Historical Range Research Articles

Results from Kentucky’s 10-year Bobwhite Recovery Plan

The northern bobwhite (Colinus virginianus; hereafter, bobwhite) has experienced a precipitous population decline through almost all its historical range over the last 6 decades. We initiated a 10-year restoration plan in Kentucky, USA in 2008 and reported on it through 3 published “Road to Recovery” reports along with 30 peer-reviewed articles and abstracts, 2 technical documents, 7 theses or dissertations, and 11 popular literature pieces. Seven Quail Focus Areas were selected across the state based on site personnel, geographic position (east to west), and land ownership (e.g., private, public, state, federal) for monitoring and habitat management. The focus areas averaged 11,895 acres and area managed for quail on an annual basis ranged from 9% to 42%. Management took the form of herbicide applications, disking, fire, planting, grazing, control of woody vegetation, and mowing. Hierarchical distance sampling models using time-of-removal information to inform detection processes were used to assess bobwhite density on each focus area. Models were based on spring breeding bird point counts in which a suite of grassland songbirds were recorded and fall covey counts in which only bobwhite were recorded. Roadside surveys (direct observation) and hunter harvest information were also used for statewide comparisons of focus areas and statewide trends. Across all years and focus areas a 40% increase in the quail population was observed in 20 years (38%) of the possible 53 years of survey data. Stable to increasing trends were also observed in focal area populations of dickcissel (Spiza americana), eastern meadowlark (Sturnella magna), eastern kingbird (Tyrannus tyrannus), field sparrow (Spizella pusilla), prairie warbler (Setophaga discolor), and Bell’s vireo (Vireo bellii). A focus on habitat management and associated monitoring on relatively small (<20,000 acres) areas was shown to be successful on an individual area, as determined by increases in bird numbers across years and challenges completed in the Quail Plan but did not result in an observed increase in statewide quail indices. Future quail restoration plans in Kentucky should be directed more toward open production land, which is made up of 6 million acres of pastureland, hay land, row crop agriculture, reverting fields, reclaimed mineland, and grasslands. This work will be completed by utilizing working lands, such as field borders in row crop systems and grazing native warm-season grasses in pasture or hay systems, for wildlife activities. Monitoring systems on these production lands will be in the breeding season only and autonomous recording devices will be

Morphological variation in skull shape and size across extinct and extant populations of the greater stick-nest rat (

Within-species morphological variation is often observed across spatial and climatic gradients. Understanding this variation is important to conservation planning, as specialised adaptations may influence a population’s persistence following translocation. However, knowing whether local adaptations are prevalent within a species can be challenging when the species has undergone range contractions. Here, we used museum specimens to study size and shape variation of the greater stick-nest rat (Leporillus conditor). We aimed to determine whether intraspecific size and shape variation previously existed within the species across its historical range, and inform on possible implications for translocations of the remaining extant population. We found significantly larger skull size in the Franklin Islands and arid populations, possibly indicating a historically continuous population experiencing similar selection pressures such as high predation pressure, competition with other large arid zone rodents or climatic extremes. Conversely, skull shape variation within the species adheres to an allometric trajectory, indicating no specific local adaptations of skull shape. This absence of local skull shape adaptation suggests that the Franklin Islands population is likely suitable for mainland translocations. However, further research into the historical phylogeography of the species is recommended to identify whether large size resulted from shared ancestry or convergent evolution.

Habitat selection and abundance of West Indian manatees Trichechus manatus at the margins of their expanding range

Habitat selection and abundances at range margins during geographic expansion may influence movement into new areas, shaping the trajectory of climate-driven changes in species distribution. The West Indian manatee is an ideal species to study how habitat selection influences range expansion because its presence has rapidly increased during the past 2 decades in the northern Gulf of Mexico (nGoM), a region outside its historical range. We estimated the habitat selection and abundances of manatees in coastal Alabama waters along the nGoM coast using resource selection functions and N-mixture models, respectively. Warm season (May-Nov) manatee abundances were estimated at 25 and 34 manatees at any given time in coastal Alabama waters in 2010 and 2019, respectively. Manatees primarily used the Mobile-Tensaw River Delta and Dog River areas, selecting nearshore shallow water habitats proximate to submerged aquatic vegetation. Distance to boat ramps and human population density had stronger effects on opportunistic sighting data but remained important for tagged data, indicating that manatee habitat selection overlapped with humans. Temperature strongly predicted manatee sightings; most sightings occurred when temperatures were &gt;20°C. Our data indicate that the key interacting factors likely to moderate manatee range expansion, and therefore be important to management and conservation of this species, include increased sea temperature, availability of nearshore habitat with submerged aquatic vegetation, and regional manatee population dynamics. As environmental conditions at the range margins continue to become more favorable to manatees and areas within the range core decline in quality, areas at the range margins may become increasingly important.

