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Koehler G, Hobson KA. Delineating origins of cheetah cubs in the illegal wildlife trade: Improvements based on the use of hair δ18O measurements. Front Ecol Evol 2023. [DOI: 10.3389/fevo.2023.1058985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Abstract
All African felids are listed as vulnerable or endangered according to the IUCN (International Union for Conservation of Nature) Red List of Threatened Species. Cheetahs (Acinonyx jubatus) in particular have declined rapidly as a result of human impacts so that development of effective strategies and tools for conservation of this highly vulnerable species, as well as African felids in general, are essential for their survival in the wild. Here we use the oxygen stable isotopic compositions of cheetah hair to determine origins of cheetah cubs destined for the illegal exotic pet trade by associating individual cubs with predicted δ18O isoscape locations. We found that cheetah cubs most likely originated in East Africa, close to the corridors responsible for this aspect of the illegal wildlife trade to the Middle East. Further refinement of these assignments using a two isotope analysis (δ18O and δ13C values) indicate that these cubs were likely sourced in Southern Ethiopia or possibly as far as Tanzania. We also demonstrate that δ18O values in tissues can provide provenance information in cases where results of δ2H analyses may be obscured by the effects of metabolic routing of nutrients during nursing, starvation, or dehydration. This study demonstrates the utility of stable isotopic tools for conservation and forensic uses for endangered mammalian species.
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OUP accepted manuscript. J Mammal 2022. [DOI: 10.1093/jmammal/gyac049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Cecchetti M, Crowley SL, Goodwin CED, Cole H, McDonald J, Bearhop S, McDonald RA. Contributions of wild and provisioned foods to the diets of domestic cats that depredate wild animals. Ecosphere 2021. [DOI: 10.1002/ecs2.3737] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Martina Cecchetti
- Environment and Sustainability Institute University of Exeter Penryn Campus Penryn Cornwall TR10 9FE UK
| | - Sarah L. Crowley
- Environment and Sustainability Institute University of Exeter Penryn Campus Penryn Cornwall TR10 9FE UK
| | - Cecily E. D. Goodwin
- Environment and Sustainability Institute University of Exeter Penryn Campus Penryn Cornwall TR10 9FE UK
| | - Holly Cole
- Centre for Ecology and Conservation University of Exeter Penryn Campus Penryn Cornwall TR10 9FE UK
| | - Jennifer McDonald
- Centre for Ecology and Conservation University of Exeter Penryn Campus Penryn Cornwall TR10 9FE UK
| | - Stuart Bearhop
- Centre for Ecology and Conservation University of Exeter Penryn Campus Penryn Cornwall TR10 9FE UK
| | - Robbie A. McDonald
- Environment and Sustainability Institute University of Exeter Penryn Campus Penryn Cornwall TR10 9FE UK
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Crossey B, Chimimba C, du Plessis C, Ganswindt A, Hall G. African wild dogs (Lycaon pictus) show differences in diet composition across landscape types in Kruger National Park, South Africa. J Mammal 2021. [DOI: 10.1093/jmammal/gyab087] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
The Kruger National Park (KNP) is home to the last genetically viable, minimally managed population of African wild dogs (Lycaon pictus, wild dogs) in South Africa. Until 2004, this population remained stable, but since has been declining. In this study, we aimed to improve our understanding of the ecology of KNP wild dogs by estimating the relative contribution of different prey types to their diet across landscape types. Based on a Bayesian mixing model, we assessed wild dog diet and foraging preferences using stable isotope analysis. We sampled 73 individuals from 40 packs found in six different landscape types. In thickets, packs predominantly prey on small browsing and mixed-feeding species (accounting for ~73% of their diet), but occasionally hunt large grazers (~24%) and large browsers (~3%). In open landscape types where lions (Panthera leo) are more or less absent, such as in the Lowveld sour bushveld, wild dogs prey on large browsers and large grazers (~67%). Our results demonstrate that KNP wild dogs occupy a broader ecological niche than previously thought, with small browsers forming an integral part of their diet. We also present the first data describing differences in wild dog diet–tissue discrimination factors for tail hair and whiskers compared to respective stable nitrogen (δ15N) and carbon (δ13C) values obtained from feces of captive wild dogs, as well as from those of South Africa’s broader managed metapopulation. While these data should be considered preliminary, we suggest that until wild dog diet–tissue discrimination factors are calculated through a controlled feeding study, the discrimination factors calculated for the gray wolf (Canis lupus) should be used for wild dog-related isotope studies, rather than the often cited values for red foxes (Vulpes vulpes).
