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Rosenblatt, E., R. Mickey, S. Creel, K. Gieder, J. Murdoch, and T. Donovan. 2023. Advances in wildlife abundance estimation using pedigree reconstruction. Ecology and Evolution 13(10):e10650.
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October 2023
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The conservation and management of wildlife populations, particularly for threatened and endangered species are greatly aided with abundance, growth rate, and density measures. Traditional methods of estimating abundance and related metrics represent trade-offs in effort and precision of estimates. Pedigree reconstruction is an emerging, attractive alternate approach because its use of one-time, noninvasive sampling of individuals to infer the existence of unsampled individuals. However, advances in pedigree reconstruction could improve its utility, including forming a measure of precision for the method, establishing required spatial sampling effort for accurate estimates, ascertaining the spatial extent of abundance estimates derived from pedigree reconstruction, and assessing how population density affects the estimator's performance. Using established relationships for a stochastic, spatially explicit simulated moose (<i>Alces americanus</i>) population, pedigree reconstruction provided accurate estimates of the adult moose population size and trend. Novel bootstrapped confidence intervals performed as expected with intensive sampling but underperformed with moderate sampling efforts that could produce abundance estimates with low bias. Adult population estimates more closely reflected the total number of adults in the extant population, rather than number of adults inhabiting the area where sampling occurred. Increasing sampling effort, measured as the proportion of individuals sampled and as the proportion of a hypothetical study area, yielded similar asymptotic patterns over time. Simulations indicated a positive relationship between animal density and sampling effort required for unbiased estimates. These results indicate that pedigree reconstruction can produce accurate abundance estimates and may be particularly valuable for surveying smaller areas and low-density populations.
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Rosenblatt, E., K. Gieder, T. Donovan, J. Murdoch, T. Smith, M. Heaton, T. Kalbfleisch, B. Murdoch, S. Bhattarai, E. Pacht, E. Verbist, V. Basnayake, and S. McKay. 2023. Genetic diversity and connectivity of moose (Alces alces americana) in eastern North America. Conservation Genetics 24:235-248.
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January 2023
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Rosenblatt, E., J. DeBow, J. Blouin, T. Donovan, J. Murdoch, S. Creel, W. Rogers, K. Gieder, N. Forti, and C. Alexander. Juvenile moose (Alces alces) stress and nutrition dynamics relate to landscape characteristics, climate-mediated factors, and survival. Conservation Physiology 9:coab048.
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July 2021
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Moose populations in the northeastern United States have declined over the past 15 years, primarily due to the impacts of winter ticks. Research efforts have focused on the effects of winter tick infestation on moose survival and reproduction, but stress and nutritional responses to ticks and other stressors remain understudied. We examined the influence of several environmental factors on moose calf stress hormone metabolite concentrations and nutritional restriction in Vermont, USA. We collected 407 fecal and 461 snow urine samples from 84 radio-collared moose calves in the winters of 2017–2019 (January–April) to measure fecal glucocorticoid metabolites (fGCM) concentrations and urea nitrogen:creatinine (UN:C) ratios. We used generalized mixed-effects models to evaluate the influence of individual condition, winter ticks, habitat, climate and human development on stress and nutrition in calf moose. We then used these physiological data to build generalized linear models to predict calf winter survival. Calf fGCM concentrations increased with nutritional restriction and snow depth during adult winter tick engorgement. Calf UN:C ratios increased in calves with lighter weights and higher tick loads in early winter. Calf UN:C ratios also increased in individuals with home ranges composed of little deciduous forests during adult winter tick engorgement. Our predictive models estimated that winter survival was negatively related to UN:C ratios and positively related to fGCM concentrations, particularly in early winter. By late March, as winter ticks are having their greatest toll and endogenous resources become depleted, we estimated a curvilinear relationship between fGCM concentrations and survival. Our results provide novel evidence linking moose calf stress and nutrition, a problematic parasite and challenging environment and winter survival. Our findings provide a baseline to support the development of non-invasive physiological monitoring for assessing environmental impacts on moose populations.
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Pearman-Gillman, S., M. Duveneck, J. Murdoch, and T. M. Donovan. 2020. Species distribution changes under alternative landscape futures: Using a scenario framework to identify drivers and consequences of landscape change on wildlife in New England. Frontiers in Ecology and Evolution 8:164. doi: 10.3389/fevo.2020.00164.
