What If Gone

Species → Little Brown Bat

Little Brown Bat

Myotis lucifugus

once one of the most common bat species in North America, numbering…
Extinction risk Endangered
AgriculturalBiological controlCatastrophic declineFungal disease
Little Brown Bat (Myotis lucifugus)
Photo: Don Pfritzer, U.S. Fish and Wildlife Service, Wikimedia Commons (Public domain)

What if it disappeared?

Impact High
Since 2006

The emergence of the fungus Pseudogymnoascus destructans at hibernation sites has caused a measured collapse in little brown bat populations — once one of the continent's most common bat species — to the point that the authors predict regional extinction in several affected areas.

Documented
Detail

Frick, W.F., Pollock, J.F., Hicks, A.C., Langwig, K.E., Reynolds, D.S., Turner, G.G., Butchkoski, C.M. & Kunz, T.H. (2010). An emerging disease causes regional population collapse of a common North American bat species. Science, 329(5992), 679-682.

The study combines decades of winter counts at hibernation caves and mines with demographic models to project the population's trajectory under the disease's continued effect, rather than simply documenting past decline.

Economic estimate

The figure of $3.7 to $53 billion saved annually for US agriculture by bats, widely repeated in popular science, comes from an extrapolation based on insect-consumption estimates — not a direct measurement of yield loss or increased pesticide spending in the regions where the little brown bat has collapsed since 2006.

Insufficient
Detail

Boyles, J.G., Cryan, P.M., McCracken, G.F. & Kunz, T.H. (2011). Economic importance of bats in agriculture. Science, 332(6025), 41-42.

The white-nose collapse constitutes, in the field, a large-scale removal experiment researchers never planned — but no one has yet compared insecticide spending or crop losses before and after the collapse in affected counties, which would allow testing the Boyles et al. range against real data rather than a model.

In New Jersey

DNA sequencing of collected guano reveals the species' diet in detail: 653 distinct prey species, of which 160 are known agricultural pests or disease vectors — direct proof of the mechanism behind the insect-regulation service farmed landscapes would lose if the species disappeared.

Documented
Detail

Maslo, B., Mau, R.L., Kerwin, K., McDonough, R., McHale, E. & Foster, J.T. (2022). Bats provide a critical ecosystem service by consuming a large diversity of agricultural pest insects. Agriculture, Ecosystems & Environment, 324, 107722.

DNA metabarcoding identifies prey from genetic fragments in droppings, a method far more precise than visually analyzing insect fragments, which often misses soft-bodied or heavily digested prey — giving concrete content to the service whose dollar estimate, in the previous point, remains uncertain.

Documentation

Last verified: August 14, 2026