Moose Population Research Articles

Regional moose (Alces alces) responses to forestry cutblocks are driven by landscape-scale patterns of vegetation composition and regrowth

Forestry activities are globally widespread and can have a large positive or negative influence on wildlife. Wildlife responses to forestry cutblocks (defined areas where trees were harvested) vary as a function of forest succession, which differs across systems. Across their distribution, moose (Alces alces) and forestry are often closely associated. Moose are predicted to select for cutblocks because of greater browse quantity in early successional vegetation, but moose responses to cutblocks are inconsistent across studies. Our objective was to compare moose spatial responses to cutblocks as a function of year since cut between study areas (Prince George South [PGS] and Bonaparte [BP]) while considering differences in vegetation composition and regrowth to better inform forestry planning in British Columbia, Canada. We characterized cutblocks by dominant tree species as a proxy for vegetation composition and estimated the normalized burn ratio (NBR) from multispectral satellite imagery as an index of vegetation regrowth (i.e., structure). We then examined the use of cutblocks by moose dependent upon vegetation composition and NBR using generalized additive mixed effects models. Next, we used locations of collared moose and nearby available locations to examine moose responses as a function of year since cut and used those responses to group cutblocks into age classes, which were incorporated into resource selection functions (RSF) to compare moose responses between study areas. Vegetation composition differed between study areas, and although cutblocks in both study areas followed similar regrowth trajectories, NBRs for cutblocks > 13 years post-logging in PGS exceeded those in BP. Moose demonstrated greater use of locations within cutblocks with intermediate NBRs and dominanted by spruce (Picea engelmannii × glauca) versus Douglas fir (Pseudotsuga menziesii var. glauca). Moose responses as a function of year since cut varied seasonally, but across seasons, moose tended to avoid new cutblocks (1–8 years), select for regenerating cutblocks (9–24 years), and avoid older cutblocks (25–40 years). In both study areas, RSFs revealed that moose avoided new cutblocks, but moose in PGS were more likely to select for regenerating cutblocks in comparison to BP. Our analyses suggest that the use of cutblocks by moose is a function of year since cut, vegetation composition, and vegetation regrowth, likely resulting from differences in browse quantity and lateral cover. To maintain stable moose populations, managers should consider vegetation composition and regrowth during forestry planning, and future research should focus on identifying region-specific forestry thresholds for moose.

Prevalence of Winter Ticks (Dermacentor albipictus) in Hunter-Harvested Wild Elk (Cervus canadensis) from Pennsylvania, USA (2017–2018)

Winter ticks (Dermacentor albipictus) are an aggressive one-host tick that infest a wide-diversity of ungulates. Infestations can result in anemia, alopecia, emaciation, and death. Most notably, the winter tick has caused negative impacts to moose (Alces alces) populations in the northeast United States and Canada. Winter ticks have been identified on other cervid species, including deer (Odocoileus virginianus) and elk (Cervus canadensis), which generally results in low tick burdens and mild or no disease. Recently, however, a wild yearling bull elk in Pennsylvania was found dead as a result of severe winter tick infestation. To obtain baseline data on winter ticks in wild elk in Pennsylvania, we collected 1453 ticks from 190 hunter-harvested wild elk between 2017–2018. Of the 204 harvested elk, 94.3% (190/204) had ticks collected for this study and none of the sampled elk had evidence of winter-tick associated disease. The average tick burden was 7.7 ticks/elk and average winter tick load on all elk was 0.5. Results of this study indicate that winter ticks do infest wild elk in Pennsylvania. However, during the fall months, the tick burden is low and rarely associated with lesions. These data herein serve as a baseline to monitor winter tick populations over time.

Sex-biased polyparasitism in moose (Alces alces) based on molecular analysis of faecal samples.

