Audible Bats Project

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Most bats echolocate at a frequency unheard by the human ear, however, some desert species emit echolocation calls within the range of human hearing. 

Spotted bats (Euderma maculatum) are an elusive and widely-distributed species throughout the semi-arid deserts of North America. Sometimes called the “Oreo cookie bat,” they sport large, pink ears and spotted fur. Spotted bats roost high among sheer cliffs, but their clicking calls can be heard while they hunt for owlet moths in the canyons of Central Oregon.

The first spotted bat was “officially” documented in Oregon in 1979 when researchers in the Alvord Desert accidentally captured one in a mist net left open overnight. Only four more spotted bat records were reported in the state over the next 24 years, and the idea that spotted bats were extremely rare, or possibly even extirpated, took hold. In 2005, however, listening surveys combined with mist-netting surveys of Central Oregon revealed that spotted bats may be more abundant in the region than previously recognized.

Biologists still have limited understanding of spotted bat distribution and seasonal patterns in Oregon. What we do know is that their calls are most commonly heard near the canyons and cliffs of eastern Oregon’s High Desert.

Pallid bats (Antrozous pallidus) are another of Oregon's high desert bat species. They have a wide range, spanning from Canada to Mexico. While pallid bats typically produce inaudible, high-frequency echolocation calls, this behavior changes while rearing pups. When in the vicinity of summertime maternity roosts, pallid bats will lower the frequencies of their calls to within the range of human hearing.

Serendipitously, both the spotted bat and pallid bat are found in similar arid cliffs and canyons habitats such that both species can be effectively surveyed simultaneously.