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Diet of the Small Cave Bear Ursus (Spelaearctos) rossicus Borissak, 1930 (Mammalia, Carnivora, Ursidae) As Revealed by 13C and 15N Isotope Analyses in Bone Collagen
Abstract
The 13C and 15N isotope contents in bone collagen were analyzed using bones of the small cave bear Ursus (Spelaearctos) rossicus Borissak, 1930 from localities in the Middle and Southern Urals. The bones date from the last interglacial (MIS 5) and glacial (MIS 3) periods. The bones were from males and females aged 3, 4, and >4 years. Sexual, geographical, and chronological differences in 13C and 15N contents were studied. Notable gender, geographic, and chronological differences were observed between samples. In the Middle Urals, females led a more predatory lifestyle than males during the interglacial period, and the trophic niches of males and females converged due to an increase in herbivory during the transition to the glacial period. In the Southern Urals, males led a more predatory lifestyle than in the Middle Urals during the interglacial period. The extent of changes in δ13C and δ15N values in the Southern Urals during the transition was found to correspond to differences between trophic levels.
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Pollen and fossil mammals of the terrigenous deposits in the Makhnevskaya Ledyanaya Cave (59°26′ N 57°41’ E), located in the northern part of the Middle Urals and on the border with the Northern Urals, were studied. The spore-and-pollen spectra are divided into four pollen zones. In all the spectra, pollen concentrations of tree species amount to 50–70%. The presence of pollen in thermophilic (Quercus robur-type, Tilia cordata-type, Ulmus sp., Carpinus betulus, Corylus avellana-type) and moderate boreal (Abies, Picea, Pinus, Betula, Alnus) species and a lack of any tundra flora elements indicate their interglacial nature. The following have been identified as small mammal fauna: 8 taxa of insectivorous mammals, 4 taxa of bats, 2 taxa of lagomorphs, 4 species of carnivores, 16 species of rodents, 1 species of odd-toed ungulates and 4 species of even-toed ungulates. The remains of cryoxerophilous (Dicrostonyx sp., Lasiopodomys gregalis) and steppe (Ochotona sp.) species are scarce in the studied fauna. Species typical of forests (genus Sorex, genus Craseomys, genus Myodes, Myopus schisticolor, Microtus agrestis) are dominant. Remains of Erinaceus sp., Talpa sp., Crocidura leucodon, Sciurus vulgaris, Hystrix brachyura, Dryomys nitedula, Apodemus flavicollis, Stephanorhinus kirchbergensis have been found. The morphology and dimensions of the teeth of Panthera spelaea fossilis, Hystrix brachyura, Dryomys nitedula, Arvicola amphibius, mice of genus Apodemus are described. The compositions of the palynocomplexes and mammal fauna as well as the SDQ values for m1 of Arvicola amphibius allow us to date the deposits from the Makhnevskaya Ledyanaya Cave to the Eemian interglacial period (MIS 5e).
First data on the contents of the 13C and 15N isotopes in collagen were obtained for 16 bones of the Ural cave bear Ursus (Spelaearctos) kanivetz Verestchagin, 1973 from the Tayn (Secrets) cave (55°25' N, 57°46' E). The bones are dated to the middle MIS 3 and belonged to males and females of about 2 years, about 3 years, and older than 4 years of age. No considerable difference in isotope signatures was observed between individuals of different ages and different genders. Cave bears were assumed to forage independently on plant food from the second year of life. The δ13C and δ15N values established for the Ural cave bear are close to the values reported for U. (S.) spelaeus ingressus.
