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Journal of the Acoustical Society of America / Volume 131 / Issue 1 / BIOACOUSTICS [80]

From echolocation clicks to animal density—Acoustic sampling of harbor porpoises with static dataloggers

J. Acoust. Soc. Am. Volume 131, Issue 1, pp. 550-560 (2012); (11 pages)

Line A. Kyhn1, Jakob Tougaard2, Len Thomas3, Linda Rosager Duve4, Joanna Stenback5, Mats Amundin6, Geneviève Desportes7, and Jonas Teilmann2

1Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
2Department of Bioscience, Aarhus University, DK-4000 Roskilde, Denmark
3Centre for Research into Ecological and Environmental Modeling, University of St. Andrews, St Andrews, KY16 9LZ, Scotland
4Department of Animal Science, Aarhus University, DK-8830 Tjele, Denmark
5Nyckelvägen 18, 554 72 Jönköping, Sweden
6Kolmården Djurpark, SE-618 92, Kolmården, Sweden
7GDnatur, DK-5300 Kerteminde, Denmark

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Monitoring abundance and population trends of small odontocetes is notoriously difficult and labor intensive. There is a need to develop alternative methods to the traditional visual line transect surveys, especially for low density areas. Here, the prospect of obtaining robust density estimates for porpoises by passive acoustic monitoring (PAM) is demonstrated by combining rigorous application of methods adapted from distance sampling to PAM. Acoustic dataloggers (T-PODs) were deployed in an area where harbor porpoises concurrently were tracked visually. Probability of detection was estimated in a mark–recapture approach, where a visual sighting constituted a “mark” and a simultaneous acoustic detection a “recapture.” As a distance could be assigned to each visual observation, a detection function was estimated. Effective detection radius of T-PODs ranged from 22 to 104 m depending on T-POD type, T-POD sensitivity, train classification settings, and snapshot duration. The T-POD density estimates corresponded to the visual densities derived concurrently for the same period. With more dataloggers, located according to a systematic design, density estimates would be obtainable for a larger area. This provides a method suitable for monitoring in areas with densities too low for visual surveys to be practically feasible, e.g., the endangered harbor porpoise population in the Baltic.

© 2012 Acoustical Society of America

ACKNOWLEDGMENTS

The following persons are thanked for a dedicated effort during data collection: Dania Wiesnewska, Daniel Wennerberg, Jakob Hansen Rye, Lisette Buholzer Søgaard, Nikolai Ilsted Bech, Nina Eriksen, Signe Sveegaard, and Trine Baier Jepsen. Oluf D. Henriksen is thanked for assistance with deployment and recovery of T-PODs in 2003. We thank the landowners at Fyns Hoved for access to the area and the Danish Forest and Nature agency for permission to conduct experiments. Magnus Wahlberg, Lee A. Miller, and Peter T. Madsen are thanked for loan of equipment and access to calibration tank. Thanks to Tiago Marques for contributing to the analysis framework at an early stage, and to Hanna Nuuttila and two anonymous reviewers for their helpful comments on the manuscript. This study was supported by the Danish Research Council for Strategic Research and the Danish Ministry of Environment.

Article Outline

  1. INTRODUCTION
  2. MATERIALS AND METHODS
    1. Theodolite observations
    2. Acoustic datalogger deployment
    3. T-POD data analysis
    4. Estimation of detection function
    5. Density estimation
    6. Independent visual estimate of density
  3. RESULTS
    1. False detection rate
    2. Detection functions
    3. Density estimates
  4. DISCUSSION

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KEYWORDS and PACS

Keywords

acoustic applications, echo, underwater sound

PACS

  • 43.80.Ev

    Acoustical measurement methods in biological systems and media

ARTICLE DATA

History
Received 24 Mar 2011
Accepted 19 Oct 2011
Revised 05 Oct 2011
Digital Object Identifier
http://dx.doi.org/10.1121/1.3662070

PUBLICATION DATA

ISSN

0001-4966 (print)  

Publisher

$abstract.society.value is a Member of CrossRef Acoustical Society of America

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