The scale of the knowledge gap that the research team confronted is striking. Georgia contains roughly 2,000 known underground sites, including more than 1,500 karst and conglomerate caves, yet only about 15 percent of them had ever been surveyed for bats. Historical accounts, written largely in Russian and Georgian and scattered across obscure journals, museum archives and gray literature, documented just 13 species from 71 sites between 1912 and 2010. To recover this fragmented record, the authors employed a snowball survey method, starting from the works of influential early bat biologists and tracing every cited reference backwards through the literature. They searched the libraries of Georgian and Russian research institutions, including the Zoological Institute of the Russian Academy of Sciences in Saint Petersburg and the Zoological Museum of Moscow State University, and combed through European databases such as GBIF and the EUROBATS underground habitats database.

On top of the historical record, the team added their own data: more than 300 surveys conducted between 1999 and 2024 across 44 previously unreported underground locations, in every season of the year. Surveys combined visual searches inside caves with mist-netting at entrances during the swarming period, when bats gather to mate and socialize. Captured animals were measured using standard morphological criteria for species identification and released at the point of capture, with all handling conducted under permits issued by Georgia’s Ministry of Environmental Protection and Agriculture. Where colonies were encountered, the researchers estimated sizes through direct counts of small visible groups, subgroup extrapolation for larger aggregations, and photographic counting for the very largest congregations, techniques that acknowledge the well-known difficulty of obtaining reliable abundance estimates for roosting bats.

The resulting dataset comprises 331 records of 20 bat species from 115 underground sites, spanning three families and ten genera. The haul includes one genuine discovery: Blasius’s horseshoe bat, Rhinolophus blasii, recorded in Georgia for the first time in 2006 and subsequently found in three additional caves. It also includes a subtle loss. Mehely’s horseshoe bat, Rhinolophus mehelyi, which had been documented as recently as 1964, could not be confirmed during any of the modern surveys, although the authors caution that its continued presence in the country cannot be definitively excluded. Six species that do not typically use underground shelters at all, including Bechstein’s bat and Leisler’s bat, two largely forest-dwelling species, turned up unexpectedly in caves and cave entrances, underscoring how much remains to be learned about the roosting flexibility of even familiar European species.

To make sense of this diversity, the researchers classified each species into six lifestyle categories based on the strength of its association with subterranean habitats, ranging from exclusively cave-dwelling species through partial cave users and forest species to generalists with no clear shelter preference. Only Rhinolophus blasii qualified as an exclusive cave dweller. Six species, including the greater horseshoe bat Rhinolophus ferrumequinum, the lesser horseshoe bat R. hipposideros, R. euryale, Myotis blythii, M. emarginatus and Schreibers’s bent-winged bat Miniopterus schreibersii, were classed as mainly or primarily cave dwelling, while seven others, among them the whiskered, Brandt’s, Daubenton’s, Natterer’s, barbastelle and two long-eared bats, use caves mainly for wintering, mating or swarming while roosting in trees during summer.

The most frequently recorded species across the two decades of surveys were Rhinolophus ferrumequinum, R. hipposideros, Miniopterus schreibersii, Myotis blythii and R. euryale, and it is these five that form the large, persistent colonies on which much of Georgia’s cave bat conservation hinges. All five are listed as priority species under the Emerald Network, the pan-European system of areas of conservation interest, and two carry formal extinction risk assessments: R. euryale is classified as Vulnerable on the Georgian Red List, and M. schreibersii is listed as Vulnerable by the International Union for Conservation of Nature. Three of the twenty cave-using species in total hold Georgian Red List status, giving the subterranean fauna a clear conservation weighting.

Mapping the records onto a grid and binning richness by elevation revealed a pronounced spatial structure. Bat diversity in underground habitats peaks at the lowest elevations, between sea level and 300 meters, and again between 1,200 and 1,500 meters above sea level, with a secondary peak at 600 to 900 meters. Geographically, the richest assemblages cluster in western Georgia, where karstic outcrops cover about 6.4 percent of the national territory, some 4,475 square kilometers, concentrated on the peripheral zone of the southern slope of the Greater Caucasus and the hills north of the Colchis lowland. Eastern Georgia, by contrast, has only weakly developed karst, and its underground roosts are largely man-made: sandstone caves along the gorges of the Mtkvari, Iori, Khrami, Algeti and Mashavera rivers, plus volcanic caverns widened by human hands and the abandoned manganese mines of the Chiatura region, many of which are too dangerous to enter.

Some of the individual colonies documented are of international significance. Ghliana Cave hosts one of Georgia’s largest nursery colonies, a mixed maternity assemblage of 4,000 to 8,000 individuals that peaks in late July and early August. Myotis blythii and Miniopterus schreibersii are present every year, joined in different seasons and years by Rhinolophus ferrumequinum, R. euryale and occasionally M. emarginatus. Samertskhle Klde Cave holds another of the country’s biggest maternity colonies, also reaching 8,000 or more individuals in favorable years, again dominated by the same two species. For wintering bats, Sakishore Cave is the standout site, sheltering more than 1,000 hibernating Schreibers’s bent-winged bats, the largest known winter aggregation in the country.

Threats loom over these strongholds. The team scored three categories of human pressure at key colony sites, excessive disturbance, habitat destruction or change of use, and light pollution, on a three-point scale, and combined these with a parallel score of cave accessibility to produce a composite vulnerability index. Ghliana Cave emerged as the most threatened site in the country, with high scores for disturbance and habitat degradation combined with easy access, a worrying combination given that a government conservation action plan was drawn up for the cave as recently as 2019. The remaining colony caves, including Melouri, Samertskhle Klde, Vardigora, Sakishore, Becho and Matkhoji, face moderate threat levels, driven mainly by human visitation.

Yet the overall message is one of cautious hope. No Georgian bat species has been lost, and several species of concern remain locally abundant, a rare positive trajectory for cave faunas in a region of accelerating tourism, quarrying and light pollution. Protection, however, lags far behind need: only 18 caves or cave complexes enjoy legal protection, just two are listed by the Emerald Network, and of all the protected sites only Ghliana and Melouri actually harbor large colonies. The authors recommend formal conservation status for four more caves, Samertskhle Klde, Vardigora, Becho and Sakishore, and single out the Imereti, Samegrelo and Apkhazeti regions as the country’s most important bat conservation landscapes, where remoteness and altitude currently provide only a fragile de facto refuge. Crucially, they argue that protecting cave mouths alone is not enough: commuting routes and foraging habitats in the surrounding landscape must be included within any effective safeguard. Sustained long-term monitoring, they conclude, is the foundation on which the future of Georgia’s underground bats will depend.

Subject of Research: Distribution and conservation of bat species in the underground habitats of Georgia

Article Title: The distribution of bat species across the underground sites of Georgia

Article References: Natradze, I., Bukhnikashvili, A., Gazaryan, S., Sheklashvili, G., & Mumladze, L. (2024). The distribution of bat species across the underground sites of Georgia. Subterranean Biology, 50, 65-77. https://doi.org/10.3897/subtbiol.50.134613

Image Credits: AI Generated

DOI: 10.3897/subtbiol.50.134613

Keywords: bats, caves, Georgia, subterranean habitats, karst, chiroptera, conservation, biodiversity hotspot, hibernation, nursery colonies, Red List, Caucasus

The study focused on two urban park lakes in the Romanian capital: the roughly 8,000-square-meter lake in Morarilor Park, bordered by concrete embankments but retaining patches of reed bed, and the slightly smaller lake in Circului, or State Circus, Park, originally four meters deep but by 2024 much shallower, edged with earth banks, reeds, and Indian lotus vegetation. Both lakes host a mix of native and alien turtles alongside waterbirds and opportunistic fish. The 2023–2024 winter was atypically mild across the region, dominated by positive air temperatures and very little snow, but it was punctuated by short cold spells in January 2024 that brought overnight frosts, occasional snow showers, and ice that formed and persisted into early February. That oscillation between false spring and genuine winter created a natural experiment on turtle behavior.

The researchers conducted periodic visual transects on selected warmer days in January and February, dedicating each observation day to a single lake and concentrating their efforts around mid-day, when insolation peaks and basking activity was expected to be highest. Air temperatures were measured with a Dwyer WT-10 digital thermometer and cross-checked against readings from nearby weather stations. Crucially, the team also ran control observations during cold spells, including January 20, when snowfall fell and thin ice covered the water. On those days, not a single turtle was seen. The pattern that emerged was stark: activity occurred only on warm days, and it stopped entirely when the weather turned.