In the rich vertebrate fauna of Imanay Cave the abundant material of the small-sized cave bears was originally assigned to the taxon Ursus savini. Teeth and metapodials of statistical amounts were compared with other cave bear faunas and the taxonomic position was determined through morphological and metric analyses. The size of teeth and metapodial bones is significantly smaller in Imanay Cave bears compared to the typical U. deningeri from Mosbach and Hundsheim. Although the teeth are smaller, they reached higher evolutionary level than those from Mosbach or Hundsheim.The bear remains from Imanay Cave show great similarities to the fossils from Kizel Cave in the Ural Mountains described as Ursus rossicus Borissiak, 1930 but also to the remains of small-bodied cave bears of the Alps described as Ursus deningeroides Mottl, 1964. Remarkable are the differences in size of the front dentition: the incisors from Imanay Cave are on average >10% longer and wider than the corresponding teeth from U. deningeroides but also wider than the classic U. deningeri. Preliminary carbon and nitrogen stable isotope analyses suggest that the small cave bears from Imanay Cave were herbivorous.
Palaeogenomes provide the potential to study evolutionary processes in real time, but this potential is limited by our ability to recover genetic data over extended timescales.¹
• Hofreiter M.
• Paijmans J.L.A.
• Goodchild H.
• Speller C.F.
• Barlow A.
• Fortes G.G.
• Thomas J.A.
• Ludwig A.
• Collins M.J.
The future of ancient DNA: Technical advances and conceptual shifts.BioEssays. 2015; 37: 284-293
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As a consequence, most studies so far have focused on samples of Late Pleistocene or Holocene age, which covers only a small part of the history of many clades and species. Here, we report the recovery of a low coverage palaeogenome from the petrous bone of a ∼360,000 year old cave bear from Kudaro 1 cave in the Caucasus Mountains. Analysis of this genome alongside those of several Late Pleistocene cave bears reveals widespread mito-nuclear discordance in this group. Using the time interval between Middle and Late Pleistocene cave bear genomes, we directly estimate ursid nuclear and mitochondrial substitution rates to calibrate their respective phylogenies. This reveals post-divergence mitochondrial transfer as the dominant factor explaining their mito-nuclear discordance. Interestingly, these transfer events were not accompanied by large-scale nuclear introgression. However, we do detect additional instances of nuclear admixture among other cave bear lineages, and between cave bears and brown bears, which are not associated with mitochondrial exchange. Genomic data obtained from the Middle Pleistocene cave bear petrous bone has thus facilitated a revised evolutionary history of this extinct megafaunal group. Moreover, it suggests that petrous bones may provide a means of extending both the magnitude and time depth of palaeogenome retrieval over substantial portions of the evolutionary histories of many mammalian clades.
More than 300 cave bear bones from all over Europe have carbon and nitrogen isotopic composition that match overwhelmingly a diet based on plants, except for samples from two caves in Romania, for which high nitrogen-15 amounts have been interpreted as reflecting an omnivorous diet. This paper aims at deciphering the various factors influencing the carbon and nitrogen isotopic composition of a potential omnivorous species like cave bear, those linked to trophic levels and variations among plants and those caused by physiological factors. The comparison of European cave bears with coeval Late Pleistocene large mammals with different diets clearly shows that all the cave bear populations, including those from Romania, present isotopic values overlapping with herbivores, not with carnivores. Therefore omnivory is very unlikely for cave bears. Consumption of plants with high δ¹⁵N values, such as graminoids, forbs and possibly fungi, could explain in part the observed isotopic pattern. In addition, the variations in δ¹⁵N values through ontogeny support the hypothesis of a different hibernation pattern for the Romanian cave bears with high δ¹⁵N values. Future investigations using new isotopic approaches, especially nitrogen isotopic composition of collagen amino acids, should contribute to decipher the paleoecology of these Romanian cave bears.
If cave bear (Ursus spelaeus) sites are suspected to be occupied during winters (hibernation), studies clearly demonstrating seasons of cave occupation by this species are still rare, and are mainly based on cementochronology. However, in numerous cave bear sites, postcranial elements belonging to non-adult individuals at different ontogenic stages are abundant and better preserved than are teeth.
