RECRUITMENT OF WINTER TICKS (DERMACENTOR ALBIPICTUS) IN CONTRASTING FOREST HABITATS, ONTARIO, CANADA E. M. Addison1,2, R. F. McLaughlin3, P. A. Addison4, and J. D. Smith5 1Wildlife Research and Monitoring Section, Ontario Ministry of Natural Resources and Forests, 2140 East Bank Drive, Peterborough, Ontario, Canada K9J 7B8; 2Present Address: Ecolink Science, 107 Kennedy St. W., Aurora, Ontario, Canada L4G 2L8; 3R.R. #3, Penetanguishene, Ontario, Canada L0K 1P0; 4Northwest Region, Regional Operations Division, Ontario Ministry of Natural Resources and Forests, 173 25th Sideroad, Rosslyn, Ontario, Canada P7K 0B9; 558 Chemin Rheaume, Val des Monts, Quebec, Canada J8N 6L5. ABSTRACT: Recruitment of winter tick larvae (Dermacentor albipictus) was studied in a forest opening and a closed canopy deciduous forest to evaluate their potential as sources of tick infestation to moose (Alces alces). Engorged female ticks were set out in early May at each site and monitored to measure the proportions of females producing larvae and the number of larvae recruited per g of sur- viving female. Recruitment was higher in the forest during the hotter, drier summer of 1983, primarily due to fewer engorged females producing larvae in the opening, and was much higher (>2 x) in the opening during the cooler, damper summer of 1984. Recruitment in the field was 20–40% of that under laboratory conditions. Desiccation of eggs and/or larvae was the probable cause for the annual vari- ation in recruitment in the opening. Most larvae were recruited earlier in the opening than in the forest site. Neither weight nor date of detachment of engorged female ticks influenced when larvae first ascended vegetation. Weather, especially temperature, and site structure and composition affect abun- dance of the free-living stages of the winter tick and larvae available for transmission to moose. Open sites should support more winter tick larvae than densely forested sites except in years of particularly hot and dry weather. ALCES VOL. 52: 29–40 (2016) Key words: Dermacentor albipictus, winter tick, moose, recruitment, weather, habitat, Alces The overall impact of winter ticks (Der- macentor albipictus) on moose (Alces alces) populations varies annually (Samuel 2004). Understanding the reasons for this variation is key to predicting when and in what habitats moose are most likely to acquire winter ticks. Survival of eggs and larvae of ixodid ticks are affected most markedly by desiccation (Sonenshine 1970), and since temperature and moisture vary annually, reproductive po- tential of ixodid ticks can also vary annually within the same habitat (Patrick and Hair 1979, Fleetwood et al. 1984). Production and survival of winter tick eggs and larvae from wapiti (Cervus canadensis) have been studied in 2 habitats in Oklahoma, USA (Patrick and Hair 1975), and from moose in a variety of habitats in central Alberta, Canada (Drew and Samuel 1986, Aalangdong et al. 2001). Objectives of this study were to establish if adult females, eggs, and larvae of the winter tick could survive in 2 contrasting forest habitats in Ontario, Canada, and to document factors related to variation in re- cruitment between years and habitats. STUDY AREA Two study sites 13.3 km apart in Algon- quin Provincial Park, Ontario were selected for their contrasting habitats: 1) a forest open- ing and 2) a closed canopy deciduous forest. The opening site was an old lumber camp 29 (45° 42′ 13″ N, 78° 15′ 9.5″ W) with ground vegetation <0.3 m high and comprised of scattered grasses, sweet fern (Comptonia per- egrina), bracken (Pteridium aquilinum), and blueberry (Vaccinea sp.); trees were limited to red pine (Pinus resinosa) and white spruce (Picea glauca) <3 m high and present in 11% of plots. The deciduous forest site (45° 35′ 6″ N, 78° 18′ 53″ W) was on a northeasterly aspect sloping away from the summer sun, with a closed canopy dominated by sugar maple (Acer saccharum) with scattered white birch (Betula papyrifera). Sub-canopy vegetation was limited and ground vegetation was pre- dominantly sugar maples 1–1.5 m high. METHODS Weather data were collected from “An Historical Climate Analysis, version 2.2” which uses latitude and longitude, Environ- ment Canada data, and topographical source data to calculate location specific weather (Cross et al. 