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June 2020
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In an era of rapid climate and land transformation, it is increasingly important to understand how future changes impact natural systems. Scenario studies can offer the structure and perspective needed to understand the impacts of change and help inform management and conservation decisions. We implemented a scenario-based approach to assess how two high impact drivers of landscape change influence the distributions of managed wildlife species (<i>n</i> = 10) in the New England region of the northeastern United States. We used expert derived species distribution models (SDMs) and scenarios developed by the New England Landscape Futures Project (NELFP) to estimate how species distributions change under various trajectories (<i>n</i> = 5) of landscape change. The NELFP scenarios were built around two primary drivers – Socio-Economic Connectedness (SEC) and Natural Resource Planning and Innovation (NRPI) – and provide plausible alternatives for how the New England region may change over 50 years (2010–2060). Our models generally resulted in species occurrence and richness declines by 2060. The majority of species (7 of 10) experienced declines in regional occurrence for all NELFP scenarios, and one species experienced a projected increase in mean regional occurrence for all scenarios. Our results indicate that the NRPI and SEC drivers strongly influenced projected distribution changes compared to baseline projections. NRPI had a greater impact on distribution change for five species (coyote, moose, striped skunk, white-tailed deer, and wild turkey), while SEC had a greater impact on four species (American black bear, bobcat, raccoon, and red fox); one species (gray fox) was equally influenced by both NRPI and SEC. These results emphasize the importance of integrating both natural resource planning and socio-economic factors when addressing issues of distribution change and offer insights that can inform proactive management and conservation planning.
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Pearman-Gillman, S., M. Duveneck, J. Murdoch, and T. Donovan. 2020. Wildlife resistence and protection in a changing New England landscape. PLOS ONE 15(9): e0239525. https://doi.org/10.1371/journal.pone.0239525
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September 2020
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Rapid changes in climate and land use threaten the persistence of wildlife species. Understanding where species are likely to occur now and in the future can help identify areas that are resistant to change over time and guide conservation planning. We estimated changes in species distribution patterns and spatial resistance in five future scenarios for the New England region of the northeastern United States. We present scenario-specific distribution change maps for nine harvested wildlife species, identifying regions of increasing, decreasing, or stable habitat suitability within each scenario. Next, we isolated areas where species occurrence probability is high (p > 0.7) and resistant to change across all future scenarios. Resistance was also evaluated relative to current land protection to identify patterns in and out of Protected Areas (PAs). Generally, species distributions declined in area over the 50-year assessment period (2010–2060), with the greatest average declines occurring for moose (-40.9%) and wild turkey (-22.1%). Species resistance varied considerably across the region, with coyote demonstrating the highest average regional resistance (91.81% of the region) and moose demonstrating the lowest (0.76% of the region). At the state level, average focal species resistance was highest in Maine (the largest state) and lowest in Massachusetts. Many of the focal species showed high overlap in resistance and land protection. Coyote, white-tailed deer, and black bear had the highest probability of resistance, given protection, while moose and wild turkey had the highest probability of protection, given resistance. Overall, relatively small portions of New England—ranging between 0.25% and 21.12%–were both protected and resistant for the focal species. Our results provide estimates of resistance that can inform conservation planning for commonly harvested species that are important ecologically, economically, and culturally to the region. Expanding protected area coverage to include resistant areas may provide longer term benefits to these species.
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Pearman-Gillman, S, J. E. Katz, R. Mickey, J. Murdoch, and T. Donovan. 2020. Predicting wildlife distribution patterns in New England USA with expert elicitation techniques. Global Ecology and Conservation 21:e00853.
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March 2020
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Understanding the impacts of landscape change on species distributions can help inform decision-making and conservation planning. Unfortunately, empirical data that span large spatial extents across multiple taxa are limited. In this study, we used expert elicitation techniques to develop species distribution models (SDMs) for harvested wildlife species (n = 10) in the New England region of the northeastern United States. We administered an online survey that elicited opinions from wildlife experts on the probability of species occurrence throughout the study region. We collected 3396 probability of occurrence estimates from 46 experts, and used linear mixed-effects methods and landcover variables at multiple spatial extents to develop SDMs. The models were in general agreement with the literature and provided effect sizes for variables that shape species occurrence. With the exception of gray fox, models performed well when validated against crowdsourced empirical data. We applied models to rasters (30 × 30 m cells) of the New England region to map each species’ distribution. Average regional occurrence probability was highest for coyote (0.92) and white-tailed deer (0.89) and lowest for gray fox (0.42) and moose (0.52). We then stacked distribution maps of each species to estimate and map focal species richness. Species richness (<i>s</i>) varied across New England, with highest average richness in the least developed states of Vermont (<i>s</i> = 7.47) and Maine (s = 7.32), and lowest average richness in the most developed states of Rhode Island (s = 6.13) and Massachusetts (s = 6.61). Our expert-based approach provided relatively inexpensive, comprehensive information that would have otherwise been difficult to obtain given the spatial extent and range of species being assessed. The results provide valuable information about the current distribution of wildlife species and offer a means of exploring how climate and land-use change may impact wildlife in the future.
