Stable isotope signatures of large herbivore foraging habitats across Europe
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We investigated how do environmental and climatic factors, but also management, affect the carbon (δ13C) and nitrogen (δ15N) stable isotope composition in bone collagen of the two largest contemporary herbivores: European bison (Bison bonasus) and moose (Alces alces) across Europe. We also analysed how different scenarios of population recovery- reintroduction in bison and natural recovery in moose influenced feeding habitats and diet of these two species and compared isotopic signatures of modern populations of bison and moose (living in human-altered landscapes) with those occurring in early Holocene. We found that δ13C of modern bison and moose decreased with increasing forest cover. Decreasing forest cover, increasing mean annual temperature and feeding on farm crops caused an increase in δ15N in bison, while no factor significantly affected δ15N in moose. We showed significant differences in δ13C and δ15N among modern bison populations, in contrast to moose populations. Variation in both isotopes in bison resulted from inter-population differences, while in moose it was mainly an effect of intra-population variation. Almost all modern bison populations differed in δ13C and δ15N from early Holocene bison. Such differences were not observed in moose. It indicates refugee status of European bison. Our results yielded evidence that habitat structure, management and a different history of population recovery have a strong influence on foraging behaviour of large herbivores reflected in stable isotope signatures. Influence of forest structure on carbon isotope signatures of studied herbivores supports the "canopy effect" hypothesis.Keywords:
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There is limited information that provides a comprehensive understanding of the trophic ecology of Mexican Pacific harbor seal (Phoca vitulina richardii) colonies. While scat analysis has been used to determine the diet of some colonies, the integrative characterization of its feeding habits on broader temporal and spatial scales remains limited. We examined potential feeding grounds, trophic niche width, and overlap, and inferred the degree of dietary specialization using stable carbon and nitrogen isotope ratios (δ13C and δ15N) in this subspecies. We analyzed δ13C and δ15N on fur samples from pups collected at five sites along the western coast of the Baja California Peninsula, Mexico. Fur of natal coat of Pacific harbor seal pups begins to grow during the seventh month in utero until the last stage of gestation. Therefore pup fur is a good proxy for the mother’s feeding habits in winter (~December to March), based on the timing of gestation for the subspecies in this region. Our results indicated that the δ13C and δ15N values differed significantly among sampling sites, with the highest mean δ15N value occurring at the southernmost site, reflecting a well-characterized north to south latitudinal 15N-enrichment in the food web. The tendency identified in δ13C values, in which the northern colonies showed the most enriched values, suggests nearshore and benthic-demersal feeding habits. A low variance in δ13C and δ15N values for each colony (<1‰) and relatively small standard ellipse areas suggest a specialized foraging behavior in adult female Pacific harbor seals in Mexican waters.
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Nearshore habitats support high levels of biodiversity and important ecological processes such as trophic dynamics. This study aims to determine the trophic dynamics of elasmobranchs and other marine species from the coastal waters of Kuala Pahang, using stable isotope analysis. Samples of invertebrates, teleosts, and juvenile elasmobranchs were collected at the coastal waters of Kuala Pahang, and the composition of stable isotopes δ13C and δ15N were determined. Of all species, teleosts had the narrowest range of δ13C values, of between -17.5‰ and -16.7‰, indicating their reliance on similar types of food resources. On the contrary, elasmobranchs had the widest range of food sources as indicated by the δ13C values, of between -26.8‰ and-16.8‰. The banded sicklefish (Drepane longimana) occupied the highest trophic level as indicated by a δ15N value of 12.4‰, whereas the red stingray (Hemitrygon akajei) had the lowest trophic level with a δ15N value of 4.9‰. The depleted δ13C values indicated resource partitioning among elasmobranchs, presumably due to the utilisation on estuarine-based carbon resources. This study highlights the potential importance of the estuary of Kuala Pahang as a feeding ground for juvenile elasmobranchs.
