Affiliation:
1. División Mastozoología, Museo Argentino de Ciencias Naturales, “Bernardino Rivadavia” CONICET, Avenida Ángel Gallardo 470, C1405DJR Ciudad Autónoma de Buenos Aires, Argentina.
2. Departamento de Ciencias Básicas, Universidad Nacional de Luján, Buenos Aires, Argentina.
Abstract
The southern elephant seal (Mirounga leonina (L., 1758)) is one of the most dimorphic mammals, but sexual dimorphism in its skull ontogeny is poorly known. We study ontogeny of sexual dimorphism by the allometric relationships between 21 measurements and its geometric mean. Based on 66 specimens (36 females, 30 males), the bivariate and multivariate analyses indicated that both approaches were congruent in most variables. We detected that sexual dimorphism was reached mostly by sexual shape differences in the ontogenetic trajectories of males and females. Twenty-four percent of variables were associated with intercept differences (pup size proportions), while 57% of variables were associated with slope intersexual differences (relative growth rates). Contrarily, sexual dimorphism was also achieved by size differences in adult stages (19% of variables), as males exhibited an extension of their common ontogenetic trajectories. Secondary growth spurt in males was detected for few variables. Our comparison with analogous data collected from southern sea lions (Otaria byronia (de Blainville, 1820)) indicated that in both species, sexual dimorphism was mostly associated with an enhanced ability to defend territories, which was linked to the polygynic behavior. However, discrepancies between both ontogenetic patterns of dimorphism were associated with interspecific differences in their life cycles.
Publisher
Canadian Science Publishing
Subject
Animal Science and Zoology,Ecology, Evolution, Behavior and Systematics
Cited by
29 articles.
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