Simultaneous infection with multiple parasite species in an individual host is often observed in wild populations. The understanding of parasite species distribution across populations of wild animals is of basic and applied importance, because parasites can have pronounced effects on the dynamics of host population. Here, we quantified prevalence and endoparasite species richness in moose and explored sex-biased polyparasitism using diagnostic PCR method coupled with DNA sequencing of moose faecal samples from the Biebrza River valley, North-Eastern Poland. This is the largest moose population in Central Europe that has not been harvested for almost 20 years. We also evaluated the appropriate quantity of faeces for detecting DNA of parasite species. Faecal samples were screened for molecular markers of 10 different species of endoparasites. Endoparasite prevalence was high in the studied population. Almost all of the samples (98%) tested positive for at least one parasite species, and we found polyparasitism in the majority of the tested individuals. The number of different parasite species found in a single individual ranged from 0 to 9. The parasite species richness was significantly higher in male than in female individuals. The most prevalent were liver fluke Parafasciolopsis fasciolaemorpha and gastrointestinal nematodes Ostertargia sp. Of the ten endoparasite species detected, only the prevalence of the tapeworm Moniezia benedeni was significantly higher in males than in females. Additionally, we identified co-occurrence associations of parasite species, which tended to be random, but we noted some evidence of both positive and negative associations. Our findings promote applications of molecular methods for parasite species identification from non-invasively collected faecal samples in management and scientific study of moose population, which should include investigation of parasite status, and in health monitoring programs for other wild cervids.

Behavioral modifications by a large-northern herbivore to mitigate warming conditions

BackgroundTemperatures in arctic-boreal regions are increasing rapidly and pose significant challenges to moose (Alces alces), a heat-sensitive large-bodied mammal. Moose act as ecosystem engineers, by regulating forest carbon and structure, below ground nitrogen cycling processes, and predator-prey dynamics. Previous studies showed that during hotter periods, moose displayed stronger selection for wetland habitats, taller and denser forest canopies, and minimized exposure to solar radiation. However, previous studies regarding moose behavioral thermoregulation occurred in Europe or southern moose range in North America. Understanding whether ambient temperature elicits a behavioral response in high-northern latitude moose populations in North America may be increasingly important as these arctic-boreal systems have been warming at a rate two to three times the global mean.MethodsWe assessed how Alaska moose habitat selection changed as a function of ambient temperature using a step-selection function approach to identify habitat features important for behavioral thermoregulation in summer (June–August). We used Global Positioning System telemetry locations from four populations of Alaska moose (n = 169) from 2008 to 2016. We assessed model fit using the quasi-likelihood under independence criterion and conduction a leave-one-out cross validation.ResultsBoth male and female moose in all populations increasingly, and nonlinearly, selected for denser canopy cover as ambient temperature increased during summer, where initial increases in the conditional probability of selection were initially sharper then leveled out as canopy density increased above ~ 50%. However, the magnitude of selection response varied by population and sex. In two of the three populations containing both sexes, females demonstrated a stronger selection response for denser canopy at higher temperatures than males. We also observed a stronger selection response in the most southerly and northerly populations compared to populations in the west and central Alaska.ConclusionsThe impacts of climate change in arctic-boreal regions increase landscape heterogeneity through processes such as increased wildfire intensity and annual area burned, which may significantly alter the thermal environment available to an animal. Understanding habitat selection related to behavioral thermoregulation is a first step toward identifying areas capable of providing thermal relief for moose and other species impacted by climate change in arctic-boreal regions.

Moose Management Strategies under Changing Legal and Institutional Frameworks

Moose (Alces alces) management strategies in Lithuania, East Europe, were analyzed. The study was intended to show the (un)sustainability of the current management approach in relation to changes in hunting rules, hunting organization and development of the responsible administrative bodies. Moose population and bag dynamics were analyzed using I index in connected scatterplots and compound annual growth rates (CAGR). In 1962–2020, the CAGR of the moose population was 3.84%, resulting in a population size increase of nearly 10 times. The seesaw principle in moose management was confirmed, showing three periods of population decrease (1973–1977, 1989–1995, 2000–2005), and two periods of hunting bag decrease (1976–1978 and 1990–1993). All decline phases were related to legal and administrative issues in the country. Since 2006, population growth has not been controlled. Lithuania has no long-term strategy of the moose population management at any administrative level. The current management approach is not sustainable, as it has not ensured long-term stability of the moose population. The current continuous growth of population, followed by only a moderate increase in the hunting bag, is related to the possibility for owners to adopt long-term planning of the hunting plot units.

