Two lines of female farm mink were selected among the offspring of 495 mothers kept under conventional farm conditions. A low-stereotyping line (n=146) arose from 75 non-stereotyping females and a high-stereotyping line (n=150) was established from the 75 most stereotyping females. In two successive generations, the incidence of stereotypies was four times higher in the offspring of high-stereotyping females than in those of non-stereotyping females indicating a genetic transmission of the trait. Stereotypies were associated with higher fertility as revealed by fewer barren females, increased litter size, and lower mortality among the pups. Stereotyping females had lower body weight than non-stereotypers, and the association between stereotypies and fertility could exclusively be explained by reducing effects of stereotypies on body weight.

Mortality in mink kits held under conventional farm conditions is believed to be related to dehydration and at least partially to thereby associated competitive aggression. In this study we demonstrated that licking saliva from the commissure of the dam's lips might serve to complement the kits’ fluid supply in a period of relative water deficit and that increasing drinking activity is correlated with reduced aggression. Moreover, we found that easier accessibility of drinking water under farm conditions decreases saliva licking. We suggest that measuring enhanced saliva licking may be used as a possible parameter to detect the risk for dehydration in an early stage. Herewith possible competitive aggressive interactions between the kits for water can be reduced.

Wild bank voles ( Clethrionomys glareolus ) kept in the laboratory under barren housing conditions develop high incidences of type 1 diabetes mellitus due to beta cell– specific lysis in association with the appearance of GAD65, IA‐2, and insulin autoantibodies. Wild‐caught and immediately analyzed voles show no histological signs of diabetes, and the disease may therefore be induced by circumstances related to the housing of the animals in captivity. We tested the possibility that postnatal stress by either maternal separation or water immersion at different intervals would induce diabetes in adult bank voles. We found that low‐frequent stress during the first 21 days of life increases, whereas high‐frequent stress markedly reduces, the incidence of type 1 diabetes in adulthood. These results differentiate the role of early‐experienced stress on subsequent type 1 diabetes development and emphasize that the bank vole may serve as a useful new animal model for the disease.

Wild bank voles (Clethrionomys glareolus) may develop diabetes in laboratory captivity. The aim of this study was to test whether bank voles develop type 1 diabetes in association with Ljungan virus. Two groups of bank voles were analyzed for diabetes, pancreas histology, autoantibodies to glutamic acid decarboxylase (GAD65), IA-2, and insulin by standardized radioligand-binding assays as well as antibodies to in vitro transcribed and translated Ljungan virus antigens. Group A represented 101 trapped bank voles, which were screened for diabetes when euthanized within 24 hours of capture. Group B represented 67 bank voles, which were trapped and kept in the laboratory for 1 month before being euthanized. Group A bank voles did not have diabetes. Bank voles in group B (22/67; 33%) developed diabetes due to specific lysis of pancreatic islet beta cells. Compared to nondiabetic group B bank voles, diabetic animals had increased levels of GAD65 (P < .0001), IA-2 (P < .0001), and insulin (P = .03) autoantibodies. Affected islets stained positive for Ljungan virus, a novel picorna virus isolated from bank voles. Ljungan virus inoculation of nondiabetic wild bank voles induced beta-cell lysis. Compared to group A bank voles, Ljungan virus antibodies were increased in both nondiabetic (P < .0001) and diabetic (P = .0015) group B bank voles. Levels of Ljungan virus antibodies were also increased in young age at onset of newly diagnosed type 1 diabetes in children (P < .01). These findings support the hypothesis that the development of type 1 diabetes in captured wild bank voles is associated with Ljungan virus. It is speculated that bank voles may have a possible zoonotic role as a reservoir and vector for virus that may contribute to the incidence of type 1 diabetes in humans.

Spontaneously stereotyping female and male bank voles were injected daily (except on days assigned for monitoring behaviour) during 3 weeks with placebo, the neurolepticum clozapine or the SSRI antidepressant citalopram. Clozapine blocks dopamine (DA) receptors and acts as a partial serotonin (5-HT) antagonist, while citalopram is a specific 5-HT agonist. Stereotypies in both sexes were left unaffected by clozapine treatment, but citalopram markedly reduced stereotypy levels in females. Animal stereotypies have been widely used in models to provide insight into the underlying pathophysiological processes in human mental disturbances. The present findings highlight the importance of examining sex as a significant variable in evaluating responses to pharmacotherapy, and the demonstrated effect of citalopram indicates that stereotyping female bank voles may be useful in new animal models for human anxiety and mood disorders.

