Biological Invasions

, Volume 20, Issue 4, pp 877–890 | Cite as

Quantifying site-level usage and certainty of absence for an invasive species through occupancy analysis of camera-trap data

  • Amy J. DavisEmail author
  • Ryan McCreary
  • Jeremiah Psiropoulos
  • Gary Brennan
  • Terry Cox
  • Andrew Partin
  • Kim M. Pepin
Original Paper


Efficient implementation of management programs for invasive species depends on accurate surveillance for guiding prioritization of surveillance and control resources in space and time. Occupancy probabilities can be used to determine where surveillance should occur. Conversely, knowledge of the certainty of site-level absence is of special interest in situations where the objective is to completely remove populations despite substantial risk of re-invasion. Indeed, the decision to shift from emphasizing control activities over the full range to emphasizing reinvasion prevention, surveillance, and response near the borders, depends on accurate knowledge of absence across space. We used a dynamic occupancy model to monitor changes in the distribution of an invasive species, feral swine (Sus scrofa), based on camera-trap data collected as part of a management program from June 2014 to January 2016 in San Diego County, California. Site usage of feral swine declined overall. The most informative predictors of site usage were spatial (latitude and longitude). Site-level non-usage rates increased over time and in response to management removal efforts; and site-level usage rates were heavily impacted by having neighboring sites that were used. Combining the detection probability estimated from the occupancy model and Bayes Theorem, we demonstrated how certainty of local (site-level) absence can be estimated iteratively in time in areas with negative surveillance (no detections) data. Our framework provides a means for using management-based surveillance data to quantify certainty of site-level absence of an invasive species, allowing for adaptive prioritization of surveillance and control resources. Our approach is flexible for application to other species and types of surveillance (e.g., track-plates, eDNA).


Camera trap Dynamic occupancy Elimination Eradication Invasive species Surveillance Sus scrofa 



Funding was provided by the U.S. Department of Agriculture Animal and Plant Health Inspection Service Wildlife Services division. Thanks to the Wildlife Services personal: Joe Albee, and Chris Freitas, who collected and organized the data for this project. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. government.

Data archiving

Data associated with this manuscript will be archived in Dryad Data Repository.

Supplementary material

10530_2017_1579_MOESM1_ESM.docx (526 kb)
Supplementary material 1 (DOCX 525 kb)


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Copyright information

© Springer International Publishing AG (outside the USA) 2017

Authors and Affiliations

  1. 1.National Wildlife Research CenterUSDA, APHISFort CollinsUSA
  2. 2.Wildlife ServicesUSDA, APHISEl CajonUSA

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