Skeletal and Dental Development Preserve Evidence of Energetic Stress in the Moose of Isle Royale

Food shortages can leave diagnostic, and in the case of the dentition, irreversible changes in mineralized tissue that persist into historical and fossil records. Consequently, developmental defects of tooth enamel might be used to track ungulate population irruptions or declines in resource availability but dental tissue’s capacity for preserving historical population density changes has yet to be investigated in wild populations. We test the ability of macroscopic enamel defects, mandible and metapodial lengths to track changes in the well-known insular moose population of Isle Royale National Park. Our study demonstrates that 1) a moose density threshold exists on the island above which there is a significant decrease in mandible and metatarsus length and a concomitant increase in enamel hypoplasias, 2) food limitation has a more pronounced effect on male than female skeletal and dental growth, and 3) combined data from tooth enamel hypoplasias and bone lengths reflect the relative density of this ungulate population, and should be broadly applicable to other ungulate osteological samples. Developmental defects in dental enamel were among the highest recorded in a wild population, and even during low-density intervals the population density of Isle Royale moose has been high enough to negatively impact skeletal and dental growth, indicating the comparatively poor health of this isolated century-old ecosystem.

Modelling the effect of moose Alces alces population density and regional forest structure on the amount of damage in forest seedling stands.

BACKGROUNDMoose (Alces alces L.) populations and moose damage in forests are debated in Nordic countries with dense moose populations. Moose populations and food resources vary greatly, both spatially and temporally, and reliable data covering both variables simultaneously at the same scale have seldom been available. We modelled the effect of moose population density and forest resources on the area of moose damage at regional scale, referring to moose management areas (MMA). Forest data and moose damage data originated from the Finnish National Forest Inventory, and the moose population data came from a Bayesian moose model. For modelling, average values of moose population, damage and forest variables were calculated for the periods 2004–2008 and 2009–2013 for each MMA. The MMAs were further classified into one of four larger geographical zones. The area of moose damage was used as a dependent variable, and the proportions of different types of forests and moose population densities per land area or area of seedling stands as explanatory variables. The relationships were modelled with a linear mixed‐effects model with an exponential spatial correlation structure.RESULTSThe area of moose damage was best explained by total forest area, proportions of plantations and mature forests, and moose population density per land area or the proportion of plantations. There were differences among the biogeographical zones in how different variables explained the amount of damage.CONCLUSIONThe results provide tools for analyzing the regional effects of moose population density and the amount of food resources on the amount of moose damage. This information can be used in reconciling sustainable moose population levels and the amount of damage.

Optimal harvesting in the presence of predation: An age-structured modelling approach

Predation of wildlife and livestock by large carnivores takes place within many ecological and institutional settings. In this paper, moose predation by wolves is studied within a Norwegian institutional setting where the landowners obtain the moose harvesting value and where the wolf population is strictly controlled by the wildlife authorities. An age-structured model consisting of four categories of the moose population (calves, yearlings and adult females and males) is formulated, and both maximum yield (MY) and maximum economic yield (MEY) harvesting are studied. We find that the direct effect of higher predation pressure on an age-sex category works in the direction of higher harvesting pressure of that group. However, this direct effect is accompanied by indirect effects working through the stock abundance of all age-sex groups, and the net effect is ambiguous. In the numerical analysis, it is shown that harvest of the adult categories typically will be the optimal strategy, irrespective of the fact that calves are the main target of the wolves.

