Successful Overwintering Research Articles

Effect of soil moisture on overwintering pupae in Spodoptera exigua (Lepidoptera: Noctuidae)

Spodoptera exigua Hubner (Lepidoptera: Noctuidae), can overwinter as pupae at depths of 0- to 5-cm beneath the ground. In order to understand the effect of soil moisture on the overwintering success of this species, we tested the supercooling point and survival of pupae, and the growth rate of prepupae that were exposed to different temperature and soil moisture in the laboratory. Results showed that supercooling points, body water contents, and survivals after the different pre-treatments were not significantly affected by the soil moisture. The developmental progress of prepupae, survival of prepupae and pupae were negatively correlated with soil moisture as well as the delay of exposure time, which supports the hypothesis that soil moisture acts as a developmental modulator. We presumed that the delay of pupation and lower prepupae survival under higher soil moisture was due to lack of a complete pupal chamber for protection at low temperatures. Low pupal survival was likely attributed to lack of oxygen in the soil, especially under the condition of higher soil moisture. We suggest that using strategies of irrigation and soil tillage during winter may decrease the overwintering population of S. exigua from the perspective of integrated pest management.

The subnivium: a deteriorating seasonal refugium

For many terrestrial organisms in the Northern Hemisphere, winter is a period of resource scarcity and energy deficits, survivable only because a seasonal refugium – the “subnivium” – exists beneath the snow. The warmer and more stable conditions within the subnivium are principally driven by snow duration, density, and depth. In temperate regions, the subnivium is important for the overwintering success of plants and animals, yet winter conditions are changing rapidly worldwide. Throughout the Northern Hemisphere, the impacts of climate change are predicted to be most prominent during the winter months, resulting in a shorter snow season and decreased snow depth. These climatic changes will likely modify the defining qualities of the subnivium, resulting in broad‐scale shifts in distributions of species that are dependent on these refugia. Resultant changes to the subnivium, however, will be spatially and temporally variable. We believe that ecologists and managers are overlooking this widespread, crucial, and vulnerable seasonal refugium, which is rapidly deteriorating due to global climate change.

Resource use by juvenile brown trout andAlpine bullhead: influence of interspecific versus intraspecific competition

AbstractStream‐dwelling salmonids and bullheads occupy similar resource niches in northern rivers. It is therefore tempting to assume that they might be involved in a competitive interaction, with potential implications for the habitat use and growth of brown trout (Salmo trutta). We conducted artificial‐stream experiments to test whether a putative competitor,Alpine bullhead (Cottus poecilopus), had an effect on the habitat use of under‐yearling (0+) and yearling (1+) trout. We hypothesised that (i) 1+ trout would be competitively superior to 0+ trout, forcing the younger fish to suboptimal habitats, and that (ii) bullhead might affect the habitat use and prey selection of 0+ trout but less so that of 1+ trout. Against our predictions, no effect of bullhead was found on the habitat use of either age class of brown trout. Instead, yearling trout seemed to force bullheads to suboptimal microhabitats with high current velocities. Presence of yearlings also decreased the growth of under‐yearling fish and caused a shift in their diet composition. These findings suggest that competitive interactions may not limit the coexistence of brown trout and bullheads in boreal rivers. Intraspecific interactions between trout age classes may be more important, with potentially detrimental effects on the growth and overwintering success of 0+ trout.

Diadromus pulchellus in North America: field release against leek moth and new characters to distinguish it from Diadromus subtilicornis, a native diamondback moth parasitoid

We report successful overwintering of Diadromus pulchellus in North America (Ontario) following introduction of this species from Europe to control the leek moth, Acrolepiopsis assectella, a recently established alien species. Field rearing revealed that the native Diadromus subtilicornis emerged only from diamondback moth, Plutella xylostella, whereas D. pulchellus was reared almost exclusively from leek moth. The single D. pulchellus reared from diamondback moth was anticipated because host range studies found this species could develop on both leek moth and diamondback moth in the laboratory, although, it had not been previously reported from diamondback moth in the field in Europe. DNA barcoding of specimens of both Diadromus spp. confirmed their species status and novel morphological characters are presented to distinguish D. pulchellus from D. subtilicornis. In addition, DNA from specimens of D. subtilicornis from Europe clustered with DNA from specimens across Canada, confirming that it is a single Holarctic species. Finally, a new host association for D. subtilicornis is recorded from the dame's rocket moth: Pseudoplutella porrectella.

