Different Ways of Measuring Bat Populations Could Lead to Different Conclusions

Activity and occurrence metrics are complementary but not interchangeable.

By the editors of Park Science magazine

About this article

This article was originally published in the "Research Roundup" section of Park Science magazine, Volume 39, Number 1, Winter 2024-25 (January 15, 2025).

Scientist programming an acoustic bat detector in a Great Lakes area national park.

Image credit: NPS

Bats get a bad rap during Halloween, but they actually help save us from being overrun by insects. One nursing mother bat can gorge herself on more than 4,000 insects a night! They’re also important pollinators. Sadly, despite efforts to protect them, these small, furry, nighttime mammals are disappearing from North America due to disease and other factors.

Researchers looked at populations of four species of bats in nine U.S. national parks in the Great Lakes area. They published their results in the October 2024 issue of Biological Conservation. The authors used two different models for determining bat population trends: one based on activity and one based on space use. They found that though related, the two metrics could give different answers.

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This means that if land use managers relied on only one metric, they might reach a different conclusion than if they relied on the other. The study authors argue that activity and occurrence measurements are complementary but not interchangeable. Understanding the differences will help managers pick the right method for their needs.

Goodwin and others. 2024. Comparing Occupancy and Activity Metrics for Assessing Temporal Trends in Vulnerable Bat Populations. Biological Conservation 298: 110773.