Rearing enrichments differentially modified hen personality traits and reduced prediction of range use

Domestic fowl have been demonstrated to individually differ in personality, dictating reactions to environmental stimuli. Free-range chickens, Gallus gallus domesticus, show individual range use varia-tion, which may be related to personality differences. Enrichment can also modify behavioural traits. This study measured behavioural impacts of rearing enrichments across pullets and young adults, testing for personality differences and whether they predicted range use variation. Laying hens were reared for 16 weeks across nine pens under three conditions comparing control floor litter rearing with two enrich-ment types (novel objects or perching structures). At 16 weeks of age, 1386 pullets were transferred to a laying facility, housed in nine identical pens and given range access at 25 weeks. A sample of birds were tested at 9-11 weeks and 20-21 weeks with a series of tests: novel arena, adaptation to the arena with food present, open field, novel maze arena training with food and maze tests. Individual range use from 27 to 31 weeks was measured via radiofrequency identification technology. Enriched pullets were significantly quicker to first step in the adaptation with food present and structurally reared hens were significantly quicker to first step in the open field during testing, but there were no significant differences observed during maze arena training and testing. Of 16 correlations among test parameters, 11 were significant for control birds and six to seven were significant for the enriched treatments. Test parameter and range use correlations were significant for the control birds only. These results support the presence of different personalities in hens with enrichment reducing fear and increasing adaptation. Fewer cor-relations in the enriched hens suggest they developed a more plastic personality type. This response strategy may have fitness benefits for free-range birds or other captive-reared animals that undergo drastic environmental change across their lifetime.