Selection for Reduced Fear of Humans Changes Intra-Specific Social Behavior in Red Junglefowl—Implications for Chicken Domestication

Abstract

The domestic fowl has a different social behavior compared to their ancestor, the red junglefowl. To examine whether selection for tameness has affected their intra-specific social behavior, 32 red junglefowl from two selection lines, one selected for increased tameness and one selected for a high fear of humans for ten generations, were kept in a group of two females and two males each and were observed in a semi-natural undisturbed enclosure. Birds selected for a low fear of humans had more social conflict, and the males from this selection crowed more and were more often observed in low social proximity to others. The high-fear birds spent more time close together with the rest of the group and performed more social, non-aggressive pecking. These results are consistent with known differences between ancestral red junglefowl and domesticated laying hens. Our results show that intra-specific social behavior has been affected as a side-effect of selection for increased tameness. This may have interesting implications for the emergence of the domestication syndrome in chickens.

Selection for Reduced Fear of Humans Changes Brain and Cerebellum Size in Red Junglefowl in Line with Effects of Chicken Domestication

“…Farm foxes selected for low fear of humans as a model for early domestication developed a suite of phenotypic traits associated with the domestication syndrome in a few generations [26], which suggests that this syndrome may be driven by reduced fear. Similar effects have previously been reported by us for Red Junglefowl selected for increased tameness, where these birds developed a range of phenotypic changes commonly associated with domesticated chickens, such as increased growth, larger eggs, increased feed conversion, and modified social behaviour [25,27]. One of the main aspects of the domestication syndrome is a reduction in relative brain size, which appears in most species [34].…”

“…Selection of ancestral Red Junglefowl in a similar manner for low fear of humans caused the tame birds to develop a range of traits associated with domesticated chickens, such as increased growth rate, larger eggs, higher feed conversion, and reduced brain mass [25]. Furthermore, the intra-specific social behaviour also changed due to this selection [27], suggesting that tameness might be linked to different social dynamics through reduction of aggressive behaviours and increased social tolerance. Since the cerebellum plays a crucial part in social behaviour and emotional control, increased tameness may potentially be a key element underlying the enlarged cerebellum in chickens.…”

Potential domestication and tameness effects on prosocial behaviour in chickens

“…From previous studies, we know that this selection for increased tameness results in trait alteration associated with the domesticated phenotype, e.g., increased body size, higher feed efficiency and production of larger eggs [16,17]. Additionally, intra-specific social behaviour is affected as a correlated side effect of this selection [18], suggesting the possibility that increased tameness caused modifications of social behaviour early on during domestication. Here, we therefore attempted to assess prosociality in both ancestral Red Junglefowl versus domesticated chickens, and in high versus low fear Red Junglefowl in order to elucidate possible effects of tameness and domestication.…”

Untitled

“…An essential role in the functioning of the endocrine system of birds belongs to the adrenal gland. Its hormones affect tissue differentiation and growth, the development of reproductive organs, and the course of the sexual cycle (Banerjee, 2018;Kot et al, 2021;Gjuen, 2022). They regulate water, protein, carbohydrate, fat and mineral metabolism (Lotfi et al, 2018;Di Lorenzo, 2020).…”