Heavy reliance on plants is rare in carnivora and mostly limited to relatively small species in s... more Heavy reliance on plants is rare in carnivora and mostly limited to relatively small species in subtropical settings. The feeding behaviors of extinct cave bears living during Pleistocene cold periods at middle latitudes have been intensely studied using various approaches including isotopic analyses of fossil collagen. In contrast to cave bears from all other regions in Europe, some individuals from Romania show exceptionally high δ 15 n values that might be indicative of meat consumption. Herbivory on plants with high δ 15 N values cannot be ruled out based on this method, however. Here we apply an approach using the δ 15 N values of individual amino acids from collagen that offsets the baseline δ 15 n variation among environments. the analysis yielded strong signals of reliance on plants for Romanian cave bears based on the δ 15 n values of glutamate and phenylalanine. these results could suggest that the high variability in bulk collagen δ 15 N values observed among cave bears in Romania reflects niche partitioning but in a general trophic context of herbivory. Bears represent the largest terrestrial members within the Carnivora alive today and the vast majority of them have carnivorous or omnivorous feeding habits. Until around 25,000 years ago, the coldest period in the Pleistocene, additional, now extinct bear species were living 1-4 , among which the so-called cave bears, a very large type of bear that formed the sister lineage of extant brown bears and polar bears (e.g., ref. 5). The paradox of the cave bear is that their diet has been said to be herbivorous despite their large body sizes while extant herbivorous Carnivora species are smaller 6,7. After their divergence from the brown bear lineage 1.2-1.6 million years ago, cave bear populations showed substantial morphological and genetic variability and multiple forms have been recognized 8 , although their taxonomic status and the relationships among them continue to be debated 9. The possible causes of the extinction of these bears are also intensively debated, involving climate change, human impacts, and (lack of) flexibility in feeding behavior 10-15. Understanding cave bear feeding behavior is therefore important as it might give insights into the extinction of this species, and also it could be relevant for the conservation of extant, herbivorous carnivoran species that are under threat of extinction (e.g., binturong, red panda, giant panda 16,17). More recent studies have shown mixed results based on different lines of evidence including anatomical properties like craniodental morphologies, tooth wear analyses, mortality patterns (e.g., sex ratio), etc. wherein the conclusions were highly context dependent and differed by sample-sets 18-23. This is also the case for stable carbon and nitrogen isotope analyses (δ 13 C and δ 15 N) on collagen extracted from bone/teeth 24-31. Relatively low δ 15 N values of most of these bears so far indicate their highly-plant-dependent feeding habits with possible exceptions for some groups in today's Romania that exhibited relatively high δ 15 N values 30,32,33. The δ 15 N value of bulk bone/
Heavy reliance on plants is rare in carnivora and mostly limited to relatively small species in s... more Heavy reliance on plants is rare in carnivora and mostly limited to relatively small species in subtropical settings. The feeding behaviors of extinct cave bears living during Pleistocene cold periods at middle latitudes have been intensely studied using various approaches including isotopic analyses of fossil collagen. In contrast to cave bears from all other regions in Europe, some individuals from Romania show exceptionally high δ 15 n values that might be indicative of meat consumption. Herbivory on plants with high δ 15 N values cannot be ruled out based on this method, however. Here we apply an approach using the δ 15 N values of individual amino acids from collagen that offsets the baseline δ 15 n variation among environments. the analysis yielded strong signals of reliance on plants for Romanian cave bears based on the δ 15 n values of glutamate and phenylalanine. these results could suggest that the high variability in bulk collagen δ 15 N values observed among cave bears in Romania reflects niche partitioning but in a general trophic context of herbivory. Bears represent the largest terrestrial members within the Carnivora alive today and the vast majority of them have carnivorous or omnivorous feeding habits. Until around 25,000 years ago, the coldest period in the Pleistocene, additional, now extinct bear species were living 1-4 , among which the so-called cave bears, a very large type of bear that formed the sister lineage of extant brown bears and polar bears (e.g., ref. 5). The paradox of the cave bear is that their diet has been said to be herbivorous despite their large body sizes while extant herbivorous Carnivora species are smaller 6,7. After their divergence from the brown bear lineage 1.2-1.6 million years ago, cave bear populations showed substantial morphological and genetic variability and multiple forms have been recognized 8 , although their taxonomic status and the relationships among them continue to be debated 9. The possible causes of the extinction of these bears are also intensively debated, involving climate change, human impacts, and (lack of) flexibility in feeding behavior 10-15. Understanding cave bear feeding behavior is therefore important as it might give insights into the extinction of this species, and also it could be relevant for the conservation of extant, herbivorous carnivoran species that are under threat of extinction (e.g., binturong, red panda, giant panda 16,17). More recent studies have shown mixed results based on different lines of evidence including anatomical properties like craniodental morphologies, tooth wear analyses, mortality patterns (e.g., sex ratio), etc. wherein the conclusions were highly context dependent and differed by sample-sets 18-23. This is also the case for stable carbon and nitrogen isotope analyses (δ 13 C and δ 15 N) on collagen extracted from bone/teeth 24-31. Relatively low δ 15 N values of most of these bears so far indicate their highly-plant-dependent feeding habits with possible exceptions for some groups in today's Romania that exhibited relatively high δ 15 N values 30,32,33. The δ 15 N value of bulk bone/
Uploads
Papers by Yuichi Naito