In order to clarify the dependency of stress-induced stereotypies on dopamine (DA) and serotonin (5-HT) functioning, undisturbed and acutely stressed stereotyping bank voles were treated during 3 weeks with the commonly used human atypical neurolepticum clozapine and the SSRI antidepressant citalopram. Clozapine blocks DA receptors (D sub (4)) and acts as a partial 5-HT antagonist (5-HT sub (2) receptors), while citalopram increases 5-HT transmitter activity. Levels of stereotypies were quantified under undisturbed conditions during the treatment period and immediately after the acute stress of handling and injections. It was demonstrated that stereotypies are markedly increased after acute stress and that citalopram effectively mitigates this stress effect. Stereotypies under undisturbed conditions were left unaffected by both clozapine and citalopram treatments.It is suggested that stress-induced increases in stereotypies are more dependent on 5-HT than DA functioning.

Nest box choice experiments were carried out outside the breeding season on adult silver and blue fox vixens with no previous permanent nest box experience. Nest boxes were varied in height of placement, number of rooms, presence of entrance room or platform and light conditions. Only one parameter was varied in any one experiment. Both fox species clearly preferred an elevated multi-room nest box; while silver foxes showed preference for boxes supplied with a platform, blue foxes preferred boxes with an entrance room. There was no significant box preference with respect to light conditions. The possible welfare implications of the preferences are discussed.

Female mink pups were weaned at 6, 8 or 10 weeks of age and subjected to two different housing conditions. They were either kept together with a single male sibling in traditional mink cages (30x45x90 cm) or housed socially with all litter-mates in an alternative system consisting of three adjoining traditional cages (90x45x90 cm). All cages were supplied with nest boxes. At 5 months of age, the siblings were removed leaving the females socially isolated in the two different cage systems. Females' stereotypies were quantified by repeated scanning observations under the social housing conditions immediately before removal of the siblings, and again at the age of 7 and 9 months, when the animals had stayed solitary in the two systems for 2 and 4 months. Solitary females showed significantly more stereotypies than females under social housing conditions in both cage systems. Stereotypies were more frequent in the smaller traditional cages. Stereotypies declined from 7 to 9 months of age among solitary animals in traditional cages but not in alternative cages. Early-weaned solitary females in traditional cages showed more stereotypies than later-weaned animals, but only when measured at the age of 7 months. It is suggested that early weaning, individual housing and small cages promote the development of stereotypies in farmed mink. The influence of early weaning on stereotypies seems to decline with age, while effects related to individual housing and small cages appear to be more persistent.

The development of stereotypies and polydipsia was studied in wild caught bank voles (P: n=92) and their laboratory-bred offspring (F1: n=248). All animals were kept isolated in barren cages in the laboratory. In the P generation, no individuals developed stereotypies, but 22% developed polydipsia (>21 ml/day water intake against normally 10 ml/day). Polydipsia was more frequent among males (34%) than females (13%). In F1, 30% developed locomotor stereotypies alone, 21% showed polydipsia alone, and, additionally, 7% developed both stereotypies and polydipsia. Fewer males than females developed stereotypies (23% vs. 38%), whereas polydipsia was more frequent in males than in females (30% vs. 11%). The occurrence and distribution of polydipsia among sexes were the same in F1 and P. The distribution of different types of stereotypies in stereotyping voles were backward somersaulting (BS, 80%), high-speed jumping (JUMP, 29%), pacing following a fixed route (PF, 12%) and windscreen wiper movement (WIN, 5%). Some individuals (10%) showed two or more different types of stereotypies. The average age for developing stereotypies was 96 days while polydipsia was registered at the age of 63 days in both sexes. Voles showing both polydipsia and stereotypies developed polydipsia later (79 days) than polydipsic voles not showing stereotypies. This difference was especially pronounced in stereotyping females in which the occurrence of polydipsia was postponed to the age of 114 days. Polydipsic voles were tested positive for glucosuria indicating that polydipsia could be a symptom of diabetes mellitus. It is suggested that the development of stereotypies and polydipsia among bank voles in the laboratory are the results of frustration and prolonged stress. Stereotypies seem to depend on frustrative experiences early in life, while polydipsia may be related to diabetes mellitus caused by the experience of prolonged stress. Moreover, circumstances related to the development of stereotypies may be adaptive by reducing the risks of prolonged stress, including the development of fatal polydipsia.

