Domestication effects on crowing in chickens: variation between wild and captive red junglefowl and domestic white Leghorn and the genetic architecture of crowing vocalizations

Abstract

The crowing of the male chicken is a charismatic example of vocal display in a bird. It is regarded as the main territorial announcement of the ancestral red junglefowl. The call has been preserved throughout domestication, although several of its elements have been altered. To assess these alterations, we assayed crowing spectrograms from wild and captive-held red junglefowl populations from India, along with two red junglefowl populations held in long-term captivity in Sweden, and a domestic white Leghorn breed. We find consistent differences between the different Indian red junglefowl and the domestic white Leghorn for a range of characteristics, including the duration of the last syllable and the number of formants and their frequency in the last and second-to-last syllable. To analyse the genetic architecture of crowing vocalization, we performed a quantitative trait loci (QTL) experiment using a wild × domestic advanced intercross to identify QTL that explained a large percentage of the variation present for the duration of the last syllable and the number of formants in the second to last syllable. With this study we thus demonstrate consistent differences in red junglefowl and white Leghorn chickens and identify a relatively simple genetic architecture for some of these traits.This article is part of the theme issue 'Unravelling domestication: multi-disciplinary perspectives on human and non-human relationships in the past, present and future'.

Keywords: crowing; domestication; quantitative trait locus.

Figure 1.

Breakdown of crowing vocalization measurements. This sample figure illustrates the phenotypes measured from each vocalization. Orange lines are used to mark the number of syllables present in each (in this illustration, four syllables are present). The duration of the last syllable is marked in pink and measured in seconds. The number of formants of the last syllable is indicated with a blue arrow, with this arrow indicating one of the formants. The same measurement is also applied to the second-to-last syllable. The most distinct formant of the last and second-to-last syllables is calculated in Hertz and is calculated using the darkest (most prominent) average trace in the particular syllable (in this case, 1200 Hz).

Figure 2.

(A) Epistatic interaction for last syllable duration QTL 1@791 and 7@173. AA, RJF genotype; AB, heterozygote genotype; BB, WL genotype. (B) Epistatic interaction for last syllable duration number of formants in second-to-last syllable QTL 3@668 and 11@104.