Winter Survival Research Articles

Supplemental Foods Affect Energetic Reserves, Survival, and Spring Reproduction in Overwintering Adult Hippodamia convergens (Coleoptera: Coccinellidae).

For insects that overwinter as adults, winter food resources may affect subsequent spring reproduction and abundance. We tested if provision of food supplements to overwintering adult Hippodamia convergens (Guerin) increased energy reserves, winter survival, and spring reproduction. During 2015-2016, H. convergens adults were placed in field cages in December; adults in each cage received water, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) eggs, bee pollen, wheast protein, sugar, honey, or no food (control). In 2016-2017, treatments were reduced to sugar, bee pollen, A. pisum with E. kuehniella eggs, and no food (control). Adults were sampled to quantify weight, lipid, carbohydrate, and protein content. In 2015-2016, A. pisum and E. kuehniella eggs increased adult weight and protein content, but adult carbohydrate content was reduced by A. pisum and wheast protein treatments. Adults receiving honey and sugar supplementation had higher lipid and carbohydrate content relative to controls. The number of live individuals at the end of the experiment in March 2016 did not differ among treatments. In 2016-2017, winter prey supplements had the greatest effect on protein content, weight, and number of live adults recovered, whereas sugar supplementation increased lipid and carbohydrate content, and number of live adults recovered. Spring reproduction of surviving pairs was evaluated among treatments in March 2017. Prey supplementation in 2016-2017 increased the number of eggs laid and decreased preoviposition period, and food treatment did not affect fertility. Our results indicate that prey and sugar resources improve the overwintering success and spring reproduction of H. convergens.

Importance of native vegetation for detection and management of rice stink bug (Tibraca limbativentris)

Tibraca limbativentris (Hemiptera: Pentatomidae) is a major pest in Neotropical rice agroecosystems. In autumn-winter, this pest takes refuge in rice stubble and in native vegetation, which allows it to re-colonize the crop during the rice growing season. However, it is still unknown whether this vegetation is a pest sink or is actually a natural trap that contributes to pest population biocontrol. Here we present information on the insect's alternative host plants, a preliminary outline of the relationship between plant phylogeny and insect abundance, and the impact that winter natural enemies have in pest population. Also, we include a proposed methodology for pest density analysis in winter hosts. Our results show significant differences in the abundance/density that T. limbativentris reaches in the 12 host plant species present in our study areas, with a plant-use pattern significantly related to the phylogenetic clade of Poales. Stink bug winter populations mainly comprised diapause adults, and 40% of insect digestive tracts had content. Survival of T. limbativentris was 56.92% in winter hosts. About mortality, 10% was due to undetermined causes and 33.08% due to entomopathogenic fungi, showing a natural regulation of the pest population. Our results suggest that native vegetation impacts winter survival of T. limbativentris. Although these plants offer shelter, they offer a greater contribution to Integrated Pest Management: the natural regulation of winter pest populations through entomopathogenic attack. Further studies on T. limbativentris population dynamics and the preservation of native areas near rice fields will be required for the development of best control practices.

Incorporating evaporative water loss into bioenergetic models of hibernation to test for relative influence of host and pathogen traits on white-nose syndrome.

Hibernation consists of extended durations of torpor interrupted by periodic arousals. The ‘dehydration hypothesis’ proposes that hibernating mammals arouse to replenish water lost through evaporation during torpor. Arousals are energetically expensive, and increased arousal frequency can alter survival throughout hibernation. Yet we lack a means to assess the effect of evaporative water loss (EWL), determined by animal physiology and hibernation microclimate, on torpor bout duration and subsequent survival. White-nose syndrome (WNS), a devastating disease impacting hibernating bats, causes increased frequency of arousals during hibernation and EWL has been hypothesized to contribute to this increased arousal frequency. WNS is caused by a fungus, which grows well in humid hibernaculum environments and damages wing tissue important for water conservation. Here, we integrated the effect of EWL on torpor expression in a hibernation energetics model, including the effects of fungal infection, to determine the link between EWL and survival. We collected field data for Myotis lucifugus, a species that experiences high mortality from WNS, to gather parameters for the model. In saturating conditions, we predicted healthy bats experience minimal mortality. Infected bats, however, suffer high fungal growth in highly saturated environments, leading to exhaustion of fat stores before spring. Our results suggest that host adaptation to humid environments leads to increased arousal frequency from infection, which drives mortality across hibernaculum conditions. Our modified hibernation model provides a tool to assess the interplay between host physiology, hibernaculum microclimate, and diseases such as WNS on winter survival.

