Marine & Environmental Sciences Faculty Articles

Document Type


Publication Title

Plos One



Publication Date





Determining trophic habits of predator communities is essential to measure interspecific interactions and response to environmental fluctuations. South American fur seals, Arctocephalus australis (SAFS) and sea lions Otaria byronia (SASL), coexist along the coasts of Peru. Recently, ocean warming events (2014–2017) that can decrease and impoverish prey biomass have occurred in the Peruvian Humboldt Current System. In this context, our aim was to assess the effect of warming events on long-term inter- and intra-specific niche segregation. We collected whisker from SAFS (55 females and 21 males) and SASL (14 females and 22 males) in Punta San Juan, Peru. We used δ13C and δ15N values serially archived in otariid whiskers to construct a monthly time series for 2005–2019. From the same period we used sea level anomaly records to determine shifts in the predominant oceanographic conditions using a change point analysis. Ellipse areas (SIBER) estimated niche width of species-sex groups and their overlap. We detected a shift in the environmental conditions marking two distinct periods (P1: January 2005—October 2013; P2: November 2013—December 2019). Reduction in δ15N in all groups during P2 suggests impoverished baseline values with bottom-up effects, a shift towards consuming lower trophic level prey, or both. Reduced overlap between all groups in P2 lends support of a more redundant assemblage during the colder P1 to a more trophically segregated assemblage during warmer P2. SASL females show the largest variation in response to the warming scenario (P2), reducing both ellipse area and δ15N mean values. Plasticity to adapt to changing environments and feeding on a more available food source without fishing pressure can be more advantageous for female SASL, albeit temporary trophic bottom-up effects. This helps explain larger population size of SASL in Peru, in contrast to the smaller and declining SAFS population.







First Page



This study is part of the doctoral dissertation of the first author, developed in partnership between the Escuela Doctoral Franco Peruana en Ciencias de la Vida, Universidad Peruana Cayetano Heredia and École Doctorale GAIA Biodiversité, Agriculture, Envrionnement, Terre, Eau, Université de Montpellier, France. Sample collection at Punta San Juan was possible thanks to the collaborative partnerships between Universidad Peruana Cayetano Heredia, SERNANP–MINAM, and AgroRural—MINAGRI. We thank SERNANP for access to Punta San Juan reserve and AgroRural for use of the facilities at PSJ. We thank Dirección de Hidrografía y Navegación (DHN) for providing the SST time series from San Juan de Marcona. Most importantly, we thank all the volunteers, interns, and personnel of the Punta San Juan Program and Nova Southeastern University who have helped with the fieldwork and sample preparation of pinniped whiskers for this study. Finally, we thank France C. from the Smithsonian Institution’s Museum Support Center for prioritizing stable isotope analyses during Covid-19 restricted operations

Additional Comments

S1 Fig. Standard ellipse area estimated for each group. Labels represent Community (Period 1 and 2) and Group (1 = SAFS females, 2 = SAFS males, 3 = SASL females, 4 = SASL males). The black points correspond to the mean standard ellipse area for each group, red cross is the standard ellipse area corrected for small sample size. Grey and white boxed areas reflect the 95, 75 and 50% confidence intervals. S2 Fig. Total area of convex hull estimated for each community or period. Community 1 = Period 1, Community 2 = Period 2. The black points correspond to the mean standard ellipse area for each group while the grey and white boxed areas reflect the 95, 75 and 50% confidence intervals. S1 Table. Change point analysis statistics. Location of point change detection in the time series, mean value for each period, test statistic and MBIC penalty value for each environmental condition.

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Peer Reviewed