Snow evens fragmentation effects and food determines overwintering success in ground‐dwelling voles

AbstractClimate instability strongly affects overwintering conditions in organisms living in a strongly seasonal environment and consequently their survival and population dynamics. Food, predation and density effects are also strong during winter, but the effect of fragmentation of ground vegetation on ground‐dwelling small mammals is unknown. Here, we report the results of a winter experiment on the effects of habitat fragmentation and food on experimental overwintering populations of bank voles Myodes glareolus. The study was conducted in large outdoor enclosures containing one large, two medium‐sized or four small habitat patches or the total enclosure area covered with protective tall‐grass habitat. During the stable snow cover of midwinter, only food affected the overwintering success, body condition, trappability and earlier onset of breeding in bank voles. However, after the snow thaw in spring, habitat fragmentation gained importance again, and breeding activities increased the movements of voles in the most fragmented habitat. The use of an open, risky matrix area increased along the habitat fragmentation. Our experiment showed that long‐lasting stable snow cover protects overwintering individuals in otherwise exposed and risky ground habitats. We conclude that a stable winter climate and snow cover should even out habitat fragmentation effects on small mammals. However, along prolonged snow‐free early winter and in an earlier spring thaw, this means loss of protection by snow cover both in terms of thermoregulation and predation. Thus, habitat cover is important for the survival of small ground‐dwelling boreal mammals also during the non‐breeding season.

The Possibility of Overwintering byIdiosepius paradoxus(Cephalopoda: Idiosepiidae) at the Northern Limits of its Distribution

Abstract. Idiosepius paradoxus (Ortmann, 1881) has been previously collected only in the four months from September to December at Usujiri, in northern Japan, which is considered its northern limit. Previous reports indicate that I. paradoxus is not able to overwinter at this distribution boundary. In winter 2006–2007, seawater temperatures were higher than in previous years. To investigate whether I. paradoxus overwinters in Usujiri, we collected specimens monthly and compared their occurrence pattern with seawater temperature data. In 2007, samples were collected between April and August, months in which they had not been previously collected in Usujiri. Winter seawater temperatures in 2007 were higher than in any other year. These results suggested that I. paradoxus successfully overwintered in Usujiri. However, winter water temperatures in 2008 returned to their usual lows, and specimens were not found in April. Therefore, overwintering success appeared to be temporary, and range expansion toward high...

Dynamics of West Nile Virus Persistence in House Sparrows (Passer domesticus)

West Nile Virus (WNV) is now endemic throughout North America, with annual recurrence dependent upon successful overwintering when cold temperatures drive mosquito vectors into inactivity and halt transmission. To investigate whether avian hosts may serve as an overwintering mechanism, groups of eight to ten House Sparrows were experimentally infected with a WN02 genotype of WNV and then held until necropsy at 3, 5, 7, 9, 12, 15, or 18 weeks post-infection (pi) when they were assessed for the presence of persistent infection. Blood was collected from all remaining birds every two weeks pi, and sera tested for WNV RNA and WNV neutralizing antibodies. West Nile virus RNA was present in the sera of some birds up to 7 weeks pi and all birds retained neutralizing antibodies throughout the experiment. The detection of persistently infected birds decreased with time, from 100% (n = 13) positive at 3 weeks post-infection (pi) to 12.5% (n = 8) at 18 weeks pi. Infectious virus was isolated from the spleens of birds necropsied at 3, 5, 7 and 12 weeks pi. The current study confirmed previous reports of infectious WNV persistence in avian hosts, and further characterized the temporal nature of these infections. Although these persistent infections supported the hypothesis that infected birds may serve as an overwintering mechanism, mosquito-infectious recrudescent viremias have yet to be demonstrated thereby providing proof of principle.