2012). Specific weather data (e.g., temperature, precipitation, snow accu- mulation) were recorded occasionally at the study sites. We attempted to minimize and control for the influence of outside factors that could affect the outcomes of live specimens. Specifically, we: 1 divided into 2 treatment groups winter ticks that detached on the same date from moose with similar exposure history and infestation level to account for immunocompetence that can sup- press fecundity in ticks (McGowan et al. 1980, 1981, Chiera et al. 1985), 2 allocated similar-sized engorged ticks between treatment groups to account for the relationship between weight and fecundity (Drummond et al. 1969, Addison and Smith 1981, Drew and Samuel 1987, Addison et al. 1998), and further, calculated fecundity relative to weight, 3 used control plots and documented dissemin- ation from points of deposition to account for ingress and egress of adult female and larval ticks, 4 assumed that losses to predation and disease were constant (Addison et al. 1989, Tuininga et al. 2009), and 5 used sites where the height of vegetation con- formed with the known ascension height of win- ter ticks (0.5–1.9 m; Drew and Samuel 1985, McPherson et al. 2000). Definitions The following terms are used in the paper: 1 Reproductive efficiency index (REI) is the num- ber of eggs produced per g of engorged adult fe- male tick (EF) (Drummond and Whetstone 1970). 2 Larval efficiency index (LEI) is the number of larvae recovered from a plot per g of EF placed on that plot, and was calculated only for plots from which larvae were recovered. 3 Flagging is the action of dragging flannel sheets over vegetation to sample larvae available for transmission. 4 Recruitment is a measure of tick larvae available for transmission by flagging and is comprised of both LEI and proportion of EFs producing larvae. 5 Season of transmission is the time from first to last collection of larvae by flagging. 6 Minimum free-living period is time (d) from de- tachment of an EF to first recovery of larvae from that EF by flagging. 7 Vapor pressure deficit (VPD) is a measure of the difference (or deficit) between the pressure (mm Hg) exerted by the moisture currently in the air and the pressure at saturation. Engorged Female Ticks (EFs) Detached EFs were collected on 1–20 April, 1983 and 15 March–27 April, 1984 from captive moose experimentally infested with ticks (see McLaughlin and Addison 1986). Prior to placement in the field, they were maintained at ambient temperature within cardboard boxes containing moist sand and soil overlaid with leaves. A total of 100 EFs were marked on the abdomen with nail polish (Revlon Nail Enamel, Ottawa, Canada K1G 3N1), and one set of 50 was placed at flagged locations in the 30 RECRUITMENT OF WINTER TICK LARVAE – ADDISON ET AL. ALCES VOL. 52, 2016 forest and opening sites in early May. Their dispersal distances were measured in early July. An egg group (3.775 g) equivalent to ~54,000–63,000 eggs (see Addison et al. 1998) was deposited at a single point in 2 grass plots in the opening site. From point of deposition, concentric 1-m wide rings were flagged 4 m outward to measure disper- sal of larvae in late September through mid- October. Fecundity and Hatching Forty EFs were selected at random and each placed in a 2 cm2 cell within wood frame trays approximately 3 cm deep, enclosed on top and bottom by insect screening. One tray was placed on the soil surface and cov- ered with ground vegetation in each study site in early May. Eggs were collected from individual EFs and counted weekly from 8 June until deposition ended. Fifty EFs were placed in each of 6, 60 cm2 wooden trays with fine screening on top and bottom. One tray was placed in each of 3 locations within each study site during mid-May and examined weekly to document initial presence of larvae. Larval Recruitment In 1983 (5–7 May), 453 and 451 EFs were placed on the ground singly, 5–10 m apart, in the opening and forest sites, respect- ively. Numbered plastic tape identified each plot with date of detachment, moose of ori- gin, and weight of the EF; placement loca- tion was the center of a 2.5 m radius plot that was the source of data for larval recruit- ment. In 1984 (3–4 May), 213 and 206 EFs were placed similarly in the opening and forest sites, respectively. Control