Use of horizontal and vertical climbing structures by captive common marmosets (Callithrix jacchus)

This study examined the effects of the orientation of bars as an aspect of internal cage design on the behaviour of 12 common marmosets (Callithrix jacchus). Each marmoset was tested individually in four separate test-cage conditions: (V) vertical bars, (H) horizontal bars, (V/H) vertical and horizontal bars, and (R) bars orientated randomly. The only alternative structures available for use by the marmosets were the nesting box and mesh sides of the unfamiliar testing cage. There was a significant effect of cage condition on the marmosets' use of these structures. They rarely used the vertical bars (4% of total time), spending significantly (eight times) more time in the nesting box and on the mesh, but they did use the horizontal bars (25% of total time), the vertically and horizontally orientated bars (33% of total time) and those angled at random (29% of total time). Cage condition affected activity levels: the marmosets were more active in conditions H, V/H and R than in V. Females were significantly more active than the males and showed (three times) greater preference for the bars in all conditions. Right-hand preferring marmosets, in particular the males, spent more time in the nesting box than left-handers. Other behavioural responses did not differ between the four conditions. The findings show that marmosets prefer to climb on bars placed horizontally and that both sex and hand preference influence the use of the bars and activity levels.