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DeBow, J., J. Blouin, E. Rosenblatt, K. Gieder, W. Cottrell, J. Murdoch, and T. Donovan. 2021. Effects of winter ticks and internal parasites on moose survival in Vermont, USA. Journal of Wildlife Management. DOI: 10.1002/jwmg.22101
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August 2021
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Moose (<i>Alces alces</i>) have experienced considerable declines along the periphery of their range in the northeastern United States. In Vermont, the population declined 45% from 2010 to 2017 despite minimal hunter harvest and adequate habitat. Similarly, nearby populations recently experienced epizootics characterized by >50% mortality. Declines have largely been associated with the effects of winter ticks (<i>Dermacentor albipictus</i>), but uncertainty exists about the effects of environmental and other parasite-related conditions on moose survival. We examined patterns of moose survival among a radio-collared population (<i>n</i> = 127) in Vermont from 2017 to 2019. Our objectives were to estimate causes of mortality and model survival probability as a function of individual and landscape variables for calves (<1 yr) and adults (≥1 yr). Observed adult survival was 90% in 2017, 84% in 2018, and 86% in 2019, and winter calf survival was 60% in 2017, 50% in 2018, and 37% in 2019. 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 (<i>Parelaphostrongylus tenuis</i>). Other sources of mortality such as vehicles, harvest, predation, deep snow, and other parasitic infections were negligible. The best supported calf model included sex differences and negative effects of tick engorgement (%/week) and parasite level (roundworm and lungworm). The best supported adult model included the effect of cumulative tick engorgement (cumulative %/week), which negatively affected survival. Our results indicate that winter tick engorgement strongly affects survival, and is probably compounded by the presence of meningeal worm and other parasites. Reduced tick effects may be achieved by decreasing moose density through harvest and managing late winter habitat to minimize tick density. Management of white-tailed deer (<i>Odocoileus virginianus</i>) density may also affect the transmission of meningeal worm.
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DeBow, J., J. Blouin, E. Rosenblatt, K. Gieder, J. Murdoch, and T. Donovan. 2023. Birth Rates and Calf Survival in a Parasite Rich Moose Herd in Vermont, USA. Alces 58: 51–73.
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February 2023
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Moose (<i>Alces alces</i>) populations have recently declined across the southern portion of their geographic range in North America. In Vermont and other northeastern U.S. states, declines have been attributed to low survival rates driven primarily by winter tick (<i>Dermacentor albipictus</i>), which may also affect birth rate and survival of new calves. We radio-collared and monitored 75 female moose (38 calves and 37 adults) in Vermont from 2017 to 2020 and examined the effects of physiological conditions and spatial and temporal factors on adult birth rates. Physiological measures included fecal glucocorticoid metabolites concentrations (fGCM), which reflect stress, and urine urea nitrogen:creatinine ratio (UN:C), which proxies nutritional state. The pregnancy rate at capture across years was 0.67 (95% CI = 0.50 – 0.80), and negatively influenced by the presence of lungworm (<i>Dictyocaulus </i>spp.). Birth rates, calculated as the average number of offspring delivered per adult female, were < 1.0 overall, did not differ among years (2017-2020, LCI = 0.22, UCI = 0.86), but differed by adult age class, where rates increased with age. We further evaluated daily calf survival rates to age 60 days, the point at which calves become independent of direct care. Logistic exposure models indicated that daily calf survival increased as Julian birth date and days since birth increased (log odds = 0.0819, SE = 0.0215). The per capita independence rate (the rate at which adult females add independent calves to the population) was negatively influenced by average UN:C ratios and positively influenced by fGCM levels. Further, this rate was related to the habitat conditions in home ranges of adult females during the fall, when ticks attach to moose. Specifically, female adults whose fall home ranges were characterized by high levels of mature (canopy) evergreen forests and wetland habitats, and low levels of mixed forests and elevation, had a higher, average binomial success rate in adding an independent calf into the population than those whose home ranges consisted of high levels of mixed forest at high elevation. Our results suggest that winter ticks negatively affect fecundity, and that efforts to reduce parasite loads on individual moose (e.g., directly by reducing moose density or indirectly through habitat alteration) may improve productivity and recruitment.