Climate Change Is Likely to Alter Future Wolf – Moose – Forest Interactions at Isle Royale National Park, United States

We evaluated how climate change and variable rates of moose browsing intensity, as they relate to wolf predation, might impact the forests of Isle Royale National Park, MI USA by conducting a simulation modelling experiment. The experiment consisted of contrasting three different scenarios of wolf management and with a static (current conditions) and changing climate (high emissions). Our results suggest that the interactive effects of wolf predation and climate change are likely to be temporally variable and dependent on biogeographic and forest successional processes. During the first 50 years of simulations, when the effects of climate change were minor, higher simulated rates of predation by wolves reduced moose population densities, resulting in greater forest biomass and higher carrying capacities for moose. However, over the longer term, early successional and highly palatable aspen and birch forests transitioned to late successional spruce and fir forests, regardless of climate or predation intensity. After 50 years, the effects of climate change and predation were driven by effects on balsam fir, a late successional species that is highly palatable to moose. High-intensity predation of moose allowed balsam fir to persist over the long term but only under the current climate scenario. Climate change caused a reduction in balsam fir and the other boreal species that moose currently feed on, and the few temperate species found on this isolated island were unable to compensate for such reductions, causing strong declines in total forest biomass. The direct effects of moose population management via reintroduction of wolves may become increasingly ineffective as the climate continues to warm because the productivity of boreal plant species may not be sufficient to support a moose population at all, and the isolation of the island from mainland temperate tree species may reduce the likelihood of compensatory species migrations.

Antibodies Against Hepatitis E Virus (HEV) in European Moose and White-Tailed Deer in Finland

The main animal reservoirs of zoonotic hepatitis E virus (HEV) are domestic pigs and wild boars, but HEV also infects cervids. In this study, we estimated the prevalence of HEV in Finnish cervid species that are commonly hunted for human consumption. We investigated sera from 342 European moose (Alces alces), 70 white-tailed deer (Odocoileus virginianus), and 12 European roe deer (Capreolus capreolus). The samples had been collected from legally hunted animals from different districts of Finland during 2008–2009. We analysed the samples for total anti-HEV antibodies using a double-sandwich ELISA assay. Seropositive sera were analysed with RT-qPCR for HEV RNA. HEV seroprevalence was 9.1% (31/342) in moose and 1.4% (1/70) in white-tailed deer. None of the European roe deer were HEV seropositive (0/12). No HEV RNA was detected from samples of seropositive animals. HEV seropositive moose were detected in all districts. Statistically, HEV seroprevalence in moose was significantly higher (p < 0.05) in the North-East area compared to the South-West area. The highest HEV seroprevalence (20.0%) in district level was more than six times higher than the lowest (3.1%). We demonstrated the presence of total anti-HEV antibodies in European moose and white-tailed deer in Finland. Our results suggest that HEV is circulating among the moose population. Infections may occur also in white-tailed deer. We were the first to report a HEV seropositive white-tailed deer from Europe. Further studies are needed to demonstrate the HEV genotypes in cervids in Finland and to evaluate the importance of the findings in relation to food safety.

Adjusting a finite population block kriging estimator for imperfect detection

AbstractA finite population version of block kriging (FPBK) estimates a total or a mean when there is perfect detection of population units. However, many environmental datasets challenge the assumption of perfect detection. We consider two extensions of FPBK that incorporate imperfect detection. Spatial population estimator with detection: ratio then add (SPEDRA) adjusts observed counts by the estimated detection probability prior to spatial modeling. Spatial population estimator with detection: add then ratio (SPEDAR) uses spatial modeling on observed counts and then adjusts by mean detection probability. Unlike classical sampling approaches such as simple random sampling, SPEDRA and SPEDAR allow for spatial correlation among counts, and, being moment‐based, are less computationally intensive than a fully Bayesian model. Both SPEDRA and SPEDAR perform similarly in some simulation settings and give comparable estimates for a moose population total when applied to data from Togiak National Wildlife Refuge (AK). In settings where detection probability varies widely across sites, however, SPEDRA outperforms SPEDAR in reducing root mean square prediction error. We recommend SPEDRA in surveys with imperfect detection because it is more theoretically sound and generally performs better.