Disturbance does not have a significant impact on waders in an estuary close to conurbations: importance of overlap between birds and people in time and space

Disturbance of wildlife is a potential cause of conservation concern, not least to overwintering waders Charadrii inhabiting estuaries close to conurbations where human recreational and economic activities are often concentrated. Disturbance from people on and alongside intertidal foraging areas could make it more difficult for birds to survive until spring in good condition by reducing the time available for foraging, increasing energy requirements and displacing birds to poorer foraging areas. We adopted a two‐part approach to testing whether such significant impacts occurred in a Special Protection Area where disturbance risk was high because of its small size and close proximity to conurbations. In part one, we recorded over the whole estuary during stages of the tidal cycle when part or all of the intertidal zone was exposed and so accessible to waders (i.e. on receding, low and advancing tides): (1) the numbers and activities of people on the intertidal flats and on the adjacent land in those places where people were visible to waders in the intertidal zone and (2) the numbers of waders present and disturbed into flight, the flight distance and flight duration in the ‘overlap’ areas where people did disturb waders. People occurred on < 25% of the 938 ha of intertidal flats, but most waders foraged on mudflats, whereas most people were on sandflats. People on land were visible to foraging waders along < 35% of the 16.5 km of shoreline. Waders and people were therefore substantially separated in space. Within overlap areas, people and waders were often frequently separated in time: for example, people on land mostly disturbed waders when only the upper shore levels were exposed. The average overwintering wader spent < 0.1% of its foraging time during daylight flying away from people and the additional energy expenditure was equivalent to < 0.02% of its daily requirements. The comparison made in part two between our study area and two comparable estuaries showed that the number of visits each day to the overlap areas would need to be 29 or 43 times greater for disturbance to have lowered the birds’ body condition and winter survival. Both parts of the study therefore suggested strongly that the amount of disturbance was too trivial to have a significant impact on waders. It is concluded that: (1) to properly assess disturbance risk to waders, both extensive and intensive observations must be made on the behaviour of people and birds to quantify the extent to which they overlap in space and time, and (2) it should not be assumed that an estuary's close proximity to conurbations, and the presence of large numbers of people in the vicinity of the SPA, necessarily implies a significant disturbance risk to waders.

Identification of a polymorphism within the Rosa multiflora muRdr1A gene linked to resistance to multiple races of Diplocarpon rosae W. in tetraploid garden roses (Rosa × hybrida).

A QTL for resistance to several races of black spot co-located with the known Rrd1 locus in Rosa. A polymorphism in muRdr1A linked to black spot resistance was identified and molecular markers were designed. Black spot, caused by Diplocarpon rosae, is one of the most serious foliar diseases of landscape roses that reduces the marketability and weakens the plants against winter survival. Genetic resistance to black spot (BS) exists and race-specific resistance is a good target to implement marker-assisted selection. High-density single nucleotide polymorphism-based genetic maps were created for the female parent of a tetraploid cross between 'CA60' and 'Singing in the Rain' using genotyping-by-sequencing following a two-way pseudo-testcross strategy. The female linkage map was generated based on 227 individuals and included 31 linkage groups, 1055 markers, with a length of 1980cM. Race-specific resistance to four D. rosae races (5, 7, 10, 14) was evaluated using a detached leaf assay. BS resistance was also evaluated under natural infection in the field. Resistance to races 5, 10 and 14 of D. rosae and field resistance co-located on chromosome 1. A unique sequence of 32bp in exon 4 of the muRdr1A gene was identified in 'CA60' that co-segregates with D. rosae resistance. Two diagnostic markers, a presence/absence marker and an INDEL marker, specific to this sequence were designed and validated in the mapping population and a backcross population derived from 'CA60.' Resistance to D. rosae race 7 mapped to a different location on chromosome 1.

