Field-based age estimation of juvenile Galapagos sea lions (Zalophus wollebaeki) using morphometric measurements

Jeglinski, J. W.E. , Mueller, B., Pörschmann, U. and Trillmich, F. (2010) Field-based age estimation of juvenile Galapagos sea lions (Zalophus wollebaeki) using morphometric measurements. Aquatic Mammals, 36(3), pp. 262-269. (doi: 10.1578/AM.36.3.2010.262)

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Abstract

Information about the age of juvenile pinnipeds is necessary for an understanding of ontogeny-specific patterns and strategies. Exact age determination of juvenile cohorts from wild populations is best achieved through birth observations and sub-sequent marking, but this involves a considerable time lag during which juveniles mature. A combination of body and teeth measurements of known-age Galapagos sea lion juveniles taken during brief routine captures in the field was used to create age prediction models. Several general linear models (GLMs) produced reliable age estimates for male and female juveniles up to an age of 2 y. Teeth measurements were important predictors of age: male age was best estimated using upper canine length (CL), mass, and girth, while the best predictors for female age were CL, canine width (CW), body length (SL), body mass, and an interaction between CL and CW. The presented method of aging wild unmarked juveniles in the field is applicable during routine captures, requires little equipment, and yields a considerable increase of information for studies involving brief sampling periods in the field. We suggest its adjustment, testing, and application in studies of juveniles of other species.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Jeglinski, Dr Jana
Authors: Jeglinski, J. W.E., Mueller, B., Pörschmann, U., and Trillmich, F.
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:Aquatic Mammals
Publisher:Western Illinois University Regional Center
ISSN:01675427
ISSN (Online):1996-7292

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