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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]

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]