Methods for wildlife monitoring in tropical forests: Comparing human observations, camera traps, and passive acoustic sensors

Joeri A. Zwerts*, P. J. Stephenson, Fiona Maisels, Marcus Rowcliffe, Christos Astaras, Patrick A. Jansen, Jaap Waarde, Liesbeth E. H. M. Sterck, Pita A. Verweij, Tom Bruce, Stephanie Brittain, Marijke Kuijk

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review


Wildlife monitoring is essential for conservation science and data-driven decision-making. Tropical forests pose a particularly challenging environment for monitoring wildlife due to the dense vegetation, and diverse and cryptic species with relatively low abundances. The most commonly used monitoring methods in tropical forests are observations made by humans (visual or acoustic), camera traps, or passive acoustic sensors. These methods come with trade-offs in terms of species coverage, accuracy and precision of population metrics, available technical expertise, and costs. Yet, there are no reviews that compare the characteristics of these methods in detail. Here, we comprehensively review the advantages and limitations of the three mentioned methods, by asking four key questions that are always important in relation to wildlife monitoring: (1) What are the target species?; (2) Which population metrics are desirable and attainable?; (3) What expertise, tools, and effort are required for species identification?; and (4) Which financial and human resources are required for data collection and processing? Given the diversity of monitoring objectives and circumstances, we do not aim to conclusively prescribe particular methods for all situations. Neither do we claim that any one method is superior to others. Rather, our review aims to support scientists and conservation practitioners in understanding the options and criteria that must be considered in choosing the appropriate method, given the objectives of their wildlife monitoring efforts and resources available. We focus on tropical forests because of their high conservation priority, although the information put forward is also relevant for other biomes.
Original languageEnglish
Article numbere568
Pages (from-to)1-19
JournalConservation Science and Practice
Issue number12
Early online date2 Nov 2021
Publication statusPublished - Dec 2021


  • Automated classification
  • camera trapping
  • evidence-based conservation
  • passive acoustic monitoring
  • wildlife conservation
  • wildlife monitoring methods


Dive into the research topics of 'Methods for wildlife monitoring in tropical forests: Comparing human observations, camera traps, and passive acoustic sensors'. Together they form a unique fingerprint.

Cite this