Early life environmental factors have a profound impact on an animal’s behavioural development. The gut microbiota could be such a factor as it inuences behavioural characteristics, such as stress and anxiety. Stress sensitivity and fearfulness are related to feather pecking (FP) in chickens, which involves pecking and pulling out feathers of conspecics. Furthermore, high (HFP) and low FP (LFP) lines differ in gut microbiota composition. Yet, it is unknown whether gut microbiota affects FP or behavioural characteristics related to FP. Therefore, HFP and LFP birds orally received a control, HFP or LFP microbiota treatment within 6 hrs post hatch and daily until 2 weeks of age. FP behaviour was observed via direct observations at pen-level between 0-5, 9-10 and 14-15 weeks of age. Birds were tested in novel object (3 days & 5 weeks of age), novel environment (1 week of age), open eld (13 weeks of age) and manual restraint (15 weeks of age) tests. Microbiota transplantation inuenced behavioural responses, but did not affect FP. HFP receiving HFP microbiota tended to approach a novel object sooner and more birds tended to approach than HFP receiving LFP microbiota at 3 days of age. HFP receiving HFP microbiota tended to vocalise sooner compared to HFP receiving control in a novel environment. LFP receiving LFP microbiota stepped and vocalised sooner compared to LFP receiving control in an open eld. Similarly, LFP receiving LFP microbiota tended to vocalise sooner during manual restraint than LFP receiving control or HFP microbiota. Thus, early life microbiota transplantation had short-term effects in HFP birds and long-term effects in LFP birds. Previously, HFP birds had more active responses compared to LFP birds. Thus, in this study HFP birds seemed to adopt behavioural characteristics of donor birds, but LFP birds did not. Interestingly, homologous microbiota transplantation resulted in more active responses, suggesting reduced fearfulness.