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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. [ABSTRACT FROM AUTHOR]

Recent decline in New Hampshire's moose (Alces alces) population is attributed to sustained parasitism by winter ticks (Dermacentor albipictus) causing high calf mortality and reduced productivity. Location of larval winter ticks that infest moose is dictated by where adult female ticks drop from moose in April when moose preferentially forage in early regenerating forest in the northeastern United States. The primary objectives of this study were to: 1) measure and compare larval abundance in 2 types of regenerating forest (clear-cuts and partial harvest cuts), 2) measure and compare larval abundance on 2 transect types (random and high-use) within clear-cuts and partial harvests, and 3) identify the date and environmental characteristics associated with termination of larval questing. Larvae were collected on 50.5% of 589 transects; 57.5% of transects in clear-cuts and 44.3% in partial cuts. The average abundance ranged from 0.11-0.36 ticks/m2 with abundance highest (P < 0.05) in partial cuts and on high-use transects in both cut types over a 9-week period; abundance was ~2 × higher during the principal 6-week questing period prior to the first snowfall. Abundance (collection rate) was stable until the onset of < 0°C and initial snow cover (~15 cm) in late October, after which collection rose temporarily on high-use transects in partial harvests during a brief warm-up. The higher abundance of winter ticks on high-use transects indicates that random sampling underestimates tick abundance and relative risk of infestation of moose. Calculating an annual index of infestation of winter ticks on moose is theoretically possible by integrating 3 factors: the infestation of harvested moose in October, the length of the questing period, and assuming a stable collection rate during the questing period. [ABSTRACT FROM AUTHOR]

High calf mortality attributed to winter tick (Dermacentor albipictus) parasitism occurs in moose (Alces alces) populations along their southern range in the northeastern United States. We analyzed habitat use of cow and calf moose during the critical drop-off and questing periods in the winter tick life cycle to determine a potential relationship between tick density and habitat. We measured habitat use using geospatial analyses of locational data from > 200 radio-marked animals at 3 sites in New Hampshire and Maine. Moose selected for optimal habitat, defined as 4-16 year-old forest openings, regardless of season or site; this was the only land cover type used more than available (1.1-2.1X availability in home range, 1.2-3.1X availability in core range). Further, the proportional availability of optimal habitat within overlapping portions of seasonal home and core ranges exceeded the absolute proportion of optimal habitat within any one range. Temporal use of optimal habitat, which is available in relatively low proportion (15-20%) across the landscape, likely exceeds the geospatial estimates of use because moose spend 30-40% of daily activity foraging. We conclude that disproportionally abundant densities of winter ticks exist in this preferred cover type because of its selective use during the drop-off and questing periods of winter ticks. [ABSTRACT FROM AUTHOR]

An isolate of the soil fungus Scopulariopsis brevicaulis was identified from the surface of female winter ticks (Dermacentor albipictus) collected from recently dead moose (Alces alces) calves in New Hampshire in the northeastern United States. It was the sole isolate, and it matched with 98% nucITS similarity (molecular systematics Blast match) to S. brevicaulis species from soil and other tick species. Inoculation of tick larvae and eggs with 108 spores/mL + 0.05% Tween (aqueous inoculum) resulted in mortality, reduced survival time, and recovery of S. brevicaulis from within tick tissues. Rapid water loss and death from dehydration were the pathogenic consequences of the fungal infection. Three entomopathogenic fungal isolates from laboratory culture (Beauveria bassiana, B. caledonica, and Metarhizium anisopliae) inoculated concurrently at the same dose, were slightly less pathogenic to eggs than larvae of winter ticks. We conclude that S. brevicaulis imposes a limitation on the freeliving stages of the winter tick population in specific environmental conditions, but commercial fungal treatments as used in local situations to control ticks, are impractical as a means of controlling winter tick density across moose habitats. [ABSTRACT FROM AUTHOR]