During the warmer, sunny days, however, even the harshest stretches of January could not keep the sliders down. In Morarilor Park, Trachemys scripta individuals were recorded active on January 5, 19, and 26 and on February 3, 8, and 24; in Circului Park, the species was active on February 4, 7, and 23. Remarkably, much of this activity took place despite partial ice cover on the lakes, and some turtles were observed swimming right at the ice edge. The January 5 count recorded eleven individuals basking and swimming at around 15–16 °C, but even on January 26, when the air was only 6–7 °C and roughly 85 percent of the lake was covered in thin ice, three sliders were seen swimming. The animals involved were mostly large adults, and the observers judged that the same five or six individuals were likely responsible for the sightings through the coldest part of the winter.

The behavior of these cold-hardy individuals revealed deliberate strategies for conserving heat. The researchers noted group basking, in which multiple turtles piled together to share warmth, as well as basking on wood and distinctive heat-conserving postures, in which a turtle draws its limbs in to minimize exposed surface area. These tactics were deployed even though alternative basking sites, mostly at the edges of reed beds, were readily available and predators were absent. Such thermoregulatory finesse suggests that the winter-active sliders were not simply disoriented by warm weather but actively managing a marginal energy budget in conditions their species did not evolve to face this far east in Europe.

The most telling result came by comparison. No other turtle species, native or alien, appeared during the mid-winter observations. Only on February 23 and 24, when temperatures climbed toward 20 °C and the ice had fully gone, did the rest of the lake’s turtle community emerge. Alongside the sliders, the team recorded the native European Pond Turtle, Emys orbicularis; the alien False Map Turtle, Graptemys pseudogeographica; and a possible hybrid of the Chinese Striped-necked Turtle and Reeves’ Turtle, an introgressive Mauremys that hints at further untangling of the park’s introduced menagerie. Counts on those late-February days surged, with 52 sliders recorded at Morarilor Park and 60 to 70 at Circului Park, compared with single digits or low teens earlier in the winter.

The biology behind this split is rooted in the slider’s remarkable but conditional physiology. Trachemys scripta is capable of prolonged anoxic overwintering, surviving roughly 45 days at temperatures of 3–5 °C while submerged and metabolizing without oxygen. Yet the species is sensitive to freezing temperatures, particularly hatchlings that overwinter in the nest, and deviations from optimal overwintering conditions can impair health and survival. Harsher winters can kill adults outright: mass mortality has been reported in Bulgaria, where the slider is likewise alien, and the authors themselves witnessed a comparable event in March 2012 at the Botanical Garden of Bucharest, where at least a dozen sliders died when their aquatic habitat froze deeply and persistently. Notably, no dead European Pond Turtles were found there, underscoring the native species’ superior tolerance of true continental winters.

At the same time, the slider’s metabolism is governed by both temperature and photoperiod, and in its native North American range, which spans temperate latitudes, it is known to emerge on warm winter days and even to remain active along or under ice. In the mild climate of southern Spain, another part of its introduced range, the species has sometimes reduced or skipped hibernation altogether. The Bucharest records now establish that this capacity for sporadic winter activity operates in Romania as well, in a non-native population experiencing a temperate continental climate, provided that unseasonably warm weather opens a window of opportunity in an urban setting. Urban lakes, with their heat-retaining concrete, shallow water, and abundant basking structures, may function as stepping stones that let warm-adapted behavior survive where it otherwise would not.

The findings also challenge a popular hypothesis about invasiveness. It has been proposed that winter activity gives the slider an advantageous early start in competing with native turtles for basking spots, a critical resource for ectotherms that need to raise their body temperature to feed and digest. The Bucharest observations suggest the opposite dynamic. When the native Emys orbicularis and the alien Graptemys pseudogeographica finally emerged in late February, they were seen climbing onto and basking atop the larger, pre-warmed sliders, effectively exploiting them as heated platforms, even though alternative basking sites were plentiful. This echoes earlier European observations and implies that the slider’s winter activity may reflect distinct ecological characteristics that actually reduce, rather than intensify, interspecific competition, a hypothesis the authors note remains to be tested by more detailed study.

What emerges from a winter of watching frozen park lakes is a portrait of an invader testing its limits. The slider population in Bucharest appears small, dominated by a handful of large, long-surviving pets, yet it has already documented reproduction in several Romanian urban settings, and the morphological diversity of the city’s sliders points to multiple introduction events and hybridization among subspecies. As climate change delivers more winters that lurch between deep freezes and spring-like thaws, the physiological windows that allowed these turtles to bask beside the ice in January 2024 may open more often. Whether that flexibility translates into genuine establishment in colder Europe remains uncertain, and a single hard winter can still wipe out an urban population. But the sight of North American turtles swimming at the edge of the ice in a Romanian January is a vivid reminder that the boundaries of invasion are drawn not on maps, but on thermometers.

Subject of Research: Winter activity and cold tolerance of the invasive Pond Slider turtle in urban park lakes in Romania

Article Title: Turtles and ice: winter activity in non-native turtles in Romania

Article References: Iftime, O., & Iftime, A. (2025). Turtles and ice: winter activity in non-native turtles in Romania. Herpetozoa, 38, 1-5. https://doi.org/10.3897/herpetozoa.38.e137934

Image Credits: AI Generated

DOI: 10.3897/herpetozoa.38.e137934

Keywords: Trachemys scripta, Pond Slider, invasive species, turtles, winter activity, hibernation, Bucharest, Romania, urban ecology, thermoregulation, Emys orbicularis, climate

The species was described in 1936 by the Austrian lepidopterist Joseph Klimesch from specimens collected in the warm inner-Alpine valleys of South Tyrol in northern Italy, near the village of Naturno, from which its name derives. For decades afterwards it was regarded as a rare, heat-loving specialist of the southern Alps, known from scattered records and considered nearly impossible to distinguish from related species by its leafmines alone. That reputation for rarity, the new study argues, was largely an artefact of identification problems rather than a reflection of true abundance.

The adult moth is a true pygmy even by nepticulid standards: males have forewings of only 1.7 to 2.2 millimetres, giving a wingspan of roughly four to five millimetres. The forewing is shining dark grey to almost black at the base, crossed by a narrow silvery-white fascia slightly beyond the middle, with a contrasting darker apical area and a distinct fringe line separating a white terminal fringe. A relatively short antenna, in females reaching less than halfway between the wing base and the fascia, helps separate it from superficially similar birch-feeding relatives. The male genitalia, with a shallow uncus, closely connected gnathos arms and a phallus bearing eight to ten strong cornuti, are highly characteristic.

The life history holds the key to the moth’s success. Females lay eggs on the upper or lower surface of birch leaves, most often away from the midrib and major veins, and in the studied samples about two-thirds of eggs were found on the underside. The larva then excavates a linear gallery mine, typically 22 to 53 millimetres long, in which the early section frequently appears green from above because the young larva feeds only in the spongy parenchyma layer, leaving the upper tissue intact. The pale larva feeds with its venter upwards and shows a single conspicuous brown circular suboesophageal ganglion, a decisive diagnostic character. Crucially, the species is one of the very few nepticulids in Europe that hibernate as adults, sheltering under bark, often of plane trees in cities, from November to March.

That adult hibernation strategy may explain the northward expansion in a warming climate. Because the moths emerge in autumn and overwinter as free adults rather than as larvae or pupae in cocoons, they can take advantage of mild winters and of an extended growing season that allows at least two generations per year, possibly more. The only other European nepticulid known to hibernate as an adult, Stigmella aceris, has likewise expanded its range considerably, although in that case the widespread planting of its maple hostplants also played a role. Birch, by contrast, is a common native tree that colonises heathlands and sandy soils spontaneously, so hostplant availability cannot be a limiting factor for S. naturnella.

The study’s author, Erik van Nieukerken of the Naturalis Biodiversity Center in Leiden, combined fresh fieldwork, re-examination of historical leafmine collections, DNA barcoding and citizen-science data to reconstruct the species’ distribution history. DNA barcodes of the mitochondrial COI gene from 35 specimens spanning the range from the Netherlands to Japan all fall within a single barcode cluster, with a maximum variation of just 1.63 percent and the greatest diversity in the Russian Far East. This pattern suggests the species spread westwards from Siberia relatively recently after the last glaciations, and that the current west European expansion involves populations showing little or no barcode variation.