Studies on brown bear (Ursus arctos) skeletal growth have considered sequences of eruption and wear of deciduous teeth, and sometimes length of skulls or long bone epiphysation. In order to appraise seasons of cave occupation by Ursids, measurements have been taken on modern and subfossil complete brown bear skeletons. Those samples concern measurements taken from pictures (one 6-day old in Natural History Museum in Vienna (Austria), one 10-day old individual) or directly taken by the present authors (2 skeletons of Pyrenean modern 6-month old individuals in Natural History museum, Toulouse; an articulated skeleton belonging to the same stage of growth coming from the Mont Ventoux natural trap n°29 (MV29); and an articulated Pyrenean juvenile skeleton coming from the Trou Sylvain natural trap). Individual ages of those skeletons have been determined with eruption sequence of deciduous teeth and concern the first 2 years of brown bear life. Measurements on those samples have been taken and have been compared to the huge Holocene samples from 2 Mont Ventoux (MV2, MV4) natural traps, yielding each several hundred non-adult postcranial elements. As far as is known, those sites yield the largest brown bear populations from Europe. Seasonality has been previously studied from deciduous teeth eruption sequences. For postcranial elements, found discarded or mixed together, no analysis has been achieved. The goals of the current work are: 1) to match estimation of age from postcranial elements with the teeth eruption sequences; 2) to present rates of growth from appendicular elements during the first 2 years of life; 3) to evaluate evidence of sexual dimorphism during early life; and 4) to compare growth of brown bear postcranial skeleton with cave bear homologues. This work might provide interesting information on chronology of osseous growth and on seasons of cave occupations (winter vs annual occupation).
Since its introduction in 19771, stable isotope analysis of bone collagen has been widely used to reconstruct aspects of prehistoric human and animal diets2–11. This method of dietary analysis is based on two well-established observations, and on an assumption that has never been tested. The first observation is that bone collagen 13C/12C and 15N/14N ratios reflect the corresponding isotope ratio of an animal's diet1–5,12. The second is that groups of foods have characteristically different 13C/12C and/or 15N/14N ratios13,14. Taken together, the two observations indicate that the isotope ratios of collagen in the bones of a living animal reflect the amounts of these groups of foods that the animal ate. Thus, it has been possible to use fresh bone collagen 13C/12C ratios to determine the relative consumption of C3 and C4 plants15–17, while 13C/12C and 15N/14N ratios have been used to distinguish between the use of marine and terrestrial foods14. The 15N/14N ratios of fresh bone collagen probably also reflect the use of leguminous and non-leguminous plants as food5, but this has not yet been demonstrated. Prehistoric consumption of these same groups of foods has been reconstructed from isotope ratios of collagen extracted from fossil bone1–11. Implicit in the application of the isotopic method to prehistoric material is the assumption that bone collagen isotope ratios have not been modified by postmortem processes. Here I present the first examination of the validity of this assumption. The results show that postmortem alteration of bone collagen isotope ratios does occur, but that it is possible to identify prehistoric bones whose collagen has not undergone such alteration.
The cave bear (Ursus spelaeus) was one of several spectacular megafaunal species that became extinct in northern Eurasia during the late Quaternary. Vast numbers of their remains have been recovered from many cave sites, almost certainly representing animals that died during winter hibernation. On the evidence of skull anatomy and low δ15N values of bone collagen, cave bears appear to have been predominantly vegetarian. The diet probably included substantial high quality herbaceous vegetation. In order to address the reasons for the extinction of the cave bear, we have constructed a chronology using only radiocarbon dates produced directly on cave bear material. The date list is largely drawn from the literature, and as far as possible the dates have been audited (screened) for reliability. We also present new dates from our own research, including results from the Urals. U. spelaeus probably disappeared from the Alps and adjacent areas – currently the only region for which there is fairly good evidence –c. 24 000 radiocarbon years BP (c. 27 800 cal. yr BP), approximately coincident with the start of Greenland Stadial 3 (c. 27 500 cal. yr BP). Climatic cooling and inferred decreased vegetational productivity were probably responsible for its disappearance from this region. We are investigating the possibility that cave bear survived significantly later elsewhere, for example in southern or eastern Europe.
