Assessing the Performance of an Open Spatial Capture-Recapture Method on Grizzly Bear Populations When Age Data is Missing.
It is often difficult in capture-recapture (CR) studies of grizzly bear populations to determine the age of detected bears. As a result, analyses often omit including age terms in CR models fit, despite past studies suggesting that age likely influences grizzly bear detection probability. This paper explores how failing to account for an age term in the detection function of an open, spatially-explicit CR model first introduced in Efford & Schofield (2019), affects this model’s estimates of apparent survival, apparent recruitment, population growth rate, and grizzly bear home-range sizes. A simulation study was conducted to accomplish this, with simulated data being partially based on the results of CR models fit to detection histories from a long-running grizzly bear monitoring program in south-eastern British Columbia. The effect of using different types of detectors to collect grizzly bear detection data on overall bias in this model’s parameter estimates was also explored.