Temperamental turkeys: Reliability of behavioural responses to four tests of fear

Open field (OF), tonic immobility (TI), voluntary approach (VA) and novel object (NO) tests are used to assess fear responses, activity levels and coping styles of poultry. Fear tests are also used as part of welfare assessment programmes. Little is known about fear responses of turkeys. Specifically, it is unknown whether turkeys' fear responses are reliable which is important when developing tests for assessing welfare. This study examined the short- (between days) and long-term (between weeks) changes in, and test-retest reliability of, turkeys' fear responses. Male commercial turkeys were housed in groups of four to six in 16 pens. Turkeys were individually tested in OF (n = 60) and TI (n = 66) tests. VA and NO tests were administered to groups of turkeys in their pens (n = 16). Turkeys were tested three times in each test. The first (Period 1) and second (Period 2) tests were administered on consecutive days between 4 and 6 weeks, and the third test (Period 3) between 8 and 10 weeks. Other than increased sitting and reduced standing during OF testing and more birds approaching and pecking the observer during VA testing (Period 2 vs. 1), frequencies of responses did not differ between test periods. However, test responses (e.g. latencies to ambulate, vocalise, approach and peck) differed between periods depending on the fear test used. All VA test measures differed between periods, whereas most TI test measures did not. Most OF and NO test measures differed between weeks, but not between days. Except for the number of vocalisations (rS = 0.39), most OF test responses were moderately reliable (rS > 0.40). The latency to vocalise (rS ≥ 0.51) and number of vocalisations (rS ≥ 0.59) were the most reliable TI test measures, whereas reliability of TI duration (rS ≤ 0.31) was low. All VA test measures were moderately to highly repeatable between days and weeks (e.g. latency to peck: rS ≥ 0.67). Reliability was lowest for the NO test, where only the latency to peck was moderately repeatable (rS = 0.61). These findings suggest that although some fear responses of turkeys change over time and with repeated testing, most OF, TI and VA responses are reliable between days and weeks. However, few NO test measures were reliable under the conditions of this study. Further research is needed to assess the validity of OF, TI, VA and NO tests for assessing fear responses of turkeys.