The Force Driving Mating Behavior in the House Musk Shrew (Suncus murinus)

Abstract

-In the present study, inter-male interaction of the domesticated house musk shrew was observed in detail under laboratory conditions. In most cases, during inter-male interaction, male house musk shrews exhibited a sequence of behavior items including tail-wagging, following, mounting and thrusting. In the minority of cases, males did not progress beyond following. Offensive behavior was not sufficiently violent to cause injury. It appeared that role assignment was decided by contact manner and vocalization. One of fundamental characters of this animal made a start of following, in which one shrew followed another, who touched and then separated. Role assignment (i.e., which male led and which followed) was decided in status battle. Roles were often reversed during following. Following behavior was maintained by 'polite' mutual contact, and the interaction progressed to thrusting in the majority cases. After role assignment, the variation in contact manner decreased. The ratio of time spent in front-andbehind contact to that spent in multi-lateral contact increased when both males commenced following behavior simultaneously. This ratio was maintained until the following male snapped after he finished thrusting. Even if the following male did not reach thrusting, he mounted the preceding male. The pairs who did not reach thrusting repeated following behavior or mounting. In those cases, while one male concentrated on touching the other to maintain following, the other attempted to divert attention from the following behavior. Male shrews were able to reach thrusting irrespective of sex.

Inter-male Mating-like Behavior in the Domesticated House Musk Shrew, Suncus murinus

“…Conspicuous behavior items between males and females include encounter, female tail-wagging, following formation, intromission, ejaculation and male continuous vocalization (Matsuzaki, 2002). The conspicuous behavior items we observed in the inter-male interaction were very similar to that observed between males and females.…”

“…At that time, the order of following formation reversed. In mating behavior, the female utters a sharp threatening call, and the male utters an ordering call that sounds like chirping (Matsuzaki, 2002). In the present study, one male's threatening call appeared to prompt the other to turn and move away temporarily.…”

“…time. Continuous reversal of following formation is not observed in heterosexual interaction (Matsuzaki, 2002).…”

“…The new preceding male wagged its tail alternatively. Status battle appears to be offensive, and it is important for deciding the order of following, because a characteristic of this species is that individuals will follow an animal that touches them and then moves away (Tsuji and Naruse, 1984;Matsuzaki, 2002).…”

“…In this species, Tsuji and Naruse (1985) stated that car-avan formation between mother and offspring in the nursing period not only facilitates care for the offspring, but also provides the young with early experiences in exploring and extending their environment. Matsuzaki (2002) speculated that following formation between adult males and females may be derived from caravan formation in the nursing period. Inter-male interaction was reported by Tsuji (personal communication) and Kawano (1992) as "mating-like behavior".…”