The effects of moonlight on nocturnal activity in bushy-tailed wood rats (Neotoma cinerea)

The nocturnal activity of bushy-tailed wood rats (Neotoma cinerea) was moni tored for two breeding seasons (1993 and 1994) in the Canadian Rockies. Rad iotelemetry was used under three levels of moonlight to assess two measures of nocturnal activity: (i) the proportion of animals crossing rocky outcro ps and entering the surrounding forest to forage, search for mates, or both , and (ii) the distance moved from the den site while in the forest. Males and females exhibited significant differences among moonlight levels, with greater activity on nights of intermediate-level moonlight and less activit y on nights with bright or dark moonlight. There was no difference in the p roportions of males and females active at any moonlight level. The distance s moved from the den did not differ among moonlight levels for either males or females. Having traversed the rocks and entered the forest, individuals moved similar distances regardless of light level. These results suggest t hat wood rats respond to moonlight only when making the decision to cross r ocks and enter the forest. This behaviour presumably serves to counteract t he increased risk of predation on bright nights.