abundance of males gradually decrease (Sepúlveda et al 2001, Acevedo et al 2003. Since pups are not able to swim long distances, females remain with their pups in the colony until May, and leave the breeding colony once pups are more proficient swimmers (Sepúlveda et al 2009).…”

Annual, seasonal and daily variation in the abundance of the South American sea lion Otaria flavescens in two breeding colonies in northern Chile

“…During this period, the abundance of sea lions in the rookeries arises due to the presence of newborn pups, and adult males and females also that remain on land defending their territories, and caring for and suckling their pups, respectively (Sepúlveda et al 2012). At the end of this period, most males disperse out to feed and rest (Sepúlveda et al 2001, Acevedo et al 2003, Muñoz et al 2011. Females on the other hand remain with their pups in the colony, alternating their time between pup attendances on land and foraging trips to the ocean (Campagna & LeBoeuf 1988, Muñoz et al 2011.…”