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

1. Introduction

Stereotypies, or stereotypic behaviour, represent a wide range of invariant and ¨ Ž frequently repeated activities with no obvious goal or function Odberg, 1978; Mason, . 1991a . In humans, stereotypies are associated with schizophrenia, autism and mental Ž retardation Hutt and Hutt, 1968; Frith and Done, 1990; Bergson et al., 1995; Bodfish et . al., 1995 . In animals, stereotypic behaviour is commonly seen as the result of caging Ž . under barren housing conditions Sørensen, 1987; Mason, 1991a , scheduled or re- Ž . Ž stricted feeding Falk, 1969; Lawrence and Terlouw, 1993 , social deprivation Sahakian ¨ . Ž . et al., 1975 , frustration Feldman, 1978; Odberg, 1978, 1987; Rushen, 1985 , or Ž . tethering Cronin et al., 1985 . Psychostimulant drugs which increase brain dopaminer- Ž gic activity also elicit stereotypies Randrup and Munkvad, 1967; Munkvad et al., 1968; Fog, 1969; Post and Rose, 1976; Cheal et al., 1978; Porsolt et al., 1982; Dantzer, 1986; . Walter and Kuschinsky, 1989; Morimasa et al., 1995 . This effect is prevented by Ž selective inhibition of dopamine receptors Robbins et al., 1990; Mittleman et al., 1991; . Cabib 1993 , and it is therefore assumed that dopaminergic pathways play an important role in mediating stereotypic behaviour. Since stereotypies are considered rare in nature, it is generally assumed that animal stereotypic behaviour results from poor coping with the environment and therefore may Ž be related to current or early experienced stress Mason, 1991b; Wurbel and Stauffacher, ¨ . Ž . 1997 . Mason 1991b suggests that, instead of reflecting current stress, adult stereotypy performance may be like a ‘‘scar’’ representing a severe problem experienced at the onset of stereotypy development. This view is supported by studies of stereotypy Ž . development in bank voles Clethrionomys glareolus reared under barren housing conditions. Bank voles stereotypic behaviour appears related to early experienced maladaptation to environmental conditions in that increasing the size and complexity of ¨ Ž . the environment reduces the incidence of stereotypies in the voles Odberg, 1987 . Old voles, however, show stronger perseverance of stereotypies than younger voles after Ž . environmental enrichment Cooper and Nicol, 1996 . With age, stereotypies may Ž . become emancipated from the eliciting stimuli Fentress, 1976, 1977 , and it has been suggested that this could imply that the underlying dopaminergic pathways become Ž . sensitised Dantzer, 1986, 1991 . Although stereotypies appear strongly related to environmental conditions, it is commonly observed that only a proportion of individuals develops stereotypies under identical conditions. This variation may relate to individual differences in response to the eliciting environmental stimuli early in life and in subsequent neuronal sensitisation Ž . Wurbel and Stauffacher, 1997 . ¨ The possible relevance of differences in genetic dispositions for the development of stereotypies is obvious, but this aspect has been subjected to only a minimum of Ž . scientific attention. Smith 1984 suggests that the occurrence of stereotypies in thor- oughbred racehorses may be of genetic origin, as indicated by stereotyping stallions producing stereotyping offspring. A similar positive correlation between the occurrence Ž of stereotypies in parents and their offspring has been indicated in other species Kiley, ¨ . 1977; Odberg, 1986; Hansen, 1993 . Drug-induced stereotypies have also been shown Ž inheritable Ciaranello and Boehme, 1982; Kendler and Davis, 1984; Cabib et al., 1985; Puglesi-Allegra et al., 1990; Skrinskaya et al., 1992; Tolliver et al., 1994; Golden et al., . 1995; Morimasa et al., 1995; Sluyter et al., 1995; Ballas et al., 1996 . The literature provides numerable examples on successful selection for normal Ž behaviour as well as non-stereotypic behavioural disorders e.g. Bruell, 1962; Murphree et al., 1967; Peters et al., 1967; Symons and Sprott, 1976; McCaffrey et al., 1980; . McDonough et al., 1981; Plomin, 1990; Benus et al., 1991; Rosengarten et al., 1994 . The present study aimed at examining the possible genetic basis of stereotypies in the bank vole. Laboratory- bred, but not wild caught, bank voles housed isolated in barren cages develop high frequencies of locomotor stereotypies, including easily recognisable ¨ Ž backwards somersaulting, jumping, and windscreen wiper movements Odberg, 1986; . Sørensen, 1987; Sørensen and Randrup, 1986; Cooper and Nicol, 1991, 1994 . We Ž . repeated this finding in our recent study Schoenecker et al., 2000 on wild caught Ž . Ž . Danish voles P: n s 92 and their laboratory-bred offspring F1: n s 248 . While none of the wild caught voles showed stereotypies under isolation, 74 or 30 of the F1 offspring developed stereotypies at the average age of 96 days. In the present study, voles from the abovementioned F1 generation were chosen for selective matings between non-stereotypers and stereotypers. The subsequent development of stereotypic Ž . behaviour in the resulting offspring F2 was then compared with the stereotypy status of their parents when the fathers were removed at the day of delivery. Moreover, we attempted to evaluate a possible influence of social facilitation by keeping the litters together after weaning for variable lengths of time before isolation and relate this to subsequent development of stereotypies.

2. Materials and methods