locations (without ticks) were also established - 10 in the opening and 8 in the forest site. Plots were flagged (sampled) with white, flannel sheets (2.3�2.6 m) every 9–13 (1983) and 11–15 (1984) days from August until after snowfall (3–22 November). One end of the flannel sheet was wrapped around a stick (2.4�0.05�0.02 m) until about 30 cm of the sheet was rolled in. The plot was flagged by dragging the sheet over the vege- tation such that no person walked within 2.5 m of the plot center; the center area (~0.5 m out from the center point) was flagged once separately. The sheet was examined and if few larvae were present, they were counted, killed, and removed. If numerous larvae were collected, the sheet was folded by 2 people, bagged, and labeled. Larvae were subsequently counted as they were evacuated (�40 kPa relative pressure) from the sheet. Sheets were washed and dried in an electric dryer prior to reuse. In 1983, all plots were flagged and larvae counted through to the end of the season. Plots were considered positive (i.e., EFs had survived) if >10 larvae were recovered. In 1984, plots were identified as positive or negative in mid-September and a random subsample of positive plots was used for fur- ther measurements of total larval count. Sur- vival was measured by flagging these and the remaining plots and categorizing them positive or negative. Data Analysis Placement of EFs on plots and subse- quent flagging of plots to establish recruit- ment occurred in both 1983 and 1984. Timing of incubation of eggs, presence of lar- vae on control plots, and dispersal of EFs and larvae were studied only in 1984. The R statistical package (R Core Team 2013) was used to analyze data on eggs, REI, and duration of the non-parasitic per- iod. Egg production and REI data were not normally distributed (Shapiro-Wilk Test) and variances were not homogenous. Since transformations did not normalize data, the Mann-Whitney-Wilcoxon test was used to test for differences in number of eggs ALCES VOL. 52, 2016 ADDISON ET AL. – RECRUITMENT OF WINTER TICK LARVAE 31 produced and REI between habitats. Dur- ation of the non-parasitic period was tested for normal distribution with the Shapiro- Wilk test. Transformations harmonized the variances (Bartlett’s test) and while normal distributions were not realized, the conse- quences of this were acceptable to use factorial ANOVA (Glass et al. 1972, Harwell et al. 1992, Lix et al. 1996). Three-way contin- gency tables and Chi-square tests were used to evaluate frequency of positive plots between years and habitats (Zar 1982). Square root transformation was applied to the number of larvae produced per g for EFs that produced larvae (LEI); this trans- formation stabilized the variance (Bartlett’s test) and normalized the distribution (Kolmogorov-Smirnov test). Data for the first appearance of larvae on vegetation, size of EFs, and date of detachment of EFs could not be normalized through trans- formation because of the discontinuous na- ture of the sampling protocol both years: 9–13 and 11–15 days in 1983 and 1984, re- spectively (Fig. 4, 5). Consequently, scatter diagrams were used to evaluate possible relationships. RESULTS Average monthly temperature and pre- cipitation varied annually (Table 1). May was wetter, June and July (the period of egg-laying and incubation) were warmer and drier, and September (period of larvae ascending) was warmer and wetter in 1983 than 1984. Temperature was intermittently low and snow fell late in the experiment. For example, in 1983 the morning air tem- perature at the forest site was �6 °C and the ground was solid with heavy frost on 15 October, 10–15 cm of snow accumulated in the forest on 8 November and was gone by 10 November, and finally 10–15 cm of snow permanently covered the ground on 22 November. Dispersal and Fecundity Mobility was limited for both EFs and larvae. In the opening, 44 of 45 EFs were recovered within 67 cm, and in the forest 41 of 42 were recovered within 34 cm of the site of deposition. In the opening, 98.5% of 26,485 larvae moved <2 m from the site of egg deposition. A similar number of EFs held in trays laid eggs in the opening (64%) and forest (70%) in 1984. However, EFs in the opening laid more (P < 0.05) eggs (median = 6226) than in the forest (median = 3632), and