Population dynamics and range shifts of moose (Alces alces) during the Late Quaternary

AbstractAimLate Quaternary climate oscillations had major impacts on species distributions and abundances across the northern Holarctic. While many large mammals in this region went extinct towards the end of the Quaternary, some species survived and flourished. Here, we examine population dynamics and range shifts of one of the most widely distributed of these, the moose (Alces alces).LocationNorthern Holarctic.TaxonMoose (A. alces).MethodsWe collected samples of modern and ancient moose from across their present and former range. We assessed their phylogeographical relations using part of the mitochondrial DNA in conjunction with radiocarbon dating to investigate the history of A. alces during the last glacial.ResultsThis species has a relatively shallow history, with the most recent common ancestor estimated at ca. 150–50 kyr. Ancient samples corroborate that its region of greatest diversity is in east Asia, supporting proposals that this is the region of origin of all extant moose. Both eastern and western haplogroups occur in the Ural Mountains during the last glacial period, implying a broader contact zone than previously proposed. It seems that this species went extinct over much of its northern range during the last glacial maximum (LGM) and recolonized the region with climate warming beginning around 15,000 yr bp. The post‐LGM expansion included a movement from northeast Siberia to North America via Beringia, although the northeast Siberian source population is not the one currently occupying that area.Main conclusionsMoose are a relatively recently evolved species but have had a dynamic history. As a large‐bodied subarctic browsing species, they were seemingly confined to refugia during full‐glacial periods and expanded their range northwards when the boreal forest returned after the LGM. The main modern phylogeographical division is ancient, though its boundary has not remained constant. Moose population expansion into America was roughly synchronous with human and red deer expansion.

Evaluating moose Alces alces population response to infestation level of winter ticks Dermacentor albipictus

Many wildlife populations are experiencing a variety of environmental pressures due to the direct and indirect consequences of a changing climate. In the northeast, USA, moose Alces alces are declining in large part because of the increasing parasitism by winter tick Dermacentor albipictus, facilitated by high host density and optimal environmental conditions. To test this hypothesis, and better understand the influence of this interaction on the stability of the regional population, we constructed a population viability model using data collected through comprehensive survival and productivity studies in 2002–2005 and 2014–2018 in northern New Hampshire. Years of heavy tick infestation (epizootics) saw a marked reduction in calf survival (< 50%), adult calving (< 60%), twinning rate (< 5%) and complete loss of yearling productivity. We conducted population viability analysis using VORTEX ver. 10.2 to model this moose population for 40 years using mean demographics from both time periods, including environmental variation measured in the field during winter tick epizootic (2002, 2014, 2015, 2016) and non-epizootic (2003, 2004, 2005, 2017) years. This exercise highlights the influence of winter tick infestation on the trajectory of the population with the potential for rapid population growth or decline depending on the frequency of epizootics. We suggest a shift in moose management strategy focused on lowering moose density, assuming continued influence of climate change on the host–parasite relationship.

О динамике численности лося на северной периферии ареала и в зоне экологического оптимума

О динамике численности лося на северной периферии ареала и в зоне экологического оптимума

Opposing fitness consequences of habitat use in a harvested moose population.

Landscape changes are happening at an unprecedented pace, and together with high levels of wildlife harvesting humans have a large effect on wildlife populations. A thorough knowledge of their combined influence on individual fitness is important to understand factors affecting population dynamics. The goal of the study was to assess the individual consistency in the use of risky habitat types, and how habitat use was related to fitness components and life-history strategies. Using data from a closely monitored and harvested population of moose Alces alces, we examined how individual variation in offspring size, reproduction and survival was related to the use of open grasslands; a habitat type that offers high-quality forage during summer, but at the cost of being more exposed to hunters in autumn. The use of this habitat type may therefore involve a trade-off between high mortality risk and forage maximization. There was a high repeatability in habitat use, which suggests consistent behaviour within individuals. Offspring number and weight were positively related to the mothers' use of open grasslands, whereas the probability of surviving the subsequent harvest season was negatively related to the use of the same habitat type. As a consequence, we found a nonsignificant relationship between habitat use and lifetime fitness. The study suggests that harvesting, even if intended to be nonselective with regard to phenotypes, may be selective towards animals with specific behaviour and life-history strategies. As a consequence, harvesting can alter the life-history composition of the population and target life-history strategies that would be beneficial for individual fitness and population growth in the absence of hunting.