Discovery of new cave-roosts of the endangered Pacific sheath-tailed bat on Ovalau Island, Fiji

The Endangered Pacific sheath-tailed bat (Emballonura semicaudata) is a small, insectivorous cave-bat that has been extirpated from much of its historic range. A rapid biodiversity assessment to Ovalau Island, Fiji was completed in January 2021 to solicit information on the species from indigenous communities and work with them to conduct searches of potential and known cave-roosts. We identified three new roosts (50–150 bats each) and confirmed that a historic cave-roost last evaluated in 2012 still had ∼100 bats. Ovalau Island is recommended as a national conservation priority for the species given there are at least four active roosts with 350–600 bats; local community members should be involved in the protection of these important cave-roosts.

Frequency of disturbance mitigates high-severity fire in the Lake Tahoe Basin, California and Nevada

Because of past land use changes and changing climate, forests are moving outside of their historical range of variation. As fires become more severe, forest managers are searching for strategies that can restore forest health and reduce fire risk. However, management activities are only one part of a suite of disturbance vectors that shape forest conditions. To account for the range of disturbance intensities and disturbance types (wildfire, bark beetles, and management), we developed a disturbance return interval (DRI) that represents the average return period for any disturbance, human or natural. We applied the DRI to examine forest change in the Lake Tahoe Basin of California and Nevada. We specifically investigated the consequences of DRI on the proportion of high-severity fire and the net sequestration of carbon. In order to test the management component of the DRI, we developed management scenarios with forest managers and stakeholders in the region; these scenarios were integrated into a mechanistic forest landscape model that also accounted for climate change, as well as natural disturbances of wildfire and insect outbreaks. Our results suggest increasing the frequency of disturbances (a lower DRI) would reduce the percentage of high-severity fire on landscape but not the total amount of wildfire in general. However, a higher DRI reduced carbon storage and sequestration, particularly in management strategies that emphasized prescribed fire over hand or mechanical fuel treatments.

БАРДОВСКАЯ ПЕСНЯ В КОНТЕКСТЕ ИСТОРИЧЕСКОГО ВЗАИМОДЕЙСТВИЯ РУССКОЙ ПОЭЗИИ И МУЗЫКИ

In the article, in a wide historical range, the prerequisites for the emergence and existence of the bard song as a significant phenomenon in the life of Russian society in the second half of the 20 th century, based on the synthesis of poetry and music, the relationship between elite art and mass culture, are considered. For many decades, poets have striven for melodiousness of the word, and musicians for singing poetry, which was embodied in bardic creativity, reflecting the essence of the Russian national character.

The Siberian flying squirrel (Pteromys volans) in Belarus: distribution, abundance, threats, and conservation

The Siberian flying squirrel (Pteromys volans L.) is one of the most poorly studied mammal species in the Belarusian fauna. In Belarus, the species inhabits the south-western border of its distribution range. Despite a multitude of its high conservation statuses, as well as extremely scarce information on the species’ distribution and biology in the country, no special studies on the species have been conducted. The last reliably documented record of the flying squirrel was made more than 20 years ago, in 1996, in Viciebsk District, in the territory of Suražski forestry [Red Data... 2015]. Other information on the state of the population, distribution of the species, or individual registrations in Belarus for the last 20 years (1996–2017) lacks in the literature. We found more than 100 territorial sites of the Syberian flying squirrel in Viciebsk and Haradok districts in 2017–2020. Potential habitats of the species in other districts of the Viciebsk and Minsk regions were also surveyed. This allowed us to establish the borders of the modern distribution area of the species in Belarus, to estimate its current population, and to study some aspects of ecology of the species. At present, the species inhabits less than 1% of the territory of Belarus, but its density in optimal habitats is relatively high. A number of publications, as far back as the last century, indicate a much wider distribution of the species in the country. Therefore, it is possible to indicate a substantial shrinkage of the species’ distribution area during the last 50–100 years. Taking into account the insignificant area of the modern distribution of the species along with the key threats and current forest management tendencies, it is possible to assert with certainty that in the absence of special protection measures, the flying squirrel might soon be gone extinct in Belarus. Some of the habitats we have identified are currently protected by land users. In addition, we have proposed a number of activities within the framework of Management plan development necessary for its conservation, as well as those aimed at further studying, including the possible restoration of its historical range.

