Natural Resources, School of

 

Document Type

Article

Date of this Version

9-15-2019

Citation

2019 The Authors.

Comments

https://doi.org/10.1016/j.gecco.2019.e00792 D. Ngoprasert et al. / Global Ecology and Conservation 20 (2019) e00792

Abstract

Large carnivores are declining globally and require baseline population estimates for management, however large-scale population estimation is problematic for species without unique natural marks. We used camera trap records of dhole Cuon alpinus, a group-living species, from three national parks in Thailand as a case study in which we develop integrated likelihood models to estimate abundance incorporating two different data sets, count data and detection/non-detection data. We further investigated relative biases of the models using different proportions of data with lower versus higher quality and assessed parameter identifiability. The simulations indicated that the relative bias on average across 24 tested scenarios was 2% with a 95% chance that the simulated data sets obtained the true animal abundances. We found that bias was high (>10%) when sampling 60 sites with only 5 sampling occasions. We tested four additional scenarios with varying proportions of count data. Our model tolerated the use of relatively low proportions of the higher quality count data, but below 10% the results began to show bias (>6%). Data cloning indicated that the parameters were identifiable with all posterior variances shrinking to near zero. Our model demonstrates the benefits of combining data from multiple studies even with different data types. Furthermore, the approach is not limited to camera trap data. Detection/non-detection data from track surveys or counts from transects could also be combined. Particularly, our model is potentially useful for assessing populations of rare species where large amounts of by-catch datasets are available.

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