Using movement ecology to investigate meningeal worm risk in moose, Alces alces

Abstract Anthropogenic habitat change and moderating climatic conditions have enabled the northward geographic expansion of white-tailed deer, Odocoileus virginianus, and of the parasitic nematode (meningeal worm) it carries, Parelaphostrongylus tenuis. This expansion can have consequences in dead-end host species for other ungulates because meningeal worm reduces health, causes morbidity or direct mortality, and has been attributed to population declines. In northeastern Minnesota, which marks the southern extent of the bioclimatic range for moose (Alces alces), the moose population has declined more than 50% in the last decade, with studies detecting P. tenuis in 25–45% of necropsied animals. We assessed the factors that most commonly are associated with meningeal worm infection by linking moose movement ecology with known P. tenuis infection status from necropsy. We outfitted moose with GPS collars to assess their space use and cause-specific mortality. Upon death of the subject animal, we performed a necropsy to determine the cause of death and document meningeal worm infection. We then created statistical models to assess the relationship between meningeal worm infection and exposure to hypothesized factors of infection risk based on the space use of each moose by season. Predictors included land cover types, deer space use and density, environmental conditions, and demographics of individual moose (age and sex). Moose with autumn home ranges that included more upland shrub/conifer, and individuals with high proportions of wet environments, regardless of season, had increased infection risk. In contrast, the strongest relationships we found showed that high proportions of mixed and conifer forest within spring home ranges resulted in reduced risk of infection. The spring models showed the strongest relationships between exposure and infection, potentially due to moose foraging on ground vegetation during spring. By incorporating movement of moose into disease ecology, we were able to take a top-down approach to test hypothesized components of infection risk with actual spatial and temporal exposure of individual necropsied moose. The probability of infection for moose was not influenced by deer density, although deer densities did not vary greatly within the study area (2–4 deer/km2), highlighting the importance of also considering both moose space use and environmental conditions in understanding infection risk. We suggest management strategies that use a combination of deer and land management prescriptions designed to limit contact rates in susceptible populations.

Patterns of parasite eggs, oocysts and larvae shedding by moose in the Biebrza marshland (NE Poland).

The study analyses patterns of endoparasite eggs, oocysts and larvae shedding by moose from the relict population in the Biebrza marshland, NE Poland, which has grown to be one of the largest in Central Europe since the ban on hunting imposed in 2001. The analysis identified 10 species or groups of parasites among 230 faecal moose samples collected over 16 consequent months. The most prevalent were the eggs of Trichostrongylidae, Trichuris spp., Nematodirella alcidis, Parafasciolopsis fasciolaemorpha and the larvae of Elaphostrongylus sp. Four parasite species were more prevalent in males, indicating male-biased parasitism, and the studied moose population exhibited a female-skewed sex ratio. Nematodirella alcidis eggs and Protostrongylid larvae were more prevalent during winter, which indicated their resistance to harsh weather conditions. The prevalence of Eimeria alces and Aonchotheca sp. increased during the growing season, as did the number of eggs per gram of faeces (EPG) of P. fasciolaemorpha, possibly due to the availability of water sources. Higher mean monthly temperature was also found to have a positive effect on the excretion of Trichostrongylidae and Moniezia spp. eggs. In addition, the time of infection and the specificity of the parasite life cycle, being sensitive to certain climatic conditions, also appeared to have a strong influence on eggs, oocysts and larvae shedding in this non-harvested moose population.

The effect of climate on population growth in a cold‐adapted ungulate at its equatorial range limit

AbstractClimatic changes are affecting the distribution and viability of species worldwide, and the effects may be greatest for heat‐sensitive organisms in populations situated near the species’ equatorial range limit. We studied the population dynamics of a cold‐adapted large herbivore, moose (Alces alces shirasi), in a population located at the extreme southern range limit of the species in Utah, USA, using a long‐term dataset of aerial counts conducted between 1958 and 2013. We used a modeling approach that acknowledges the uncertainty in the number of moose counted. To determine how climate influenced this population, we tested four models corresponding to different hypotheses suggested by previous studies of moose population dynamics: (1) High summer rainfall increases population growth, (2) severe winters reduce population growth, (3) high summer and winter temperatures cause heat stress which reduces population growth, and (4) snow conditions favorable to winter ticks reduce population growth. We then ranked these models against two additional hypotheses that tested the combined effects of the best‐performing models. The best‐supported model included summer rainfall and the number of days with snow cover in late winter, which described the conditions influencing winter tick numbers, a common parasite of moose in the region. Reproductive female ticks drop off their hosts at the end of winter to lay eggs, and fewer ticks survive in years with abundant snow cover. Positive effects of snow and rainfall indicated that moose population growth was higher following summers with more rainfall and late winters with more days of snow cover, the latter because those conditions likely reduced winter tick numbers. In accordance with global patterns in which altered precipitation regimes are influencing the dynamics of many species, the top‐performing model suggested that both summer and winter precipitation acted together to explain the most variation in moose population growth. Our analysis demonstrates the multiple pathways by which climate and population density can affect the dynamics of temperate species living at their equatorial range limits, including potential parasite‐mediated effects.