The predicted effect of the polar vortex of 2019 on winter survival of emerald ash borer and mountain pine beetle

We use simulation models of the winter biology of two forest insects — emerald ash borer (Agrilus planipennis Fairmaire, 1888) and mountain pine beetle (Dendroctonus ponderosae Hopkins, 1902) — to illustrate the anticipated effect of the polar vortex of the winter of 2019 on overwintering survival. Cold spells in late January and early and mid-February were cool enough that relatively high levels of mortality of both species may be expected in many parts of northern Canada. However, the high mortality response is not ubiquitous, and neither is it particularly severe compared with winter weather patterns from earlier decades. Forest insect pest managers will be required to carry on their usual work of population assessment and response. As Earth’s climate continues to warm, overwintering survival should, on average, increase in both species. However, the common occurrence of a split polar vortex associated with increasingly meridional jet stream flows should bring the odd winter of heavy mortality.

Legal regulation of supplementary cervid feeding facing chronic wasting disease

ABSTRACTThe supplementary feeding of cervids is a widespread practice across the northern hemisphere. There are few studies, however, regarding the extent of feeding in space and time. There are adverse effects of supplementary feeding, of which the most severe are increased parasite and disease transmission. With the recent emergence of chronic wasting disease (CWD) among cervids in Norway, a legal regulation was issued that banned all supplementary cervid feeding. We quantified the spatial extent and intentions of feeding cervids across all of Norway using a questionnaire at the municipality scale. We also compared spatial extent of feeding before and after the feeding ban to shed light on the ability of regulations to control supplementary feeding. Supplementary feeding to increase winter survival and targeting roe deer (Capreolus capreolus) was more common (48.4% of the municipalities) than the feeding of red deer (Cervus elaphus; 20.5%) and moose (Alces alces; 7.4%). The main feeding period was January–March, but extensive feeding also occurred from November to December and in April. Reducing traffic accidents was also a motivation, particularly for the feeding of moose (14.5%), and this was the main motivation (86%) for public feeding. Among the 65.7% that responded, 53.3% reported they knew about supplemental feeding of cervids in their municipality. In the region with the first feeding ban, 80.2% of municipalities were feeding in 2015–2016 before the ban, which was reduced to 68.4% in 2016–2017 and remained at 68.4% in 2017–2018. In the remainder of Norway, 81.4% were feeding in 2015–2016, and 72.6% were feeding in 2016–2017, but after the ban, this increased to 78.6% in the harsh winter of 2017–2018. Our study highlights that regulations across broad scales may not be followed and that more spatially targeted regulations and increased enforcement are required for disease transmission to be more effectively combated. © 2019 The Authors. Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.

Survival, Site Fidelity, and Territory Size of American Kestrels Wintering in an Agricultural Landscape of South Texas

American Kestrels (Falco sparverius) are North America's most abundant falcon, but they are declining throughout much of their range. Studies of nesting success are common, but far less is known about kestrels during migration and on the wintering grounds. We studied kestrels wintering along county roadways in South Texas. We trapped and color-marked 65 kestrels during October through December in 2014 and 2015 and searched for marked individuals once per week using a spotting scope, until birds started departing from the wintering grounds. We also searched for returning kestrels from September to March, 2015–2016 and 2016–2017. We used the Cormack–Jolly–Seber (CJS) models in Program MARK to estimate apparent survival, and we estimated two metrics of site fidelity as well as a spatial metric of site fidelity. We estimated territory size for individuals with ≥10 locations using the maximum linear distance between locations. We estimated winter survival (20 wk) as 67.1 ± 7.1% for kestrels in the winter they were marked and 84.4 ± 6.3% for returning birds. The 2-yr average apparent winter site fidelity was 27.8% for males and 50.2% for females, and the 2-yr average adjusted winter site fidelity was 41.7% for males and 65.7% for females. Linear average territory size ranged from 539 ± 34 m in Winter 3 to 738 ± 74 m in Winter 1. Our estimates of site fidelity are 12–15% greater than previously reported, and our linear winter territory sizes (pooled over 3 yr) were less than half the size of those previously reported for wintering American Kestrels. Small territories and high winter site fidelity suggest that South Texas agricultural areas are likely an important region for wintering kestrels.