The historical detective work also corrected the record. Old leafmine reports from Germany and Bohemia, identified in the 1930s by the amateur specialist Hugo Skala, had long been doubted. Re-examination of the preserved mines showed that the specimens collected by Albert Wörz near Stuttgart in 1935 were indeed correctly identified, confirming the species’ presence in Baden-Württemberg nearly ninety years ago, while most of Buhr’s records from Berlin and elsewhere proved to belong to other species such as S. glutinosae and S. luteella. A lectotype was designated for Nepticula naturnella, and the Far Eastern name Astigmella dissona Puplesis, 1984 remains a synonym, confirming that the species ranges continuously from the North Sea to Japan.

Identifying the mines remains the central challenge, and the paper provides a revised diagnostic key to the linear leafmines of European Stigmella species on birch to help. Mines of S. naturnella are most easily recognised when the egg sits on the leaf upperside or when the early mine appears green; vacated mines without these features can be confused with those of S. confusella, although the latter produces considerably longer and wider mines. Adding to the confusion, two species normally feeding on alder, S. glutinosae and S. alnetella, were confirmed by rearing and DNA barcoding to occur occasionally on birch and are now included in the key. The author cautions that single vacated mines, especially in areas where a species has not been recorded before, should never be the sole basis for identification, and that studying a series of mines from a population is always preferable.

The speed of the recent spread is striking. Online observations suggest the moth first appeared in Belgium and the Netherlands around 2017, and by 2020 it was already established throughout the southern half of the Netherlands, often ranking among the commonest leafminers on birch. Between 2020 and 2022 its known Dutch distribution shifted roughly 50 kilometres northwards, reaching the province of Overijssel and the coastal dunes of Zeeland. The author predicts that Denmark, Sweden, the Baltic states and even the United Kingdom may be next, and calls for birch stands in northern Germany, Poland and the Low Countries to be monitored for the tell-tale mines.

The ecological consequences remain uncertain. Leafmine densities appear generally low, but earlier studies of birch-feeding Stigmella communities found fine-grained ecological segregation among species, possibly driven by limited availability of suitable leaves, so the arrival of an abundant new competitor could disturb existing populations. The author also notes that the moisture-loving northern species S. lapponica and S. confusella were seldom encountered during recent Dutch fieldwork, a decline more plausibly attributed to warming and drying conditions than to competition. Beyond the biology, the study is a testament to the power of open biodiversity platforms: photographs uploaded by naturalists to waarneming.nl, waarnemingen.be and iNaturalist, once validated, provided the crucial early records that formal science had missed, and the author urges collection managers to digitise historical leafmine herbariums so that future range shifts can be traced with the same rigour.

Subject of Research: Range expansion and identification of the birch leafmining moth Stigmella naturnella in Europe

Article Title:  Stigmella naturnella (Klimesch, 1936) ( Lepidoptera , Nepticulidae ) a fast-spreading European leafminer of Betula , with a revised key to linear leafmines on Betula

Article References: van Nieukerken, E. J. (2023). Stigmella naturnella (Klimesch, 1936) (Lepidoptera, Nepticulidae) a fast-spreading European leafminer of Betula, with a revised key to linear leafmines on Betula. Nota Lepidopterologica, 46, 37-82. https://doi.org/10.3897/nl.46.99360

Image Credits: AI Generated

DOI: 10.3897/nl.46.99360

Keywords: Stigmella naturnella, Nepticulidae, leafminer, Betula, range expansion, DNA barcoding, citizen science, hibernation, Notа Lepidopterologica, lectotype, birch, insect spread

The rationale for the model stems from a long-standing puzzle in biological control. Ladybirds are voracious aphid predators, but their effectiveness in suppressing aphid outbreaks varies dramatically across contexts. In 1999, Kindlmann and Dixon proposed the generation time ratio hypothesis, which holds that a predator’s efficiency as a biological control agent declines as its generation time lengthens relative to that of its prey. Because ladybird larvae have low mobility and the prey keeps reproducing, depleting an aphid colony is not necessarily in the predator’s interest. Aphid control can improve when multiple agents act together, for instance alongside parasitoid wasps, but predicting these dynamics has proven stubbornly difficult. Aphid populations fluctuate wildly under the influence of intrinsic factors such as fecundity and migration, and external drivers, particularly temperature, making forecasting models fragile and contingent on unpredictable seasonal weather.

The new formal model tackles these problems by splitting them into three parts: predicting aphid occurrence, building a multi-species system for control analysis, and capturing the environmental and ecological factors beyond aphid presence that determine where ladybirds occur, including land-use change, agricultural management, climate, and interactions with predators and diseases. The authors assume, for the moment, that aphid occurrence in time and space is predictable, because a companion spatially and temporally detailed aphid model is being developed concurrently within ALMaSS. Once the two models are coupled, the system should allow researchers to explore both optimal control strategies and the population dynamics of the ladybird itself.

What sets this effort apart from earlier ladybird-aphid models is its combination of individual-based realism and landscape detail. Previous mathematical models captured within-season dynamics in ecological patches but ignored movement between patches. Landscape-scale extensions redistributed aphids and ladybirds among patches at season boundaries, revealing the importance of scale but with little spatial realism. Later spatially explicit models, such as those of Bianchi and Van Der Werf, simulated foraging at 20-metre resolution with hourly timesteps, but treated each grid cell as a sub-population. The ALMaSS approach goes further: each ladybird is a separate code object with defined properties such as age, appetite and the number of developed ovarioles, navigating a landscape represented at one-square-metre resolution. Vegetation height and leaf cover are updated daily, crop rotations follow multi-annual farm plans, and crop distribution derives from European Common Agricultural Policy subsidy claims. Farming activities, including pesticide spraying that can kill ladybirds, unfold throughout the year according to crop-specific management plans.

The model’s daily timestep updates temperature, rainfall and local aphid abundance, with no upper limit on the interactions an individual can perform per step. Life history parameters come from laboratory and field studies of C. septempunctata where available, and from calibrated data of sister ladybird species where not. Development is driven by temperature through a day-degree framework: each juvenile stage has a lower development threshold and a sum of effective temperatures required for completion. Eggs, for example, need 42 day-degrees above 11.5 degrees Celsius, while pre-oviposition adults require 151.9 day-degrees above 12.4 degrees. Crucially, larval development is also modulated by prey density through a second-order polynomial function, so that food shortage lengthens each instar. Larvae that endure three consecutive days of starvation die. A prey quality scaler adjusts these rates when the model is coupled to specific aphid species, reflecting evidence that prey type strongly influences growth, survival and fecundity.

Feeding behaviour follows a well-established distinction in coccinellid ecology between essential food, which enables oviposition and larval development, and alternative food, which merely sustains survival. Aphids are the only known essential food for C. septempunctata, so the model links aphid intake directly to growth, development and reproduction rather than building a full energetic budget. Adults require ten aphids daily, while maximum consumption rises from 45 aphids per day for first-instar larvae to 120 for fourth instars. Foraging follows a decision framework in which ladybirds land on plants, initiate localised search upon detecting prey, and aggregate in high-density patches. The model incorporates empirical residence times proportional to aphid density, and a detection threshold of ten aphids per square metre, the minimum density known to attract the beetles. When foraging fails entirely, cannibalism kicks in as a last resort, with each stage able to consume only less advanced stages, and nutritional values assigned per life stage based on body weight comparisons with aphids.

Oviposition, the engine of population growth, is modelled as a function of temperature and prey density. Females lay clutches of roughly 20 to 40 eggs, with laboratory maxima reaching 72 eggs per day on high-quality prey, but only when temperatures exceed 11 degrees Celsius and local aphid density crosses crop-dependent thresholds, which field studies in the Czech Republic place between roughly 9 and 161 aphids per square metre. Lifetime fecundity varies enormously with prey species, from about 200 eggs on the poor-quality oleander aphid to more than 1,700 on Lipaphis erysimi, and the model captures this through a prey quality scaler applied to a saturating relationship between aphid density and egg production. Once a female has laid her full complement of eggs, she is removed from the simulation, a design choice that makes total egg count a proxy for life expectancy.

