Noncaged laying hens remain unflappable while wearing body-mounted sensors: Levels of agonistic behaviors remain unchanged and resource use is not reduced after habituation.

Unique markings or body-mounted sensors facilitate data collection from individuals in large groups of similar-looking conspecifics but may have unintended consequences on behavior. A wireless sensor attached to the back of laying hens via a harness has been developed to monitor space use and activity. Prior to collecting experimental data, effects of the sensor on resource use and social interactions were assessed. Four rooms of 135 hens each were weighed and 10 hens/room were randomly fitted with sensors at 11 wk of age (0 d). Instantaneous scan samples recorded the number of hens (SEN: sensor-wearing hen, and NON: hen without sensor) using resources (feeder, water, nest box, perch) every 5 min over 24 h on -5 d, -4 d, -2 d, -1 d, 1 d, 2 d, 4 d, 8 d, and 16 d. Logistic regression determined that SEN feeder use was less on 1 d and 2 d and more on 16 d than NON feeder use. The SEN water use was reduced only on 1 d. The SEN nest box use increased on 1 d, 2 d, and 16 d. The SEN perched more on 1 d, 2 d, and 4 d, and less on 8 d. Initial resource use was affected by wearing a sensor, but by 16 d, all resources were used similarly or more by SEN than NON. No difference in BW was observed on 17 d, suggesting that long-term resource use was not affected. No differences were observed among the number of agonistic observations -5 d, 8 d, and 16 d. With the exception of SEN hens acting as aggressors toward NON hens, agonistic interaction types occurred close to expected proportions. These factors indicate that hens habituate to wearing sensors within 2 wk.