Species Inventories Help Protect Bats and Owls at Devils Postpile National Monument

July 2024

At Devils Postpile National Monument (NM), a species inventory has helped park managers ensure that management actions designed to help preserve bats and owls of conservation concern didn’t end up harming them, instead.

NPS

In 2023, land managers in the greater Reds Meadow Valley, which surrounds the monument, planned to do fuel treatments including selective fuels thinning and prescribed burning. The goal was to prevent severe fires that could harm wildlife—but it was also possible these treatments could remove trees that bats and owls might use for habitat.

The California spotted ow (Strix occidentalis occidentalis). USFWS/Kuyper

Nature's Contributions

Devils Postpile NM sustains a diverse community of nocturnal animals, including several bat and owl species. Both perform important ecosystem services: bats control insect populations and help reduce mosquito-borne illnesses by consuming up to 100% of their body weight in insects each night, while owls are efficient predators of rodents and other small mammals. Many of California's bat species are tracked by the California Natural Diversity Database as special-status animals due to habitat loss, rarity, population declines, and other conservation concerns. The California spotted owl has also experienced alarming declines from habitat loss, justifying its recent listing under the Endangered Species Act.

Before the forest-thinning projects proceeded, staff from the National Park Service Inventory and Monitoring Program arranged for an inventory of bat species and the threatened California spotted owl to see if they were present in the park—and, if so, where. They also wanted to compare bat activity in areas with high, medium, and low disturbance from previous fires and trees falling from strong winds. This information would shed light on how disturbance could impact bats in the park, helping park managers better understand how they can support bats when planning fuel treatments.

The sensitive pallid bat (Antrozous pallidus). NPS

Revealing the Results

Acoustic recorders detected 15 bat species, including two sensitive species: pallid bat (Antrozous pallidus) and fringed myotis (Myotis thysanodes). Three species of special concern were also identified: spotted bat (Euderma maculatum), western mastiff bat (Eumops perotis californicus), and western red bat (Lasiurus blossevillii). The study found no strong evidence that bat species richness or activity varied across low-, medium-, and high-disturbance areas. This could be due in part to the study’s small scale. However, the findings align with other research suggesting that moderate disturbance levels may be optimal for bats in Sierra Nevada forests.

To inventory owls, researchers used active call surveys—broadcasting owl vocalizations and documenting any responses. No California spotted owls were detected during the study.

Conserving Habitats

The prescribed fuels thinning and burning would introduce a moderate level of disturbance to the ecosystem. Results from this inventory suggest these management actions would not severely impact bats living in Devils Postpile National Monument. And given the likely minimal or nonexistent presence of California spotted owls in the forest, it is anticipated that the management actions will have negligible effects on these owls.

Park staff noted the inventory results “support the goals of the Inyo National Forest fuels treatments and prescribed fire – to generally open the forests to increase resilience to wildfire while retaining large diameter trees for habitat.” With this knowledge, park managers better understand how to conserve habitat for these special night-roaming animals.

Want to learn more?

Visit the final products from this project, discover more about bats, or check out the table below.

Table 1. Bat species identified in this inventory.

Information in this article was summarized from the sources below:

Blakey, R, M. Buhler, L. Young, B. Wilkerson, and R. B. Siegel. 2023. Inventory surveys for bats and California spotted owls at Devils Postpile National Monument: Final report. Natural Resource Report NPS/DEPO/NRR—2023/2575. National Park Service, Fort Collins, Colorado.https://doi.org/10.36967/2300702

Human-wildlife conflicts: Bats. California Department of Fish and Wildlife. (n.d.). https://wildlife.ca.gov/HWC/Bats

By Christina Martin, I&M Research Scientist and Communication Specialist

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