[MARMAM] review on Estimating animal population density using passive acoustics

Tiago Marques tiago at mcs.st-and.ac.uk
Sat Dec 1 05:03:17 PST 2012

Dear MARMAMers,

This recent paper still in early view might be of interest to some of you.

Marques, T. A.; Thomas, L.; Martin, S. W.; Mellinger, D. K.; Ward, J. 
A.; Moretti, D. J.; Harris, D. & Tyack, P. L. (2012) Estimating animal 
population density using passive acoustics Biological Reviews. DOI: 

Abstract follows below. A pdf is available upon request.

This output is closely related to DECAF, a large project on passive 
acoustics density estimation, which ended a couple of years ago. 
Additional resources and outputs can be found in DECAF's webpage


which includes links to pdfs of papers on related issues.

All the best


Reliable estimation of the size or density of wild animal populations is 
very important for effective wildlife management, conservation and 
ecology. Currently, the most widely used methods for obtaining such 
estimates involve either sighting animals from transect lines or some 
form of capture-recapture on marked or uniquely identifiable 
individuals. However, many species are difficult to sight, and cannot be 
easily marked or recaptured. Some of these species produce readily
identifiable sounds, providing an opportunity to use passive acoustic 
data to estimate animal density. In addition, even for species for which 
other visually based methods are feasible, passive acoustic methods 
offer the potential for greater detection ranges in some environments 
(e.g. underwater or in dense forest), and hence potentially better 
precision. Automated data collection means that surveys can take place 
at times and in places where it would be too expensive or dangerous to 
send human observers. Here, we present an overview of animal density 
estimation using passive acoustic data, a relatively new and 
fast-developing field. We review the types of data and methodological 
approaches currently available to researchers
and we provide a framework for acoustics-based density estimation, 
illustrated with examples from real-world case studies. We mention 
moving sensor platforms (e.g. towed acoustics), but then focus on 
methods involving sensors at fixed locations, particularly hydrophones 
to survey marine mammals, as acoustic-based density estimation research 
to date has been concentrated in this area. Primary among these are 
methods based on distance sampling and spatially explicit 
capture-recapture. The methods are also applicable to other aquatic and 
terrestrial sound-producing taxa.
We conclude that, despite being in its infancy, density estimation based 
on passive acoustic data likely will become an important method for 
surveying a number of diverse taxa, such as sea mammals, fish, birds, 
amphibians, and insects, especially in situations where inferences are 
required over long periods of time. There is considerable work ahead, 
with several potentially fruitful research areas, including the 
development of (i) hardware and software for data acquisition, (ii) 
efficient, calibrated, automated detection and classification systems, 
and (iii) statistical approaches optimized for this application. 
Further, survey design will need to be developed, and research is needed 
on the acoustic behaviour of target species. Fundamental research on 
vocalization rates and group sizes, and the relation between these and 
other factors such as season or behaviour state, is critical. Evaluation 
of the methods under known density scenarios will be important for 
empirically validating the approaches presented here.

Key words: acoustic surveys, bioacoustics, density estimation, distance 
sampling, passive acoustic monitoring, spatially explicit 
capture-recapture, fixed sensors, hydrophones.


Tiago André Marques
Research Unit for Wildlife Population Assessment
Centre for Research into Ecological and Environmental Modelling
University of St Andrews
The Observatory
Buchanan Gardens
St Andrews
Fife KY16 9LZ

Tel: 00441334461842 Fax: 00441334461800 (Scotland office)
Tel: 00351210198736 (Portugal home)


The University of St Andrews is a charity registered in Scotland : No 

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