Mortality is handled through several distinct channels. Temperature-dependent survival follows a parabolic relationship for each life stage, with an optimum between 25 and 30 degrees Celsius, and supercooling points as low as minus 27 degrees for fresh eggs protect against winter extremes. Farming activities carry stage-specific mortality risks: ploughing and harrowing kill half of eggs and larvae, while insecticide applications impose 80 percent mortality on larvae, pupae and adults. Hibernation mortality depends on clump size, with smaller groups suffering twice the mortality of larger ones, and extreme temperatures add a further 25 percent chance of death. Parasitism by the braconid wasp Dinocampus coccinellae, which can strike more than 30 percent of post-dormancy adults in the wild, is simplified in this first version to a single stochastic mortality event sampled uniformly between zero and 33 percent when adults disperse from hibernacula.

The hibernation and movement modules reveal both the ambition and the acknowledged limits of the model. Hibernation is triggered by photoperiod and falling aphid densities from August onward, with beetles aggregating at forest edges, road verges and hedgerows rather than the mountain peaks documented in the literature, a simplification imposed by the 10-by-10 to 50-by-50 kilometre landscape windows the model is designed for. The model also assumes the ladybird is univoltine, producing one generation per year, which holds at the northern and central European latitudes where the tool will first be applied but would fail in warmer climates where partial multivoltinism occurs. Movement is split into short-range walking, whose speed scales linearly with temperature above 4 degrees, and long-range flight, permitted only above 15 degrees Celsius and in winds below 10 metres per second. Males are not simulated at all, on the grounds that mating opportunities are effectively unlimited.

The authors are candid about the challenges ahead. Laboratory data, the primary source for parameters, rarely captures how factors co-vary in nature, and the simple day-degree development model cannot represent the effects of temperature extremes as accurately as biophysical or thermal performance models would. Some potentially important processes, notably intra-guild predation and disease transmission, are folded into general mortality during calibration, risking the loss of deterministic population drivers. Nevertheless, the seven-spot ladybird serves as a representative species for the entire Coccinellidae family, and the model’s mechanistic structure should make it adaptable to other ladybird species as data becomes available. The next phase, implementation and calibration within ALMaSS, will determine whether this digital beetle can truly forecast how farming decisions ripple through one of agriculture’s most iconic predator-prey relationships.

Subject of Research: Agent-based modelling of the seven-spot ladybird Coccinella septempunctata for landscape-scale simulation of aphid biological control

Article Title: The Formal Model for Coccinella septempunctata for implementation in Animal Landscape and Man Simulation System

Article References: Topping, C. J., Ziółkowska, E., Chuhutin, A., & Duan, X. (2025). The Formal Model for Coccinella septempunctata for implementation in Animal Landscape and Man Simulation System. Food and Ecological Systems Modelling Journal, 6, Article e152914. https://doi.org/10.3897/fmj.6.152914

Image Credits: AI Generated

DOI: 10.3897/fmj.6.152914

Keywords: Coccinella septempunctata, seven-spot ladybird, ALMaSS, agent-based model, biological control, aphids, Integrated Pest Management, landscape ecology, temperature-dependent development, cannibalism, hibernation, agricultural modelling

To appreciate why this is so surprising, it helps to understand how fuel delivery normally works in vertebrates. In most animals, ketone bodies are manufactured far from the brain, in the liver. When glucose levels fall during fasting, starvation, or prolonged exercise, the liver breaks down fatty acids into these compact energy molecules, which then travel through the circulation to hungry organs, including the brain. Neurons, which are among the most energy-demanding cells in the body, typically have little capacity to make this fuel themselves. The conventional view, as Santin put it, is that ketones are always delivered to the brain from elsewhere in the body. His team’s experiments revealed that bullfrogs bypass that supply chain entirely, generating ketones locally and creating an energy reserve exactly where it is needed most. He compared the discovery to finding a backup generator inside a building that everyone assumed had only one power source.

The technical heart of the study lies in showing that neural circuits can keep functioning when glucose metabolism is cut off, provided the brain can switch on its own ketone production. The researchers describe this in the study’s title as transforming neural activity to operate without glucose metabolism using brain-derived ketone bodies. In practical terms, that means the frog brain does not simply shut down when its primary fuel disappears. Instead, it appears to reconfigure its metabolic machinery so that critical neural functions continue on the alternative fuel. The team does not believe the metabolic shift is permanent; rather, it seems to act as a robust backup system that engages when the usual energy supply falls short. What remains unknown, and what the researchers flag as a key question for future work, is what molecular signal triggers the switch and how long the brain can sustain production before reserves are exhausted.

The evolutionary logic behind such a system becomes clear when you consider the bullfrog’s annual calendar. Each winter, the animals enter a hibernation-like state that slows their metabolism to a crawl and steadily drains their energy reserves. By the time spring arrives, oxygen and stored fuel are running dangerously low, yet the frogs must immediately reactivate the essential brain circuits that control breathing, heart rate, and other bodily functions. There is no grace period; a frog that cannot bring its neural command centers back online quickly will not survive the transition. The newly discovered metabolic backup system may be one reason bullfrogs can make that leap from near-dormancy to full alertness so reliably. Local ketone production would give the brain a way to keep its most vital circuits powered even as glucose availability collapses, buying the animal time until normal feeding resumes.

The work builds on years of prior research in Santin’s laboratory into how frogs endure conditions that would severely injure or kill most other animals. Earlier studies from the group showed that the hibernation-like state helps protect neural circuits during extreme oxygen deprivation, a capability that has long fascinated comparative physiologists. The new findings add a second layer to that survival strategy: the ability to maintain brain activity even when glucose metabolism is compromised. Together, the two capabilities suggest that the bullfrog brain is equipped with a layered defense against energy crisis, one that safeguards circuits against oxygen starvation and fuel starvation alike. That combination is rare among animals and makes the bullfrog an unusually valuable model for studying how neural tissue copes with metabolic stress.

What makes the result resonate beyond amphibian biology is the growing recognition that impaired brain energy metabolism sits at the center of several devastating human neurological conditions. Alzheimer’s disease, ALS, and schizophrenia have all been linked to defects in the way neurons generate or use energy. In Alzheimer’s, for example, brain glucose metabolism often declines measurably before significant memory loss appears, and researchers have debated for years whether that metabolic failure is a cause or a consequence of the disease. Because bullfrogs and humans share many of the same fundamental biological processes, according to Santin, understanding how a frog brain reprograms itself to run on self-made ketones could suggest new angles for studying what happens when human brains cannot get enough energy. The frog’s trick may not translate directly into a therapy, but it identifies a biological capability that was previously invisible and therefore never a target of investigation.

The discovery also carries a broader lesson about the assumptions embedded in neuroscience. The dependence of the mammalian brain on a continuous glucose supply is so well established that it functions as a foundational principle, taught in introductory courses and baked into experimental designs. Studies of stroke, hypoglycemia, and metabolic disease often take for granted that fuel must come from outside the brain. A vertebrate that violates that principle forces researchers to ask which other species might share the capability and what cellular machinery makes it possible. If bullfrog neurons can express the enzymes needed to synthesize ketone bodies on demand, the question becomes whether dormant or stressed brains in other animals, perhaps even under certain conditions in mammals, retain vestiges of a similar program. The Missouri team’s result does not answer those questions yet, but it makes them legitimate and urgent.

For now, the most immediate payoff is conceptual: a demonstration that the brain’s fuel economy is more flexible than assumed, and a natural experiment in how neural circuits can be retooled to survive an energy shortage. The study, titled Transforming neural activity to operate without glucose metabolism using brain-derived ketone bodies, appeared in the Proceedings of the National Academy of Sciences in early September 2026. Its authors suggest the finding could eventually inform research into neurological disorders tied to failing brain metabolism, from Alzheimer’s disease to ALS and schizophrenia, by revealing mechanisms that keep neurons alive when their preferred fuel is scarce. The open questions, including what triggers the switch to ketone production and how long bullfrogs can sustain it, now define the next phase of work in the Santin lab. In the meantime, the bullfrog has earned a new reputation: not just a hardy survivor of frozen winters, but the owner of a built-in backup generator that science is only beginning to understand.