Identification of a prosurvival neuroprotective mitochondrial peptide in a mammalian hibernator.

Hibernation requires the intricate regulation of physiological and biochemical adaptations to facilitate the decrease in metabolic rate and activation of prosurvival factors needed for winter survival. Mitochondria play important roles in eliciting these responses and in coordinating the required energy shifts. Herein, we report the presence of a novel mitochondrial peptide, s-humanin, in the hibernating 13-lined ground squirrel, Ictidomys tridecemlineatus. S-humanin was shown to have strong structural and sequence similarities to its human analogue, humanin-a powerful neuroprotective mitochondrial peptide. An assessment of the protein and gene expression levels of this peptide in ground squirrels revealed stark tissue-specific regulatory responses whereby transcript levels increased in brain cortex, skeletal muscle, and adipose tissues during hibernation, suggesting a protective torpor-induced activation. Accompanying peptide measurements found that s-humanin levels were suppressed in liver of torpid squirrels but enhanced in brain cortex. The enhanced transcript and protein levels of s-humanin in brain cortex suggest that it is actively involved in protecting delicate brain tissues and neuronal connections from hibernation-associated stresses. We propose that this squirrel-specific peptide is involved in modulating tissue-specific cytoprotective functions, expanding its role from human-specific neuroprotection to environmental stress protection. SIGNIFICANCE OF THE STUDY: Understanding the molecular mechanisms, which protect against oxidative stress in a model hibernator such as the ground squirrel, could be pivotal to the regulation of cytoprotection. This study expands on our knowledge of metabolic rate depression and could suggest a potential role for humanin therapy in neurodegenerative diseases.

Preceding crop and tillage system affect winter survival of wheat and the fungal communities on young wheat roots and in soil.

ABSTRACTAgricultural practices like tillage and cropping sequence have profound influence on soil-living and plant-associated fungi, and thereby on plant growth. In a field experiment, we studied the effects of preceding crop and tillage on fungal communities in the soil and on young winter wheat roots in relation to plant winter survival and grain yield. We hypothesized that plant performance and fungal communities (described by amplicon sequencing) differ depending on tillage system and preceding crop; that the effect of preceding crop differs depending on tillage system, and that differences in fungal communities are reflected in plant performance. In line with our hypotheses, effects of preceding crop on plant growth and fungal communities on plant roots and in soil were more pronounced under non-inversion tillage than under inversion tillage (ploughing). Fungal communities on plant roots in treatments with low winter survival were different from those with better survival. In soil, several fungal OTUs (operational taxonomic units) differed significantly between tillage systems. OTUs representing putative plant pathogens were either more abundant (Parastagonospora sp._27) or less abundant (Fusarium culmorum/graminearum_5) after non-inversion tillage. Our findings highlight the influence of cultural practices on fungal communities and thereby on plant health and yield.

Agronomic potential of winter grain legumes for Central Europe: Development, soil coverage and yields

Shifting from spring-sowing to autumn-sowing of crops might be a way to address expected changes in agro-climatic conditions in Central European cropping systems. Therefore, a two-year field experiment was conducted under Pannonian climate conditions in eastern Austria for assessing development, soil coverage and yields of winter faba bean and winter pea in comparison to spring faba bean and spring pea and winter wheat and winter oat. Both winters were mild and both winter grain legumes showed a high winter survival. Winter grain legumes had lower soil coverage in autumn than winter wheat but higher soil coverage than spring-sown grain legumes up to mid-May. Autumn-sowing resulted in earlier flowering, a longer duration of developmental stages and higher grain and residue yields than spring-sown grain legumes. Winter pea had higher grain yield than winter faba bean. Autumn-sowing of both faba bean and pea can be recommended in Central European growing conditions.

