TY - JOUR
T1 - Trophic variation between the two existing Guadalupe fur seal colonies on Guadalupe Island and the san benito Archipelago, Mexico
AU - Amador-Capitanachi, María José
AU - Moreno-Sánchez, Xchel G.
AU - Juárez-Ruiz, Ariadna
AU - Ferretto, Giulia
AU - Elorriaga-Verplancken, Fernando R.
N1 - Funding Information:
Financial support was provided by the projects CONACYT CB-181876 and SIP-20130944-IPN. We thank the Secretaría de Medio Ambiente y Recursos Naturales through the Dirección General de Vida Silvestre en México for granting us research permit SGPA/DGVS/11744/13 as well as the Comisión Nacional de áreas Naturales Protegidas (CONANP)-Reserva de la Biósfera Isla Guadalupe (National Commission for Protected Areas-Guadalupe Island Biosphere Reserve). We also thank the Secretaría de Marina (SEMAR; Mexican Navy), Cooperativa Pesquera "Abuloneros y Langosteros de Isla Guadalupe" (Fishermen Society in Guadalupe Island) and Sociedad Cooperativa de Pescadores Nacionales de Abulón (Cedros Island, Baja California) for their support in the field. We acknowledge the valuable help of M. Sc. Casandra Gálvez in the scat recollection from Guadalupe Island. FREV and XGMS thank the Instituto Politécnico Nacional (IPN; National Polytechnic Institute) for the support received through the Programa de Contratación por Excelencia (Contracting Excellence Program) and fellowship EDI. We also thank Kristin Sullivan for editing the manuscript.
PY - 2017
Y1 - 2017
N2 - Scat analysis and stable isotope analysis (δ13C and δ15N) were used to perform a trophic com-parison between two existing Guadalupe fur seal (Arctocephalus philippii townsendi) colonies on Guadalupe Island (GI) and the San Benito Archipelago (SBA) during the 2013 breeding season. The stable isotope analysis included 67 samples from GI and 36 from the SBA, indicat- ing that this otariid is a teuthophagous specialist. The two colonies showed different trophic levels: (1) 4.5 for GI, for which the most dominant prey was the jumbo squid, and (2) 4.0 for the SBA, for which the main item was the opalescent squid. The stable isotope analysis included 15 fur samples from each site. Both analyses were complemen- tary, identifying prey species from an oceanic habitat, with fur seal δ13C values that are typically associated to that environment. Although assigned a higher trophic level (scat analysis), GI had lower δ15N and δ13C values, suggesting latitudinal segre- gation. These differences between colonies may be related to their distinct age proportions or a strategy to avoid intrapopulation competition. Our contribu- tion regarding trophic variation is based on a snap-( shot regarding scat analysis and a time window of ~16 wks prior to collection reflected by stable isotope analysis in fur. Additionally, this species is currently experiencing population growth, which increases the possibility of overlap for resources between both colonies. Therefore, it is important to establish baselines and continue these comparative analyses over time to determine their significance within its recovery.
AB - Scat analysis and stable isotope analysis (δ13C and δ15N) were used to perform a trophic com-parison between two existing Guadalupe fur seal (Arctocephalus philippii townsendi) colonies on Guadalupe Island (GI) and the San Benito Archipelago (SBA) during the 2013 breeding season. The stable isotope analysis included 67 samples from GI and 36 from the SBA, indicat- ing that this otariid is a teuthophagous specialist. The two colonies showed different trophic levels: (1) 4.5 for GI, for which the most dominant prey was the jumbo squid, and (2) 4.0 for the SBA, for which the main item was the opalescent squid. The stable isotope analysis included 15 fur samples from each site. Both analyses were complemen- tary, identifying prey species from an oceanic habitat, with fur seal δ13C values that are typically associated to that environment. Although assigned a higher trophic level (scat analysis), GI had lower δ15N and δ13C values, suggesting latitudinal segre- gation. These differences between colonies may be related to their distinct age proportions or a strategy to avoid intrapopulation competition. Our contribu- tion regarding trophic variation is based on a snap-( shot regarding scat analysis and a time window of ~16 wks prior to collection reflected by stable isotope analysis in fur. Additionally, this species is currently experiencing population growth, which increases the possibility of overlap for resources between both colonies. Therefore, it is important to establish baselines and continue these comparative analyses over time to determine their significance within its recovery.
KW - Arctocephalus philippii townsendi
KW - Guadalupe Island
KW - Guadalupe fur seal
KW - San Benito Archipelago
KW - Scat analysis
KW - Stable isotopes
KW - Trophic variation
UR - http://www.scopus.com/inward/record.url?scp=85010611996&partnerID=8YFLogxK
U2 - 10.1578/AM.43.1.2017.14
DO - 10.1578/AM.43.1.2017.14
M3 - Artículo
SN - 0167-5427
VL - 43
SP - 14
EP - 25
JO - Aquatic Mammals
JF - Aquatic Mammals
IS - 1
ER -