Evaluation of the impact of transgenic maize BT799 on growth, development and reproductive function of Sprague-Dawley rats in three generations

BT799 was Bacillus thuringiensis-genetic modified (GM) maize, and Sprague-Dawley (SD) rats were treated with different diet formulations containing BT799 maize grain (33% and 66%) or its non-transgenic Zhengdan 958 (ZD958, 33% and 66%). The feeding lasted for 10 (P)/14 (F1 and F2) weeks. The reproductive capacity and pathological responses were detected in each generation of rats fed with BT799 and ZD958. During the growth and development of parental rats, each group showed the same trend in body weight gain and food intake, with a few fluctuations at individual time points. No statistically significant difference was observed in reproductive data (copulation index, fertility index, and live birth rate) of rats fed with transgenic maize compared with non-transgenic maize. We observed some apparent changes in reproductive data (sperm numbers and motility) and pathological responses (organ relative weights, hematological parameters, serum chemistry parameters, and sex hormone levels) among rats fed with BT799 maize grain. However, these differences were within the laboratory's historical normal range of control SD rats and not maize grain dose-dependent. These changes were not considered to be adverse or toxic. No significant difference in macroscopic or histological adverse effects was observed between rats consuming transgenic BT799 diet and non-transgenic diet. In conclusion, the long-term intake of BT799 maize was as safe as the corresponding non-transgenic maize for three-generation SD rats.

Resurrecting an Idaho Icon: How Research and Management Reversed Declines of Native Westslope Cutthroat Trout

Westslope Cutthroat Trout Oncorhynchus clarkii lewisi (WCT), the dominant nonanadromous salmonid in central and northern Idaho, historically were extremely abundant and widely distributed. Despite restricted harvest methods and limits since 1899, many WCT populations declined and by the 1960s, populations in several major drainages were on the brink of collapse. In response, fisheries biologists began investigating WCT population dynamics, life histories, and habitat requirements and developed evidence‐based regulations and habitat restoration alternatives. Here we describe fluvial WCT case histories that illustrate how research and management collaborated to rebuild populations. The sustained and successful effort to restore fluvial WCT in Idaho offers insights to assist WCT recovery efforts elsewhere. Today, populations in many watersheds have been rehabilitated and WCT currently inhabit about 80% of their historical stream range. Despite continued threats, many Idaho WCT populations are relatively secure, provide unique recreational opportunities, and remain an important ecological, cultural, and economic resource.

IPODfish – A new method to infer the historical occurrence of diadromous fish species along river networks

Available information on diadromous fish species historical occurrences is generally biased and incomplete across species distribution range and spatial scales. This work aims to establish a new methodological framework (iPODfish – Inferring Past Occurrences of Diadromous Fish) to obtain a more complete representation of the historical occurrences of diadromous fish species over their full distribution range. The iPODfish is based on assumptions, rules and thresholds derived from the interplay between freshwater network features, diadromous fish species ecology and known historical occurrence. These are used to establish historical pseudo-occurrences at the segment scale, i.e., locations where the species was most likely to be present or absent. The methodology is expressed by a tree-like representation of a stepwise, information supported, decision process. It has five steps (separating main river segments from tributary segments; accounting for segments specificities; imposing the relative distance threshold; imposing the Strahler value threshold, and; establishing the sub-basin Strahler threshold), divides into two moments of application (main river followed by the tributaries) and establishes presences, pseudo-presences and pseudo-absences. The iPODfish can deal with multiple information sources, cope with data bias and provide a reliable consistent historical occurrence output at the segment scale for the known historical geographical range of the species. Despite its inference nature, iPODfish is still a conservative procedure leading to ecologically coherent outputs that may be applied to any diadromous fish species (with a relevant amount of historical data available) in any river network throughout the globe because the concepts and definitions used are general ecological features of diadromous and freshwater networks. The method outputs are applicable in biogeographical and/or macroecological studies using historical data and may prove useful to the management and conservation of diadromous fish species.