Evaluation of Maternal Penning to Improve Calf Survival in the Chisana Caribou Herd

Evaluation of Maternal Penning to Improve Calf Survival in the Chisana Caribou Herd

39 Management of cereal-grain forages for yield and quality

Abstract Cereal-grains have a long history of providing quality forage for livestock operations. Our objective is to review the existing literature and describe the principle factors controlling the yield and quality of cereal-grain forages. Generally, cereal-grain forage production can occur via management scenarios that include: 1) winter-annuals planted during fall and then grazed or harvested the following spring; 2) cereals not requiring vernalization planted during early spring and harvested during late-spring or summer; and 3) cereals not requiring vernalization planted during late-summer and harvested before winter. Winter-annuals planted during fall also are used extensively for fall grazing, particularly for backgrounding stocker cattle. The requirement for vernalization before plants elongate and produce viable seed plays a large role in synchronizing management strategies with producer goals. For example, maximization of fall growth can be attained by choosing a species or cultivar that does not require vernalization and will elongate, but this choice will likely eliminate winter survival and subsequent spring forage production. Ambient temperature during plant maturation affects lignin formation positively; therefore, forages grown during cooler fall temperatures will typically exhibit greater NDF digestibility than those maturing during summer. Most nutritional characteristics are influenced heavily by two competing processes that include the normal negative maturation effects that reduce the quality of most forages. However, this process is juxtaposed against the physiological process of grain fill, which can dilute concentrations of forage fiber components, increase energy density, and improve DM digestibility at advanced plant-growth stages. Digestibility of NDF declines with plant maturity, and generally is not affected by grain fill. A boot-stage harvest for silage often exhibits the most favorable nutritional characteristics for lactating dairy cows; however, producers making this management choice will need to accept a substantial yield penalty compared with a commonly recommended harvest at soft-dough stage, which would likely maximize yield.

Cold adaptation in the Asian tiger mosquito's native range precedes its invasion success in temperate regions.

Adaptation to environmental conditions within the native range of exotic species can condition the invasion success of these species outside their range. The striking success of the Asian tiger mosquito, Aedes albopictus, to invade temperate regions has been attributed to the winter survival of diapause eggs in cold environments. In this study, we evaluate genetic polymorphisms (SNPs) and wing morphometric variation among three biogeographical regions of the native range of A. albopictus. Reconstructed demographic histories of populations show an initial expansion in Southeast Asia and suggest that marine regression during late Pleistocene and climate warming after the last glacial period favored expansion of populations in southern and northern regions, respectively. Searching for genomic signatures of selection, we identified significantly differentiated SNPs among which several are located in or within 20kb distance from candidate genes for cold adaptation. These genes involve cellular and metabolic processes and several of them have been shown to be differentially expressed under diapausing conditions. The three biogeographical regions also differ for wing size and shape, and wing size increases with latitude supporting Bergmann's rule. Adaptive genetic and morphometric variation observed along the climatic gradient of A. albopictus native range suggests that colonization of northern latitudes promoted adaptation to cold environments prior to its worldwide invasion.

Overwintering ability of a flightless strain of the ladybird beetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)

We examined the overwintering ability of a flightless strain of the ladybird beetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), which is used as a biological control agent for aphids. The flightless strain was established via artificial selection for reduced flight ability and with no exposure to cold temperature (winter) during the selection. To examine the overwintering ability of the flightless strain, the survival rates were compared with those of wild strains under low temperature laboratory conditions and field winter conditions. In the laboratory experiment, survival rates of flightless strain individuals directly transferred to 5 °C were significantly lower than those with low temperature acclimation. Effects of aggregation on the survival rate at 5 °C were not confirmed. No significant differences were detected between the flightless strain and a wild strain originated from Saga, Kyushu, Japan. In the field experiment, winter survival of the flightless strain was significantly lower than the wild strain both in males and females while not significantly different from another wild strain originated from Fukuyama, Honshu (close to the original locality of the flightless strain). These results suggest that the artificial selection for reduced flight ability did not affect the overwintering ability of H. axyridis.