Subject of Research: Local brain-derived ketone body production in bullfrogs as a backup fuel system during glucose shortage

Article Title: Researchers discover bullfrog brains can make their own backup fuel

Article References: Researchers discover bullfrog brains can make their own backup fuel. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: bullfrogs, ketone bodies, glucose metabolism, brain energy, hibernation, neuroscience, Alzheimer's disease, ALS, schizophrenia, University of Missouri, neural circuits, PNAS

The team examined four desert-dwelling reptiles that occupy different ecological niches and differ in how deeply and reliably they brumate: the Egyptian spiny-tailed lizard Uromastyx aegyptia, the desert monitor Varanus griseus, Savigny’s agama Trapelus savignii, and the ringed wall gecko Tarentola annularis. For each species, kidney tissue was collected during the active season and again during brumation, allowing direct within-species comparison. This design matters because brumation is not a uniform state across reptiles. Some species are obligate brumators that reliably spend the entire cold season dormant, while others are more facultative, emerging during warm spells and adjusting their dormancy to prevailing conditions. The researchers hypothesized that this behavioral difference might be mirrored in the intensity of the physiological responses they measured.

Under the microscope, the brumating kidneys showed clear signs of degeneration. The authors report glomerulosclerosis, a scarring and hardening of the glomeruli, the tufts of capillaries where blood filtration begins, along with necrotic renal tubules and cytoplasmic vacuolization, in which the cells lining the tubules accumulate fluid-filled spaces. These changes echo earlier observations in hibernating mammals, where renal tissue undergoes structural remodeling during cold ischemia and then recovers on arousal. In mammals such as ground squirrels and bears, the kidney has become a natural model of organ preservation, because it tolerates months of reduced blood flow and low temperature without permanent injury. The Egyptian lizards appear to be running a comparable program, with structural changes that look damaging in a snapshot but are presumably reversible when the animals rewarm in spring.

Morphometric analysis, in which structures are measured and compared statistically, revealed that the direction of renal change was not uniform across species. Glomerular diameter decreased significantly during brumation in Uromastyx aegyptia and Tarentola annularis, but increased in Varanus griseus and Trapelus savignii. The proximal tubules, which reabsorb the bulk of the filtrate, widened in T. savignii but narrowed in U. aegyptia. The distal tubules, important for fine-tuning ion and water balance, followed the same split pattern, expanding significantly in T. savignii while contracting in U. aegyptia. In other words, two species shrank their filtration and transport machinery while the other two enlarged theirs, a divergence the authors interpret as species-specific renal adaptation rather than a single universal hibernation phenotype.

Why would closely related desert reptiles remodel the same organ in opposite directions? The answer likely lies in their different water economies and dormancy strategies. Uromastyx aegyptia, a large herbivorous agamid that spends long periods underground, may prioritize water conservation by reducing glomerular filtration, a strategy consistent with seasonal kidney studies in the related Saharan species Uromastyx acanthinura, where winter morphology shifts with body water economy. The desert monitor, an active predator with a wide thermal niche, and the smaller agama may maintain or even expand renal structures to handle intermittent arousal and feeding. Seasonal remodeling of visceral organs is well documented in squamates, including previous work on the same gecko species showing dramatic reshaping of internal organs between seasons, so the kidney appears to be one component of a whole-body seasonal reorganization.

The biochemical side of the story centers on reactive oxygen species. Even when metabolism is depressed, cells continue to leak electrons from mitochondria, and the reoxygenation events that accompany periodic arousal can generate bursts of superoxide and other radicals that damage lipids, proteins, and DNA. The study measured malondialdehyde, or MDA, a standard end product of lipid peroxidation, as an index of oxidative damage. In all four species, MDA rose significantly during brumation, confirming that winter dormancy imposes genuine oxidative stress on reptilian kidneys. This finding aligns with a growing body of literature on hibernating frogs, turtles, toads, and mammals, and with the preparation for oxidative stress hypothesis, which proposes that animals anticipating a stressor preemptively bolster their antioxidant arsenal.

The enzymatic defenses responded, but each species in its own way. Superoxide dismutase, or SOD, which converts superoxide radicals into hydrogen peroxide, and catalase, or CAT, which then splits hydrogen peroxide into water and oxygen, both showed increased activity during brumation, with distinct patterns in each species. At the level of gene expression, SOD transcript abundance increased by 0.77-fold in U. aegyptia, 1.79-fold in V. griseus, 0.12-fold in T. savignii, and 0.51-fold in T. annularis. Catalase expression told an even more divergent tale, rising 5.24-fold in U. aegyptia, 0.86-fold in V. griseus, and 0.35-fold in T. annularis, while actually falling by 0.90-fold in T. savignii. The five-fold catalase upregulation in the spiny-tailed lizard stands out as the strongest single transcriptional response in the dataset.

When the authors sorted the species by dormancy strategy, a pattern emerged. The two obligate brumators, Uromastyx aegyptia and Varanus griseus, showed more consistent upregulation of their antioxidant genes than the facultative species Trapelus savignii and Tarentola annularis. The researchers suggest that the intensity of antioxidant defense correlates with the depth and duration of winter dormancy. An animal that commits to months of uninterrupted cold torpor faces a prolonged oxidative challenge and must invest heavily in enzymatic protection, whereas a species that brumates intermittently may rely more on behavioral buffering, such as basking during warm spells, and less on constitutive molecular defenses. This framing connects the histology and biochemistry to ecology, turning a kidney study into a window on how life histories shape stress physiology.

The broader significance of the work reaches beyond herpetology. Hibernation and brumation are among the most extreme physiological states in the animal kingdom, and understanding how dormant animals protect organs like the kidney has long interested biomedical researchers, because mammalian kidneys suffer severe injury during cold ischemia in transplantation and surgery. Studies of hibernating ground squirrels, bears, and dormice have shown that dormant kidneys are natural models of organ preservation, and the lizard data extend that comparative framework to ectotherms, which experience body temperatures that track their surroundings rather than staying warm. Reptiles may therefore harbor additional, evolutionarily independent solutions to the problem of protecting filtration tissue through cold and hypoperfusion.

There are also conservation and climate dimensions. Desert reptiles already live at the edge of their thermal tolerances, and warming winters could shorten or destabilize brumation, forcing animals to balance energy budgets in new ways, as recent work on hibernating lizards exposed to insecticides and rising temperatures has suggested. If antioxidant capacity is tuned to a particular depth and duration of dormancy, then climate-driven changes in dormancy behavior could leave kidneys mismatched to their oxidative environment. The authors collected and handled all animals under the approval of the Institutional Animal Care and Use Committee of Kafrelsheikh University, and they note that the datasets are available from the corresponding author on reasonable request. For now, the study stands as a detailed demonstration that four lizards sleeping through the same Egyptian winter are, at the level of their kidneys, solving the problem in four different ways.

Subject of Research: Renal histological changes and antioxidant enzyme responses during brumation in four Egyptian desert lizard species

Article Title: Renal histological and antioxidant response in Egyptian desert lizards during brumation

Article References: Hammad, A. R., Mahfouz, M. E., Bakr, S. M., & Alm-Eldeen, A. A. (2026). Renal histological and antioxidant response in Egyptian desert lizards during brumation. Environmental Science and Pollution Research, 33(30), 15298-15309. https://doi.org/10.1007/s11356-026-38195-9

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38195-9

Keywords: brumation, desert lizards, kidney histology, oxidative stress, antioxidant enzymes, superoxide dismutase, catalase, malondialdehyde, gene expression, Uromastyx aegyptia, Varanus griseus, hibernation

The award carries substantial weight in both funding and prestige. It provides $3.8 million over five years under grant number DP2DK152025-01, resources that will support the continued development of Lal’s laboratory and its ambitious agenda. Established in 2007, the NIH Director’s New Innovator Award is part of the agency’s High-Risk, High-Reward Research program, and it is deliberately structured differently from conventional grants. Unlike most traditional funding opportunities, it does not require preliminary data or a detailed experimental plan. That design gives investigators an unusual degree of freedom to pursue unconventional ideas, the kind of projects that might struggle to survive the standard peer-review gauntlet but that could, if successful, open entirely new fields of inquiry.

