Haul out patterns in harbor rookeries of Southern sea lion males

GIARDINO, GISELA; MANDIOLA, M. AGUSTINA; BASTIDA, RICARDO; RODRÍGUEZ DIEGO

Tampa, FL,

Congreso; 19th Biennial Conference on the Biology of Marine Mammals; 2011

The Society for Marine Mammalogy

Permanent non-breeding Southern sea lion (Otaria flavescens) male rookeries are found in Mar del Plata (38º 02’ S, 57º 31’ W) and Quequén (38º 35’ S, 58º 42’ W) harbors in northern Argentina. These rookeries are located in an intermediate area between two main breeding sites (Uruguay and Patagonia) with a gap of 1,000 kilometers, and a significant number of adult and subadult males move to these colonies during summer and return in early autumn. In order to characterize the duration of the alternate periods of foraging and land resting, the haul out pattern of 180 individually identified (pelage bleached) sea lions was followed during 4 seasons (2003-04, 2008-09, 2009-10 and 2010-11). A total of 1732 feeding trips and 2001 land resting periods were recorded, with a mean of 10 ± 5.63 (2- 31) trips and 12 ± 5.36 (4-32) land periods per animal. Feeding trips lasted 3.2 ± 1.7 (1-15) days with no differences with the age (ANOVA F=0.63; df=178 p=0.6). Land periods lasted 2.9 ± 2.6 (1- 35) days, with significant differences with age (Kruskal-Wallis H (3;N= 185) = 22.21811; p =0.0001) as juveniles remained on land for longer periods than adults. No significant differences were found comparing the mean duration of both feeding trips (t=0.68; df=106;p=0.497) nor land periods (Mann Whitney U=638.0; p= 0.306) between males that migrate during the breeding season and those that remain in non-breeding harbor colonies. These results suggest that haul out pattern is conservative and probably related with the energetic balance between foraging and resting in SSL, regardless their reproductive condition