Occupancy dynamics of South American Sea-Lions in Brazilian Haul-outs

Abstract

Along the Brazilian coast only two haul-outs of South American sea lions (Otaria flavescens) are known: Ilha dos Lobos and Molhe Leste, both located in the southernmost state of Brazil, Rio Grande do Sul. Most sea lions observed in these haul-outs are adult and sub-adult males. It is supposed that the species' presence in these areas is due to food supply and absence of parental assistance by males. This study analysed the use of these haul-outs by O. flavescens between 1993 and 2002 based on counting data of observed individuals. Bayesian generalised linear mixed models were used to evaluate differences in abundance between areas, long term trends and seasonal patterns. Results showed that for O. flavescens abundance had a long term trend of increased average occupancy over the study period, with seasonal variation reaching the highest within-year value in August (Ilha dos Lobos) and October (Molhe Leste). The novel application of this powerful statistical modelling approach resulted in a useful tool to quantify occupancy dynamic.

Otaria flavescens and Arctocephalus australis abundance in poorly known sites: a spatial expansion of colonies?

“…This is because the new haul-outs found in the present study are close to fishing ports. A similar situation has been recorded in Chile where a distribution change has been reported in relation to salmon farms in the South (OLIVA et al, 2006;SEPÚLVEDA et al, 2011) and in southern Brazil (Molhe Leste and Ilha dos Lobos haul-outs) fish abundance, mainly demersal teleosts on the continental shelf, may explain the linear, long-term increase in sea lion abundance (PAVANATO et al, 2013).…”

“…Due to its structure and proportional abundances, Las Pipas is classified as a nonbreeding colony, it would mainly be used as a resting site within the feeding area. The months of maximum abundance coincide with other haul outs (e.g in southern Brazil, PAVANATO et al, 2013, Puerto Quequén, Argentina, GIARDINO et al, 2009). This new site may be explained by the response of some individuals to a higher availability of food.…”

“…Additionally, the Cabo Polonio breeding rookeries located to the east of Isla de Lobos are also increasing (DIRECCIÓN NACIONAL DE RECURSOS ACUÁTICOS, 2012). Another evidence that supports this theory is the significant population increase of O. flavescens that took place at the Brazilian haulouts at Molhe Lleste and Ilha dos Lobos, Rio Grande do Sul, Brasil from 1993(PAVANATO et al, 2013. The monthly occupancy of these two haul-outs shows that sea lions arrive from Uruguayan breeding areas and return there for the subsequent reproductive season.…”

Otaria byronia: Cárdenas-Alayza, S., Crespo, E. & Oliveira, L.

“…The Chilean population is estimated to be approximately 197,000 animals (Venegas et al 2001, Bartheld et al 2008, Contreras et al 2014. There are at least 105,000 individuals in Peru (IMARPE 2013), and no more than 200 on the Brazilian coast (Sanfelice et al 1999, Pavanato et al 2013. Therefore, the total global population is approximated to be at least 445,000 individuals.…”

Patrones locales de alimentación del león marino sudamericano <i>Otaria byronia</i>: el caso de Punta Patache, Norte de Chile

“…Sobre esta base se concluye que frente a la falta de anchoveta durante el desarrollo de eventos ENOS, el LMS ajustaría su dieta a otros recursos, situación que determina un 'estrés nutricional' derivado de una nutrición inadecuada, cuyas consecuencias son reducción del crecimiento, bajas en la tasa de natalidad, enfermedades, desnutrición y en muchos casos muerte, tal como se ha reportado para los ENOS fuertes 1982/83 y 1997/98. Palabras clave: Análisis fecal, patrón de alimentación, Otaria byronia, norte de Chile Argentina y hasta el sur de Brasil (29º20'S) (Sanfelice et al 1999, Pavanato et al 2013) y en forma aislada tan al norte como Río de Janeiro (Vaz-Ferreira 1982, Pinedo 1990, Rosas et al 1993. También es posible registrar esta especie en las Islas Falkland (Crespo et al 2012, Baylis et al 2015.…”