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Affiliation(s)
- Bruce Crossey
- Mammal Research Institute (MRI), Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- Endocrine Research Laboratory, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa
| | - Christian Chimimba
- Mammal Research Institute (MRI), Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- DSI-NRF Centre of Excellence for Invasion Biology (CIB), Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Cole du Plessis
- Carnivore Conservation Program, Endangered Wildlife Trust (EWT), Wierda Park, South Africa
| | - Andre Ganswindt
- Mammal Research Institute (MRI), Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- Endocrine Research Laboratory, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa
- Centre for Veterinary Wildlife Studies, University of Pretoria, Onderstepoort, South Africa
| | - Grant Hall
- Mammal Research Institute (MRI), Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- University of Pretoria Stable Isotope Laboratory, Mammal Research Institute (MRI), University of Pretoria, Pretoria, South Africa
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Rioux È, Pelletier F, St-Laurent MH. From diet to hair and blood: empirical estimation of discrimination factors for C and N stable isotopes in five terrestrial mammals. J Mammal 2020. [DOI: 10.1093/jmammal/gyaa108] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AbstractCarbon and nitrogen stable isotope ratios are used widely to describe wildlife animal diet composition and trophic interactions. To reconstruct consumer diet, the isotopic differences between consumers and their diet items—called the trophic discrimination factor (TDF)—must be known. Proxies of diet composition are sensitive to the accuracy of TDFs. However, specific TDFs are still missing for many species and tissues because only a few controlled studies have been carried out on captive animals. The aim of this study was to estimate TDFs for hair and blood for carbon and nitrogen stable isotopes for caribou, moose, white-tailed deer, eastern coyote, and black bear. We obtained stable isotope ratios for diet items, hair, and blood samples, of 21 captive adult mammals. Diet–tissue discrimination factors for carbon in hair (∆ 13CLE) ranged from 0.96‰ to 3.72‰ for cervids, 3.01‰ to 3.76‰ for coyote, and 5.15‰ to 6.35‰ for black bear, while nitrogen discrimination factors (∆ 15N) ranged from 2.58‰ to 5.95‰ for cervids, 2.90‰ to 3.13‰ for coyote, and 4.48‰ to 5.44‰ for black bear. The ∆ 13CLE values in coyote blood components ranged from 2.20‰ to 2.69‰ while ∆ 15N ranged from 3.30‰ to 4.41‰. In caribou serum, ∆ 13CLE reached 3.34 ± 1.28‰ while ∆ 15N reached 5.02 ± 0.07‰. The TDFs calculated in this study will allow the evaluation of diet composition and trophic relationships between these five mammal species and will have important implications for the study of endangered caribou populations for which the use of noninvasive tissue sampling is highly relevant.
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Affiliation(s)
- Ève Rioux
- Centre for Northern Studies & Centre for Forest Research, Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, allée des Ursulines, Rimouski, Québec, Canada
| | - Fanie Pelletier
- Centre for Northern Studies, Département de Biologie, Université de Sherbrooke, boul. de l’Université, Sherbrooke, Québec, Canada
| | - Martin-Hugues St-Laurent
- Centre for Northern Studies & Centre for Forest Research, Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, allée des Ursulines, Rimouski, Québec, Canada
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Burgess KB, Broadhurst MK, Raoult V, Laglbauer BJL, Coleman MA, Bennett MB. Short- and long-term diets of the threatened longhorned pygmy devil ray, Mobula eregoodoo determined using stable isotopes. JOURNAL OF FISH BIOLOGY 2020; 97:424-434. [PMID: 32415778 DOI: 10.1111/jfb.14381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 05/05/2020] [Accepted: 05/12/2020] [Indexed: 06/11/2023]
Abstract
Most mobulids are listed as near threatened to endangered. Nonetheless, effective conservation measures are hindered by knowledge gaps in their ecology and behaviour. In particular, few studies have assessed diets and trophic ecologies that could inform methods to avoid fishing mortality. Here, a shortfall in data for the longhorned pygmy devil ray, Mobula eregoodoo was addressed by describing temporal variability in dietary preferences using stable isotope analysis. During summer and autumn in 2017, five bather-protection gillnets were deployed off eastern Australia (29° S, 153.5° E). From the catches of these gillnets, 35 adult M. eregoodoo had liver, muscle and stomach contents sampled to determine δ13 C and δ15 N profiles. Analyses revealed that surface zooplankton and zooplanktivorous teleosts were important dietary components across short- and long-term temporal scales. Large quantities of undigested sandy sprat, Hyperlophus vittatus, in the stomachs of some specimens unequivocally confirm feeding on teleosts. A narrow isotopic niche and minimal isotopic overlap with reef manta rays, Mobula alfredi from the same geographic region in eastern Australia implies M. eregoodoo has unique and highly specialised resource use relative to other mobulids in the area. The species is clearly vulnerable to capture during inshore migrations, presumably where they feed on shallow-water shoaling teleosts. Female M. eregoodoo likely have a low annual reproductive output, so population recoveries from fishing-induced declines are likely to be slow. Measures to reduce the by catch of M. eregoodoo in local bather-protection gillnets, and artisanal fisheries more broadly, should be given priority.
