European Cave Research Articles

Cave bear tracks (Ursichnus europaeus Diedrich, 2011) from Honseca Cave, Palencia, Spain

References to ichnofossils attributed to ursids are scarce in the literature and only two ichnogenera attributed to ursids have been described: Platykopus Sarjeant, Reynolds and Kissell-Jones, 2002 and Ursichnus Diedrich, 2011. In contrast, tracks informally attributed to Late Pleistocene cave bears (Ursus spelaeus Rossenmüller and Heinroth, 1794) are frequent in European caves. However, their formal descriptions are extremely scarce; the only exception is the rich ichnocenosis from Urşilor Cave (Romania), the type locality of the ichnotaxon Ursichnus europaeus Diedrich. The Honseca Cave in northern Spain, contains a set of plantigrade pentadactyle tracks, which represent the first record of Ursichnus europaeus from a cave in the Iberian Peninsula. Although distinguishing cave bear from brown bear tracks is complex, cave bears are considered the most likely tracemakers in Honseca.

Palaeogenomic data from a Late Pleistocene coprolite clarifies the phylogenetic position of Sicilian cave hyena

Cave hyenas (genus Crocuta) were among the most representative large carnivorans of Eurasian ecosystems during the Middle-Late Pleistocene. They are close relatives of the extant African spotted hyenas, the only extant member of the genus Crocuta. However, the taxonomy of these forms is still debated. Using palaeogenetic and palaeogenomic evidence, previous studies suggested a complex evolutionary history between spotted and Eurasian cave hyenas. Up to now, no molecular data have been retrieved from their Mediterranean counterparts, leaving a gap in the understanding of population dynamics of the genus Crocuta. To investigate the relationships of the Sicilian hyena to other cave and extant spotted hyenas we obtained palaeogenomic data from a Late Pleistocene coprolite chronologically dated between 32 and 21 Ka. Surprisingly, we found that the Sicilian genome forms a basal lineage of cave hyena. Moreover, results show that the Sicilian cave hyena is less admixed with African spotted hyena than the German and Russian specimens are, thus rejecting any large scale gene flow from Africa to Sicily. Our findings show that the genetic structure of European cave hyenas was more complex than previously documented, and offers new insights into the phylogeny of the genus Crocuta.

Four years monitoring of the endangered European plethodontid salamanders

The ongoing biodiversity crisis is strongly threatening amphibians, mostly because of their peculiar physiology, their sensitivity to climate change and the spread of diseases. Effective monitoring involving assessments of pressure effects across time and estimation of population trends play a key role in mitigating amphibian decline. To improve implementation of standardized protocols and conservation efforts, we present here a dataset related to one of the amphibian genera whose onservation status is considered the most declining according to the IUCN. We report information on 66 populations of the endangered European cave salamanders, genus Speleomantes, that was collected through a standardized monitoring along a four-year period (2021–2024). Demographics data of the populations and fitness-related data of single individuals are reported. Furthermore, we include 3,836 high quality images of individuals that can allow to perform studies aiming to assess the phenotypic variability within the genus, and to perform long-term capture-mark-recaptured studies.

Functional convergence underground? The scale‐dependency of community assembly processes in European cave spiders

AbstractAimQuantifying the relative contribution of environmental filtering versus limiting similarity in shaping communities is challenging because these processes often act simultaneously and their effect is scale‐dependent. Focusing on caves, island‐like natural laboratories with limited environmental variability and species diversity, we tested: (i) the relative contribution of environmental filtering and limiting similarity in determining community assembly in caves; (ii) how the relative contribution of these driving forces changes along environmental gradients.LocationEurope.Time periodPresent.Major taxa studiedSubterranean spiders.MethodsWe used data on distribution and traits for European cave spiders (n = 475 communities). We estimated the trait space of each community using probabilistic hypervolumes, and obtained estimations of functional richness independent of the species richness of each community via null modelling. We model functional diversity change along environmental gradients using generalized dissimilarity modelling.ResultsSixty‐three percent of subterranean spider communities exhibited a prevalence of trait underdispersion. However, most communities displayed trait dispersion that did not depart significantly from random, suggesting that environmental filtering and limiting similarity were both exerting equally weak or strong, yet opposing influences. Overdispersed communities were primarily concentrated in southern latitudes, particularly in the Dinaric karst, where there is greater subterranean habitat availability. Pairwise comparisons of functional richness across caves revealed these effects to be strongly scale‐dependent, largely varying across gradients of cave development, elevation, precipitation, entrance size and annual temperature range. Conversely, geographical distance weakly affected trait composition, suggesting convergence in traits among communities that are far apart.Main conclusionsEven systems with stringent environmental conditions maintain the potential for trait differentiation, especially in areas of greater habitat availability. Yet, the relative influence of environmental filtering and limiting similarity change with scale, along clear environmental gradients. The interplay of these processes may explain the assembly of species‐poor subterranean communities displaying high functional specialization.