Overwintering assessment of camelina (Camelina sativa) cultivars and congeneric species in the northeastern US

Recent breeding and genetic engineering of the oilseed crop camelina [Camelina sativa (L.) Crantz] has raised concerns because the crop species and several congenerics are already weeds in North America. To better understand Camelina species weed risk, a two-year field experiment was conducted with six C. sativa cultivars, a wild C. sativa line, five congenic species, and two winter annual weeds in the Brassica family. The goal was to test the effect of fall seeding date on seed emergence, seed dormancy, plant establishment, winter survival, and spring flowering date. All of the C. sativa cultivars and Camelina species functioned as winter annuals and survived soil temperatures as low as -23.3 °C. Of the cultivars tested, ‘Calena’ had the highest percent winter survival. Seeds of C. sativa, Camelina alyssum (PI650132), and Camelina microcarpa (633190) showed no dormancy in the soil and germinated immediately. Seeds of Camelina rumelica (650138), Camelina laxa (Ames32859), and Camelina hispida (PI650133) partly showed dormancy surviving the winter with 0.3–1% seed emergence in the spring. All taxa overlapped in their spring flowering dates suggesting potential for pollen-mediated gene flow. Viable seeds were produced by all taxa except in C. hispida. These results suggest that weedy Camelina populations can persist as winter annuals in the northeastern United States. The new information on Camelina overwintering, seedbanks and flowering synchrony will help to lay fundamental basis for assessment of risks associated with gene flow from genetically engineered cultivars of C. sativa to Camelina species and contribute to ecological risk assessments, biocontainment for experimental field trails, and weed management.

Changes in cold tolerance during the overwintering period in Apis mellifera ligustica

Winter is the honey bee’s non-productive season. The colony’s main task during the winter is to withstand the cold and to reduce bee losses. Losses during the winter can restrict the colony reproduction in spring, even more the production in the next whole year. Thus, the evaluation of the colony’s overwinter ability by studying its cold-hardiness is crucial. The goal of this study was to determine the variation of the cold tolerance during the overwintering period and the major physiological responses to the cold climate. Samples were collected from the late October 2016 to March 2017 in Taian, China. The super-cooling points (SCPs), which ranged from –7.41 to –6.49 °C, were lower than the average daily lowest temperature (–4 °C) in January. The protein content first increased and then decreased during winter. Glycogen is a major energy source, and its content level declined sharply in the middle of overwintering. Glycerol and some low-molecular weight sugars and polyols (mannitol, sorbitol, and trehalose) were found to serve as the primary cryoprotectants for overwintering bees, as their contents accumulated significantly during the winter (P<0.0001). For the first time, this study investigated antifreeze protein, protein lethal (2) essential for life-like (l(2)efl), and vitellogenin protein (Vg) mRNA expression pattern in the overwintering period. The results indicate that seasonal super-cooling capacity is assisted by the accumulation of a complex mixture of winter specific metabolites. Our findings may help in integrated feeding and management of honey bees to increase winter survival.