The development of stereotypies was studied in two successive laboratory-bred generations of bank voles representing F1 (n=248) and F2 (n=270) of an originally wild caught stock. It was shown that the propensity to develop stereotypies under barren housing conditions strongly relates to the same propensity of the parents. Stereotypies were approximately seven times more frequent in the offspring of stereotyping parents than in the offspring of permanent non-stereotypers. This held true even when only one of the parents was stereotyper. The paternal and maternal contributions to stereotypies in the offspring appeared to be equal. Males showing stereotypies but prevented from any physical contact with the offspring were as potent as stereotyping females in producing stereotyping offspring. Moreover, the specific type of stereotypy appearing in the offspring after isolation was very much related to the type of stereotypy developed in the mothers. We found no support for the possible importance of social facilitation from littermates, in that the development of stereotypies was independent of the length of time the voles were kept socially with littermates before isolation. We suggest that the possible genetic basis of individual differences in the propensity to develop stereotypies in captivity may result from differences in genetic predispositions and their interactions with discrete frustrating stimuli early in life and/or to genetically different predispositions to cope with frustrating experiences later in life.

During the last decade, the study of fluctuating asymmetry (FA) in relation to different fitness aspects has become a popular issue in evolutionary biology, FA is suggested to be important as an index of selective advantage in both sexual and natural selection. Evidence for these hypotheses is obtained from field studies in which FA is found to be negatively correlated with various fitness components. In this paper, we demonstrate that the apparent significance of FA may depend on assumptions of linearity between size of a trait and FA, and between trait size and fitness, By means of numerical examples, me show that even small, and probably common, deviations from the assumed linearity can bias the statistical analyses to such an extent that it casts serious doubt on the validity of the postulated causal relationship between FA and fitness. We recommend reanalyses of existing data and emphatically suggest that the underlying statistical assumptions are critically evaluated in future studies of FA, especially concerning linear relationships between the variables.

Ninety-six pigs, half females and half castrated males from 12 litters, were housed in 24 groups of four litter mates. From an age of 115 days half of the groups were subjected to chronic stress for 33 days consisting of a schedule of unpredictable, inescapable electroshocks, and half served as controls. Behavior and performance were measured on all animals in the group, hormone data on one female in each group, and data on ulceration on the castrates. Behaviorally, the pigs did not habituate to 31 days of stress treatment. One to 2 days of stress treatment produced a behavioral activation that after 9 to 10 days was restricted to the time period of potential stress treatment. After 30 to 31 days it was replaced by passive behavior. In the beginning as well as after 30 to 31 days of intermittent stress, time spent sitting was increased. In addition, 6 days of intermittent stress reduced the baseline mean of plasma ACTH. After 33 days of stress the baseline mean of plasma ACTH was normalized, but the time course of diurnal secretion of ACTH was shifted. No effects of the chronic intermittent stress on basic levels of plasma cortisol, performance, or gastric ulceration were evident. In conclusion, the effect of intermittent stress depends on the number of days of intermittent stress treatment and it does not inevitably include changes in the basic levels of cortisol. Thus, assessment of stress must be based on a wide range of variables describing the process.