the REI in the opening (median = 8150) was greater (P < 0.05) than that in the forest (median = 4620). Further, EFs in the opening completed ovipositing on 27 July, a month earlier than in the forest (30 August). Larval Recruitment Larvae hatched about 2 weeks earlier in the opening (4 August) than the forest (17 August) in 1984, were recruited earlier in the opening than the forest both years, but not until 2–4 weeks post-hatch in 1984 (Table 2, Fig. 1). Most opening plots became positive for larvae later in 1983 than 1984 (Fig. 1); in contrast, forest plots were positive at the same time both years (Fig. 1). Approxi- mately 80% of all larvae were recruited in the opening by late September, about 2 weeks prior to the forest (Fig. 2). Minimal numbers Table 1. Average monthly temperatures and pre- cipitation at opening and forest study sites in Algonquin Park, Ontario, 1983–1984. temperature (°C) precipitation (mm) Month 1983 1984 1983 1984 May 8.8 9.1 167.5 116.3 June 16.8 16.6 51.9 83.7 July 19.6 18.0 62.4 102.8 August 18.8 18.7 97.8 96.6 September 14.7 11.7 104.2 87.7 October 6.3 8.5 112.9 64.1 32 RECRUITMENT OF WINTER TICK LARVAE – ADDISON ET AL. ALCES VOL. 52, 2016 of larvae were collected during flagging in early to mid-November both years (Figs. 2, 3). In the opening, <13 larvae were recovered in 9 of 10 control plots; 1 plot yielded 5,283 larvae. In the forest, 2 control plots had <10 larvae and 6 plots had none. A higher propor- tion of EFs produced larvae in the forest than the opening in 1983 (P < 0.05); no difference was found in 1984 (P > 0.05) (Table 2). At both sites fewer plots yielded larvae in 1983 (P < 0.05) (Table 2). Recruitment of larvae ranged from 10– 7,347 larvae per surviving EF. The mean LEI was similar (P > 0.05) both years in the forest; however, the LEI in the opening was higher (>2x) in the cool, wet summer of 1984 than the hot, drier summer of 1983, as well as both years in the forest (P < 0.05) (Table 2, Fig. 3). In both habitats in 1983, LEI from EFs from which larvae were available in September (early samples) was higher (P < 0.05) than from EFs from which larvae were first recovered in October (late samples) (Table 2, Fig. 3). Minimum Free-Living Period The minimum free-living period ranged from 122–215 days (n = 699, μ = 162). Effects of habitat, year, and the interaction between habitat and year on the minimum free-living period were significant (P < 0.05), but neither weight nor date of detach- ment of EFs influenced duration of the free- living period (Fig. 4, 5). DISCUSSION Winter tick larvae were available in both contrasting habitats, hence, are likely avail- able for transmission in most terrestrial habitats frequented by moose in the Great Lakes – St. Lawrence forest ecosystem. An- nual differences in fecundity and recruitment of larvae and between habitats reflected the influence of weather, habitat structure and composition, and their interactions. Many tick studies have documented higher tem- perature, lower RH, and higher VPD in open (e.g., fields) compared to forest habitats during summer; e.g., in Alberta (Aalangdong et al. 2001), Oklahoma (Patrick and Hair 1975), Virginia (Sonenshine 1970), east- central Texas (Fleetwood et al. 1984), and Connecticut (Bertrand and Wilson 1996). Wind also has a drying effect, open habitats being usually drier than closed habitats (Schütte and King 1965), and sites with Table 2. Recovery of Dermacentor albipictus larvae from contrasting habitats of the Great Lakes – St. Lawrence forest ecosystem, Algonquin Park, Ontario, 1983–1984. Open Field Deciduous Forest 1983 1984 1983 1984 1st Larvae Flagged Sept 6 Aug 28 Sept 13 Sept 18 % Engorged Females (EFs) with Larvae 38 (n = 453) 88 (n = 193) 67 (n = 450) 85 (n = 196) LEI1 for EFs with Early2 Larvae 1502 ± 1186 (n = 71) 1520 ± 1112 (n = 50) LEI for EFs with Late3 Larvae 346 ± 506 (n = 19) 868 ± 711 (n = 19) Total LEI 1258 ± 1176 (n = 90) 3214 ± 1734 (n = 49) 1340 ± 1054 (n = 69) 1463 ± 1315 (n = 50) 1Larval Efficiency Index = number of larvae/gram of engorged female from which larvae recovered). 2Larvae first flagged in September. 