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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]

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]

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]

We report that larvae ofDermacentor albipictuscan detect CO2from a dry ice source at distances up to 3.0 m and initiate increased activation, movement and questing behaviour. The maximum distance that larvae spread was ~0.5 m after 24 h, compared to <0.1 m without CO2as an excitant. In Petri dish bioassays, 2,6-dichlorophenol, methyl salicylate ando-nitrophenol acted as attractants, albeit with mixed results at 1.0 m, 2.0 m and 3.0 m, respectively. The 2,6-dichlorophenol target was the most effective, although few larvae crawled >1.0 m and CO2was required as a carrier. In Petri dish bioassays, larvae arrested into dense aggregations on eggshells collected after hatching. This arrestment was associated with the eggshell lipids cholesteryl oleate and cholesteryl palmitate, implying that cholesteryl esters act as assembly pheromones for larvae. Faster response was evident at 65% relative humidity (RH) versus 95% RH. Larvae were not arrested by tick excreta, guanine or related purines. Although larvae can be activated from long distances, in the field they remain fairly localized around the egg mass (hatching location), have limited dispersal and are more responsive in drier conditions. Given their arrestant properties, cholesteryl oleate and cholesteryl palmitate may prove useful in pheromone-assisted control methods becauseD. albipictuslarvae are the single stage of infestation to the host. [ABSTRACT FROM AUTHOR]

Moose (Alces alces) populations in northern New Hampshire and western Maine experienced 3 successive years of high winter tick infestations (epizootics) in 2014-2016 that resulted in late-winter calf mortality rates >70%. To assess productivity in these populations, we measured fecundity rates of yearling and adult cow moose, and neonatal and summer calf survival. Parturition, fecundity, and survival were measured via direct observation by stalking VHF and GPS radio-collared cows (n = 177) in May-August, 2014-2016. Calving rates for yearlings and adults averaged 0 and 57%, respectively; there was no twinning documented. Summer calf survival to August was high overall (83%), with 85% of the mortality occurring in the first week of life. Calving and twinning rates declined since last measured in New Hampshire in 2002-2005 and were below the North American average; conversely, summer survival of calves was considered normal. Given that optimal habitat has increased in the past 15 years in the study area that is dominated by commercial forestry, lower productivity is presumably related to the additive impacts of successive winter tick epizootics on year-round condition of cows. [ABSTRACT FROM AUTHOR]

To explore how the one-host tick Dermacentor albipictus survives off-host, we determined water balance characteristics of eggs and larvae. In contrast to eggs, larvae lost water fast, absorbed water vapour and died from a low amount of water loss. Placing mated females under near water-saturated conditions yielded larvae that absorbed and survived only at high relative humidities. We observed larvae forming clusters. Water loss rate of larvae decreased as group size increased. In response to day length, larvae lost water slower under long day than short day conditions. Larvae could switch quickly between fast water loss rate (short day) and slow water loss rate (long day) within a day, independent of the photoperiodic experience of the egg or mother. Long day exposure had no effect on water relations, incubation and survival of eggs. We conclude that eggs are modified for water conservation. Larvae survive by having a water balance maternal effect; i.e. capacity for water vapour absorption in the larva is determined by the relative humidity experienced by the mother. Larvae regulate water loss behaviourally through larval clustering and summer quiescence. Understanding these water balance attributes and effects of desiccation on egg and larval survival during summer are important to better predict the potential population impacts of winter ticks on moose. [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]

Biological data collected from harvested moose (Alces alces) were analyzed to assess whether temporal change has occurred in the physical and reproductive condition of moose from 1988-2009 in New Hampshire. Measurements included age and field-dressed body weight of both sexes, number of corpora lutea (CL) and ovulation rate of females, and antler beam diameter (ABD) and antler spread of males. Similar data were obtained from Maine and Vermont for comparative analysis. The only significant changes (P <0.05) occurred in the yearling age class: mean body weight of both sexes, number of CL, and ABD all declined in New Hampshire. The current ovulation rate (~20%) and mean body weight (<200 kg) of yearling females in New Hampshire and Vermont were considered low. The declines measured in yearlings, yet relative stability in adults, are consistent with the presumption that winter ticks (Dermacentor albipictus) impact the productivity of moose populations through reduced calf survival and growth and fecundity of yearlings. Density-dependent factors related to habitat change are also discussed given the recent, rapid expansion of moose in the 3 states. Continued monitoring of physical parameters and productivity of harvested moose, particularly the yearling cohort, is warranted to better assess the relationships among winter ticks, habitat quality, and moose populations. [ABSTRACT FROM AUTHOR]

Abundance indices suggested that the moose Alces alces population in northern New Hampshire was stable despite favourable habitat and conservative harvest. Causes and rates of mortality were unknown because moose reproduction and survival was unstudied in the region. Our study was designed to investigate the dynamics of the regional population in 2002-2005.Atotal of 92 moose (33 cows and 59 calves) were captured and fitted with radio-collars (VHF=83, GPS= 9). Parturition ranged from 8 May to 13 July (median = 19 May) with 78% of births occurring during 13-27 May. Calving rate of yearlings and adults (>2 years old) averaged 30 and 85%, respectively; twinning rate was 11%. Analysis of reproductive data from harvested cows (1988-2004) indicated that the average weight of adult cows increased but their corpora lutea count declined from ; 1.4 to 1.2/cow. Both ovulation rate and average weight of yearling cows declined about 25 and 4%, respectively. There were 39 mortalities (49% calves) with winterkill/parasite (41%), vehicle collision (26%) and hunting (18%) as the leading causes. Major sources of mortality of radio-marked cows were human-related; survival was 0.87. Annual calf survival was 0.45. Unmarked calf (0-2 months of age) survival was 0.71 with 76% of mortality in the first month of life. Radio-marked calves (∼7-12 months of age) had a survival rate of 0.67; 74% of the mortality was winterkill/parasite related. Calf mortality was concentrated (88%) in late winter-early spring. The unseasonably warm and snowless fall in 2001 probably favoured high tick transmission and increased tick loads on moose that resulted in high calf mortality (0.51) and measurable cow mortality (10%) in mild winter-spring 2002. Documentation of substantial tick-related mortality of radio-marked moose calves was unique to this study. The stability of the moose population probably reflects the variation in annual recruitment and lower fecundity of yearling cows associated with heavy infestations and epizootics of winter tick. Given that fertility, calving rate and body condition of adult cows, and summer calf survival are annually high, the population should recover from tick epizootics that periodically inhibit population growth. [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]

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]