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MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 450:229-241 (2012) - DOI: https://doi.org/10.3354/meps09562 Ontogenetic changes in feeding habits of northern elephant seals revealed by δ15N and δ13C analysis of growth layers in teeth Marjorie Riofrío-Lazo1,*, David Aurioles-Gamboa1, Burney J. Le Boeuf2 1Laboratorio de Ecología de Pinnípedos 'Burney J. Le Boeuf', Centro Interdisciplinario de Ciencias Marinas, Instituto Politécnico Nacional Ave. Instituto Politécnico Nacional s/n, Col. Playa Palo de Santa Rita. C.P. 23096 La Paz, Baja California Sur, México 2University Affiliated Research Center, 29 Clark Kerr Hall, University of California, Santa Cruz, California 95064, USA *Email: marjorieriofrio@gmail.com ABSTRACT: Stable isotope analysis is useful for examining the feeding strategies of mammals. Isotopes in the annual deposition growth layers of dentine in teeth permit assessment of ontogenetic dietary shifts in individuals, because this metabolically inert tissue is not resorbed after deposition. Profiles of stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) from the teeth of northern elephant seals Mirounga angustirostris, aged between 1 and 11 yr, were described from stranded individuals in San Benito and Magdalena Islands, Mexico, between 2000 and 2009. δ13C and δ15N values differed with age in each sex indicating shifts in feeding habits throughout life, as well as in their physiological condition. Although steady δ13C values within each individual suggest fidelity to feeding grounds, differences in δ13C values between males and females were likely a reflection of sexual segregation on the feeding areas, which begins during the juvenile stage. Mean δ15N values of males (18.3‰) and females (18.2‰) would suggest that both groups feed at a similar trophic level; however a combination of differences in benthic versus pelagic and longitudinal foraging habitats would be masking real sex differences in trophic level, estimated for the species at 4.6. δ15N and δ13C values varied markedly between individuals of the same sex, suggesting the potential existence of diverse feeding strategies leading to a resource partitioning in this species. The alleged fetal growth layer has a δ15N value 1.8‰ higher than the average of the adult female stage, suggesting that the fetal layer is more likely the product of the intensive nursing during the first month of life. KEY WORDS: Mirounga angustirostris · Stable isotope · Dentine growth layer · Ontogenetic dietary shifts · Feeding strategy · Isotope fractionation Full text in pdf format PreviousNextCite this article as: Riofrío-Lazo M, Aurioles-Gamboa D, Le Boeuf BJ (2012) Ontogenetic changes in feeding habits of northern elephant seals revealed by δ15N and δ13C analysis of growth layers in teeth. Mar Ecol Prog Ser 450:229-241. https://doi.org/10.3354/meps09562 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 450. Online publication date: March 29, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.
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Abstract Harbour porpoises are the most common small cetaceans in the North Sea and Dutch coastal waters. To study their trophic level and feeding location, stable carbon and nitrogen isotope ratios (δ13C and δ15N) were analysed in muscle and bone samples collected from 157 porpoises stranded along the Dutch coast (2006–2008). In addition, samples from 30 prey species were analysed. Prey samples showed high δ15N values in species of higher trophic level. In addition, geographic differences in isotopic composition were found, with higher δ15N and δ13C values in prey from more southern, coastal and estuarine areas. Based on muscle δ15N values, we found neonatal enrichment and that larger porpoises, in particular males, seem to feed on lower trophic level species, compared to smaller individuals. Also bone δ15N values show that larger animals had fed on lower trophic levels in distant times. Porpoises from the Eastern Scheldt reveal distinct δ13C values in muscle, but not in bone. This shows that these animals had foraged in the Eastern Scheldt for a longer time period but were not born there. Seasonal variation in bone δ15N and δ13C values revealed two distinct groups of porpoises along the Dutch coast, a winter group (mainly males) that migrated from neighbouring regions and a Dutch subpopulation in summer. These results furthered our insight about shifts in trophic level and feeding location of harbour porpoises from the southern North Sea over time.
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The trophic ecology of the small yellow croaker (Larimichthys polyactis) was studied using stable isotope analyses. Samples were collected from July to September 2009 and 34 individuals from eight sites were examined for stable carbon and nitrogen isotopes. Stable carbon isotope ratios (δ13C) ranged from -20.67 to -15.43, while stable nitrogen isotope ratios (δ15N) ranged 9.18-12.23. The relationship between δ13C and δ15N suggested high resource partitioning in the sampling area. Significant differences in stable isotope values among the eight sampling sites may be linked to environmental diversities involving various physical processes (such as ocean current, wind and tide) and different carbon sources. Furthermore, the stable isotope ratios may also explain the ontogenetic variability in diet and feeding, because δ13C and δ15N varied significantly with increasing body size. The findings are consistent with other studies on diet analyses in small yellow croaker. It was also demonstrated that stable isotope analysis could be used to estimate the trophic characters of small yellow croaker in feeding patterns and migrating habits.
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A bstract This study used naturally occurring carbon and nitrogen stable isotopes of teeth to study the diets of marine mammals. The isotopic ratios of nonchemically preserved teeth from eight species of marine mammals, representing 87 individuals that spanned the trophic continuum, were found to reflect nutritional sources. The δ 13 C signals distinguished animals that lived in waters dominated by different primary producers ( e. g. , seagrass, kelp, and phytoplankton), and δ 15 N values indicated the diet and trophic level of the species. This research suggests that isotopic signatures of teeth can be used in dietary studies to show differences and similarities among age classes, genders, geographic locations, and time periods.
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