THE INFLUENCE OF MOONLIGHT ON VEGETATION HEIGHT PREFERENCE AND TRAPPABILITY OF SMALL MAMMALS

The trappability of small mammals was compared between moonlit and ove rcast nights, and between clear and overcast nights, and between clear and overcast days, for different heights of vegetation. Regardless of moonlight, all species captured showed a preference for traps in tall vegetation (approximate to 60 cm), and although wood mice and common shrews were occasionally captured in short vegetation (approximate to 4 cm), bank voles and field voles were not captured there. Bank voles are thought to rely on vegetation cover to avoid predators and by rema ining in tall vegetation had no need to respond to cloud cover on moon lit nights. Wood mice, which are thought to rely on speed and agility to avoid predators, were captured in short vegetation, but only when t he sky was overcast. Two types of camouflaging trap-covers (cut grass and wooden board) were tested to control for differences in trap visib ility that might have contributed to the observed avoidance of short g rass on moonlit nights. Wood mice preferred uncovered traps when the s ky was overcast but their preference was not affected by vegetation he ight. The proportion of captures of voles and shrews in covered, as op posed to uncovered, traps was not affected by either cloud cover or ve getation height. It was concluded that the animals were genuinely usin g plots with short grass less, as opposed to merely avoiding very visi ble traps.