Continuing research on cause-specific mortality and annual survival of moose (Alces alces) calves in northeastern Minnesota, USA, is important to understanding the long-term trajectory of the population. In 2013 and 2014, we observed global positioning system (GPS)-collared, female moose exhibit a specific behavior (i.e., mortality movement) associated with the death of their GPS-collared neonate. The females made a rapid, long-distance movement (flee), followed by a return to the calf mortality site. We used characteristics of this movement in 2013–2014 (n = 46) to develop models for assessing calf survival, and then evaluated these models using female movement rates (n = 49) in 2015−2016. Using this behavior as an indicator of calf mortality in 2016, we conducted field investigations, leading to evidence of 15 mortalities at a mean age of 30.6 ± 15.5 (SE) days (range = 3–243 days). We launched 21 investigations in response to a mortality movement and they resulted in confirmation of 11 of the 15 calf mortalities. Specific causes of mortality included 9 wolf (Canis lupus)-kills, 3 black bear (Ursus americanus)-kills, 1 unknown predator-kill, and 2 deaths following vehicle collisions. The mean distance females fled after a mortality was 1,873 ± 412 m (range = 126–5,805 m, n = 14). Females that made return visits returned a mean 2.8 ± 0.5 times (range = 1–5, n = 8) to within a mean 106 ± 22 m (range = 34–230 m, n = 8) of the mortality site. Calf survival to 30 days of age was 67 ± 8% (95% CI = 53–84%, n = 36) but declined to 53 ± 8% (95% CI = 39–72%, n = 36) by 3 months of age. We developed 2 population-level movement models to improve the efficacy of using the mortality movement to identify and locate calf mortalities in real time via field investigations. The first approach, a temporal-based model, used a 3-day average movement velocity threshold (118 m/hr) for all females to indicate calf mortality and accurately predicted survival status in 51% (n = 105) of the cases. The second approach, an age-specific model using different thresholds (28–135 m/hr) for females relative to calf age, was 80% (n = 231) accurate. Using movement behavior of females to assess calf mortality yielded important insights into mechanisms influencing the population decline that will inform future management decisions.
Bibliographical noteFunding Information:
We thank B. D. Smith, J. L. Goethlich, and R. A. Willaert for their technical contributions to the fieldwork. We appreciate the Wildlife Health Program’s (M. Carstensen, M. H. Dexter, E. C. Hildebrand, C. S. Jennelle, and D. M. Plattner) cooperation during the calving season, and J. D. Forester’s preparation of the automated calving reports using 4‐hour fix rates. We also thank J. H. Giudice and V. St‐Louis for their data analysis expertise and M. A. Larson, L. J. Cornicelli, T. W. Arnold, and L. D. Mech for their guidance during this project. We are grateful to R. G. Wright for assistance with the buffered search areas using ArcMap, and L. J. Schmidt for providing microscopes for identifying hair samples. We also thank T. D. Gable and K. L. Pilgrim for hair and DNA analyses. We recognize all the observers who emailed us photos and information on calf sightings, including K. Crowley, J. Greenlee, and J. Hicks. This study was funded in part by the Minnesota Environmental and Natural Resources Trust Fund (ENRTF), the Wildlife Restoration (Pittman‐Robertson) Program, and MNDNR Section of Wildlife’s Wildlife Populations and Research Unit.
© The Wildlife Society, 2019
- Alces alces
- animal movement