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Does Moonlight Change Vertical Stratification of Activity by Forest-Dwelling Insectivorous Bats?

Kerry R. Hecker , R. Mark Brigham
DOI: http://dx.doi.org/10.2307/1383170 1196-1201 First published online: 6 December 1999

Abstract

We hypothesized that bats would not change total nightly activity in response to the lunar cycle but would exhibit a shift in habitat among vertical levels (different degrees of spatial complexity and light penetration) of temperate rainforest with changing levels of lunar light. As predicted, we found no evidence that activity of bats varied directly with intensity of moonlight. However, activity changed depending on height within the forest, and there was a significant interaction between moonlight and height. The shift between vertical levels was not expected if risk of predation was an important selective pressure, because activity was highest in the canopy and lowest at the level of shrubs on bright nights. The most likely explanation for interaction between height and moonlight is that bats adjust use of microhabitats to match distribution of prey.

Key words
  • Vespertilionidae
  • bats
  • echolocation
  • activity
  • habitat use
  • moonlight
  • British Columbia