Taphonomic data from the transitional Aurignacian of El Castillo cave (Spain) reveals the role of carnivores at the Aurignacian Delta level

Palaeolithic sites are complex palimpsests due to the recurrent presence of human groups and carnivores through time, as documented in several European caves and rock shelters. Within these contexts, it can be challenging to identify the main contributors to bone accumulations and interpret human subsistence strategies and the role of carnivores. Consequently, taphonomic analyses are crucial for distinguishing the origins of these occupation episodes. One example of alternating occupations is found at El Castillo cave (Cantabria, Spain), specifically in the so-called Transitional Aurignacian level (∼46-42 ka uncal BP). According to a recent study conducted at this level (Luret et al., 2020), the human groups had a hunting specialisation focused on red deer, while carnivores had little influence on the assemblage. However, these interpretations were based only on the faunal assemblage from the recent excavations (1980–2011). A previous excavation phase was conducted on this site from 1910 to 1914, and after that, the faunal remains recovered were separated across several institutions, lacking a complete archaeozoological and taphonomic analysis of the whole level. In this work, a new taxonomic assessment and, for the first time, a taphonomic study of the macrofauna recovered in the Aurignacian Delta level during the initial excavations, stored at Museo Nacional y Centro de Investigación de Altamira (Cantabria, Spain), is carried out. This work provides new information about the human and carnivore groups that occupied El Castillo, constructing new hypotheses to interpret this relevant archaeological level.

Inferring on Speleomantes Foraging Behavior from Gut Contents Examination.

We here provide the first comprehensive analysis and discussion on prey consumed by the European cave salamanders of the genus Speleomantes. Our study stems from the need to shed light on the still unknown foraging behavior adopted by Speleomantes cave salamanders. Starting from the published datasets on gut contents from all Speleomantes species (including hybrids), we here discuss additional information (i.e., species ecology, lower taxonomic level), which were systematically omitted from those data sets. We analyzed a data set consisting of 17,630 records from 49 categories of consumed prey recognized from gut contents of 2060 adults and juveniles Speleomantes. Flying prey accounted for more than 58% of the prey items, while elongated crawling prey accounted for no more than 16% of the diet within a single population. Among the total recognized prey items, only three can be surely ascribed to the group of strictly-cave species (i.e., troglobites), meaning that European cave salamanders mostly forage in surface environment, and therefore represent one of the major drivers of allochthonous organic matter in subterranean environments. Some of the consumed prey seemed to be aquatic, allowing us to hypothesize whether Speleomantes are able to catch prey from a shallow body water. Furthermore, European cave salamanders possess the ability to prey upon taxa characterized by particular anti-predator defenses, while morphological constraints seem to be the most important limit to prey consumption. For each specific case, we provide insights and propose hypotheses concerning the foraging behavior that need to be tested to properly understand the foraging behavior of this cryptic salamanders.

Different patterns of introgression in a three species hybrid zone among European cave salamanders.