What makes the Arctic ground squirrel such a compelling subject is a suite of physiological feats that appear to defy the rules of mammalian biology. To prepare for hibernation, the animals gain substantial weight and become less responsive to insulin, a hormonal state that in humans would be a hallmark of progressing toward type 2 diabetes. Yet when they emerge from their torpid state, they reverse those changes without ever developing the disease. The squirrels also withstand the slowest body and brain temperatures ever recorded for any mammal, dropping into a chilled state that would cause devastating damage in most species. Understanding how they accomplish these reversals, Lal argues, could reveal evolutionary solutions to some of medicine’s most stubborn problems.

The implications extend across several major categories of chronic illness. Lal’s research program is aimed at uncovering novel therapeutic strategies for diabetes, muscle wasting disorders, and ischemic injuries, conditions that collectively affect millions of patients worldwide. Ischemic injury, in which tissue is damaged by restricted blood flow and the oxygen deprivation that follows, shares mechanistic ground with the metabolic stresses hibernating animals endure. Muscle wasting, or atrophy, is a central feature of aging, prolonged immobility, cancer, and critical illness, and it remains poorly served by existing treatments. If hibernators have evolved molecular safeguards that protect their muscles and metabolic organs through months of dormancy, decoding those safeguards could point drug developers toward targets that no one has thought to pursue.

A distinctive feature of Lal’s approach is methodological. His team is developing what are known as NAMs, or New Approach Methodologies, alongside genetic tools to investigate how the squirrels’ protective abilities operate at every scale, from individual cells to the whole animal. New Approach Methodologies is an umbrella term for innovative testing strategies, often built on cell cultures, organoids, computational models, and other alternatives to traditional approaches, that are increasingly valued in biomedical research for their ability to capture complex biology in controlled, tractable systems. Pairing these tools with genetic techniques allows the lab to probe mechanisms directly rather than merely observing correlations, an essential step if findings in squirrels are ever to be translated into therapies for people.

Equally distinctive is the conceptual framing. Rather than studying only what goes wrong in disease, as much of biomedical research necessarily does, Lal’s group is asking fundamental questions about what goes right in an animal that has already solved the problem. This inversion of the standard disease model reflects a growing appreciation in physiology that nature has run countless evolutionary experiments, and that some species hold working answers to questions medicine is still formulating. Hibernation biology has attracted renewed attention in recent years precisely because the animals that hibernate appear to sidestep conditions, from insulin resistance to muscle disuse atrophy to reperfusion injury, that plague human patients.

The Arctic ground squirrel is a particularly striking example of this phenomenon. Its hibernation cycle involves dramatic swings in body mass, metabolism, and hormonal signaling, all orchestrated and then reversed with apparent ease. In humans, sustained insulin resistance typically progresses toward diabetes, and the metabolic consequences of obesity are among the most intensively studied problems in modern medicine. The squirrel’s ability to pack on weight, suppress insulin sensitivity, and then recover full metabolic health without intervention suggests the existence of endogenous protective mechanisms. Identifying the molecular switches behind that recovery is precisely the kind of fundamental question the New Innovator Award is designed to enable.

The award also marks a significant milestone for the Monell Chemical Senses Center itself. Founded in 1968, Monell is an independent nonprofit research institute in Philadelphia, Pennsylvania, dedicated to advancing and sharing discoveries in the science of the chemical senses: smell, taste, chemesthesis, and interoception. The institute’s mission explicitly ties basic sensory science to solving the world’s health, societal, and environmental challenges. Lal’s program fits within that tradition of pursuing fundamental biology with an eye toward broad human relevance, even though his model organism might seem, at first glance, far removed from the center’s sensory roots. Interoception, the sense of the body’s internal state, connects directly to the metabolic and neural signals that govern hibernation, appetite, and energy balance.

For early-career scientists, the New Innovator Award represents more than money. It is a signal from the NIH that an investigator’s ideas are considered genuinely original and potentially field-changing, and it often serves as a foundation on which subsequent research careers are built. The program’s explicit tolerance for uncertainty, its willingness to fund projects without preliminary data, reflects a philosophy that the most transformative science often begins as a question that cannot yet be answered with conventional pilot experiments. Lal’s bet on a hibernating rodent as a guide to human chronic disease is exactly the kind of proposition the award exists to test.

The work ahead is substantial. Translating observations from Arctic ground squirrels into treatments for diabetes, muscle wasting, or ischemic injury will require identifying the relevant molecular pathways, validating them in appropriate models, and eventually determining whether they can be safely modulated in humans. The five-year timeline and $3.8 million budget give the Lal laboratory the runway to build the NAMs and genetic toolkits needed to begin that work in earnest, moving from whole-animal observations down to cellular mechanisms and back up again. Whether the squirrels’ secrets can be bottled into therapies remains an open question, but it is precisely the sort of high-stakes, high-curiosity question that the NIH Director’s New Innovator Award was created to champion, and one whose answer could reshape how medicine thinks about chronic disease.

Subject of Research: Hibernation physiology of Arctic ground squirrels as a model for novel treatments of chronic metabolic and neurological diseases

Article Title: Monell investigator receives prestigious NIH director's new Innovator Award

Article References: Monell investigator receives prestigious NIH director's new Innovator Award. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: NIH Director's New Innovator Award, Monell Chemical Senses Center, Arctic ground squirrel, hibernation, insulin resistance, diabetes, muscle wasting, ischemic injury, New Approach Methodologies, early-career investigator, metabolism, chronic disease

Bd is arguably the most destructive pathogen ever documented in wild vertebrates. The chytrid fungus has decimated amphibian populations on every continent where amphibians live, driving scores of species toward extinction and reshaping entire ecosystems in its wake. Because Bd is an aquatic organism that infects its hosts through the skin, researchers and wildlife managers have generally focused their attention on the water bodies where amphibians congregate to breed, treating those brief aquatic gatherings as the principal arenas of transmission. For the Yosemite toad, a species that spends the vast majority of its life on land, this reasoning suggested a comforting conclusion: the toads should be at comparatively low risk, vulnerable only during the short window of the mating season when they enter the water.

The new study, published in Functional Ecology by UCLA ecologist Dave Daversa and colleagues, demolishes that assumption. When the researchers surveyed toads emerging from their winter hibernation burrows, they found previously healthy animals carrying heavy fungal loads. The infections, in other words, were not being acquired in the breeding pools at all. They were building up underground, during the coldest and most hostile months of the Sierra Nevada year, in the abandoned rodent burrows that the toads use as winter refuges. The results of the surveillance study, Daversa said, were completely unexpected, sharply contrasting with the prevailing view that the high-risk season for Bd infection occurs when amphibians are breeding in water.

The Yosemite toad, Anaxyrus canorus, is a small and distinctive resident of the high country, living almost exclusively within Yosemite National Park and neighboring Sequoia and Kings Canyon national parks. The toads measure only about one to three inches long, and they walk rather than hop, an unusual gait that suits their slow, deliberate lifestyle in meadow habitats. Females are larger than males and wear bumpy skin mottled in attractive shades of green, while males are less colorful. The species breeds in small pools formed by snowmelt, but for much of the year the toads keep to land, sheltering from predators and extreme temperatures in burrows abandoned by rodents. When the brutal High Sierra winter arrives, they hibernate in these underground chambers, sometimes buried beneath many feet of snow.

That lifestyle has not shielded the species from decline. Climate change is rendering the toads’ mountain habitats drier and hotter, and fewer tadpoles are surviving to adulthood. Infection with Bd, which is fatal to the toads, is widespread across their range. The combined pressures led the federal government to list the Yosemite toad as threatened under the Endangered Species Act in 2014, and California classifies it as a highest-priority species of special concern. In an effort to bolster wild populations, toads have been reared at the San Francisco Zoo and returned to Yosemite, but until now it was not understood how the fungus might be undermining those reintroduction efforts.

To find out, a team of researchers from UCLA and Yosemite National Park conducted an intensive surveillance program from 2021 through 2023, designed to determine how Bd prevalence and severity varied across seasons and life stages. The researchers compared toads before and after cohorts entered winter dormancy, capturing metamorphs — juvenile toads that had recently completed metamorphosis — from high-altitude locations near Tioga Pass. They took skin swabs from the animals immediately after they emerged from hibernation in May, again during the summer, and once more before hibernation in September. The following spring, during early snowmelt, they returned and sampled the same individual toads as they emerged from hibernation. A parallel survey sampled toads at every phase of the life cycle, producing a total of 1,800 samples collected over three years at six sites.