3Larvae first flagged in October. ALCES VOL. 52, 2016 ADDISON ET AL. – RECRUITMENT OF WINTER TICK LARVAE 33 aspect towards the summer sun being hotter and drier (Londt and Whitehead 1972). We had no weather data at the microsite level (i.e., in the duff layer where eggs and larvae reside). However, because microsites in open habitats have higher temperature, lower relative humidity (RH), and higher wind speed (Londt and Whitehead 1972, Daniel et al. 1977, Daniel 1978), we assumed that our flat opening had lower RH, and higher temperatures, wind speeds, and vapor pressure deficits (VPDs) at the microsite level than the forest habitat with dense canopy cover and northeast sloping aspect. Weather and Desiccation Both eggs and larvae lose moisture under conditions of VPD, with temperature the main influence on vapor pressure. Desicca- tion of eggs is detrimental because eggs can- not reabsorb water even at high RH (Rechav and Maltzahn 1977). Desiccation of eggs (Dermacentor variabilis) occurred when RH was reduced 6–8 h daily, fewer eggs hatched at 85% than 95% RH (Sonenshine and Tigner 1969), and weight and hatchability of Boo- philus decoloratus eggs were reduced at lower RH (Rechav and Maltzahn 1977). High VPD is correlated positively with weight loss in Boophilus microplus and B. annulatus eggs, with a strong negative rela- tionship between weight loss and percent hatched (Teel 1984). The ~50% lower recruit- ment of larvae in the opening in 1983 versus 1984 presumably reflected higher desiccation and mortality of eggs during oviposition and incubation in the hotter and drier June and July of 1983. Desiccation also threatens tick larvae (Knülle 1966). For example, survival of Amblyomma hebraeum larvae dropped pre- cipitously at 70% RH compared to higher RHs (Londt and Whitehead 1972), Ixodes ricinus larvae died sooner in open, grassy than in forest habitats (Daniel et al. 1977), and A. americanum larval survival was shorter Fig. 2. Proportion of total seasonal recruit- ment of larvae of Dermacentor albipictus acquired during individual sampling peri- ods in opening and forest habitats, Algon- quin Park, Ontario, autumn 1983 and 1984. Fig. 3. Larvae per gram of engorged female (LEI) Dermacentor albipictus recruited from opening and forest habitats, Algon- quin Park, Ontario during early and late autumn 1983 and autumn 1984. Fig. 1. Accumulation of tick plots with larvae of Dermacentor albipictus in open- ing and forest habitats, Algonquin Park, Ontario, autumn 1983 and 1984. 34 RECRUITMENT OF WINTER TICK LARVAE – ADDISON ET AL. ALCES VOL. 52, 2016 (10–19 d) in meadow than forest habitat (33–106 d) in Oklahoma (Patrick and Hair 1979). Incubation of winter tick eggs occurs more rapidly at higher than lower tempera- tures (Addison et al. 1998). In 1984, larvae first appeared in early August and presum- ably earlier in 1983 given the hotter June and July. Thus, although desiccation in July 1983 may have impacted larval survival, the higher average monthly September tem- perature (3 °C) than in 1984 may also have contributed to reduced larval survival and recruitment in 1983. Overall desiccation of larvae may have been moderated by higher precipitation in September 1983 and the relatively lower VPD associated with cooler weather in late August and September. We conclude that reduced recruitment of larvae due to desiccation in the opening in 1983 likely had a minimal role in overall reduced LEI, particularly relative to desiccation of eggs. Fecundity While the reduced proportion of EFs with larvae in the opening in 1983 could be attrib- uted to higher desiccation and mortality of eggs and larvae, it is possible that high mor- tality occurred in EFs prior to egg-laying in the hotter and drier June and July of 1983. In 1984, the REI values in cells within the for- est site were ~50% lower than in the opening; in contrast, Drew and Samuel (1986) reported similar REI values for EFs in open and closed habitats. In 1984, the REI values in the open- ing were similar (median = 7538) to those produced under laboratory conditions (μ = 7097–9443) (Addison et al. 1998), indicating that conditions in the opening were highly fa- vorable for egg production and more so than at the forest site (May mean monthly tem- perature of 9.1 °C) where the microsite temperature was presumably lower. Egg pro- duction was also lower at 15 °C than at 20 and 25 °C in Rhipicephalus sanguineus (Sweatman 1967). In general, it is anticipated that overall fecundity of EFs would be lower in cooler than warmer