Surviving winter: diapause syndrome in the southern green stink bug Nezara viridula in the laboratory, in the field, and under climate change conditions

The southern green stink bug Nezara viridula (L.) (Heteroptera: Pentatomidae) has long attracted attention not only as a serious pest of numerous agricultural crops, but also as a species expanding its range in many parts of the world. Nezara viridula has also been widely used as a model in different experimental studies. The present review focuses on reproductive (i.e. adult) winter diapause, which is the pivotal element of the species' seasonal cycle. Results from numerous field experiments and observations, as well as laboratory ecophysiological investigations conducted during the few last decades, are analyzed and interpreted. Experimental findings are used to describe in detail the dynamics of physiological changes during overwintering. Reproductive diapause in N. viridula is controlled in both sexes by photoperiodic conditions. The induction of diapause is associated with a reversible change of body colour from green or yellow to russet (or brown). The proper timing of adult emergence and the induction of diapause, as well as the size of adults, is vitally important for successful overwintering. Nezara viridula has been shown to respond strongly to the current trend in climate change by shifting the limit of its northern range, particularly in central Japan. Analysis of historic climate data suggests that the environmental conditions during the last few decades have become more favourable for the overwintering survival of N. viridula in many locations in central Japan. This has likely promoted the northward spread of the species. The relationships between reproductive diapause, reversible body colour change, overwintering success and the recent range expansion are analyzed. Perspectives of the range dynamics of the species are discussed in light of further predicted climate change.

Potential importance of lagoons as breeding grounds for bluegill Lepomis macrochirus in Lake Biwa, Japan

Exotic bluegill Lepomis macrochirus have been propagating in the littoral region of Lake Biwa and its tributary lagoons. To investigate the reproductive activity of bluegill in the prespawning season, fish samples were collected from three sites at the littoral region of the lake and their nearby lagoons. The number of females relative to the total number of specimens tended to be higher in lagoons than in the adjacent littoral sites in the lake. The females collected from lagoons had significantly larger ovaries than those from the lake. The means of gonadal somatic index of females in the lake ranged from 1.77 to 3.44, whereas those in lagoons ranged from 4.35 to 12.2. The higher temperature conditions of lagoons appeared to be responsible for the higher maturation of ovaries of the fish in lagoons. The environmental condition of lagoons is potentially suitable for the active growth of larvae, subsequently increasing their overwintering success. Therefore, earlier spawning of bluegill in lagoons might have contributed to the propagation of bluegill in Lake Biwa to some extent.

Environmental interactions during host race formation: host fruit environment moderates a seasonal shift in phenology in host races of Rhagoletis pomonella

Summary1. Host race formation is a common form of ecological speciation during which new populations that exploit a novel host (e.g. nutritional resource) experience divergent natural selection, causing adaptive divergence from the ancestral population. Typically, multiple selection pressures drive this divergence, suggesting that interactions among environmental effects may be critical during the speciation process.2. Host‐race‐forming phytophagous insects often experience divergent natural selection imposed by seasonality and nutritional environment, two factors likely to interact through their effects on growth and life‐history timing. We tested for the presence of such an interaction in the apple maggot fly, Rhagoletis pomonella, asking whether nutritional effects interact with seasonality to determine overwintering success.3. We find evidence for such an interaction, wherein feeding on a novel host fruit actually mitigates the negative effects of novel seasonality. Feeding on apple (novel) compared to hawthorn (ancestral) fruit conferred greater fly lipid reserves the overwintering, diapause stage. Earlier, seasonal emergence characteristic of the apple host race imposes an overwintering survival cost. But feeding on apples offsets this cost, which confers greater pupal lipid reserves and consequently larger adult body size post‐winter. Seasonality and host fruit interact to determine fly lipid reserves, and host race differences in lipid content are maximized under the most stressful conditions typically experienced by the apple host race. F1 rearing and genetic association tests revealed no evidence for genetically based divergence in lipid content, suggesting that differences in lipid storage among the fly host races are driven primarily by the host fruit environment.4. Our results suggest that interactions between seasonality and host plant environment shape natural selection and therefore influence adaptive divergence during host race formation.

Effects of acclimation and diapause on the thermal tolerance of the two-spotted spider mite Tetranychus urticae

The two-spotted spider mite, Tetranychus urticae, is a worldwide pest species that overwinters as diapausing females. Cold hardening is presumed to start during diapause development to ensure the successful overwintering of this species. To address this hypothesis, we compared cold tolerance between non-diapausing and diapausing females. We measured supercooling point (SCP) and survival to acute cold stress by exposing the mites at a range of sub-zero temperatures (from −4 to −28°C for 2h). The mean SCPs of non-diapausing and diapausing females were −19.6±0.5 and −24.7±0.3°C respectively, and freezing killed the mites. Diapausing females were significantly more cold tolerant than non-diapausing ones, with LT50 of −19.7 and −13.3°C, respectively. Further, we also examined the effects of cold acclimation (10d at 0 or 5°C) in non-diapausing and diapausing females. Our findings indicated that diapause decreased SCP significantly, while cold acclimation had no effect on the SCP except for non-diapausing females that were acclimated at 5°C. Acclimation at 5°C enhanced survival to acute cold stress in diapausing and non-diapausing females, with LT50 of −22.0 and −17.1°C, respectively. Altogether, our results indicate that T. urticae is a chill tolerant species, and that diapause and cold acclimation elevate cold hardiness in this species.

