Date of Award:

8-2024

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Committee Chair(s)

Daniel MacNulty

Committee

Daniel MacNulty

Committee

Mary Conner

Committee

Johan T. du Toit

Abstract

Moose (Alces alces) are the largest and only solitary members of the deer family. The species can be found across many northern regions around the world. Moose are considered to have high intrinsic, recreational and ecological value. In recent years, there have been concerns about declining moose populations in portions of the species circumpolar range. Moose in Utah (Alces alces shirasi) belong to the Shiras subspecies, which is the smallest of the four subspecies found in North America. Utah moose are the southernmost naturally occurring moose population in the world. The Utah Division of Wildlife Resources (UDWR) has been concerned about possible moose population declines in Utah and with collaboration from Utah State University they initiated a study that began in 2013. The initial phase of the study estimated vital rates that included pregnancy, calving rates, calf recruitment and adult survival along with maternal age and body condition. This initial study found that adults had relatively high survival rates and maternal age and body condition influenced reproductive rates. In addition, fluctuating reproductive rates were identified a potential source of population instability.

The research reported in this thesis represents the second phase of the moose study. My UWDR colleagues and I continued to collect data on moose vital rates and body condition. We also initiated a new effort to measure winter tick (Dermacentor albipictus) loads on radio-collared moose because observations and analyses during phase one of the study suggested that winter ticks were limiting population growth. In phase two of the study, I found evidence that winter ticks limited moose reproductive success. I found that poor body condition and high tick loads decreased rates of calving rates and calf survival. Pregnancy rates were affected but in unexpected ways.

Results from this study will help wildlife managers in achieving management objectives and help make future decisions. These results highlight the potential for winter ticks to limit the population growth of moose in Utah via reduced reproductive success. My results also suggest that the impact of winter ticks on reproductive success is mediated to some extent by maternal body condition, such that moose in excellent condition are more likely to overcome the harmful effects of winter ticks on reproduction.

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