Effects Of Winter Ticks And Internal Parasites On Moose Survival And Fecundity In Vermont, Usa
Moose (Alces alces) have experienced considerable declines along the periphery of their range in the northeastern United States. In Vermont, the population declined by approximately 44% from 2010 to 2017 despite minimal hunter harvest and adequate habitat. Populations in New Hampshire and Maine have...
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| Format: | Text |
| Language: | English |
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UVM ScholarWorks
2020
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| Online Access: | https://scholarworks.uvm.edu/graddis/1196 https://scholarworks.uvm.edu/context/graddis/article/2196/viewcontent/DeBow_uvm_0243N_10996.pdf |
| Summary: | Moose (Alces alces) have experienced considerable declines along the periphery of their range in the northeastern United States. In Vermont, the population declined by approximately 44% from 2010 to 2017 despite minimal hunter harvest and adequate habitat. Populations in New Hampshire and Maine have shown similar declines, associated primarily with the impacts of winter ticks (Dermacentor albipictus). However, uncertainty exists about the effects of environmental and other parasite related conditions on moose survival and reproduction. I examined patterns of moose survival and productivity among a radio-collared population (n = 127) in Vermont from 2017 to 2019. In terms of productivity, I estimated pregnancy rates, birth rates, and neonate daily survival (the probability that a newborn would survive to day 60). Across years, pregnancy rates were estimated at 67% (95% CI = 0.51 - 0.82). The average birth rate was 0.64 offspring per adult female per year, but varied as a function of age and year, where the probability of giving birth increased with cow age. Neonate daily survival was estimated with a logistic exposure analytical framework, and closely associated with days since birth. Survival to day 60 was estimated at 0.65 (95% CI = 0.44 to 0.79). Observed adult survival of collared individuals was 90% in 2017 (27 of 30), 84% in 2018 (38 of 45), and 86% in 2019 (38 of 44), and observed winter calf survival was 60% in 2017 (18 of 30), 50% in 2018 (15 of 30), and 37% in 2019 (11 of 30). Most mortalities occurred in March and April, when winter tick engorgement on moose peaked. Necropsy analyses indicated that winter tick infestation was the primary cause of mortality (91% of calves, 25% of adults), and 32% of all mortalities had evidence of meningeal worm (Parelaphostrongylus tenuis). Known fates analyses of weekly calf survival (01 Jan – 18 May, n = 90) and monthly adult survival probability (Jan to Jan) confirmed that survival in both calves and adults was negatively related to winter ticks, and in the case of ... |
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