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Affiliation(s)
- Katherine B Burgess
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Matt K Broadhurst
- New South Wales Government Department of Primary Industries, Fisheries Conservation Technology Unit, 2 Bay Drive, Charlesworth Bay, Coffs Harbour, Australia, Australia
- Marine and Estuarine Ecology Unit, School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Vincent Raoult
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, New South Wales, Australia
| | - Betty J L Laglbauer
- Department of Oceanography and Fisheries, University of the Azores, Horta, Portugal
| | - Melinda A Coleman
- Department of Primary Industries, New South Wales Fisheries, National Marine Science Centre, 2 Bay Drive, Coffs Harbour, NSW, 2450, Australia
| | - Michael B Bennett
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
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McDonald BW, Perkins T, Dunn RR, McDonald J, Cole H, Feranec RS, Kays R. High variability within pet foods prevents the identification of native species in pet cats' diets using isotopic evaluation. PeerJ 2020; 8:e8337. [PMID: 32002325 PMCID: PMC6982418 DOI: 10.7717/peerj.8337] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 12/03/2019] [Indexed: 11/30/2022] Open
Abstract
Domestic cats preying on wildlife is a frequent conservation concern but typical approaches for assessing impacts rely on owner reports of prey returned home, which can be biased by inaccurate reporting or by cats consuming prey instead of bringing it home. Isotopes offer an alternative way to quantify broad differences in animal diets. By obtaining samples of pet food from cat owners we predicted that we would have high power to identify cats feeding on wild birds or mammals, given that pet food is thought to have higher C isotope values, due to the pervasive use of corn and/or corn by-products as food ingredients, than native prey. We worked with citizen scientists to quantify the isotopes of 202 cat hair samples and 239 pet food samples from the US and UK. We also characterized the isotopes of 11 likely native prey species from the southeastern US and used mixing models to assess the diet of 47 cats from the same region. Variation in C and N isotope values for cat food was very high, even within the same brand/flavor, suggesting that pet food manufacturers use a wide range of ingredients, and that these may change over time. Cat food and cat hair from the UK had lower C values than the US, presumably reflecting differences in the amount of corn used in the food chains of the two countries. This high variation in pet food reduced our ability to classify cats as hunters of native prey, such that only 43% of the animals could be confidently assigned. If feral or free ranging cats were considered, this uncertainty would be even higher as pet food types would be unknown. Our results question the general assumption that anthropogenic foods always have high C isotope values, because of the high variability we documented within one product type (cat food) and between countries (US vs. UK), and emphasize the need to test a variety of standards before making conclusions from isotope ecology studies.
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Affiliation(s)
- Brandon W McDonald
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC, United States of America.,North Carolina Museum of Natural Sciences, Raleigh, NC, United States of America
| | - Troi Perkins
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC, United States of America.,North Carolina Museum of Natural Sciences, Raleigh, NC, United States of America
| | - Robert R Dunn
- Department of Applied Ecology, North Carolina State University, Raleigh, NC, United States of America.,Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark
| | - Jennifer McDonald
- Center for Ecology and Conservation, University of Exeter, Penryn, United Kingdom
| | - Holly Cole
- Center for Ecology and Conservation, University of Exeter, Penryn, United Kingdom
| | | | - Roland Kays
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC, United States of America.,North Carolina Museum of Natural Sciences, Raleigh, NC, United States of America
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Burstahler C, Terwissen C, Roth J. Latitudinal gradient in cortisol concentrations in Canada lynx (Lynx canadensis) is not explained by diet. CAN J ZOOL 2019. [DOI: 10.1139/cjz-2018-0204] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Food limitation is an important stressor for most wildlife, and many specialist consumers will expand their dietary niche to contend with preferred prey limitation. How these dietary responses feed back into stress-axis regulation, however, is unknown. If alternative prey does not sufficiently fill the energetic requirements normally satisfied by preferred resources, then long-term glucocorticoid concentrations could be elevated in individuals consuming alternative prey. We measured cortisol concentrations and stable isotope ratios (δ13C and δ15N) in hair of Canada lynx (Lynx canadensis Kerr, 1792) across their distribution to determine the influence of diet on glucocorticoids while controlling for harvest location. We calculated the Euclidean distance between lynx and regional snowshoe hare (Lepus americanus Erxleben, 1777) stable isotope ratios as an index of diet specialization. We found no relationship between this index and cortisol, suggesting that prey types are interchangeable for lynx in terms of long-term stress axis activation. However, lynx cortisol increased significantly towards the northwestern region of lynx distribution, contrasting with our prediction, and highlighting important considerations for future research. This combination of glucocorticoid and diet analyses suggests that dietary plasticity does not necessarily alter an individual’s experience of potential stressors, despite important implications to population and community dynamics.
