Maternal Behavior Indicates Survival and Cause-Specific Mortality of Moose Calves

• Published in: The Journal of wildlife management 2019-05, Vol.83 (4), p.790-800
• Main Authors: OBERMOLLER, TYLER R., DELGIUDICE, GLENN D., SEVERUD, WILLIAM J.
• Format: Article
• Language: English
• Subjects: Age; Alces alces; animal movement; Bears; behavior; calf; Calves; Featured Article; Females; Field investigations; Field tests; Global positioning systems; GPS; Maternal behavior; Moose; Mortality; neonates; Population decline; Satellite navigation systems; Survival; Wildlife; Wildlife management
• ISSN: 0022-541X; 1937-2817
• DOI: 10.1002/jwmg.21658

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 ± 412m (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.