Effects of isolation on aggression in the domesticated house musk shrew (Suncus murinus)

Abstract

The house musk shrew, Suncus murinus, belongs to the primitive mammalian order of Insectivora. It has been successfully domesticated by Kondo & Oda (1977) in Japan and by Dryden (1968) in the United States. As Tsuji (1981) pointed out, it is laboratory animal useful for the studies of both comparative psychology and ethology. In previous studies, some behaviors of this species were investigated: for example, caravaning (Tsuji & Ishikawa, 1984; Tsuji et al., 1986), mating (Tsuji, 1987; Rissman & Bronson, 1987), marking (Balakrishnan et al., 1984), and aggressive behavior (Kawano, 1992). However, the factors that affect aggression have not been examined in detail. Effects of isolation on interactive behaviors are well known for other mammalian species. Isolated animals generally become more aggressive than group-reared ones (e.g., Levine et al., 1965, for mice; Hatch et al., 1963, for rats; Mason, 1960, for rhesus monkeys), but this varies among species. Rosen & Hart (1963) reported an example of this within the same genus (Peromyscus). The effect of isolation has not yet been investigated in Insectivora. This study aimed to clarify whether isolation increases aggression of the domesticated house musk shrew (Suncus murinus), and focused on the effect of sex. Because females of this species are as aggressive as males and have no estrous cycle, the same procedure can be applied to both sexes. This study provides basic information on the effect of isolation upon interactive behaviors of Insectivora.