New fossil remains of the commensal barnacleCryptolepas rhachianectiprovide evidence of gray whales in the prehistoric South Pacific

AbstractWe report the finding of two partial specimens ofCryptolepas rhachianecti(Cirripedia, Coronulidae), a coronulid barnacle known only to inhabit the skin of gray whales (Eschrichtius robustus), in Pleistocene-aged sediments from the Canoa Basin, Ecuador. While the historical range of gray whales includes the North Pacific and North Atlantic, to our knowledge this is the first inferred evidence of a gray whale population having resided within the South Pacific. We describe the twoCryptolepas rhachianectifossils, use isotopic analysis to investigate evidence of migration in their host whales, and discuss their implications for our understanding of gray whale evolutionary history.

Influence of Pliocene and Pleistocene climates on hybridization patterns between two closely related oak species in China.

Contemporary patterns of genetic admixture reflect imprints of both ancient and recent gene flow, which can provide us with valuable information on hybridization history in response to palaeoclimate change. Here, we examine the relationships between present admixture patterns and past climatic niche suitability of two East Asian Cerris oaks (Quercus acutissima and Q. chenii) to test the hypothesis that the mid-Pliocene warm climate promoted while the Pleistocene cool climate limited hybridization among local closely related taxa. We analyse genetic variation at seven nuclear microsatellites (1111 individuals) and three chloroplast intergenic spacers (576 individuals) to determine the present admixture pattern and ancient hybridization history. We apply an information-theoretic model selection approach to explore the associations of genetic admixture degree with past climatic niche suitability at multiple spatial scales. More than 70 % of the hybrids determined by Bayesian clustering analysis and more than 90 % of the individuals with locally shared chloroplast haplotypes are concentrated within a mid-Pliocene contact zone between ~30°N and 35°N. Climatic niche suitabilities for Q. chenii during the mid-Pliocene Warm Period [mPWP, ~3.264-3.025 million years ago (mya)] and during the Last Glacial Maximum (LGM, ~0.022 mya) best explain the admixture patterns across all Q. acutissima populations and across those within the ancient contact zone, respectively. Our results highlight that palaeoclimate change shapes present admixture patterns by influencing the extent of historical range overlap. Specifically, the mid-Pliocene warm climate promoted ancient contact, allowing widespread hybridization throughout central China. In contrast, the Pleistocene cool climate caused the local extinction of Q. chenii, reducing the probability of interspecific gene flow in most areas except those sites having a high level of ecological stability.

Distribution and density of the Critically Endangered estuarine pipefish across its range – implications for conservation

Abstract The identification and development of locally significant conservation actions require comprehensive and current ecological species information. Logistically this can be difficult, especially when studying rare and cryptic species which are at greater risk of becoming extinct. This study investigated the current distribution and density of the estuarine pipefish Syngnathus watermeyeri, the only Critically Endangered pipefish in the world, and the commonly found longsnout pipefish Syngnathus temminckii. Pipefish were surveyed using a seine net in the Kariega, Bushmans, Kasouga and Kleinemonde East and West estuaries, located on the south coast of South Africa, in October 2019, March 2020 and July 2020. The habitat and physico‐chemical characteristics of each site were measured to determine whether these factors had an effect on the presence of S. watermeyeri. In addition, available habitat extent within the Bushmans and Kariega estuaries was mapped. Pipefish were only detected in two of the five estuaries within the historical range of S. watermeyeri and a total of 59 S. watermeyeri and 45 S. temminckii were found across all three surveys. Zostera capensis and Codium sp. were the dominant submerged vegetation within the Bushmans and Kariega estuaries and the presence of pipefish was positively associated with the availability of vegetation, especially Codium sp. This is the most extensive targeted survey for S. watermeyeri to date, both temporally and spatially, and provides important insights into what threatens this species. This information should be used to inform future IUCN Red List assessments and the development of locally significant conservation actions.

Men and wolves: Anthropogenic causes are an important driver of wolf mortality in human-dominated landscapes in Italy

Over the last 40 years the gray wolf ( Canis lupus ) re-colonized its historical range in Italy increasing human-predator interactions. However, temporal and spatial trends in wolf mortality, including direct and indirect persecution, were never summarized. This study aims to fill this gap by focusing on the situation of Tuscany and Emilia-Romagna regions, hosting a significant proportion of the Italian wolf population, by: ( i ) identifying the prevalent causes of wolf mortality, ( ii ) summarizing their temporal and spatial patterns and ( iii ) applying spatially-explicit Generalized Linear Models to predict wolf persecution. Between October 2005 and February 2021, 212 wolf carcasses were collected and subjected to necropsy, being involved in collisions with vehicles (n = 104), poisoned (n = 45), wounded with gunshot (n = 24) or blunt objects (n = 4) and being hanged (n = 2). The proportion of illegally killed wolves did not increase through time. Most persecution events occurred between October and February. None of our candidate models outperformed a null model and covariates such as the density of sheep farms, number of predations on livestock, or human density were never associated to the probability of having illegally killed wolves, at the municipal scale. Our findings show that conventional correlates of wolf persecution, combined with a supposedly high proportion of non-retrieved carcasses, fail to predict illegal wolf killings in areas where the species have become ubiquitous. The widespread spatial distribution of illegal killings indicates that persecution probably arises from multiple kinds of conflicts with humans, beyond those with husbandry. Wolf conservation in Italy should thus address cryptic wolf killings with multi-disciplinary approaches, such as shared national protocols, socio-ecological studies, the support of experts’ experience and effective sampling schemes for the detection of carcasses.