Winter Survival, Habitat Use, and Hypoxia Tolerance of Montana Arctic Grayling in a Winterkill‐Prone Lake

AbstractWinter hypoxia in shallow, ice‐covered lakes can be a significant limiting factor for overwintering fish populations. In this study we tested the hypothesis that low overwinter survival due to winter hypoxia is a limiting factor for a rare, adfluvial population of native Arctic Grayling Thymallus arcticus inhabiting Upper Red Rock Lake, Montana. We used a combined laboratory and telemetry study to document the extent of hypoxia over two winters and to assess the physiological tolerance, behavioral response, and winter survival in relation to hypoxia. In the laboratory, we observed a significant behavioral and physiological response to dissolved oxygen (DO) levels ≤ 4.0 mg/L and determined acute 24‐h LC50 values (concentration lethal to 50% of test fish) of 0.75 mg/L DO for adults and 1.50–1.96 mg/L for juveniles at temperatures of 1–3°C. In the field study, we observed dynamic DO concentrations (DO &lt; 1.0 to 10.0 mg/L) during winter ice cover, ranging from persistent near‐anoxic conditions near the bottom to DO concentrations &gt; 4.0 mg/L in the epilimnion. Radiotelemetry indicated adult winter survival rate was high (0.97 in 2014, 0.95 in 2015) and that telemetered fish selected deeper (&gt;1 m), more oxygenated habitat during ice cover. Our study demonstrated that Arctic Grayling have a high tolerance to acute hypoxia exposure and exhibit a physiological and behavioral stress response to DO concentrations ≤ 4.0 mg/L. Although hypoxia was present in parts of the lake, sufficient suitable habitat with DO &gt; 4.0 mg/L was available in the lake epilimnion in both study winters. However, winter conditions more severe than those observed during our 2‐year study occur periodically in the lake, and thus winterkill could still be a limiting factor for the population.

Differences in seasonal survival suggest species-specific reactions to climate change in two sympatric bat species.

Long‐lived animals with a low annual reproductive output need a long time to recover from population crashes and are, thus, likely to face high extinction risk, if the current global environmental change will increase mortality rates. To aid conservation of those species, knowledge on the variability of mortality rates is essential. Unfortunately, however, individual‐based multiyear data sets that are required for that have only rarely been collected for free‐ranging long‐lived mammals. Here, we used a five‐year data set comprising activity data of 1,445 RFID‐tagged individuals of two long‐lived temperate zone bat species, Natterer's bats (Myotis nattereri) and Daubenton's bats (Myotis daubentonii), at their joint hibernaculum. Both species are listed as being of high conservation interest by the European Habitats Directive. Applying mixed‐effects logistic regression, we explored seasonal survival differences in these two species which differ in foraging strategy and phenology. In both species, survival over the first winter of an individual's life was much lower than survival over subsequent winters. Focussing on adults only, seasonal survival patterns were largely consistent with higher winter and lower summer survival but varied in its level across years in both species. Our analyses, furthermore, highlight the importance of species‐specific time periods for survival. Daubenton's bats showed a much stronger difference in survival between the two seasons than Natterer's bats. In one exceptional winter, the population of Natterer's bats crashed, while the survival of Daubenton's bats declined only moderately. While our results confirm the general seasonal survival pattern typical for hibernating mammals with higher winter than summer survival, they also show that this pattern can be reversed under particular conditions. Overall, our study points toward a high importance of specific time periods for population dynamics and suggests species‐, population‐, and age class‐specific responses to global climate change.

Overwintering of reproductively mature females of a pro‐ovigenic parasitic wasp, Leptopilina heterotoma (Hymenoptera: Figitidae)

AbstractLeptopilina heterotoma is a Drosophila parasitoid mainly occurring in temperate regions, and females of this species are pro‐ovigenic (i.e. all or nearly all of their lifetime eggs are already mature at emergence). Here I investigated how L. heterotoma overwinters in Sapporo, Japan, a cool temperate region, by outdoor and laboratory experiments. Females of this species had mature eggs at emergence as expected, and they did not resorb eggs even if they were exposed to cold or starvation. Nevertheless, females were able to overwinter, and post‐overwintering females retained parasitization capacity. In this species, thus, adult overwintering is not associated with reproductive diapause. However, females grown in late autumn or at low temperatures (e.g. 5°C) had a fewer number of mature eggs and higher winter survival. At low temperatures, female larvae could save energy by reducing egg production and allocate the saved energy to expenditure for overwintering. In contrast to females, males and pre‐adult individuals were not able to overwinter.