Hybrid zones occur where genetically distinct populations meet, mate and produce offspring with mixed ancestry. In Plethodontid salamanders, introgressive hybridization is a common phenomenon, where hybrids backcross with parental populations leading to the spread of new alleles into the parental genomes. Whereas many hybrid zones have been reported in American Plethodontid salamanders, only a single hybrid zone has been documented in European plethodontids so far, which is located at the Apuan Alps in the Italian Peninsula. Here, we describe a previously unreported hybrid zone in the Northern Apennines involving all the three Plethodontid salamander species inhabiting the Italian Peninsula. We found 21 new Speleomantes sites of occurrence, from a hitherto unexplored area located at the boundaries between three Speleomantes species ranges. Using mitochondrial (Cytb and ND2 genes) and nuclear markers (two diagnostic SNPs at the NCX1 gene), we revealed a three-way contact zone where all the three mainland species hybridize: S. strinatii, S. ambrosii and S. italicus. We observed a strong mitonuclear discordance, with mitochondrial markers showing a conspicuous geographic pattern, while diagnostic nuclear SNPs coexisted in both the same populations and individuals, providing evidence of hybridization in many possible combinations. The introgression is asymmetric, with S. italicus mitogenome usually associated with S. a. ambrosii and, to a lesser extent, to S. strinatii nuclear alleles. This finding confirms that Plethodontid are a group of choice to investigate hybridization mechanisms and suggests that behavioural, genetic and ecological components may concur in determining the direction and extent of introgression.

Starvation hardiness as preadaptation for life in subterranean habitats

Most subterranean habitats, especially caves, are considered extreme environments, mainly because of the limited and erratic food supply and constant darkness. In temperate regions, many climatic conditions, such as temperature and air humidity, are periodically less adverse or even more favourable in caves than the harsh seasonal weather on the surface. Accordingly, many animal species search for hibernacula in caves. These overwintering, non-specialized subterranean species (non-troglobionts) show various modes of dormancy and ongoing development. Since they do not feed, they all undergo periodic starvation, a preadaptation, which might evolve in permanent starvation hardiness, such as found in most specialized subterranean species (troglobionts). To this end, we performed a comparative analysis of energy-supplying compounds in eleven most common terrestrial non-troglobiont species during winter in central European caves. We found highly heterogeneous responses to starvation, which are rather consistent with the degree of energetic adaptation to the habitat than to overwintering mode. The consumption of energy-supplying compounds was strongly higher taxa-dependant; glycogen is the main energy store in gastropods, lipids in insects, and arachnids rely on both reserve compounds. We assume that permanent starvation hardiness in specialized subterranean species might evolved in many different ways as shown in this study.

On the identity and distribution of the rare Rymosia tolleti Burghele-Balacesco, 1965 (Diptera, Mycetophilidae) encountered in European caves

The identity and distribution of a neglected fungus gnat species, Rymosia tolleti Burghele-Balacesco, 1965, in Europe is reviewed based on examination of newly collected specimens as well as available museum mate-rials. Rymosia tolleti is widespread but rather rare in Central Europe, with confirmed records from Romania, Slo-vakia, Germany, and France. All the specimens with known collection details originate from cave environments. Detailed photographs of the male terminalia are provided for the first time, along with two unique DNA barcodes for the species.

An Upper Palaeolithic Proto-writing System and Phenological Calendar

In at least 400 European caves such as Lascaux, Chauvet and Altamira, Upper PalaeolithicHomo sapiensgroups drew, painted and engraved non-figurative signs from at least ~42,000bpand figurative images (notably animals) from at least 37,000bp. Since their discovery ~150 years ago, the purpose or meaning of European Upper Palaeolithic non-figurative signs has eluded researchers. Despite this, specialists assume that they were notational in some way. Using a database of images spanning the European Upper Palaeolithic, we suggest how three of the most frequently occurring signs—the line<|>, the dot <•>, and the <Y>—functioned as units of communication. We demonstrate that when found in close association with images of animals the line <|> and dot <•> constitute numbers denoting months, and form constituent parts of a local phenological/meteorological calendar beginning in spring and recording time from this point in lunar months. We also demonstrate that the <Y> sign, one of the most frequently occurring signs in Palaeolithic non-figurative art, has the meaning <To Give Birth>. Thepositionof the <Y> within a sequence of marks denotes month of parturition, an ordinal representation of number in contrast to the cardinal representation used in tallies. Our data indicate that the purpose of this system of associating animals with calendar information was to record and convey seasonal behavioural information about specific prey taxa in the geographical regions of concern. We suggest a specific way in which the pairing of numbers with animal subjects constituted a complete unit of meaning—a notational system combined with its subject—that provides us with a specific insight into what one set of notational marks means. It gives us our first specific reading of European Upper Palaeolithic communication, the first known writing in the history ofHomo sapiens.