Prey-predator collagen enrichment values for carbon and nitrogen isotopic compositions are investigated. New enrichment values are given for the well-monitored ecosystem of Bialowieza primeval forest (Poland) for lynx and wolf. The impact of using different approximations in calculating such enrichment values is discussed. Several case studies of ancient vertebrate communities from Upper Palaeolithic sites in southwestern France are presented to check whether the enrichment values estimated for these past ecosystems are consistent with those measured in well-monitored modern ecosystems. The use of ranges of values rather than average ones is recommended, tentatively 0 to 2‰ for δ13C and 3 to 5‰ for δ15N. Copyright © 2003 John Wiley & Sons, Ltd.
An isotopic investigation of upper Pleistocene mammal bones and teeth from Scladina cave (Sclayn, Belgium) demonstrated the very good quality of collagen preservation. A preliminary screening of the samples used the amount of nitrogen in whole bone and dentine in order to estimate the preserved amount of collagen before starting the extraction process. The isotopic abundances of fossil specimens from still-extant species are consistent with their trophic position. Moreover, the15N isotopic abundance is higher in dentine than in bone in bears and hyenas, a phenomenon already observed in modern specimens. These results demonstrate that the isotopic compositions of samples from Scladina cave can be interpreted in ecological terms. Mammoths exhibit a high15N isotopic abundance relative to other herbivores, as was the case in Siberian and Alaskan samples. These results suggest distinctive dietary adaptations in herbivores living in the mammoth steppe. Cave bears are clearly isotopically different from coeval brown bears, suggesting an ecological separation between species, with a pure vegetarian diet for cave bear and an omnivorous diet for brown bear.
The influence of diet on the distribution of carbon isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant carbon isotopic composition.
The isotopic composition of the whole body of an animal reflects the isotopic composition of its diet, but the animal is on average enriched in δ^(13)C by about 1‰ relative to the diet. In three of the four cases examined, the ^(13)C enrichment of the whole body relative to the diet is balanced by a ^(13)C depletion of the respired CO_2. The isotopic relationships between the whole bodies of animals and their diets are similar for different species raised on the same diet and for the same species raised on different diets. However, the δ^(13)C values of whole bodies of individuals of a species raised on the same diet may differ by up to 2‰. The relationship between the ^(13)C/^(12)C ratio of a tissue and the ^(13)C/^(12)C ratio of the diet depends both on the type of tissue and on the nature of the diet. Many of the isotopic relationships among the major biochemical fractions, namely the lipid, carbohydrate and protein fractions, are qualitatively preserved as diet carbon is incorporated into the animal. However, the difference between the δ^(13)C values of a biochemical fraction in an animal and in its diet may be as large as 3‰. The δ^(13)C values of the biochemical components collagen, chitin and the insoluble organic fraction of shells, all of which are often preserved in fossil material, are related to the isotopic composition of the diet.
These results indicate that it will be possible to perform dietary analysis based on the determination of the ^(13)C/^(12)C ratio of animal carbon. Analysis of the total animal carbon will in most cases provide a better measure of diet than the analysis of individual tissues, biochemical fractions, or biochemical components. The limits of accuracy of this method will generally restrict its application to situations in which the diet is derived from sources with relatively large differences in their δ^(13)C values, such as terrestrial vs aquatic organisms or C_3 vs C_4 plants. The method should be applicable to fossil as well as to living material.
Mineralogical and geochemical features of cave fossilization of bone detritus on the example of Imanay cave
- V I Silaev
- M N Parshukova
- D O Gimranov
Cave Bears (Ursus spelaeus sensu lato) of the Urals
- D O Gimranov
- P A Kosintsev
Variation in Diet Reconstructions Based on Stable Carbon Isotopic Evidence
- B S Chisholm