Seasonal shifts in the diet of the big brown bat (Eptesicus fuscus), Fort Collins, Colorado

Southwestern Naturalist
By:  and 



Recent analyses suggest that the big brown bat (Eptesicus fuscus) may be less of a beetle specialist (Coleoptera) in the western United States than previously thought, and that its diet might also vary with temperature. We tested the hypothesis that big brown bats might opportunistically prey on moths by analyzing insect fragments in guano pellets from 30 individual bats (27 females and 3 males) captured while foraging in Fort Collins, Colorado, during May, late July–early August, and late September 2002. We found that bats sampled 17–20 May (n = 12 bats) had a high (81–83%) percentage of volume of lepidopterans in guano, with the remainder (17–19% volume) dipterans and no coleopterans. From 28 May–9 August (n = 17 bats) coleopterans dominated (74–98% volume). On 20 September (n = 1 bat) lepidopterans were 99% of volume in guano. Migratory miller moths (Euxoa auxiliaris) were unusually abundant in Fort Collins in spring and autumn of 2002 and are known agricultural pests as larvae (army cutworms), suggesting that seasonal dietary flexibility in big brown bats has economic benefits.

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Publication type Article
Publication Subtype Journal Article
Title Seasonal shifts in the diet of the big brown bat (Eptesicus fuscus), Fort Collins, Colorado
Series title Southwestern Naturalist
DOI 10.1894/SGM-28.1
Volume 59
Issue 4
Year Published 2014
Language English
Publisher Southwestern Association of Naturalists
Publisher location Washington, D.C.
Contributing office(s) Fort Collins Science Center
Description 6 p.
First page 511
Last page 516
Time Range Start 2002-05-01
Time Range End 2002-09-30
Country United States
State Colorado
City Fort Collins
Online Only (Y/N) N
Additional Online Files (Y/N) N
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