A trait database and updated checklist for European subterranean spiders

Species traits are an essential currency in ecology, evolution, biogeography, and conservation biology. However, trait databases are unavailable for most organisms, especially those living in difficult-to-access habitats such as caves and other subterranean ecosystems. We compiled an expert-curated trait database for subterranean spiders in Europe using both literature data (including grey literature published in many different languages) and direct morphological measurements whenever specimens were available to us. We started by updating the checklist of European subterranean spiders, now including 512 species across 20 families, of which at least 192 have been found uniquely in subterranean habitats. For each of these species, we compiled 64 traits. The trait database encompasses morphological measures, including several traits related to subterranean adaptation, and ecological traits referring to habitat preference, dispersal, and feeding strategies. By making these data freely available, we open up opportunities for exploring different research questions, from the quantification of functional dimensions of subterranean adaptation to the study of spatial patterns in functional diversity across European caves.

Season‐of‐death and age‐at‐death of the easternmost European cave bears: Cementum and dentine increment analysis provides new insight into the cave bear ecology

Cementum and dentine increment analysis was used for the first time to study the remains of cave bears from European Russia, the Urals and the Caucasus. This study analysed 12 canines belonging to 12 different individuals (five males and seven females) from genetically different lineages of cave bears. The increment analysis showed that all studied cave bears belong to the categories adults and old animals (from 10 to 32.5 years). The enamel crowns of all 12 canines were broken and/or had wear facets. Seven canines studied were severely broken (more than one‐third of a canine crown missing). Significant damage to dental crowns may indicate old age, conflict between males and/or high food abrasion. The absence of significant differences in the extent of canine breakage between the youngest and the oldest animals, as well as between the males and the females, may indicate a significant role of food abrasiveness in the process of the grinding of canines. Until now, the question of whether these animals visited caves year‐round or stayed there mainly for overwintering remained open. The increment analysis showed different seasons of the bears’ death. Six individuals died in the warm season and four individuals died in the cold season. In all of the studied caves (excluding Medvezhiya Cave) the animals died in the warm season as well as in the cold season. All of the studied females perished either during the cold season or at the very beginning of the warm season. On the contrary, almost all of the examined males perished in the warm season. Thus, the cave bears visited the caves year‐round. This study raises new questions in the study of the ecology of cave bears from different parts of their range.

Evidence of cave lion (Panthera spelaea) from Pleistocene Northeast China

ABSTRACT The cave lion (Panthera spelaea) was one of the most widespread carnivores in the Pleistocene. The species ranged throughout Eurasia and even into North America as a member of the Mammuthus-Coelodonta fauna. However, the species has not previously been reported from the Mammuthus-Coelodonta fauna from the Pleistocene assemblages of the Songhua River. This study presents evidence of two Panthera spelaea specimens from the Middle and Late Pleistocene Songhua River fossil assemblages (MIS 10–8 and MIS 5–3). A combination of lower population due to vegetation shifts in the region and misidentification of specimens as Panthera tigris may explain why Panthera spelaea has not previously been reported in the region. The Middle Pleistocene specimen displays traits regarded as primitive in European cave lions. The Late Pleistocene specimen displays a mixture of primitive and advanced traits. These traits indicate a morphological transition within the species and also a possible ancestral relationship to Panthera atrox.

Early Detection of Phototrophic Biofilms in the Polychrome Panel, El Castillo Cave, Spain

European caves contain some of the world’s greatest Paleolithic paintings, and their conservation is at risk due to the use of artificial lighting. Both lighting and high CO2 promotes the growth of phototrophic organisms on walls, speleothems and ground sediments. In addition, the combined effect of increases in CO2, vapor concentration and temperature variations induced by visitors can directly affect the development of corrosion processes on the cave rock surfaces. An early detection of the occurrence of phototrophic biofilms on Paleolithic paintings is of the utmost importance, as well as knowing the microorganisms involved in the colonization of rocks and walls. Knowledge of the colonizing species and their ecology will allow the adoption of control measures. However, this is not always possible due to the limited amount of biomass available for molecular analyses. Here, we present an alternative approach to study faint green biofilms of Chlorophyta in the initial stage of colonization on the Polychrome Panel in El Castillo Cave, Cantabria, Spain. The study of the biofilms collected on the rock art panel and in the ground sediments revealed that the lighting of the cave promoted the development of the green algae Jenufa and Coccomyxa, as well as of complex prokaryotic and eukaryotic communities, including amoebae, their endoparasites and associated bacteria and fungi. The enrichment method used is proposed as a tool to overcome technical constraints in characterizing biofilms in the early stages, allowing a preliminary characterization before deciding for direct or indirect interventions in the cave.