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Blouin, J., J. DeBow, E. Rosenblatt, J. Hines, C. Alexander, K. Gieder, N. Fortin, J. Murdoch, and T. Donovan. 2021. Moose habitat selection and fitness consequences during two critical winter tick life stages in Vermont, USA. Frontiers in Ecology and Evolution 9:642276.
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May 2021
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Moose (<i>Alces Alces</i>) are a charismatic species that has been in decline across much of their southern range.<b> </b>In New England, USA, the reduction has been attributed, in part, to winter tick (<i>Dermacentor albipictus</i>) infestations. Winter ticks tend to be fairly immobile throughout all life stages, and therefore their distribution patterns at any given time are shaped largely by the occurrence of moose across the landscape during the peak of two critical time periods; fall questing (when ticks latch onto a moose, which coincides with the rut) and spring drop-off (when engorged female ticks detach from moose and lay their eggs in leaf litter). We used recent land cover and lidar data within a dynamic occupancy modeling framework to estimate first-order habitat selection (use vs non-use) of female moose (n = 74) during the questing and drop-off periods. Patch (1 km<sup>2</sup>) extinction and colonization rates during spring drop-off periods were strongly influenced by habitat and elevation, but these effects were diminished during the questing period when moose were more active across the landscape. In the spring drop-off period, patches where colonization was high and extinction low (highest probability of female moose occupancy) had higher proportions of young (shrub/forage) mixed forest at greater elevations. We evaluated the fitness consequences of individual-based habitat selection (second-order habitat selection) by comparing Resource Selection Functions (RSF) for 5 females that successfully reared a calf with 5 females whose calf perished. Second-order habitat selection analyses showed adult female moose whose offspring perished selected patches during the questing period that matched the first-order selection during the spring drop-off period. In contrast, adult female moose whose offspring survived selected areas with proportions of young deciduous habitats, as well as higher proportions of mature (canopy) evergreen forests and wetlands at lower elevations, i.e., their second-order habitat selection patterns deviated from the overall patterns illuminated by the multi-season occupancy analysis. Our model coefficients and mapped results define “hotspots” that are likely encouraging the deleterious effects of the tick-moose cycle. Knowledge about the composition and structure of these hotspots may influence more direct (i.e. hunter harvest) and indirect (i.e. conservation, modification, or formation of habitats) management decisions.
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Blouin, J., J. DeBow, E. Rosenblatt, C. Alexander, K. Gieder, J. Murdoch, and T. Donovan. Modeling moose habitat use by age, sex, and season in Vermont, USA using high-resolution lidar and National Land Cover data. Alces 57:71-98.
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September 2021
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Moose (<i>Alces alces</i>) populations have experienced unprecedented declines along the southern periphery of their range, including Vermont, USA. Habitat management may be used to improve the status of the population and health of individuals. To date, however, Vermont wildlife managers have been challenged to effectively use this important tool due to the lack of fine-scale information on moose space use and habitat characteristics. To assess habitat use, we combined more than 40,000 moose locations collected from radio-collared individuals (n = 74), recent land cover data, and high resolution, 3-dimensional lidar (light detection and ranging) data to develop Resource Utilization Functions (RUF) by age (mature and young adult), season (dormant and growth), and sex. Each RUF linked home range use to average habitat conditions within 400 m or 1 km of each 30 m2pixel within the home range. Across analyses, the top RUF models included both composition (as measured through the National Land Cover Database) and structure (as measured through lidar) variables, and significantly outperformed models that excluded lidar variables. These findings support the notion that lidar is an effective tool for improving the ability of models to estimate patterns of habitat use, especially for larger bodied mammals. Generally speaking, female moose actively used areas with proportionally more regenerating forest (i.e., forage < 3.0 m) and more mature forest (i.e., canopy structure > 6.0 m), while males actively used more high elevation, mixed forest types. Further, moose exhibited important seasonal differences in habitat use that likely reflect temporal changes in energetic and nutritional requirements and behavior across the year. Moose used areas with proportionally more regenerating forest (i.e., forage < 3.0 m) during the growth period and female moose had strong positive associations with lidar-derived canopy structure during the growth (but not the dormant) period. Ultimately, the resultant maps of habitat use provide a means of informing management activities (e.g., the restoration or alteration of habitats to benefit moose) and policies around land use that may contribute to population recovery.
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