| I investigated the interactions between a forest pest (western spruce budworm, Choristoneura occidentalis), and insectivorous bats (Chiroptera) in southern interior British Columbia, Canada. Because budworm moths occur in large numbers during an outbreak and could represent dense patches of prey, I hypothesized that bats would alter their foraging behaviour in response to the outbreak. I did not detect an aggregative numerical response (change in foraging site), suggesting that prey availability was not the dominant factor influencing bats' choices of foraging sites. Myotis evotis and aerial-foraging Myotis bats showed a functional response (change in diet) in 1 out of 2 years. The bats' foraging strategies and the availability of alternative prey seemed to be important in determining the response. I estimate that bats could have eaten approximately 140,000 budworm moths per 10km2 over the season, and discuss the potential impact of bat predation. Bats also consumed relatively large numbers of budworm-like caterpillars. |
