Document Type

Thesis - University Access Only

Award Date

2007

Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

Abstract

Mist nets are commonly used to survey bat populations and to estimate bat biodiversity, but several studies have found that mist net capture data and methods are biased due to a number of factors, including size and placement of nets, and the frequency at which investigators check their nets (Francis 1989; Jenni and Leuenberger 1996; Kunz and Anthony 1977; Simmons and Voss 1998). Despite the wealth of literature and anecdotal reports, few investigators have quantified the interactions of bats with mist nets directly (Berry et al. 2004; Francis 1989; Kunz and Anthony 1977; Lang et al. 2004; Maccarthy et al. 2006). I employed night vision camcorders to monitor bat behavior when bats encountered a mist net and then utilized these data to re-evaluate years of survey data collected on Montserrat, Lesser Antilles. Observations were conducted on four successive nights at four different sites that provided evidence of avoidance-learning behavior. I recorded 2523 bat passes on 43.3 hours of videotape during work in July 2005 and June 2006. When a mist net was present, 5.4% of bats captured on film came into contact with the net giving an overall capture rate of 3.2% (range 0--10.3%). After observing the low capture rates, I decided to take a closer look at surveys conducted on Montserrat from 1994, 1997-98, and 2000-2006. The amount of effort expended in the 10 years of survey was important in determining numbers of bats being captured. Several species were not being caught on a regular basis on Montserrat; therefore a careful analysis of the previous surveys was conducted to find more species specific information. Using the Jamaican fruit-eating bat (Artibeus jamaicensis) as a reference species, I reassessed some assumptions about capture biases. Mist nets did not accurately sample bats utilizing flyways on Montserrat and such fieldwork thereby generated potentially misleading data. Mist nets are valuable tools used to survey bats, but the limitations of mist nets must be considered when choosing appropriate capture devices to study the bat fauna of a particular area. Biodiversity assessments and conservation guidelines based on short-term mist net surveys alone are not sufficient or reliable. The pragmatic solution is to repeatedly sample a target region in different seasons and years, utilize various netting sites and net sets, carefully analyze species over time, and quantify and account for biases in sampling methods.

Library of Congress Subject Headings

Bats -- Monitoring -- Montserrat

Bird surveys -- Montserrat

Mist netting

Format

application/pdf

Number of Pages

73

Publisher

South Dakota State University

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