The contribution of the vegetable material layer to the insulation capacities and water proofing of artificial Mus spicilegus mounds

Successful overwintering of small mammals in temperate and cold climates requires behavioural and physiological adaptations. There are several strategies to survive food shortages and the cold. Most species of small mammals use multiple methods simultaneously but nest building and burrowing are the most widespread among them. A well-constructed, dry nest insulates animals from harsh ambient conditions. Mound-building mice build large banks in the autumn and establish a burrow system with nest chambers beneath them. These overwintering structures are built from soil and a considerable amount of plant material. Recent studies presume that the stored vegetable matter does not, or not exclusively, serve as food and indicate that the mounds might have insulating role. To investigate the function of their plant fill, we built artificial mounds with varying plant content, similar to those built by mound-building mice. We measured temperature change at three levels, at the surface, under the mound and at the nest depth, and investigated their water retaining properties. We showed that the plant fill plays a major role in their thermal insulation and waterproofing properties. Mounds reduced temperature variation of the soil and may protect the nest from absorbing precipitation during the winter.

Interactive effects of past and present environments on overwintering success—a reciprocal transplant experiment

Life-history traits are influenced by environmental factors throughout the lifespan of an individual. The relative importance of past versus present environment on individual fitness, therefore, is a relevant question in populations that face the challenge of temporally varying environment. We studied the interacting effects of past and present density on body mass, condition, and survival in enclosure populations of the bank vole (Myodes glareolus) using a reciprocal transplant design. In connection with the cyclic dynamics of natural vole populations, our hypothesis was that individuals born in low-density enclosures would do better overwintering in low-density enclosures than in high-density enclosures and vice versa. Our results show that the effect of summer (past) density was strong especially on survival and body mass. The response of body mass to summer density was negative in both winter (present) density groups, whereas the response of survival probability was nonlinear and differed between the winter density groups. In particular, our data show a trend for higher overwintering success of individuals originating from the lowest summer densities in low winter density and vice versa. We therefore conclude that the capacity of individuals to respond to a change in density was constrained by the delayed density-dependent effects of environment experienced in the past. These effects have the potential to contribute to vole population dynamics. Possible mechanisms mediating the effects of past environment into present performance include both intrinsic and environmental factors.

Body mass and growth of overwintering brown trout in relation to stream habitat complexity

AbstractIn winter, juvenile salmonids hide within the substrate during the day and emerge to feed on drifting invertebrates at night. In channelized streams, where the streambed heterogeneity has been artificially reduced, suitable microhabitats (low‐flow refugia) may be in short supply. Therefore, restoration of stream habitat by enhancement structures might improve the overwintering conditions of juvenile salmonids. We used a set of artificial streams to test whether individually‐marked juvenile brown trout of two age‐classes (age‐0 and age‐1 trout) loose mass during the winter differently in channelized and semi‐natural streams. Fish of both age‐classes lost mass early in the winter (November to January), but age‐0 fish in the channelized streams lost more of their initial mass than did the restored‐stream fish (ca. 10% vs. 2.5% on average, respectively). They then exhibited zero‐growth in both treatments in late winter (January to April), and by early spring (May), the channelized‐stream fish had completely caught up for their greater initial mass loss. In control tanks where the fish were fed continuously, age‐0 trout exhibited zero‐growth from November to January, then gaining mass constantly through the rest of the experiment. Significant time*treatment interaction was also detected for age‐1 trout, but all differences were caused by the faster growth of fish in the control tanks, whereas the two channel treatments did not differ significantly. The shortage of suitable sheltering sites in the channelized streams apparently intensified competition and caused greater initial mass loss in age‐0 trout. Furthermore, growth compensation exhibited by juvenile trout may have negative impacts on the long‐term fitness of individuals. Therefore, by increasing the amount of sheltering sites, in‐stream restoration may have potential to enhance the overwintering success of juvenile salmonids. Copyright © 2010 John Wiley & Sons, Ltd.

