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Foraging ecology of harbour seals (Phoca vitulina) and Northern elephant seals (Mirounga angustirostris) from Baja California, Mexico: inferences from stable isotopes in pups

Published online by Cambridge University Press:  22 December 2015

Fernando R. Elorriaga-Verplancken*
Affiliation:
Departamento de Pesquerías y Biología Marina, Centro Interdisciplinario de Ciencias Marinas-Instituto Politécnico Nacional (CICIMAR-IPN), Ave. IPN s/n, Colonia Playa Palo de Santa Rita, C.P. 23096 La Paz, Baja California Sur, México
Laura Morales-Luna
Affiliation:
Departamento Académico de Biología Marina, Universidad Autónoma de Baja California Sur (UABCS), Carretera al sur, km 5.5, Apartado Postal 19-B, C.P. 23080 La Paz, Baja California Sur, México
Gisela Heckel
Affiliation:
Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Carretera Ensenada-Tijuana No. 3918, Pedregal Playitas, C.P. 22860 Ensenada, Baja California, México
Yolanda Schramm
Affiliation:
Facultad de Ciencias Marinas, Universidad Autónoma de Baja California (UABC), Km 103 Carretera Tijuana-Ensenada s/n, 22830 Ensenada, Baja California, México
*
Correspondence should be addressed to:F.R. Elorriaga-Verplancken, Departamento de Pesquerías y Biología Marina, Centro Interdisciplinario de Ciencias Marinas-Instituto Politécnico Nacional (CICIMAR-IPN), Ave. IPN s/n, Colonia Playa Palo de Santa Rita, C.P. 23096 La Paz, Baja California Sur, México email: felorriaga@ipn.mx

Abstract

Harbour seals (Phoca vitulina) and northern elephant seals (Mirounga angustirostris) are the only phocid species found in Mexico. There is evidence that harbour seals at other latitudes exhibit non-migratory behaviour; however, there is lack of knowledge regarding this species' movements in Mexico. In contrast, elephant seal migrations to high latitudes are documented. In order to analyse this behaviour in harbour seals, hair samples (N = 19) were collected from weaned, or nearly weaned, pups on Natividad Island, Baja California (BC), during the 2013 breeding season (February). Lanugo samples (N = 20) were also collected from elephant seal pups on the San Benito Archipelago (60 km north of Natividad) during the same season, providing information on maternal foraging during the last 4–5 months before sampling. Of the two species, BC harbour seals had higher isotope values, reflecting their non-migratory behaviour. These differences may be due to the depleted base values in the higher latitude foraging areas used by northern elephant seals relative to the areas around Natividad frequented by harbour seals. A lower trophic position by elephant seals was considered but taken as an unlikely explanation for this variation. Bayesian analysis confirmed the distinction, with a low overlap value (0.4) and different isotopic spaces (Phoca: 0.5, Mirounga: 1.6). Building upon previous studies of the trophic ecology of the two phocids that inhabit the region, we provide new information by comparing the two species during the same season using the same tissue type sampled from individuals of similar age classes.

Information

Type
Research Article
Copyright
Copyright © Marine Biological Association of the United Kingdom 2015 

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