Abstract

It is not clear when and how animals start to discriminate between male and female conspecifics and how this distinction drives their social behaviour. A study on pheasants found that 1-week-old chicks (Phasianus colchicus) preferentially aggregated with same-sex peers and this trend became more pronounced through development, suggesting that sexual segregation increases during ontogeny. However, it remains unclear whether this ability depends on experience or develops spontaneously. Using a similar experimental protocol, we investigated whether sex discrimination is present at birth in domestic chickens (Gallus gallus) by testing the social preferences of young chicks with clutch mates. We measured the amount of time spent close to male and female conspecifics in visually inexperienced chicks. Soon after hatching, both males and females preferentially aggregated with females. To clarify whether the experience with conspecifics modifies the initial preference for females, we used an imprinting procedure. We exposed chicks to conspecifics of the same sex, different sex or both sexes for 3 days and then tested their preferences to aggregate with males or females. No sex preference was observed after 3 days of imprinting exposure. The disappearance of the initial sex preference shows that, although chicks can discriminate between conspecifics of different sex, sex segregation does not influence sex preferences in the first week of life. We suggest that the absence of sexual assortment in the first week of age can enhance the social cohesion of the flock.

Significant statement

The ability to discriminate males from females affects a wide range of social behaviours, including the preferences for own sex conspecifics during sex segregation and the choice of a partner in the mating period. However, it remains unclear when and how males and females start to discriminate members of the same/different sex. We tested the domestic chicks to explore whether sex discrimination is present at birth or appears later on. Males and females discriminated between sexes at hatching and preferred to spend more time with female chicks. However, this preference disappeared after exposure to same-sex, different-sex or mixed-sex chicks. The lack of a preference for a specific sex may increase group cohesion postponing the appearance of sex segregation later in life, when chicks move further from their group.

中文翻译：

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年轻的小鸡很快就失去了与雌性聚集的自发偏好

摘要

目前尚不清楚动物何时，如何开始区分雌雄同体以及这种区别如何驱动其社会行为。对野鸡的研究发现，1周龄的小鸡（Phasianus colchicus）优先与同性同伴聚集，并且这种趋势在发育过程中变得更加明显，这表明在个体发育过程中，性别隔离增加了。但是，尚不清楚这种能力是依靠经验还是自发发展。使用类似的实验方案，我们调查了家禽（鸡鸡）出生时是否存在性别歧视），通过测试与同伴交配的雏鸡的社会偏好。我们测量了在视觉上缺乏经验的雏鸡中接近雄性和雌性同种异型的时间。孵化后不久，雄性和雌性都优先与雌性聚集。为了阐明同种异体的经历是否会改变对女性的最初偏爱，我们使用了一个印记程序。我们将小鸡暴露于同性，异性或两性的同种异体中3天，然后测试它们对雄性或雌性的偏好。压印暴露3天后未观察到性别偏爱。最初的性别偏好的消失表明，尽管小鸡可以区分不同性别的同种异体，但性别隔离不会影响到出生后第一周的性别偏好。

重要声明

区分男性和女性的能力会影响广泛的社会行为，包括性别隔离期间对自己性别的偏好以及在交配期间选择伴侣的能力。然而，目前尚不清楚男性和女性何时以及如何开始歧视同性/异性成员。我们对家禽进行了测试，以探讨性别歧视是在出生时出现还是在以后出现。雄性和雌性在孵化时对性别进行区分，并倾向于花更多的时间与雌性小鸡在一起。但是，在暴露于同性，异性或混合性雏鸡后，这种偏好消失了。当小鸡从其群中移开时，缺乏对特定性别的偏爱可能会增加群体的凝聚力，从而推迟晚年出现性别隔离的现象。