Winter distribution of small mammals in relation to snow cover in the subalpine zone, Australia

Abstract

We present the results of a study that is the first to investigate the landscape-scale distribution of small mammals in direct relation to the spatial and temporal variation of snow cover. We investigated the distribution of the dusky antechinus Antechinus swainsonii and bush rat Rattus fuscipes in the subalpine zone of Kosciuszko National Park in the Snowy Mountains of south-eastern Australia. A new hair tube technique was used to detect the presence of small mammals active in the subnivean space. In 2002, we sampled 72 sites stratified by elevation (1501-1600, 1601-1700, 1701-1800 m), aspect (accumulating, ablating) and habitat type (woodland, wet heath, dry heath, grassland). These factors were considered important in influencing snow accumulation and generally reflected the types of habitats available to small mammals. In 2003, the presence of small mammals was investigated at 30 high-elevation sites including six boulderfields. The development of the subnivean space in the Snowy Mountains is dependent on the presence of structures such as shrubs, boulders and microtopographic features that are capable of supporting a snow layer above ground level. When snow was present, small mammal detections were negatively correlated with snow depth and duration, and positively correlated with the complexity of structures and microtopography. At high elevations detections were largely confined to boulderfields, and at mid and low elevations small mammals were detected primarily in habitats where the subnivean space was most extensive. Antechinus swainsonii and R. fuscipes responded differently to snow cover, with the latter seeming better able to overwinter where snow cover was shallow and patchy, in contrast to A. swainsonii whose occurrence was correlated to the size of the subnivean space.