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 age terms in CR models despite past studies suggesting age influences detection probability. This paper explores how failing to account for age in the detection function of an open, spatially-explicit CR model, introduced in Efford & Schofield (2019), affects estimates of apparent survival, apparent recruitment, population growth, and grizzly bear home-range sizes. Using a simulation study, it was found that estimates of all parameters of interest excluding home-range size were robust to this omission. The effects of using two different types of detectors for data collection (bait sites and rub objects) on bias in estimates of above parameters was also explored via simulation. No evidence was found that one detector type was more prone to producing biased parameter estimates than the other.