Offspring sex ratio in domestic goats: Trivers-Willard out of natural selection

J. Polák, V. Mareš, R. Konrád and D. Frynta
Additional contact information
J. Polák: Department of Zoology, Faculty of Science, Charles University in Prague, Prague, Czech Republic
V. Mareš: Union of Sheep and Goat Breeders, Brno, Czech Republic
R. Konrád: Union of Sheep and Goat Breeders, Brno, Czech Republic
D. Frynta: Department of Zoology, Faculty of Science, Charles University in Prague, Prague, Czech Republic

Czech Journal of Animal Science, 2015, vol. 60, issue 5, 208-215

Abstract: The Trivers-Willard hypothesis (TWH) predicts the ability of mothers to adaptively adjust offspring sex ratio through differential maternal investment based on their relative body condition. In the present study we have analyzed an extensive data set on the secondary sex ratio (SSR) including 59 335 goat kids born in 30 633 litters to 11 644 mothers on farms all over the Czech Republic during the years 1992-2004. We found a male-biased SSR 0.568, which significantly deviates from the predicted balanced Fisherian equilibrium 1 : 1 (P < 0.0001). A generalized estimating equation model controlled for mother's identity revealed a significant effect of maternal age and season of conception (P < 0.001). Conversely, neither paternal age, gestation length, nor litter size were found to explain the sex ratio variation. We also failed to prove any effect of variables associated with maternal condition, particularly her body weight, breed, arbitrary ranking of genetic quality, and hornedness that were available in a data subset. Thus, unlike in some other ungulate species, our findings do not support the TWH in the domestic goat despite the tendency for male-biased litters and we discuss some alternative adaptive and proximate mechanism of the mammalian SSR.

Keywords: maternal age; parental investment; sex allocation; sex ratio manipulation; Trivers-Willard hypothesis; ungulates (search for similar items in EconPapers)
Date: 2015
References: View references in EconPapers View complete reference list from CitEc
Citations:

Downloads: (external link)
http://cjas.agriculturejournals.cz/doi/10.17221/8170-CJAS.html (text/html)
http://cjas.agriculturejournals.cz/doi/10.17221/8170-CJAS.pdf (application/pdf)
free of charge

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:caa:jnlcjs:v:60:y:2015:i:5:id:8170-cjas

DOI: 10.17221/8170-CJAS

Access Statistics for this article

Czech Journal of Animal Science is currently edited by Bc. Michaela Polcarová

More articles in Czech Journal of Animal Science from Czech Academy of Agricultural Sciences
Bibliographic data for series maintained by Ivo Andrle ().