Hormonal Correlates of Siblicide in Galápagos Nazca Boobies

Tarlow, Elisa M.; Wikelski, Martin; Anderson, David J.

Hormonal Correlates of Siblicide in Galápagos Nazca Boobies

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Date

2001

Authors

Tarlow, Elisa M.

Wikelski, Martin

Anderson, David J.

DOI (citable link)

10.1006/hbeh.2001.1661

Collections

Biologie

Publication type

Journal article

Publication status

Published

Published in

Hormones and Behavior ; 40 (2001), 1. - pp. 14-20. - ISSN 0018-506X. - eISSN 1095-6867

Abstract

Nazca boobies (Sula granti) show unconditional obligate siblicide immediately after hatching, reducing the typical two-egg clutch size to one. We studied body mass changes and levels of testosterone (T), corticosterone (CORT), and progesterone (P) for A-chicks (dominant, first hatched), B-chicks (subordinate, second hatched), and singletons, during the first 7 days after hatching, when siblicide normally occurs. Mass increase with age was higher for A-chicks than for singletons and B-chicks. This exaggerated the existing developmental advantage of A- over B-chicks that is due to hatching asynchrony. In nests with two chicks, CORT titer was significantly higher in B-chicks than in A-chicks. During ontogenetic development, CORT decreased with age for A-chicks, but did not change for singletons. P showed qualitatively similar ontogenetic changes to CORT, remaining unchanged for A-chicks but increasing for singletons. Thus, both CORT and P levels were lower for A-chicks than for singletons, and both hormones varied inversely with body mass. Overall, T levels did not differ between different categories of chicks. However, one B-chick in the process of reversing the dominance relationship with its older, but weakened, sibling had significantly elevated T. We suggest that CORT and P are regulated to promote exaggerated mass gain in socially challenged A-chicks, facilitating siblicide. Whether T induces aggressiveness during short time intervals of intense sibling rivalry needs further attention.

Subject (DDC)

570 Biosciences, Biology

Keywords

siblicide; challenge hypothesis; Nazca booby; Sula granti; testosterone; corticosterone; progesterone; Galápagos; seabird; hormones

Cite This

ISO 690

TARLOW, Elisa M., Martin WIKELSKI, David J. ANDERSON, 2001. Hormonal Correlates of Siblicide in Galápagos Nazca Boobies. In: Hormones and Behavior. 40(1), pp. 14-20. ISSN 0018-506X. eISSN 1095-6867. Available under: doi: 10.1006/hbeh.2001.1661

BibTex

@article{Tarlow2001-08Hormo-42527,
  year={2001},
  doi={10.1006/hbeh.2001.1661},
  title={Hormonal Correlates of Siblicide in Galápagos Nazca Boobies},
  number={1},
  volume={40},
  issn={0018-506X},
  journal={Hormones and Behavior},
  pages={14--20},
  author={Tarlow, Elisa M. and Wikelski, Martin and Anderson, David J.}
}

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