Each swab was screened for Bd using established molecular techniques, including polymerase chain reaction tests of the same kind that became familiar worldwide during the COVID-19 pandemic. Daversa noted that the pandemic made it easier to explain to hikers he encountered along the trails what he was doing as he swabbed toads. The laboratory results, however, were anything but routine. The data unambiguously identified the winter months of underground dormancy as the key season of rapid Bd proliferation, and the effect was particularly pronounced in metamorphs, the youngest and most vulnerable life stage. Toads that had tested clean or carried only trace infections in the autumn emerged from their burrows in spring bearing strong infections acquired on land.

The finding stunned the research community because it contradicted nearly everything scientists believed they knew about the pathogen’s biology. Bd was thought to grow best under more moderate conditions, and the toads were assumed to be at low risk precisely because they spend so little time in water. The idea that the fungus could not merely survive but actively multiply at the super-low temperatures of a Sierra winter — either above ground or inside the burrows — came as a genuine surprise. UCLA conservation biologist and study co-author Brad Shaffer said it certainly appears that the Bd fungus has the ability to move between individuals, adding that its capacity to increase in number on land at such low temperatures is a real surprise.

Several important questions remain unresolved. The researchers cannot yet say for certain that toads are contracting new infections inside the burrows themselves. An alternative explanation is that the animals enter hibernation carrying very light, undetectable infections, and that for reasons still unknown each individual then develops a heavy fungal load over the winter. Studying the burrows directly during hibernation is extraordinarily difficult because the chambers lie buried beneath deep snow for months at a time. UCLA wildlife disease ecologist and co-author Jamie Lloyd-Smith framed the puzzle in terms of how pathogens persist in host populations with extremely seasonal life histories, observing that this fungus is not supposed to grow happily at such low temperatures. One hypothesis the team speculates about involves the host’s own defenses: the immune state of a hibernating toad may drop even lower than the fungus’s ability to grow, allowing infections to run unchecked while the animal lies dormant and cold-stunned.

Whatever the precise mechanism proves to be, the discovery has already changed conservation practice on the ground. Reintroducing captive-reared toads at the metamorphic stage, or younger, would be cheaper and easier for the program based at the San Francisco Zoo. But because the youngest toads are precisely the ones most at risk of devastating overwinter Bd infections, managers now release animals only after several years of growth, when they have reached a size and maturity at which the winter fungal surge poses less of a threat. Follow-up studies are planned to pin down exactly how the fungus persists and spreads in the burrows, and whether the hibernating toads’ suppressed immune systems hold the key. For a species clinging to survival in one of America’s most beloved national parks, the finding offers something rare: a genuine strategic insight into an enemy that, until now, had been hiding in the toads’ own homes.

Subject of Research: Winter proliferation of the amphibian chytrid fungus Batrachochytrium dendrobatidis in the hibernation burrows of Yosemite toads

Article Title: Yosemite toad killer may be hiding in their own homes

Article References: Yosemite toad killer may be hiding in their own homes. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Yosemite toad, Batrachochytrium dendrobatidis, chytrid fungus, amphibian disease, hibernation, burrows, conservation biology, Endangered Species Act, captive rearing, reintroduction, Sierra Nevada, UCLA

The research, led by Marloes Oosterhof and Louis Coussement of the University of Groningen together with colleagues in Belgium, Austria and the Netherlands, focused on the liver, the metabolic command center that manages the fuel switch from glucose to fat oxidation that hibernation demands. Because facultative hibernators like the Syrian hamster enter torpor only in response to environmental cues, shortening days, cold and food scarcity, their bodies must actively reprogram gene expression rather than simply follow a fixed seasonal clock. That flexibility makes epigenetic mechanisms, the chemical systems that switch genes on and off without altering the underlying sequence, prime suspects for orchestrating the transition.

To test this idea, the team induced hibernation in Syrian hamsters by shortening the light-dark cycle and lowering ambient temperature, then collected liver samples at carefully defined phases: summer euthermia, when animals were active and warm; late torpor, more than 72 hours after the animals had settled into a bout; and both early and late arousal, shortly after the animals rewarmed. Using infrared motion detectors, the researchers confirmed each animal’s state before euthanasia, ensuring that the molecular snapshots truly reflected the hibernation phase rather than guesswork about body temperature.

The first layer of analysis examined the expression of 94 genes encoding epigenetic writer and eraser enzymes, the proteins that add or remove chemical marks on histones and DNA. Of the 83 genes that could be reliably measured, 11 shifted significantly between phases. Strikingly, four histone acetyltransferases, KAT6A, KAT6B, KAT7 and KAT13D, better known as the circadian gene CLOCK, were differentially expressed, with most declining during torpor and rebounding during arousal. Three deacetylases, SIRT2, SIRT7 and HDAC11, also changed, along with two histone methyltransferases, one demethylase and the DNA demethylating enzyme TET2.

Notably, several of these enzymes, including PCAF, GCN5L2, HAT1 and CBP, had been flagged in previous work on the thirteen-lined ground squirrel, an obligatory hibernator, but showed no expression changes in the hamster. This divergence suggests that facultative hibernators may deploy a distinct epigenetic toolkit, one tailored to switching hibernation on and off in response to the environment rather than to an internal circannual rhythm. The downregulation of CLOCK in the hamster liver is particularly intriguing, since recent work indicates that the liver pauses its circadian rhythms during hibernation while the brain retains them.

Gene expression, however, is only an indirect readout. The team therefore measured histone acetylation directly, first by Western blot and then by quantitative mass spectrometry, a technique that can determine exactly how many acetyl groups sit on specific lysine residues of histones H3 and H4. The results were consistent and telling. Overall acetylation of histone H3 dropped during late torpor, with the acetylation of lysines 18 and 23 falling by roughly 5 and 14 percent respectively, and rising again during arousal. H3K27ac, a mark classically associated with active enhancers and open chromatin, was lowest in torpor and recovered as animals rewarmed, a pattern that fits the idea of chromatin condensing, and transcription shutting down, while the animal is cold and metabolically dormant.

Histone H4 told a subtler story. Unlike H3, whose acetylation largely rebounded during arousal, the H4 peptide spanning lysines 5, 8, 12 and 16 remained under-acetylated even after the animals had rewarmed. The single most heavily used site, H4K16, a modification with the unusual ability to both promote and repress transcription depending on context, was significantly less acetylated in late arousal than in summer-active animals. The researchers point to SIRT2 and SIRT7, both of which target H4K16 and both of which were upregulated during arousal, as plausible culprits, noting that these sirtuins can translocate into the nucleus during cell-cycle transitions and stress, both of which accompany the metabolic turbulence of rewarming.

On the enzyme-activity side, histone acetyltransferase activity stayed flat across all phases, but histone deacetylase activity peaked in late torpor. Inhibitor profiling revealed that a single enzyme, HDAC6, accounted for roughly 71 percent of total hepatic HDAC activity. Yet here the plot thickened: although HDAC6 activity was high and histone acetylation low during torpor, the acetylation of alpha-tubulin, HDAC6’s best-known cytosolic target, actually increased. The authors suggest that HDAC6 may relocate to the nucleus during torpor, deacetylating histones there while leaving tubulin untouched, and note that the enzyme is also tied to hepatic gluconeogenesis and to protective responses in ischemic liver injury, processes highly relevant to both hibernation and, potentially, human organ preservation.

Perhaps the most surprising negative result concerned DNA methylation. Using both the Luminometric Methylation Assay and whole-genome bisulfite sequencing, the team found no significant differences in global cytosine methylation at CpG or non-CpG sites across any hibernation phase, and promoter methylation of the differentially expressed genes was likewise unchanged. This stability mirrored the near-absence of changes in the expression of DNA methyltransferases and demethylating enzymes, and it contrasts with reports of methylation shifts in ground squirrels and horseshoe bats. In the Syrian hamster, at least, the epigenetic levers of hibernation appear to be pulled at the histone level rather than at the DNA level.