Growth and chemical responses of balsam fir saplings released from intense browsing pressure in the boreal forests of western Newfoundland, Canada

For ungulates, balsam fir (Abies balsamea (L.) Mill.) is thought to be a low quality forage due to high levels of indigestible fiber and secondary metabolites. Regardless, intensive browsing of fir saplings by overabundant moose (Alces alces L.) populations has led to the failure of fir-dominated forests in Newfoundland, Canada to regenerate following disturbance. The construction of moose exclosures in Gros Morne National Park (GMNP), western Newfoundland, presented an opportunity to compare levels of secondary metabolites (e.g. phenols and tannins), thought to act as anti-herbivore allelochemicals in balsam fir, under extremes of moose browsing pressure. We examined browsing damage to fir saplings and compared levels of carbon (C), nitrogen (N), total phenols and condensed tannins in current-year foliage outside and inside of eight moose exclosures. Outside of exclosures, 74% of fir saplings showed apical browsing while 97% were browsed laterally. At five exclosures, exposed saplings had significantly greater total phenol concentrations than inside exclosures. Such trends for condensed tannins were observed at only two exclosures, both locations having relatively high moose density and browsing damage. Unlike condensed tannins, total phenols were responsive to different patterns and levels of browsing. Foliar phenol concentration was negatively related to canopy closure, and to height and diameter of saplings, and positively related to the foliar C level. Foliar tannin level was unrelated to canopy or growth characteristics but positively related to the foliar N concentration. Moose browsing affected the defense chemistry of balsam fir; however, phenols and tannins responded differently, this likely being influenced by time of year. Foliar nitrogen levels were greater for inside saplings at only the two exclosures having highest moose density and browsing damage. Our data suggest that balsam fir employs constitutive chemical defense; however, this investment appears to be ineffective in deterring moose browsing.

Using agent-based models to inform the dynamics of winter tick parasitism of moose

North American moose (Alces alces) populations along the southern extent of their range have been experiencing high levels of calf mortality in recent years. In New England, this phenomenon has been linked to extensive blood loss resulting from extreme winter tick (Dermacentor albipictus) parasitism. Moose are symbolic of the region and generate income through tourism and the auction of hunting permits; thus, successive years of greater than 50% calf mortality (epizootics) are of concern to wildlife managers and others. It is hypothesized that high localized moose density coupled with climate change are the driving forces behind moose-winter tick epizootics; however, the impact that variable combinations of these and other factors have on the occurrence and magnitude of epizootics has not been previously simulated. We, therefore, developed and implemented a spatially explicit agent-based model with two model environments, each representative of a distinct location within an ongoing field study site in northern New Hampshire that differed in the proportional availability of optimal moose habitat. Three experiments were devised to test the sensitivity of the outcome variables, calf infestation level and calf mortality, to 1) winter tick abundance, 2) winter tick aggregation, and 3) moose density, for the length of the winter tick questing period. Each experiment was conducted in both model environments. This model generated similar mortality levels to those measured in the field study under representative moose density and weather conditions. Additionally, the modeled moose agents and the radio-collared moose in the field reflect comparable habitat usage. While the infestation levels reported by calf agents are considered conservative, we believe that future versions of this model, parameterized with more accurate estimates of winter tick abundance and moose density, may be an effective tool for managing moose against winter tick parasitism.