habitats in northerly parts of winter tick range, that more open habitats are the likely nidus for transmission in cooler summers, and that fecundity might be correlated with latitude within winter tick range. Fig. 4. Scatter gram of weight of detached engorged female Dermacentor albipictus versus first date of appearance of larvae on vegetation in opening and forest habitats, Algonquin Park, Ontario, autumn 1983 and 1984. Fig. 5. Scatter gram of date of detachment of engorged female Dermacentor albipic- tus from moose versus first date of appearance of larvae on vegetation in opening and forest habitats, Algonquin Park, Ontario, autumn 1983 and 1984. ALCES VOL. 52, 2016 ADDISON ET AL. – RECRUITMENT OF WINTER TICK LARVAE 35 Rate of Development Oviposition occurred earlier in the open- ing than in the forest. This is consistent with earlier oviposition by winter ticks at 24 °C than at 20 °C under laboratory conditions (Addison et al. 1998) and oviposition of other species of ticks occurring more quickly in open field than in forested sites (Daniel et al. 1977, Dusbabek et al. 1979, Patrick and Hair 1979, Koch 1984). Incubation of winter tick eggs is also accelerated at higher tempera- tures (Addison and Smith 1981, Addison et al. 1998), hence, the accelerated incubation in the opening as compared to the forest was likely due to higher microsite temperatures. As with earlier oviposition, this could have contributed to the earlier appearance of larvae in the opening than in the forest in both years. Similarly, the incubation period for D. albi- pictus in Alberta was shorter in an open grassland than in an aspen forest (Drew and Samuel 1986), and shorter incubation periods in open fields as compared to forests have been reported for A. americanum in Oklahoma (Patrick and Hair 1979) and D. reticularis in Slovakia (Dusbabek et al. 1979). Recruitment of Larvae LEI, one measure of recruitment, was based only on those EFs that produced lar- vae. Total recruitment also is affected by the proportion of EFs producing larvae. The LEIs in 1983 and in the forest in 1984 were <20% of the REIs of egg-laying EFs in la- boratory conditions (see Addison et al. 1998) indicating about 80% attrition of the maximum potential recruitment from EFs producing larvae; the 1984 LEI in the open- ing was ~40% of the maximum potential. Total recruitment in 1984 was higher at both sites, particularly in the opening where twice as many plots (EFs) were productive compared to 1983. Conversely, total recruit- ment in 1983 was highest in the forest habi- tat where 29% more EFs produced larvae. These results are consistent with the hypothesis that weather and ground condi- tions are primary influences on which habi- tats have highest potential to contribute viable larvae in any given year. No compensatory increased production of larvae was observed from plots not produ- cing larvae until late in the season. Thus, earlier ascent onto vegetation should be a major advantage if increased availability (time) for transmission to moose is a primary selective advantage; however, desiccation of larvae is also more likely in warmer weather characteristic of earlier transmission in early September. Winter tick larvae do not descend vegeta- tion to rehydrate like certain tick species (see Knülle and Rudolph 1982). After ascending, they remain on vegetation (Patrick and Hair 1975, Drew and Samuel 1985) and must em- ploy alternative strategies to avoid desicca- tion and death when VPD is high. In 1984, the first larvae to ascend vegetation in the open plots were recovered 3–4 weeks after the initial appearance of larvae in closed cells at both sites. This delayed ascent was syn- chronous with the transition to cooler night air and abundant dew on vegetation (lower VPD) that would help rehydrate larvae per- manently exposed after ascending vegetation, and might also account for why larvae appeared on vegetation earlier during the cooler September of 1984 as compared to 1983. Timing of ascent by winter tick larvae varies annually with weather (Samuel and Welch 1991) and habitat in the same area (Patrick and Hair 1975, current study), and between ecosystems at the continental scale. For example, winter tick larvae experienced 4–8 month post-hatch delays before appear- ing on vegetation or hosts during October– November