Moose (Alces alces) are a species uniquely adapted to northern climates and are thought to be more susceptible to thermoregulatory constraints driven by warm, dry weather than many other northern ungulates (Weiskopf et al. 2019). Moose also face threats from winter ticks (Dermacentor albipictus) driven by warming summers and winters (Hoy et al. 2021; Samuel 2007). In response, moose have been expanding northward at the leading end of their geographic range in North America, likely due to increased food resources associated warming temperatures in the Alaskan tundra (Tape et al. 2016). On the trailing, southern end of the moose geographic range, however, population and distributional responses of moose to a warming climate and increased tick numbers are varied. Some moose populations are negatively impacted by a warming climate (Weiskopf et al. 2019); for example, moose in northern Minnesota have increased nutritional stress, reduced survival and productivity, and increased parasite loads (Murray et al. 2006). Conversely, other moose populations, including some in the western and northeastern U.S., have expanded their distribution and grown in population despite warming temperatures over the last century (Ruprecht et al. 2020; Teitelbaum et al. 2021). For example, an analysis of moose recruitment rates on the trailing edge of their distribution in the western U.S. showed that 10 of 18 herds did not exhibit temporal trends in recruitment, and weak to no effect of climate (Monteith et al. 2015). These varied responses of moose to climate and parasites across their distribution prompts the question -- how are these trailing edge populations succeeding despite warming climates, declining habitat suitability, and increased parasites? Are there spatial refugia or behavioral adaptations that allow moose to thrive in these changing conditions (Teitelbaum et al. 2021)? Moose in Utah are a prime example of range and population expansion despite a warming climate, seemingly suboptimal habitat, and increasing parasites. Moose began colonizing northern Utah in the early 1900s, and continued to strongly increase in abundance until the 1990s, stabilizing to current levels and potentially at or near carrying capacity (Ruprecht et al. 2020; Wolfe et al. 2010). Past research has suggested that moose in the western U.S. at the southern end of their range have reduced reproductive metrics compared to those in the more northerly part of their range (Ruprecht et al. 2016). Moose population growth in Utah was positively correlated with snow cover, presumably because these conditions reduced tick loads (Ruprecht et al. 2020). In addition, winter ticks have been found to impact moose reproductive success (Robertson 2022). However, it is unclear how changing climate conditions, habitat, density-dependence, and tick numbers will affect the movement, habitat, demography, and ultimately, the population trajectory of moose in Utah at the southern end of their range. Parasite infection, especially from the winter tick (Dermacentor albipictus) and arterial worm (Elaeophora schneideri) are of particular concern for moose populations (Samuel 2007; Wolfe et al. 2010). Tick infections can exceed 100,000 ticks per moose (Samuel & Welch 1991), causing extensive blood loss and potentially fatal anemia. Increasing reports of the arterial worm in moose also suggests that this filarial nematode, typically hosted by mule deer, is an emerging threat to moose populations. Transmitted by tabanid flies (e.g., deer flies), infection with this parasite can cause blindness, necrosis, and brain damage in moose (Grunenwald et al. 2018). Tick and tabanid fly distributions are both linked to environmental conditions, particularly temperature and moisture. Little is known about the environmental requirements and distribution of arterial worms (and their tabanid vectors) in Utah. The distribution and requirements of winter ticks are also poorly studied; however, recent work suggests that moose exhibit greater population growth when colder winters reduce tick survival (Ruprecht et al. 2020; Samuel 2007). Low temperatures should limit both tick and tabanid fly populations, suggesting that with increasingly warm winters, the persistent cold temperatures and snowpack at high elevations sites will create refugia from these two parasites. The present study will build on the work of (Robertson 2022; Ruprecht 2016) to better understand the factors governing the population dynamics of moose in Utah. A central hypothesis is that moose may be using spatial refugia or movement-related strategies to adapt to the warming climate and reduce parasite exposure (Teitelbaum et al. 2021). The rationale for the research is that information about the factors (including climate and parasites) that limit the distribution and population growth of Utah moose is necessary to set management objectives for the future.

1. Determine the climate and habitat factors which relate to tick numbers. a. Obtain estimates of tick exposure risk across elevations used by moose. b. Determine how environmental factors (e.g., temperature, snow depth, moisture) limit tick survival. c. Develop resource selection models for ticks to inform moose management in Utah. 2. Evaluate methods for non-lethal assessment of arterial worm risk to moose. a. Determine whether larval arterial worms (L3 stage) can be detected in tabanid fly vectors. b. If detectable, assess whether arterial worm transmission risk (a function of tabanid density and arterial worm prevalence) varies across elevation gradients. 3. Determine differences in dispersal, movement, and habitat use for moose. a. Develop resource selection and movement models to determine how climate factors and tick load relate to moose movement and habitat use. b. Obtain estimates of moose site fidelity, migration routes, and seasonal movements within and between units. c. Determine if there are spatial refugia and/or movement-related strategies that allow moose to adapt to changing climate factors and parasite exposure risk. 4. Determine how moose reproduction, recruitment, survival, and population growth rate are affected by climate factors, density-dependence, harvest, and tick loads. a. Develop an individually based, spatially-explicit integrated population model to understand how moose are impacted by climate factors and ticks across spatiotemporal scales. 5. Determine how moose distributions will change in response to climate and ticks. a. Develop resource selection models to understand how moose utilize habitat across the state to inform moose management in Utah.

Wasatch Unit

Strategy f of the population management goal states f. "Continue research projects to determine limiting factors to moose populations in Utah."