Temperature and Resource Availability May Interactively Affect Over-Wintering Success of Juvenile Fish in a Changing Climate

The predicted global warming may affect freshwater systems at several organizational levels, from organism to ecosystem. Specifically, in temperate regions, the projected increase of winter temperatures may have important effects on the over-winter biology of a range of organisms and especially for fish and other ectothermic animals. However, temperature effects on organisms may be directed strongly by resource availability. Here, we investigated whether over-winter loss of biomass and lipid content of juvenile roach (Rutilus rutilus) was affected by the physiologically relatively small (2-5°C) changes of winter temperatures predicted by the Intergovernmental Panel on Climate Change (IPCC), under both natural and experimental conditions. This was investigated in combination with the effects of food availability. Finally, we explored the potential for a correlation between lake temperature and resource levels for planktivorous fish, i.e., zooplankton biomass, during five consecutive winters in a south Swedish lake. We show that small increases in temperature (+2°C) affected fish biomass loss in both presence and absence of food, but negatively and positively respectively. Temperature alone explained only a minor part of the variation when food availability was not taken into account. In contrast to other studies, lipid analyses of experimental fish suggest that critical somatic condition rather than critical lipid content determined starvation induced mortality. Our results illustrate the importance of considering not only changes in temperature when predicting organism response to climate change but also food-web interactions, such as resource availability and predation. However, as exemplified by our finding that zooplankton over-winter biomass in the lake was not related to over-winter temperature, this may not be a straightforward task.

Successful overwintering of arthropods in roadside verges

In densely populated areas, roadside verges often provide the last semi-natural habitats available. Their ecological value is often stressed by bio survey results. Yet insect summer surveys potentially misjudge the value of a biotope (roadside or otherwise) since the occurrences of species may only be seasonal, or even transient. To effectively ascertain the importance of a site for insects, species must be shown to complete their life cycle there or at least be shown to successfully accomplish critical life stages, such as reproduction or overwintering. To confirm overwintering of arthropods in roadsides, sods were cut in late winter in a verge where several years of summer survey data were available. The sods were placed in transparent semi-permeable cages and kept alive during subsequent spring, summer and autumn. All emerging arthropods were caught inside the cages using pitfall and funnel traps and identified to order or family level. Most of the terrestrial arthropod phyla and orders occurring in NW-Europe appeared to be represented. Several groups were further identified to the species level: Carabidae (Coleoptera), Curculionidae (Coleoptera), Araneae, Orthoptera, Apidae (Hymenoptera), Syrphidae (Diptera) and Dephacidae/Cercopidae (Hemiptera). Particularly for the Carabidae, Araneae and Curculionidae, many species recorded in summer were also found to overwinter; species overlap amounted to approximately 67%. Rarefaction of the summer sample or excluding possible summer vagrants, raised this overlap to as much as 88% for the Carabidae. Many of the species successfully overwintering in the roadside verge were generalists, but less common, more stenotopic species were present as well. Not only species hibernating as adults were involved, but also species overwintering in immature stages, indicating reproduction also takes place in the roadside verge. Apparently the roadside occurrence of many arthropod species, including stenotopic and declining ones, is not merely seasonal or incidental, and roadside verges do not necessarily act as a sink only. The ecological importance often attributed to roadside verges should clearly be taken seriously.

Elucidating the Biochemical Overwintering Adaptations of Larval Cucujus clavipes puniceus, a Nonmodel Organism, via High Throughput Proteomics

Cucujus clavipes puniceus (C.c.p.) is a nonmodel, freeze-avoiding beetle that overwinters as extremely cold-tolerant larvae in the interior boreal forests of Alaska to temperatures as low as -100 °C. Using a tandem MS-based approach, we compared the proteomes of winter- and summer-collected C.c.p. to identify proteins that may play functional roles in successful overwintering. Using Gene Ontology (GO) analysis and manual interpretation, we identified 104 proteins in winter and 128 proteins in summer samples. We found evidence to indicate a cytoskeletal rearrangement between seasons, with Winter NDSC possessing unique actin and myosin isoforms while summer larvae up-regulated α actinin, tubulin, and tropomyosin. We also detected a fortification of the cuticle in winter via unique cuticle proteins, specifically larval/pupal rigid cuticle protein 66 precursor and larval cuticle protein A2B. Also, of particular interest in the winter larvae was an up-regulation of proteins related to silencing of genes (bromodomain adjacent to zinc finger domain 2A and antisilencing protein 1), proteins involved with metabolism of amines (2-isopropylmalate synthase and dihydrofolate reductase), and immune system process (lysozyme C precursor), among others. This represents the first high throughput MS/MS analysis of a nonmodel, cold-tolerant organism without a concurrent microarray analysis.