in warm climates of Texas, Oklahoma, and parts of coastal central California (Table 3). Ascent of vegetation at a south-facing site near Kamloops, British Columbia occurred as early as in central 36 RECRUITMENT OF WINTER TICK LARVAE – ADDISON ET AL. ALCES VOL. 52, 2016 Alberta and central Ontario, but not until ~2 months post-hatch (Wilkinson 1967). In central Alberta and central Ontario, larvae were first reported on vegetation after a mini- mum post-hatch delay of 2–4 weeks (Table 3). Although the timing of transmission of winter tick larvae may seem to be an adaptation co- incident with increased movement of moose during the mating season (Drew and Samuel 1985), the wide variation in the presence of lar- vae before ascending vegetation likely reflects a weather-induced evolutionary adaptation to reduce desiccation and mortality. One disadvantage of delayed ascent could be a truncated transmission period that would occur more frequently in colder and more northern moose range; the opposite may explain more frequent epizootics in southern moose range. We collected limited larvae following cold weather and substan- tial snowfall in 1983 and, like Drew and Samuel (1985), observed that larvae were much slower in response to movement and less effective in attaching to a flagging sheet at colder temperatures. Summary This study compared recruitment of win- ter tick larvae in 2 different habitats, a forest opening and a closed canopy, deciduous for- est, by measuring survival of known adult fe- male ticks and their productivity relative to weather. Recruitment varied annually both within and between habitats indicating that weather and microsite conditions influence recruitment of winter tick larvae. This influ- ence was most important during the egg- laying and incubation periods in summer and Table 3. Timing of ascent of Dermacentor albipictus larvae. Location 1st Larvae on Vegetation 1st Larvae on Host Post-hatch Delay in Ascent Edwards Plateau, Texas (1) early Nov. San Antonio/Kerrville Texas (2) Oct. eastern Oklahoma (3) - open meadow Nov. 15 151 d - forest Nov. 15 133 d central California (4) Sept. 15 -Sept. 18 -Aug. 20–27 ~ 4–8 mon Kamloops, British Columbia (5) Sept. 19 ~ 2 mon Oct. 3–6 central Alberta (6) early Sept. ~ 2 wk 1985 (7) Oct. 3 1986 (7) Sept. 30 1987 (7) Sept. 6 1988 (7) Sept. 11 central Ontario (8) 1983 opening Sept. 6 1983 forest Sept. 13 1984 opening Aug. 28 17–24 d min 1984 forest Sept. 18 25–32 d min Numbers in parentheses refer to references: (1) Parish and Rude 1946; (2) Drummond 1967; (3) Patrick and Hair 1975; (4) Howell 1939; (5) Wilkinson 1967; (6) Drew and Samuel 1986; (7) Samuel and Welch 1991; (8) current study. ALCES VOL. 52, 2016 ADDISON ET AL. – RECRUITMENT OF WINTER TICK LARVAE 37 when larvae ascended vegetation in autumn. Open and warmer habitats are presumably the nidus for transmission of larvae to moose except in years of hot, dry weather in summer and autumn that increases egg and larval des- iccation. The end of the diapause that occurs between hatching and ascent of vegetation appears synchronous with cooler, more humid conditions that would reduce desic- cation of larvae both on the ground and questing on vegetation in late summer and autumn. ACKNOWLEDGEMENTS We greatly appreciate the efforts of D. Fraser, S. Fraser, S. Gadawaski, A. Jones, S. McDowell, L. Berejikian, K. Long, K. Paterson, L. Smith, D. Bouchard, V. Ewing, J. Jefferson, M. van Schie, A. MacMillan, A. Rynard, N. Wilson, C. Pirie, M. McLaughlin, D. Carlson, C. McCall, and P. Methner for their strong commitment to some or all of capturing, raising, and maintaining moose calves and collection of ticks. Field work was conducted at the Wildlife Research Sta- tion in Algonquin Park where the OMNR staff was of great help. We thank D. 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ALCES VOL. 52, 2016 http://www.R-project.org/ http://www.R-project.org/ RECRUITMENT OF WINTER TICKS (DERMACENTOR ALBIPICTUS) IN CONTRASTING FOREST HABITATS, ONTARIO, CANADA STUDY AREA METHODS Definitions Engorged Female Ticks (EFs) Fecundity and Hatching Larval Recruitment Data Analysis RESULTS Dispersal and Fecundity Larval Recruitment Minimum Free-iving Period DISCUSSION Weather and Desiccation Fecundity Rate of Development Recruitment of Larvae Summary ACKNOWLEDGEMENTS REFERENCES