Ninetysix pigs, half females and half castrated males from 12 litters, were housed in 24 groups of 4 litter mates (2 females, 2 castrates). The pigs were weaned at 4 weeks of age and from the age of 115 days half of the groups were subjected to a schedule of unpredictable, inescapable electroshocks for 33 days. and half served as control. The adrenocortical reactivity to ACTH stimulation and to an emotional stressor (the procedure associated with initiation of blood collection) was measured in females, whereas the behavioural and pituitary-adrenocortical reactivity to an open field test was measured in castrates. as was the behavioural reactivity in a social test. Intermittent stress increased adrenocortical reactivity to ACTH stimulation significantly. This effect was present within the first week of intermittent stress (p < 0.06), but no difference was found after 4-5 weeks of stress. In contrast, the adrenocortical reactivity to additional emotional stressors was unaffected by stress after one week of intermittent stress, but increased after 4-5 weeks. In the open field test, centre location increased after one week of intermittent stress, whereas exploration decreased and walking and ambulation increased after 4-5 weeks of stress. In addition. 4-5 weeks of intermittent stress decreased aggressiveness in a social test. In conclusion, the change in reactivity to an additional acute stressor during intermittent stress appeared in different variables and contexts at different times during the course of intermittent stress. Thus, assessment of stress based on changed reactivity has to include several distinct measures of behavioural and hormonal reactivity.

When caged in groups of three and fed ad libitum, dominant male mice survived longer than subordinate group members which again lived longer than males caged in groups of nine, among whom no rank order was established. In groups of nine the social structure was not affected when the food supply was reduced to the lowest level not affecting survival, but in groups of three, food reduction made the survival of both dominant and subordinate animals drop to a level matching that of groups of nine. After challenge with a small dose of Moloney virus, leukemia developed among ad libitum fed subordinate mice in groups of three and members of groups of nine, but not among the dominant animals. Food restriction enhanced the leukemia incidence, but dominant animals continued to go free. We conclude that subordinance and also lack of social hierarchy result in a higher incidence of virus induced leukemia, that severe food restriction does the same, and that the effect of social order on leukemia development prevails even under feeding conditions that nearly abolish group-related differences in survival.

Stereotyped and normal behaviours were quantified from April to June 1989 among 187 adult male and female ranch mink. It was shown that mink devote no more than 3% of the day to stereotyped behaviour. The frequency of stereotypies is markedly increased leading up to feeding time in the middle of the day and declines to very low levels in the afternoon. Environmental disturbances such as human proximity and transport and unloading at other farm sections, have strong inhibitory effects on the performance of stereotypies. The relation between stereotypies and stress is discussed, and it is suggested that chronic intermittent stress (e.g. stress induced by daily fresh food deprivation), is a prerequisite for the occurrence of stereotypies, but that additional conditions involving low level external stimulation are important. A total of 147 adult females were divided into two groups: one exhibiting a low level of stereotypy ( n = 24 ) and one exhibiting a high level of stereotypy (n = 24). These two groups were studied from the weaning of pups in June 1989 until mating in March 1990. Normal behavioural activity as well as specified stereotypies were compared and related to stressful experiences. Again, it appeared that acute stress reduces the occurrence of stereotypies. It was found, however, that stereotypies are differentially affected by stress. Stereotypies in caged mink G.J. Mason Sub-department of Animal Behaviour, University of Cambridge, Madingley Road, Cambridge CB3 8AA, UK ABSTRACT Stereotypy was studied in 105 adult mink on a commercial farm. Stereotypy largely involved locomotor movements such as pacing. Individuals differed in the amount performed, in the exact movements involved, and in the complexity and variability of behavioural sequences. All 102 stereotypic individuals showed stereotypy before the daily delivery of food. Pre-feeding, there were significant negative correlations between stereotypy and inactivity ( r= -0 .839 , P<0.001 ), and stereotypy and normal activity (r--0 .449 , P < 0.001 ). Immediately before food delivery, stereotypies were particularly rapid, and were usually performed in the part of the cage nearest to the approaching feeding machine. This would suggest that the stereotypy is related to appetitive behaviour. However, it is not simply the captive equivalent of hunting; mink also performed stereotypy in response to a number ofStereotypy was studied in 105 adult mink on a commercial farm. Stereotypy largely involved locomotor movements such as pacing. Individuals differed in the amount performed, in the exact movements involved, and in the complexity and variability of behavioural sequences. All 102 stereotypic individuals showed stereotypy before the daily delivery of food. Pre-feeding, there were significant negative correlations between stereotypy and inactivity ( r= -0 .839 , P<0.001 ), and stereotypy and normal activity (r--0 .449 , P < 0.001 ). Immediately before food delivery, stereotypies were particularly rapid, and were usually performed in the part of the cage nearest to the approaching feeding machine. This would suggest that the stereotypy is related to appetitive behaviour. However, it is not simply the captive equivalent of hunting; mink also performed stereotypy in response to a number of

