Miniature radio-transmitters were used to follow movements over a 10-day period of the 10 g honey possum Tarsipes rostratus, and the areas covered were compared with home-range estimates calculated from long-term mark-and-recapture records using pitfall traps. The study was carried out in the Scott National Park, in the extreme south-west of Western Australia, and shows that honey possums may move far greater distances than is apparent from trapping records. The overall mean area used determined by radio-tracking was significantly larger at 0.54±0.19 ha than the apparent home range of 0.03 0.01 ha determined by trapping. The area used by males was significantly greater than that of females when measured by radio-telemetry (0.79±0.24 ha vs 0.14±0.08 ha, P = 0.058), but did not differ significantly when estimated from trapping records (0.03±0.01 ha vs 0.01±0.01 ha). These data suggest that honey possums frequent plant assemblages at night where they are vulnerable to pitfall trapping, but that males, particularly, spend the day in other areas that may be as far as 200 m distant.

Behavioural and anatomical analyses were undertaken to determine the visual capabilities of a small nectivorous Australian marsupial, the honey possum Tarsipes rostratus. It is proposed that, despite a crepuscular lifestyle and a low visual acuity, vision contributes substantially to the honey possum's perception of its environment. Visual acuity, determined using a discrimination task, revealed a slightly higher performance in daylight (0.63 cycles/degree) than in moonlight and starlight (0.60 cycles/degree). Ultrastructural analysis of the outer retina revealed a rod to cone ratio comparable to that found in diurnal retinae (20:1 in the central retina). Two types of oil droplets were distinguished on the basis of size. The degree of neural convergence was also similar to that found in a diurnal retina, with a ratio of 12 photoreceptors:1 ganglion cell. The remarkable total field of view, approaching 240° of visual angle and including a binocular overlap of 80° in the horizontal plane, provides an efficient predator detection capacity. The visual capabilities of the honey possum are discussed in relation to its lifestyle and the associated visual requirements.