N/A

N/A

N/A

Moose Fieldwork For this study, in January 2026, we propose to capture 40 adult females and 20 8-month calves. This will allow us to track annual adult and calf survival rates, as well as investigate and determine cause of death when an animal dies. In January 2027 and January 2028, we plan to capture another 20 adults and 20 8-month old calves each year. This will ensure we have a sufficient sample to continue to monitor adult and calf survival annually for a total of 3 years. Additionally, approximately 10-15 of the adults captured in 2026 and 2027 will be recaptured animals. This will provide us with longitudinal data on a subset of the moose and provide data on how animals vary from year to year and how any variation may relate to their habitat use throughout the year. Captures will be conducted by the DWR contracted capture company using standard net-gunning techniques. Once a moose is captured, the capture company will transport UDWR employees/researchers to the captured animals for processing. Data collected from the animal will include age, sex, various body measurements, blood samples, tick loads, reproductive condition, and body condition (Cook et al. 2010). All animals will be processed as quickly as possible and released on site. Satellite GPS collars will be used and programmed to record a location every 2 hours and send data to researchers via satellite communication every 12 hours. The expected life of the GPS collar is 4-5 years. Using location data, we will be able to address questions regarding seasonal movements, site fidelity, migration routes, and a variety of important demographic parameters (survival by age/condition, resource selection, etc.). The collars will also send a notification when switched to mortality mode. All mortalities will be investigated as quickly as possible to determine the cause of death and collect any necessary samples (e.g., tick loads, arterial worms, tooth for aging, liver sample for mineral analysis, bone marrow, etc.). When feasible, live adult female ticks will be collected from mortalities to use in experiments assessing how environmental conditions (e.g., snow depth and temperature) effect tick fecundity and survival. Each year from May-August, ground personnel (1 USU graduate student and 1 USU technician) will monitor moose movements. When an animal forms a cluster and calving is expected to have occurred, ground crews will visually locate the moose to confirm whether a calf is present and, if so, whether it is a single or twins. We will continue to monitor moose throughout the summer initially observing every week or so through mid-July and every 2 weeks through August. We will also attempt to monitor calves monthly through December. This will provide us with estimates of summer and 6-month calf survival. Finally, each March/April, we will use a combination of ground and helicopter surveys to determine annual calf survival and recruitment. These surveys will also be used to evaluate the amount of hair loss in moose and the visual impacts of winter tick infestation. Ground personnel will also monitor adult female survival and conduct field examinations of any moose mortalities to determine likely cause of death. All field necropsies will be conducted as soon after death as possible. Necropsy samples will be sent to the Utah Veterinary Diagnostics Lab for more detailed analysis, with additional sequencing-based parasite identifications conducted in the Weinstein lab. Parasite Fieldwork As time permits during this summer field period, ground personnel will also set out canopy traps (Hribar et al. 1991) to collect tabanid flies. Flies will be frozen until they can be sorted, identified to genus, and subjected to DNA extraction. Extracted DNA will be screened for nematodes using a PCR reaction with the Nem18s primers and positive reactions will be sanger sequenced to identify nematodes (Grunenwald et al. 2018). Our preliminary work confirms that these primers amplify adult Elaeophora schneideri collected from moose in Utah, suggesting that they should also work for larval worms. Fly collections will be distributed across elevations and initially focus on wetter, riparian habitats where fly density is expected to be the highest. Testing this approach for estimating arterial worm exposure will lay the foundation for a future, more widespread survey to quantify spatial variation in disease risk. In the fall (September- November) of years 1 and 2, ground personnel (1 USU graduate student and 1 USU technician) will conduct tick surveys to determine how questing tick density varies with geographic and environmental variables. Preliminary surveys conducted by UDWR in 2018 suggest that tick density may peak between 7000-7500 ft in elevation (Robertson 2022). To determine if questing larvae exhibit consistent elevation patterns, tick abundance will be measured by dragging (flagging) a flannel sheet over vegetation along transects (Bergeron & Pekins 2014). Transects will be set across the distribution of elevations occupied by moose in both the spring (when ticks drop off) and fall (when new infections are acquired). Ticks will be collected in the field for later quantification and identification in the lab. Each transect site will be visited at least twice per season and questing tick surveys will continue through the entire questing period until winter conditions (i.e., substantial snowfall/freezing temperatures) kill remaining unattached larvae). A subset of collected larval ticks will be used for experiments to evaluate how relevant environmental conditions (i.e., moisture, temperature, snowfall) effect survival of questing ticks. Analysis Results from experiments with adult and larval ticks will be analyzed using regression models to identify how tick survival varies with environmental conditions. Using field survey data, we will test whether tick density significantly differs by elevation and other measured factors. We will build resource selection functions to determine how climate and habitat factors relate to tick density across the Wasatch to help inform moose management. Subsequently, these data on tick habitat use, niche space, and distribution will then be used to help parameterize moose-focused models described below. We will use moose movement data and movement modeling packages in R (e.g., "moveHMM") to determine moose movement related-strategies in response to changing climate factors, parasites, and other human-use and landscape variables. In addition, we will use resource selection functions in R to understand how moose habitat use/distributions respond to climate and ticks. We will use Bayesian survival and reproduction models in the R package "nimble" to estimate moose demography in response to age, body condition, climate, and ticks. Lastly, we will build individually-based, spatially-explicit integrated population models (Chandler & Clark 2014) using both movement and demographic data to understand how moose are impacted and adapt to climate factors and tick loads across space and time.

Moose will be monitored by GPS collars and ground and aerial surveys.

This project is a partnership with DWR, USU, and conservation organizations.

Results of this study will further our understanding of limiting factors for moose in Utah and will allow us to implement management strategies to improve moose populations across the state.

N/A