The broader implications reach well beyond rodent physiology. Because facultative hibernators can trigger hypometabolic, cytoprotective states essentially on command, understanding their epigenetic switches could inform strategies to protect organs during transplantation, to limit ischemic damage, and even to slow aging, given recent evidence that epigenetic aging is effectively stalled during hibernation in yellow-bellied marmots. The authors caution that their bulk liver measurements largely reflect hepatocytes and that single-cell follow-up work will be needed to resolve contributions from rarer cell types, and that the expression changes, though modest in fold change, match the magnitude of the measured histone modifications. Still, the message is clear: when a hamster decides to hibernate, it does not rewrite its DNA. It retunes the packaging, loosening and tightening the spools of chromatin to silence the genome through the cold and swing it back open for the warmth of arousal.

Subject of Research: Epigenetic regulation of gene expression, specifically histone acetylation and DNA methylation, in the liver of facultatively hibernating Syrian hamsters

Article Title: Changes in histone lysine acetylation, but not DNA methylation during facultative hibernation in Syrian hamster liver

Article References: Oosterhof, M. M., Coussement, L., van Pijkeren, A., Kwiatkowski, M., Zwinderman, M. R. H., Dekker, F. J., de Meyer, T., Reitsema, V. A., Bischoff, R., Guryev, V., Bouma, H. R., Henning, R. H., & Rots, M. G. (2024). Changes in histone lysine acetylation, but not DNA methylation during facultative hibernation in Syrian hamster liver. Epigenetics Communications, 4(1), Article 1. https://doi.org/10.1186/s43682-023-00024-2

Image Credits: AI Generated

DOI: 10.1186/s43682-023-00024-2

Keywords: hibernation, Syrian hamster, epigenetics, histone acetylation, DNA methylation, HDAC6, sirtuins, liver metabolism, torpor, chromatin, KAT6A, epigenetics communications

The technical achievement at the heart of the study is considerable. Building a truly complete genome has long been one of genomics’ most stubborn challenges, because repetitive DNA sequences near the centers and ends of chromosomes resist standard sequencing methods. The research team overcame this by combining PacBio HiFi long-read sequencing, which produces highly accurate reads spanning tens of thousands of DNA letters, with Hi-C technology, which captures the physical contacts between distant stretches of chromosomes and allows the sequences to be anchored into their correct chromosomal positions. The final assembly spans 2.42 gigabases, with a scaffold N50 of 72.35 megabases and a contig N50 of 66.56 megabases, meaning that half of the assembled genome resides in stretches longer than those figures. The guanine-cytosine content of the assembly sits at 42.36 percent. In practical terms, the contiguity of this assembly approaches the ideal of a single gap-free sequence per chromosome, giving researchers an unprecedented view of the bear’s genome architecture.

With that high-resolution reference in hand, the team turned to comparative genomics, aligning the Tibetan brown bear’s chromosomes against those of its closest living relative, the polar bear. The analysis revealed high chromosomal synteny between the two species, meaning that large blocks of genes retain the same order and orientation across both genomes despite millions of years of separate evolution. This structural conservation is scientifically valuable for two reasons. It confirms that the assembly is accurate, since genuine chromosome-scale structure should be preserved between closely related ursids, and it provides a stable framework for pinpointing the regions that have instead diverged, which are precisely the locations where adaptation to very different environments, Arctic sea ice versus high-altitude steppe, is most likely to leave its mark.

The genomic record also preserves a vivid portrait of the species’ demographic turbulence. By reconstructing changes in effective population size through time, the researchers found that the Tibetan brown bear expanded during the early Pleistocene, a period of dynamic climate and habitat change. That expansion, however, was followed by two severe population bottlenecks. The first occurred approximately two million years ago, coinciding with the pre-Poyang Glaciation, and the second struck around one hundred thousand years ago during the Last Glacial Period. Together, these crashes reduced the bear’s cumulative effective population size by nearly eighty percent. For a species that today persists only on the Qinghai-Xizang Plateau, this history of repeated near-collapses carries a sobering message about the genetic fragility that may still lurk beneath its wild, unbroken landscape.

Yet survival through those bottlenecks suggests the species carries more than vulnerability. Enduring glacial cycles on a plateau whose average elevation exceeds 4,000 meters demands a physiology unlike that of lowland relatives, and the most striking discovery of the study concerns exactly that. When the researchers examined candidate hibernation-related pathways, they found that the Tibetan brown bear displays a distinctly carbohydrate-dominated metabolic signature. This stands in sharp contrast to the hibernation strategy documented in North American brown bears, which rely primarily on lipid, or fat-based, metabolism to fuel their long winter dormancy. In other words, two populations of the same widespread species appear to have evolved fundamentally different biochemical approaches to the same survival problem.

The implications of that finding extend well beyond bears. Fat is the standard fuel of hibernation across most studied mammals, because it stores more energy per gram and spares blood sugar during months of fasting. A sugar-first strategy on the Tibetan Plateau hints at selective pressures unique to that environment, where the short growing season, the composition of available foods, and the metabolic demands of life at low oxygen levels may have favored a different balance of carbohydrate and lipid pathways. The authors emphasize that this distinct metabolic adaptation highlights the bear’s unique mechanisms for surviving the extreme plateau environment, and it gives physiologists a natural experiment in alternative hibernation biochemistry encoded within a single species.

For conservation biologists, the new genome arrives at a critical moment. The Tibetan brown bear sits at the top of the plateau’s food web, playing a crucial ecological role, yet high-quality genomic resources for the species have been scarce until now. A chromosome-level reference genome transforms what conservation managers can do: it enables accurate estimates of genetic diversity and inbreeding, allows the tracking of gene flow between populations, and provides the resolution needed to identify locally adapted lineages that deserve special protection. Given the roughly eighty percent historical reduction in effective population size documented in the study, such tools are not a luxury. They are the baseline data upon which any serious plan for the species’ long-term management on the plateau must rest.

The study also strengthens the broader evolutionary picture of the bear family. Ursids have long fascinated evolutionary biologists because the family contains species with radically different ecologies, from the omnivorous brown bear to the hypercarnivorous, ice-bound polar bear. A near telomere-to-telomere assembly for the Tibetan brown bear adds a critical high-quality data point for reconstructing the phylogenomic relationships within Ursus and for dating the divergences that produced today’s brown bear lineages. Because structural variants, gene duplications, and regulatory regions can now be examined in their full chromosomal context rather than through fragmented assemblies, questions about how bears colonized and adapted to some of Earth’s harshest habitats can be addressed with far greater precision than before.

The research was carried out by Muran Zhao, Anmin Wang, Hai Liu, Chenxing Yu, Yanlin Liu, Nan Sun, and Guogang Li of Qinghai Normal University, with fieldwork, sample collection, and laboratory analysis conducted under permits granted by the university. The work was supported by the National Natural Science Foundation of China. The team notes that the new assembly is intended as a resource for the wider community, facilitating future studies of ursid evolutionary history and supporting conservation and management of the plateau’s wildlife. Because the genome is derived from a female bear, it also enables improved analysis of the sex chromosomes, an area where earlier fragmented assemblies often fell short.

What began as a technical sequencing project has ended with a discovery that may echo well beyond the Qinghai-Xizang Plateau. If a close relative of the brown bears studied across North America and Eurasia can hibernate on a carbohydrate-dominated metabolic program, then hibernation is not a single fixed solution that evolution produced once and reused everywhere. It is a flexible toolkit, and different populations have assembled it from different parts. As climate change alters the length and severity of winters across the world’s mountains, understanding that flexibility, and the genes that underpin it, could prove essential not only for protecting the Tibetan brown bear but for predicting which hibernating species can adjust and which cannot. The near-complete genome of this high-altitude survivor is now available as the roadmap for answering those questions.

Subject of Research: Chromosome-level genome assembly and hibernation-related evolution of the Tibetan brown bear (Ursus arctos pruinosus)

Article Title: Near telomere-to-telomere genome reveals the phylogenomics and hibernation-related evolution in Tibetan brown bear (Ursus arctos pruinosus)

Article References: Zhao, M., Wang, A., Liu, H., Yu, C., Liu, Y., Sun, N., & Li, G. (2026). Near telomere-to-telomere genome reveals the phylogenomics and hibernation-related evolution in Tibetan brown bear (Ursus arctos pruinosus). BMC Genomics. https://doi.org/10.1186/s12864-026-13324-3

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13324-3

Keywords: Tibetan brown bear, telomere-to-telomere genome, genomics, hibernation, Qinghai-Xizang Plateau, population bottlenecks, PacBio HiFi, Hi-C sequencing, phylogenomics, conservation genomics, carbohydrate metabolism, Ursidae evolution