European Plethodontid Salamanders on the Forest Floor: Testing for Age-Class Segregation and Habitat Selection

Spatial distribution of animals is affected by environmental and social factors, acting both at inter- and intraspecific levels, and generating patterns of segregation or aggregation. Several studies investigated age-class segregation of the European Cave Salamander Speleomantes strinatii, in underground environments, showing a clear spatial segregation. We investigated the spatial distribution of S. strinatii on the forest floor, on 111 plots surveyed three times/season for two consecutive seasons, in northern Italy during autumn 2017 and spring 2018. We analyzed count data to model co-abundance of adults and juveniles, using a conditional two-species N-mixture model, incorporating environmental covariates. In contrast with what was observed in underground environments, we recorded no spatial segregation between juvenile and adult of S. strinatii on the forest floor. Instead, we found that adults and juveniles showed different responses to environmental features.

A Review of Ice Core Drilling in Cave Environment – Challenges, Achievements and Future Directions

Worldwide, more than 141 m of ice cores has been extracted from 20 cave ice deposits, with the drilling projects focusing mainly in Central European caves. The fact that half of the cave ice cores (3 out of 6) published in 2020 represent non-European localities, however, predicts that an increasing number of cave ice drilling projects will be carried out in the near future in other geographical areas hosting ice caves. Based on the gathered experience the most commonly encountered technical challenge of ice-core drilling problems in cave environment is englacial rocky/woody debris. The complex stratigraphy of cave ice deposits represents a crucial methodological problem. We propose an (Cave Ice Sedimentary Architecture and Deposition - CISAD) approach to take into consideration of the stratigraphic peculiarities of the investigated cave ice deposit and additional crucial meta-data before establishing the location of a drilling site best-suited to obtain the highest quality paleoenvironmental data.

ПЕЩЕРА — СВЯТИЛИЩЕ — МИФ: КРИТЕРИИ ИНТЕРПРЕТАЦИИ ВЕРХНЕПАЛЕОЛИТИЧЕСКИХ ДЕКОРИРОВАННЫХ ПЕЩЕР УРАЛА

Caves with the Upper Paleolithic wall paintings are known in the Southern Urals — Kapova (Shulgan-Tash) and Ignatievskaya (Yamazy-Tash). They represent the largest karst cavities in their areas with lots of figurative and non-figurative motifs. In many respects, the Urals’ decorated caves are similar to those in Western Europe: in terms of the structural organization of space, pictorial assemblages and their context. The Western European caves are often referred to as “deep sanctuaries”. Within the framework of this article, the authors address to the works of foreign experts, who have been developing this subject for more than a dozen years, in order to identify the criteria for such an interpretation. Due to the kinship of the Ice Age cave art from the Atlantic to the Urals, the interpretations of Western European art are also applicable to the Ural cave sites. Archaeological, phenomenological and mythological criteria stand out as the most important ones. Archaeological criteria were formulated by C. Renfrew: focusing attention; the border zone between this and other worlds; the presence of a deity; participation and offering. Phenomenological criteria are relied on a person’s sensory experience which is based on the main sense organs — sight, hearing, smell, touch. It is they which provide the caves with indicators of hierophony, constructing, according to M. Eliade, a collective sacred space. Of all the characteristics of myth in relation to the Paleolithic art, M. Groenen considers the presence of composite anthropomorphic creatures, composite animals and surreal, fantastic animals. Comparing unreal and hybrid creatures from the regions of Franco-Cantabria and the Urals shows their close similarity. Together with the considered archaeological criteria and criteria of the sensory experience of an ancient man in relation to the underground cavity, we can assert that the Ural decorated caves of the Upper Paleolithic are sanctuaries of the Ice Age, preserving fragments of the mythology of that distant time.

Taphonomic analysis of the MIS 4–3 (Late Pleistocene) faunal assemblage of Biśnik Cave, Southern Poland: Signs of a human-generated depot of naturally shed cervid antlers?

