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MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps14203

Strategies for segregation during foraging in sympatric otariids of the Peruvian upwelling Humboldt Current System

Susana Cárdenas-Alayza, Michael J. Adkesson, Dimitri Gutiérrez, Hervé Demarcq, Yann Tremblay

*Corresponding author:

ABSTRACT: The competitive exclusion principle predicts that species exhibit segregation mechanisms to coexist. In the Humboldt Current System, South American sea lions (Otaria byronia; SASL) coexist with South American fur seals (Arctocephalus australis; SAFS); however, the existence of temporal and spatial partitioning in foraging strategies remains unknown. To compare foraging strategies, we analyzed locations of 35 adults (18 SASL, 17 SAFS; 4 and 8 females, 9 and 14 males) equipped with satellite tags in Punta San Juan, Peru (2013-2017). We evaluated: 1) distance and duration of foraging trips; 2) utilization distributions (UD); 3) foraging by hour and 4) association of foraging with environmental variables. Regular interval tracks (e/30min) were modeled and residence time was estimated to determine foraging events. Proportion overlap and analysis of similarity compared groups in core areas (50% UD) and home ranges (95% UD). Generalized Additive Mixed Models (GAMM) were built to determine if hour of day and environmental conditions had an effect on foraging. Multiple mechanisms for foraging segregation that explain coexistence were found. Duration and distance between species-sex groups are significantly different, except for trip duration between SASL sexes. SAFS travelled longer distances and duration than SASL; while males travelled longer distances and duration than females. Female UD overlap, while males do not. Core areas between sexes overlap in SAFS and SASL, but home ranges are significantly different. Hour of day had a significant effect on foraging events in SAFS females and SASL males. Environmental conditions during foraging by SASL females reflect coastal habitat and SAFS females the offshore habitat. However, interspecific segregation is not evident between males.