Assessing Abundance of a Cryptic Viper Using N-Mixture Models

Dreslik, Michael J. 

dreslik@illinois.edu

 

Illinois Natural History Survey                                                                                                                       

Prairie Research Institute                                                                                                                           

University of Illinois Urbana-Champaign                                                                                      

Champaign, Illinois, USA

 

Crawford, John A.   

National Great Rivers Research and Education Center

Alton, Illinois, USA

 

Baker, Sarah J.  

Arizona Game and Fish Department

Phoenix, Arizona, USA

 

For effective conservation and recovery, an adaptive management framework is often best when paired with monitoring population-level responses. In many species, monitoring abundances over time using traditional capture-mark-recapture (CMR) methods is logistically challenging. N-mixture models are an extension of the occupancy and detection probability framework and can estimate abundances across multiple populations. The models use raw abundance counts taken during surveys, model the distributions of capture frequencies, incorporate density-dependent effects, and can provide population estimates when recaptures are too few. When validated with traditional CMR estimates, they can provide robust estimates for multiple populations across the landscape. We chose to determine the effectiveness of an N-mixture modeling approach to generate population size estimates for the Eastern Massasaugas within the Carlyle Lake region in Illinois. Our results will be used to determine regional population trends and provide a foundation to assess the effectiveness of conservation actions.

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