Two experiments were conducted to examine the effects of repeated immobilisations and food restriction on normal activity and stereotypies in low and high stereotyping female ranch mink. Repeated immobilisations had immediate inhibitory effects on normal activity and stereotypies in both groups, whereas food restriction had the opposite immediate effects. Subsequent to both immobilisations and food restriction, stereotypies were increased, whereas normal activities returned to pre-experimental levels. Repeated immobilisations were followed by increases in cortisol levels in both low and high stereotyping females. High stereotyping females had lower baseline cortisol levels than low stereotypers but tended to show higher cortisol responses to immobilisations. These results indicate that stressful experiences may affect stereotypies, but that the direction of the changes depends on type of stressor as well as the duration of exposure to the stressor. It is moreover suggested that stereotypies can be emancipated.

Effects of different mother-infant separation procedures on experienced stress by adults and young were studied using changes in circulating eosinophil levels as a stress indicator. It was found that (1) the amount of stress experienced by the mothers increases with the age of the pups at separation, when separation occurs as 6-week-, 8-week-, and 10-week-old pups, (2) eosinophil levels of mink pups show an ontogenetic development which complicates interpretations of the levels in terms of experienced stress, and (3) complete separation from 6-week-, 8-week-, or 10-week-old pups reduces experienced stress of the mothers more radically than simple physical separation involving removal of the pups to adjoining cages.

Two experiments were conducted to examine the role of the pituitary-adrenocortical axis in the mediation of the effects of single and repeated electric footshock on subsequent agonistic responding in castrated male mice. It was found that (1) preventing corticosterone responses to shock occludes the facilitatory effects of single shock on both aggressive and submissive behaviour and occludes the additional increases in submissive behaviour which normally occur after repeated shock, and (2) blocking pituitary release of ACTH by dexamethasone treatment restores aggressive behaviour after repeated shock, independently of the initial levels of corticosterone and testosterone. These findings suggest that (1) increases in aggressive and submissive behaviour in response to single shock depend on shock-induced increases in corticosterone levels; (2) further increases in submissive behaviour in response to repeated shock require further increases in the corticosterone levels; and (3) inhibition of aggressive behaviour after shock repetition appears to depend on increases in ACTH levels, and occurs independently of the initial corticosterone and testosterone levels.

One experiment was conducted to separate the roles of corticosterone and ACTH in the mediation of the facilitatory effects of experiencing shock on subsequent fighting behaviour in male mice. It was found that (1) treatment with electric foot-shock and single injections of ACTH (one dose level) lead to comparable increases in subsequent fighting in intact males; (2) preventing changes in testosterone secretion by combined castration and testosterone replacement does not occlude or modify the facilitatory effects of shock or ACTH on subsequent fighting; and (3) preventing changes in both testosterone and corticosterone secretion by combined castration-adrenalectomy and testosterone-corticosterone replacement prevents shock and ACTH induced increases in fighting. These findings suggest that corticosterone plays a more important role than ACTH in the mediation of the facilitatory effects of shock on subsequent fighting behaviour in male mice.

Two experiments were conducted to examine the role of corticosterone in controlling fighting subsequent to electric foot-shock in male mice. It was found that (1) treatment with corticosterone restores post-shock fighting in adrenalectomized males but not in castrated-adrenalectomized males; (2) raising cortieosterone levels induces post-shock fighting in castrated-adrenalectomized males treated with testosterone but not in castrated-adrenalectomized controls treated with a placebo; and (3) preventing corticosterone responses to shock occludes the increasing in fighting which normally follow shock in intact males. These findings suggest that (1) corticosterone plays an important role in the control of post-shock fighting in mice; (2) this importance of corticosterone is dependent on the presence of circulating testosterone, or other androgens; and (3) corticosterone responses to the experience of shock may be involved in the mediation of the facilitatory effects of this experience on subsequent fighting behaviour.