Results Directory UMM :Data Elmu:jurnal:A:Applied Animal Behaviour Science:Vol68.Issue4.2000:

were either weaned at the age of 20 days and allowed company with their littermates for 12 days before transference to isolation, or they were weaned at the age of 32 days and immediately transferred to isolation. The isolation period for F2 pups lasted until they reached the age of 180 days after which the study was terminated. 2.2. ObserÕations and classification The occurrence of stereotypic behaviour was examined before and after isolation by one-zero sampling every 15 min for 3–4 h every day during the whole study period. When stereotypies were recognisable, the age and sex of the voles were noted along Ž . with the type of stereotypy performed. Voles were classified as stereotypers S if individual stereotypic behaviour were noted in bouts of at least five repetitions during the daily observation periods. These bouts, separated by small intervals, could continue Ž . for hours. The classification S covered voles showing backward somersaulting BS , Ž . Ž . high speed jumping JUMP , pacing following a fixed route PF and windscreen wiper ¨ Ž . Ž . Ž . movements WIN as previously defined by Odberg 1986 , Sørensen 1987 , Sørensen Ž . Ž . and Randrup 1986 , and Cooper and Nicol 1991, 1996 . Voles neither showing Ž . stereotypies nor polydipsia were classified as non-stereotypers N . At the end of the study, the proportion of voles classified as S and N in F2 was calculated and related to the development of stereotypies in their parents. This allowed investigation of stereotypy development among the offspring of the following four possible F1 mating groups: N male mating N female, S male mating N female, N male mating S female, and S male mating S female. Some voles in F1 developed severe Ž polydipsia after delivery and the age of 180 days water intake 21 mlrday vs. . normally 10 mlrday . The offspring of these voles were omitted from the present study, Ž . leaving 187 F2 voles 93 males and 94 females in 42 litters for further data treatment. 2.3. Statistical analyses Differences in proportions of voles classified as S or N in F1 and F2 were tested by chi square tests using Yates continuity correction factor when n - 20. Spearman rank Ž . correlation tests corrected for ties were used to estimate effects of isolation age on stereotypies. The chosen significance level was 0.05 and all tests were two-tailed.

3. Results

Table 1 shows the development of stereotypies in F2 voles according to the four F1 mating groups. There was no significant sex effect on stereotypy development in the offspring descending from non-stereotypers or from parents with only one stereotyper. When both parents were stereotypers, however, stereotypies were more frequent in the Ž . female than in the male offspring P - 0.05 . The propensity of F2 voles to develop stereotypies was markedly related to the occurrence of stereotypies in their parents. When one or both parents developed stereotypies, 53 of the offspring also developed stereotypies, whereas the same Table 1 Ž . Ž . Ž The number of individuals n F2 , the number of stereotypers n S F2 and the percentage of stereotypers . S F2 in the offspring of the four different mating types in F1 Mating type F1 n F2 n S F2 S F2 P Ž . N male=N female F2 malesqfemales 86 7 8 Ž . S male=N female F2 malesqfemales 11 6 55 Ž . N male=S female F2 malesqfemales 14 5 36 Ž . S male=S female F2 males 48 23 48 Ž . S male=S female F2 females 28 20 71 Indicates P -0.01 in comparisons of n S F2 with N male=N female. Indicates P -0.001 in comparisons of n S F2 with N male=N female. proportion was only 8 in the offspring from parents that did not develop stereotypies Ž . P - 0.01–0.001 . There were no significant differences in the proportions of stereotyp- ing F2 voles descending from the two different mating groups involving only one stereotyping parent, although stereotyping fathers tended to produce more stereotyping Ž . offspring than stereotyping mothers 55 vs. 36 . Two stereotyping parents produced Ž more stereotypers than mating pairs involving only a single stereotyper P - 0.05 for . female offspring, NS for male offspring . There was a close relationship between the maternal type of stereotypy developed in F1 and the type of stereotypy developed in the offspring. The two most commonly observed stereotypies were BS and JUMP. In the stereotyping offspring from BS mothers, 94 developed BS and 6 developed JUMP, whereas mothers developing Ž JUMP had 83 offspring showing JUMP and 17 showing BS P - 0.001 in compari- . son with preferred stereotypy in the offspring . There was a non-significant negative correlation between age at isolation and the Ž . number of voles developing stereotypies in F2 P s 0.067 , but there was no correlation between the time spent with littermates and subsequent tendencies to develop stereotyp- ies.

4. Discussion