Epidemics of Ray Blight on Pyrethrum are Linked to Seed Contamination and Overwintering Inoculum of Phoma ligulicola var. inoxydabilis

Ray blight, caused by Phoma ligulicola var. inoxydabilis, is the most damaging disease of pyrethrum (Tanacetum cinerariifolium) in Australia. Data collected from 72 plots in commercial pyrethrum fields since 2001 to 2009 revealed substantial annual variations in isolation frequency of the pathogen during semidormancy of the crop in autumn and winter. Isolation frequency of the pathogen during this time and subsequent outbreaks of ray blight in spring were similar across the eight production regions where sampling was conducted, and isolation frequency of the pathogen was linearly correlated (r = 0.88; P < 0.0001) with subsequent defoliation severity when plants commenced growth in spring. Isolation frequency and defoliation severity also were correlated with the incidence of seed infested with P. ligulicola var. inoxydabilis (r = 0.71 and 0.44, respectively; P < 0.0001 in both correlations). Highly accurate risk algorithms for the occurrence of severe epidemics of ray blight were constructed using logistic regression. A model based solely on isolation frequency of the pathogen over autumn and winter correctly predicted epidemic development in 92% of fields. Another model utilizing the incidence of infested seed and rain-temperature interactions in early autumn (austral March and April) and late winter (austral June and July) had similar predictive ability (92% accuracy). Path analysis modeling was used to disentangle interrelationships among the explanatory variables used in the second logistic regression model. The analysis indicated that seedborne inoculum of P. ligulicola var. inoxydabilis contributes indirectly to ray blight defoliation severity through directly increasing overwintering frequency of the pathogen. Autumn and fall weather variables were modeled to have indirect effects on defoliation severity through increasing overwintering success of the pathogen but also direct effects on defoliation severity. Collectively, the analyses point to several critical stages in the disease cycle that can be targeted to minimize the probability of regional epidemics of ray blight in this perennial pathosystem.

Morphology and function of communal mounds of overwintering mound-building mice (Mus spicilegus)

Mound-building mice (Mus spicilegus) construct large mounds of soil and plant material in autumn, where juvenile animals overwinter in groups without reproducing. The mounds have several functions, including food storage, thermoregulation, and protection from predators. We examined whether these mounds have food storage or thermoregulatory function. Mice used mainly seeds and ears of certain plants (Echinochloa sp., Chenopodium spp., and Setaria spp., depending on availability) as building materials, but microhistological analysis of mice feces revealed that the cached plants are not represented in their actual diet. By comparing the features of soil under the mound to neighboring random points we found that the mounds have water-insulating and thermoregulatory properties. We also found a positive correlation between the size of the mound, its vegetal content, and its effectiveness to lessen the impact of the harsh conditions of the outside environment. Mound size was dependent on the number of inhabitants, indicating that larger mounds are constructed by and shelter bigger groups. The existence of communal mound building thus can contribute greatly to successful overwintering and the relatively low fluctuation in population size in this species.

Higher Pre-Hibernation Energy Storage in Anurans from Cold Environments: A Case Study on a Temperate FrogRana chensinensisAlong a Broad Latitudinal and Altitudinal Gradients

Temperate amphibians in colder regions are expected to store more energy prior to hibernation for successful overwintering and subsequent spring breeding. We tested this prediction on a capital breeding species — Rana chensinensis — using samples collected from 27 populations across 1200-km latitudinal (33.6–4.2°N) and 1768-m (112–1880 m) altitudinal gradient in northern China. Our data showed that frogs from colder regions (high latitude or altitude) had relatively heavier liver and fat bodies than those from warmer regions, but that the weight of carcasses tended to become smaller. The greater pre-hibernation energy reserves in colder regions could be an adaptive response to the longer and colder winter period, whereby meeting the energy demands for overwintering, and the subsequent energy requirements of reproduction in the spring.