In New Hampshire, winter ticks (Dermacentor albipictus) probably have more influence on the moose (Alces alces) population than other mortality factors, and predicting the frequency of tick epizootics is an important management consideration. Weather, moose density, and habitat use influence abundance and distribution of winter ticks. We evaluated the usefulness of 3 techniques to index winter tick abundance in 3 regions with variable moose density: 1) flagging for tick larvae, 2) line-transect counts of ticks on harvested moose, and 3) roadside surveys of tick-induced hairloss on moose. Although counts of tick larvae from fall flagging were not significantly different between years or regions, absolute tick abundance was measurably different (>50%) relative to moose density and years. Tick abundance on harvested moose reflected annual and regional differences; in general, abundance was correlated positively with moose density and annual trends within regions were similar. Tick abundance was highest for calves and lowest for cows. Hair-loss surveys indicated that hair loss was generally related to moose density, and similar annual differences were reflected in all regions. We suggest measuring tick abundance on harvested moose and conducting annual roadside hair-loss surveys to create indices and threshold values useful in predicting an epizootic of winter ticks. [ABSTRACT FROM AUTHOR]

Moose (AIces alces) are susceptible to late winter mortality from infestation of winter ticks (Dermacentor albipictus) throughout much of North America. Calves, perhaps more so than other ages of moose, likely experience chronic, and eventually acute anemia from blood removal by adult female ticks that peaks during weeks 4 - 6 of the 8-week engorgement period. We modeled the potential metabolic impact on protein and energy balance of moose calves associated with blood loss during four levels, low to severe, of winter tick infestation. Our conservative estimates indicated that total blood loss in weeks 4 - 6, as a percent of total blood volume, ranged from 27 to 48% and 64 to 112% during moderate (30,000 ticks) and severe (70,000 ticks) infestations, respectively. The percent of the daily metabolizable energy requirement needed to replace daily blood loss during weeks 4 - 6 was 4.9- 8.2% and 11.4 - 19.2% during moderate and severe infestations, respectively. The protein deficit associated with blood loss and regeneration was the most critical metabolic impact. Daily protein loss during weeks 4 - 6 was 29 - 49% and 68 - 114% of the daily protein requirement in moderate and severe infestations, respectively. Daily protein losses of ∼ 30 to > 100% occurred for 2 continuous weeks. Energy costs associated with compensating for blood loss would likely elevate the daily energy deficit normal at end of winter, accelerate nutritional decline and weight loss, and cause increased physiological stress related to concurrent anemia. Severely infested calves are obviously susceptible to late winter mortality, and the impact of moderate infestations would be exacerbated by secondary parasitic infestations, severe winters, and poor body condition. [ABSTRACT FROM AUTHOR]

• Agent-based models, parameterized using existing studies on moose (Alces alces) and winter ticks (Dermacentor albipictus), can be used to simulate populational trends similar to those observed in the field and are therefore a promising tool for managing moose populations in northern New England against epizootic events. • Highly concentrated optimal habitat is an important driver of winter tick epizootics. • Winter tick infestations are positively correlated with moose density. • At densities ≤ 0.40 moose/km2, weather conditions including summer drought and late onset of snow become less important in predicting epizootics than at densities > 0.40 moose/km2. • The number of winter ticks aggregating in a cluster is an important variable to consider when modeling winter tick epizootics and warrants focus in field studies. 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. [ABSTRACT FROM AUTHOR]

Soil fungi were cultured from 24 wallows and proximal control sites in Maine and New Hampshire, USA during the autumn moose (Alces alces) breeding season of 2016 to investigate the presence of soil fungi pathogenic to winter tick larvae (Dermacentor albipictus). Twenty genera of fungi were isolated, and all are considered common in a forested ecosystem. The predominant genera isolated in wallows were pathogenic to winter tick larvae and included Aspergillus spp. (in particular A. flavus), Beauveria bassiana, Mortierella spp., Mucor spp., Paecilomyces spp., Penicillium spp., and Trichoderma spp. Wallow soils had specific characteristics and differed from proximal control sites by having: 1) lower fungal diversity, 2) a higher frequency of primary colonizers including Mortierella spp., Mucor spp., Penicillium spp., and Trichoderma spp., and 3) a more variable total amount of fungi indicative of changing (disturbed) soil conditions. We conclude that wallows are sites of soil disturbance that concentrate fungi known to be pathogenic to larval winter ticks. Fungi acquired by breeding moose using wallows might subsequently act as an on-host mechanism of tick control. [ABSTRACT FROM AUTHOR]