Cumulative downstream turbine‐induced mortality and thresholds for facilitating upstream passage of American eel

AbstractAmerican eels (Anguilla rostrata) are vulnerable to turbine‐induced mortality during outmigration along regulated rivers. Turbine‐induced mortality is cumulative when multiple facilities are encountered along the route. This level of mortality may be unsustainable such that facilitating upstream movement ostensibly for recovery purposes, may in fact be detrimental to the population or an ecological trap. The objectives of this study were to estimate a theoretical threshold for facilitating upstream movement passed hydroelectric facilities and estimating cumulative turbine mortality within waterbodies across American eel's historical range within Ontario, Canada. A stage‐structured model was used to estimate mortality thresholds parameterized by published life stage survival probabilities using a maternal effect and altering silver eel survival to mimic turbine mortality. The threshold was exceeded when population growth (λ) declined below 1.0. Site mortality was estimated based on the generating station characteristics including turbine type, size, proportion of flow through turbines, and sluice gate height. Cumulative mortality within a waterbody was projected using a Bayesian network (i.e., conditional probability) and the calculated site‐specific mortality. The survival required for a stable population using the stage‐structured model was 0.75; (0.65–0.85) therefore, annual mortality greater than 0.25 (0.15–0.35) would result in population decline (λ &lt; 1). The effects of turbine mortality increased with additional hydroelectric facilities encountered along the route. Across Ontario, there was no eel habitat deemed to be safe in terms of levels of cumulative turbine mortality during outmigration. Moreover, 89.1% of eel habitat was considered to be within the cautionary range of turbine mortality, whereas 10.9% of eel habitat was considered to be above the threshold for sustainable passage during outmigration. Lake Ontario accounted for 98.2% of the area within the cautionary range, whereas most of the tributaries and watersheds associated with the Ottawa River and Lake Ontario were above the threshold.

Using a climate attribution statistic to inform judgments about changing fisheries sustainability

Sustainability—maintaining catches within the historical range of socially and ecologically acceptable values—is key to fisheries success. Climate change may rapidly threaten sustainability, and recognizing these instances is important for effective climate adaptation. Here, we present one approach for evaluating changing sustainability under a changing climate. We use Bayesian regression models to compare fish population processes under historical climate norms and emerging anthropogenic extremes. To define anthropogenic extremes we use the Fraction of Attributable Risk (FAR), which estimates the proportion of risk for extreme ocean temperatures that can be attributed to human influence. We illustrate our approach with estimates of recruitment (production of young fish, a key determinant of sustainability) for two exploited fishes (Pacific cod Gadus macrocephalus and walleye pollock G. chalcogrammus) in a rapidly warming ecosystem, the Gulf of Alaska. We show that recruitment distributions for both species have shifted towards zero during anthropogenic climate extremes. Predictions based on the projected incidence of anthropogenic temperature extremes indicate that expected recruitment, and therefore fisheries sustainability, is markedly lower in the current climate than during recent decades. Using FAR to analyze changing population processes may help fisheries managers and stakeholders to recognize situations when historical sustainability expectations should be reevaluated.

