Various selection pressures induce the degree and direction of sexual size dimorphism in animals. Selection favors either larger males for contests over mates or resources, or smaller males are favored for maneuverability; whereas larger females are favored for higher fecundity, or smaller females for earlier maturation for reproduction. In the genus of Larus (seagulls), adult males are generally known to be larger in size than adult females. However, the ontogeny of sexual size dimorphism is not well understood, compared to that in adults. The present study investigates the ontogeny of sexual size dimorphism in Saunders's gulls (Larus saundersi) in captivity. We artificially incubated fresh eggs collected in Incheon, South Korea, and measured body size, locomotor activity, and foraging skill in post-hatching chicks in captivity. Our results indicated that the sexual differences in size and locomotor activity occurred with the post-hatching development. Also, larger males exhibited greater foraging skills for food acquisition than smaller females at 200 days of age. Future studies should assess how the adaptive significance of the sexual size dimorphism in juveniles is linked with sexual divergence in survival rates, intrasexual contests, or parental effort in sexes.
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1 April 2013
Sexual Differences in Post-Hatching Saunders's Gulls: Size, Locomotor Activity, and Foraging Skill
Jongmin Yoon,
Seung-Hee Lee,
Eun-Jin Joo,
Ki-Jeong Na,
Shi-Ryong Park
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Zoological Science
Vol. 30 • No. 4
April 2013
Vol. 30 • No. 4
April 2013
foraging skill
growth
Larus saundersi
locomotor activity
sexual size dimorphism