Date of Award

8-16-2024

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Wildlife Ecology and Wildlife Conservation

Advisor

Sabrina Morano

Second Committee Member

Pauline Kamath

Third Committee Member

Erin Simons-Legaard

Abstract

The moose (Alces alces) population in the northeastern United States has experienced regional declines in recent years, primarily due to parasitism by winter ticks (Dermacentor albipictus). Three factors drive winter tick epizootics: climate change, moose density, and overlap in moose seasonal space use. Previous research has shown that moose density increases with the proportion of optimal habitat (regenerating forest stands) available on the landscape, and average individual tick load is positively correlated with moose density. We used data from GPS-collared moose from 2014–2022 in Maine to explore relationships between moose space use, seasonal overlap, climate, and tick loads on moose.

For Chapter 1, we identified drivers of seasonal moose space use and overlap moose corresponding to the drop-off (spring) and questing (fall) periods of winter ticks. We modeled seasonal home and core range area and seasonal home range overlap, using generalized linear models, and modeled habitat selection of overlap areas using resource selection functions. Fall area increased with precipitation and decreased with later first frost dates. Juveniles had larger fall areas than adults. Spring area decreased with the availability of optimal habitat (forest aged 4-20 years) and snow depth, and it increased with the availability of older forest (aged 21-37 years). Seasonal overlap was positively correlated with the availability of older forest and negatively correlated with snow depth and percent hardwood. Moose selected for optimal habitat within overlap areas compared to the surrounding landscape. Our findings indicate that moose concentrate space use in optimal habitat. Additionally, moose appeared to overlap less in areas with more hardwood, likely due to habitat preferences during the leaf-off season. These results provide insight into demographic and environmental drivers of moose seasonal space use, which play a role in the winter tick system.

In Chapter 2, we modeled tick loads on moose as a function of fall space use, spring-fall home range overlap, and weather variables. To examine the effects of space use and overlap, we made inferences about moose behavior in the period prior to capture based on data from collared individuals after capture. We used generalized linear mixed models to analyze these relationships. Fall precipitation was negatively correlated with tick loads on moose, while late summer drought and snow depth in early spring had positive effects on tick loads. Tick loads were lower on individuals that generally had higher percentages of hardwood in their fall home ranges. Moose with higher seasonal overlap on average had higher tick loads. Our results support the hypothesis that the degree to which moose overlap space use between drop-off and questing seasons may expose individuals to higher tick loads due to re-infection. Additionally, the observed relationship between percent hardwood and tick loads suggests that forest type may affect tick distribution and moose exposure. We recommend that future research focus on winter tick distribution and survival on the landscape at different life stages. Overall, results from this study build upon previous research in the moose-winter-tick system, highlighting the potential importance of space use in parasite transmission.

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