Moose abundance and calf:cow ratios on the Blackfeet Indian Reservation and Glacier National Park

Magee, Landon

Many moose (Alces alces; Sikihtsisoo) populations across North America, especially along their southern range, are declining due to factors such as climate change, parasites and disease, predation, habitat loss and degradation, and overharvest. These declines highlight broader ecological concerns, as moose play a critical role as prey within their ecosystems. Despite their importance, data on crucial demographic parameters like abundance and age ratios are sparse for moose, complicating management efforts. Conventional monitoring methods, including radio-collaring, harvest data, public surveys, and aerial surveys, face significant logistical and financial challenges, and often fail to provide a comprehensive understanding of moose demographics due to the species' solitary, low-density nature and preference for dense habitats. This study proposes a cost-effective alternative by evaluating the use of camera traps to estimate moose abundance and calf:cow ratios. In 2022, we randomly deployed 100 trail cameras across the Blackfeet Indian Reservation and Glacier National Park. Using time-lapse images collected from 13 July to 13 September, we used a space-to-event (STE) model to estimate adult moose abundance and summer calf:cow ratios to serve as a proxy for calf recruitment. We estimated a total of 284 (95% CI: 204–397) adult (≥ 1-yr old) moose — including bulls, cows, and unidentified individuals — within our study area. Further analysis yielded a total of 183 adult females (95% CI: 121-277) and 42 calves (95% CI: 18-96) in our study area, resulting in a summer calf:cow ratio of 0.23 (var = 0.013) calves per adult female. Our study demonstrates the STE model's effectiveness in providing robust estimates of important moose demographics, especially with sparse data. We recommend further research examine solutions for reducing biases from repeated observations and to extend the sampling duration to better capture changes in population structure. We also suggest careful consideration of the timing of sampling to ensure demographic closure. To our knowledge, our study was the first to evaluate the use of camera trap data in a STE model framework to estimate abundance and age ratios for a moose population. These results also provide the first available demographic data for moose on the Reservation and in the Park