Thermal Imaging Reveals Significantly Smaller Brazilian Free-Tailed Bat Colonies Than Previously Estimated

By Margrit Betke, D. Hirsh, N. Makris, G. McCracken, M. Procopio, N. Hristov, Shuang-Li Tang, Angshuman Bagchi, Jonathan D. Reichard, Jason W. Horn and 3 more. Journal of Mammalogy, 2008

170 citations recorded by the source corpus.

Abstract Using data collected with thermal imaging technology, we found a major reduction in population estimates of colony size in the Brazilian free-tailed bat (Tadarida brasiliensis) from 54 million, obtained in 1957 without this technology, to 4 million in 6 major cave colonies in the southwestern United States. The 1957 census was based on human visual observations of cave emergence flights that were subject to potentially high errors. The recent census was produced using an accurate, reproducible counting method and based on complete temporal records of colony emergences. Analysis of emergence flights from dusk through darkness also revealed patterns in group behavior that would be difficult to capture without thermal infrared technology. Flow patterns of bats during emergence flights exhibited characteristic single, double, or triple episodes, with the peak flow during the 1st episode. A consistent rhythmic pattern of flow episodes and pauses was revealed across colonies and was independent of emergence tempo.

Subfields: Ecology, Ecology, Evolution, Behavior and Systematics

View Paper: https://www.semanticscholar.org/paper/5c1f6883773fe8606394f1092177cba8693f24ff

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Citations in the corpus

Perspectives in machine learning for wildlife conservation (2021, background): “For example, humans conducting counts of seabird colonies (12) and bats emerging from cave roosts (13) tend to significantly underestimate the number of individuals present.”
A comparison of bats and rodents as reservoirs of zoonotic viruses: are bats special? (2013, background): “Additionally, many bat species are gregarious, some living in dense aggregations: for example, some Mexican free-tailed bat (Tadarida brasiliensis mexicana) colonies can reach densities of 3000 bats per square metre, in populations of up to a million individuals per roost [12,13].”
Long-term monitoring of tropical bats for anthropogenic impact assessment: Gauging the statistical power to detect population change (2010, background): “However, current monitoring programs for bats are restricted to temperate regions and mostly limited in scope and scale, primarily focusing on single-species at a local level (Betke et al., 2008; Hristov et al., 2010; O’Shea and Bogan, 2003; Walsh et al., 2003).”
Infrared thermography: A non-invasive window into thermal physiology. (2016, unknown): “Similarly, although at a much larger scale, Betke et al. (2008) used IRT to monitor flight behaviour of whole colonies of Brazilian free-tailed bats, discovering emergence flights occurred at AC C EP TE D M AN U SC R IP T population-specific rhythms, as well as using IRT to enhance accuracy of…”
Conservation Ecology of Cave Bats (2016, background): “…aggregations are characteristic of molossid bats in caves in both Old and New Worlds and despite repeated efforts to harness modern technology such as Doppler radar (Horn and Kunz 2008) and thermal infrared video (Betke et al. 2008), accurate counting of the numbers involved has proved elusive.”