Hormonal correlates of siblicide in Galápagos Nazca boobies.
Horm Behav
; 40(1): 14-20, 2001 Aug.
Article
em En
| MEDLINE
| ID: mdl-11467880
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.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Progesterona
/
Relações entre Irmãos
/
Testosterona
/
Corticosterona
/
Agressão
/
Comportamento Agonístico
/
Dominação-Subordinação
Limite:
Animals
País/Região como assunto:
America do sul
/
Ecuador
Idioma:
En
Revista:
Horm Behav
Ano de publicação:
2001
Tipo de documento:
Article
País de afiliação:
Estados Unidos
País de publicação:
Estados Unidos