The faded stripes of Bengal: a historical perspective on the easternmost distribution of the striped hyena

The striped hyena (Hyaena hyaena) is an understudied large carnivore with no known historic range map. Knowledge of the past and present extent of its easternmost distribution beyond 85° east longitude is dubious. Through a comprehensive review of historical evidence and contemporary records, we investigated striped hyena presence in Bengal, i.e., Bangladesh and the Indian state of West Bengal in South Asia. We found 14 historical records, with the oldest one dating to 1876. Our review establishes Bangladesh as a former striped hyena range country and the striped hyena as one of the first large carnivores to go extinct in Bangladesh. We identified northern Bangladesh as part of its historical range (until ~1965), and south-central Bangladesh as a possible part of its historical range. In West Bengal, India, hyenas were historically present up to the southern tributaries of the Brahmaputra River, but the present range is reduced. The area south of the Damodar River is its last refuge in Bengal. We also found 15 contemporary records (2010–2021) in Bengal, from sites situated on the eastern limit of the Chota Nagpur Plateau. These records noted 25 sightings including 9 deaths due to poaching, train accidents, and retaliatory killings. Our review demonstrates that hyenas are currently present up to 87° east longitude, which extends the currently documented easternmost range for the species by almost 1,000 km. We recommend methods which can be applied to delineate the historical extent of striped hyenas elsewhere as well as for other poorly understood species.

Heatwave implications for the future of longleaf pine savanna understory restoration.

The longleaf pine (LLP) savanna ecosystem once covered ~ 92 million acres of the Southeast USA, but due to anthropogenic activities such as logging and fire suppression, only 3% of its once widespread historic range remains. While many restoration efforts are underway to conserve this biodiverse ecosystem, restoration must be done in the context of climate change. In the last few decades, heatwaves have increased in frequency and intensity across the Southeastern USA with further increases predicted. To expand our understanding of LLP savanna restoration in light of these changes, we ran a series of three simulated heatwave greenhouse experiments through a Course-based Undergraduate Research Experience (CURE) incorporating ~ 150 undergraduate researchers per experiment. We measured plant growth metrics for four understory grasses commonly used in LLP savanna restoration efforts. We found that while most grass plug individuals survived heatwave conditions, aboveground production was reduced due to heatwaves. This productivity decrease could result in less biomass available for the essential vegetation fire feedback loop, where fire increases grass biomass, and in turn, more grass provides more fuel for fire. These results imply that land managers can proactively compensate for biomass loss due to heatwaves by planting more grass plugs during initial restoration.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11258-021-01212-7.

Regulatory Fragmentation: An Unexamined Barrier to Species Conservation Under Climate Change

Requirements for the protection or restriction of species are based on regulatory classifications such as “native” or “invasive,” which become anachronistic when climate change drives species outside of their historical geographic range. Furthermore, such regulatory classifications are inconsistent across the patchwork of land ownership that species must traverse as they move between jurisdictions or when transported by humans, which obstructs effective regional management. We surveyed the U.S. laws and regulations relevant to species movement and found that the immigration of species to new jurisdictions makes paradoxical existing regulatory language that sets the categories of species deserving protection or removal. Climate change is universal and progressing rapidly, which provides a shrinking window to reconcile regulatory language originally developed for a static environment.

Microclimate conditions alter Ixodes scapularis (Acari: Ixodidae) overwinter survival across climate gradients in Maine, United States

The incidence and geographic range of vector-borne diseases have been expanding in recent decades, attributed in part to global climate change. Blacklegged ticks (Ixodes scapularis), the primary vector for multiple tick-borne pathogens in North America, are spreading rapidly beyond their historic post-colonial range and are thought to be constrained mainly by winter temperature at northern latitudes. Our research explored whether winter climate currently limits the distribution of blacklegged ticks and the pathogens they transmit in Maine, U.S.A., by contributing to overwinter mortality of nymphs. We experimentally tested tick overwinter survival across large-scale temperature and snowfall gradients and assessed factors contributing to winter mortality in locations where blacklegged tick populations are currently established and locations where the blacklegged tick has not yet been detected. We also tested the hypothesis that insulation in the tick microhabitat (i.e., by leaf litter and snowpack) can facilitate winter survival of blacklegged tick nymphs despite inhospitable ambient conditions. Overwinter survival was not significantly different in coastal southern compared to coastal and inland northern Maine, most likely due to sufficient snowpack that protected against low ambient temperatures at high latitudes. Snow cover and leaf litter contributed significantly to overwinter survival at sites in both southern and northern Maine. To further assess whether the current distribution of blacklegged ticks in Maine aligns with patterns of overwinter survival, we systematically searched for and collected ticks at seven sites along latitudinal and coastal-inland climate gradients across the state. We found higher densities of blacklegged ticks in coastal southern Maine (90.2 ticks/1000 m2) than inland central Maine (17.8 ticks/1000 m2) and no blacklegged ticks in inland northern Maine. Our results suggest that overwinter survival is not the sole constraint on the blacklegged tick distribution even under extremely cold ambient conditions and additional mechanisms may limit the continued northward expansion of ticks.