The present is a palaeobiological and taphonomic analysis of a Marine Isotope Stages (MIS) 4–3 (Late Pleistocene) assemblage of animal remains and hominin artefacts from layers 7–5 of Biśnik Cave, Częstochowa Upland, Poland. The analysis indicates that the bone assemblage is the result of a time-averaged palimpsest of both biotic and episodic abiotic events, the former consisting of many successive generations of animals and hominins that frequented the cave, and the latter including hydraulic winnowing. In fact, the taphonomic history of the fossil assemblage from Biśnik Cave's layers 7–5 is partially obscured by the overprint of hydraulic winnowing, which purportedly removed a certain amount of the original specimens. Besides evidence of cave bear deaths from non-violent, hibernation-related mortality and of occupation by generations of denning wolves and hyaenas, there is a wealth of flint artefacts, alongside remains of a few fireplaces and of a structure built in the cave by hominins to partition the cave chambers. The studied layer contains an impressive number of shed antlers, primarily of the red deer Cervus elaphus. Crocuta crocuta spelaea is normally held responsible for such accumulations of shed antlers in various European caves; Biśnik Cave's layers 7–5 will therefore simply add to the list. However, the role of accumulator of shed antlers attributed to the Pleistocene spotted hyena does not match the behaviour of its modern counterpart and seems not accounted for metabolically. The only reasonable alternative is that the antlers were collected by hominins. From this alternative perspective the cave would have functioned as a warehouse, where naturally shed antlers were stored as raw material, potentially to be shaped into tools and/or employed as tools to make other tools. The palaeobiological and taphonomic analysis presented here provides new insights into the succession of pre- and postdepositional events that involved the bone remains accumulated in the cave, as well as into the interactions between the animals and hominins of the time. More importantly, if hominins, and not hyaenas, were responsible for the amassment of the shed antlers in Biśnik Cave, this study raises doubts as to the hyaenid or human origin of other similar cave accumulations of shed antlers throughout Europe.

Paleodiet and niche partitioning among the easternmost European cave bears based on tooth wear analysis

ABSTRACT Extinct cave bears inhabited a large part of Eurasia in a wide diversity of habitats during the Pleistocene. This study investigates via tooth wear analysis the feeding habits of 66 individuals belonging to three genetically different species located in the Urals and eastern Europe: Ursus rossicus from Kizel cave, U. kanivetz from Secrets cave, and U. ingressus from Shiriaevo 1 cave. For the microwear analysis, the three species were compared with a reference collection of extant ursids. The dietary space of U. kanivetz does not match any of the extant species’ spaces. U. rossicus and U. ingressus tended towards some of the extant species’ measurements without any overlapping. For all three sites, the same microwear pattern was identified for all age groups (juvenile, prime, and old adult), meaning no differences related to ontogeny were found. The extinct species presented a larger number of coarse scratches compared to extant species, pointing to a preference for abrasive food items like dry grass or shrubs typical of the mammoth steppe biome during the cold season. These results indicate a niche partitioning between U. rossicus and U. kanivetz that co-existed in the same area, and in this way they avoiding competition.

The genomics of phenotypically differentiated Asellus aquaticus cave, surface stream and lake ecotypes.

Organisms well suited for the study of ecotype formation have wide distribution ranges, where they adapt to multiple drastically different habitats repeatedly over space and time. Here we study such ecotypes in a Crustacean model, Asellus aquaticus, a commonly occurring isopod found in freshwater habitats as diverse as streams, caves and lakes. Previous studies focusing on cave vs. surface ecotypes have attributed depigmentation, eye loss and prolonged antennae to several south European cave systems. Likewise, surveys across multiple Swedish lakes have identified the presence of dark-pigmented "reed" and light-pigmented "stonewort" ecotypes, which can be found within the same lake. In this study, we sequenced the first draft genome of A. aquaticus, and subsequently use this to map reads and call variants in surface stream, cave and two lake ecotypes. In addition, the draft genome was combined with a RADseq approach to perform a quantitative trait locus (QTL) mapping study using a laboratory bred F2 and F4 cave×surface intercross. We identified genomic regions associated with body pigmentation, antennae length and body size. Furthermore, we compared genome-wide differentiation between natural populations and found several genes potentially associated with these habitats. The assessment of the cave QTL regions in the light-dark comparison of lake populations suggests that the regions associated with cave adaptation are also involved with genomic differentiation in the lake ecotypes. These demonstrate how troglomorphic adaptations can be used as a model for related ecotype formation.