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Affiliation(s)
- C.M. Burstahler
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - C.V. Terwissen
- Department of Biology, Trent University, Peterborough, ON K9L 1Z8, Canada
| | - J.D. Roth
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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L'Hérault V, Lecomte N, Truchon MH, Berteaux D. Discrimination factors of carbon and nitrogen stable isotopes from diet to hair in captive large Arctic carnivores of conservation concern. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2018; 32:1773-1780. [PMID: 30030922 DOI: 10.1002/rcm.8239] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 05/30/2018] [Accepted: 07/12/2018] [Indexed: 06/08/2023]
Abstract
RATIONALE Stable isotope analysis is widely used to reconstruct diet, delineate trophic interactions, and determine energy pathways. Such ecological inferences are based on the idea that animals are, isotopically, what they eat but with a predictable difference between the isotopic ratio of a consumer and that of its diet, coined as the discrimination factor. Providing correct estimates of diet-consumer isotopic discrimination in controlled conditions is key for a robust application of the stable isotopes technique in the wild. METHODS Using a Finnigan Mat Delta Plus isotope-ratio mass spectrometer, we investigated isotopic discrimination of carbon and nitrogen isotope ratios (δ13 C and δ15 N values) in guard hairs of four Arctic predators; the wolf (n = 7), the wolverine (n = 2), the grizzly bear (n = 2), and the polar bear (n = 3). During a 3-month trial, carnivores were fed a mixed diet. The δ13 C and δ15 N values, and the mass (g) of diet items, were monitored weekly for each individual to determine their Total Diet Average ratios. RESULTS Diet-hair isotopic discrimination (Δx) varied according to species, ranging [1.88 ± 0.69‰: 3.2 ± 0.69‰] for δ13 C values, and [1.58 ± 0.17‰: 3.81 ± 0.22‰] for δ15 N values. Adult wolves Δ13 C average (2.03 ± 0.7‰) was lower than that of young wolves (2.60 ± 0.8‰) and any other species (combined average of 2.59 ± 0.28‰), except for the wolverine (2.12 ± 0.23‰). Wolves Δ15 N averages (juveniles: 3.51 ± 0.34‰, adults: 3.68 ± 0.28‰) were higher than those of any other species (combined average: 2.50 ± 0.58‰). CONCLUSIONS The discrimination factors for δ13 C and δ15 N values calculated in this study could be used in ecological studies dealing with free-ranging animals, with implications for non-invasive research approaches. As in other controlled discrimination studies, we recommend caution in applying our discrimination factors when the population structure is heterogeneous.
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Affiliation(s)
- Vincent L'Hérault
- Canada Research Chair on Northern Biodiversity and Centre for Northern Studies, Université du Québec à Rimouski, QC, Canada, G5L 3A1
- ARCTIConnexion, Québec City, QC, Canada, G1L 1Y8
| | - Nicolas Lecomte
- Canada Research Chair in Polar and Boreal Ecology, Université de Moncton, Moncton, NB, Canada, E1A 3E9
| | | | - Dominique Berteaux
- Canada Research Chair on Northern Biodiversity and Centre for Northern Studies, Université du Québec à Rimouski, QC, Canada, G5L 3A1
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Mutirwara R, Radloff FGT, Codron D. Growth rate and stable carbon and nitrogen isotope trophic discrimination factors of lion and leopard whiskers. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2018; 32:33-47. [PMID: 28971533 DOI: 10.1002/rcm.8003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 09/23/2017] [Accepted: 09/25/2017] [Indexed: 06/07/2023]
Abstract
RATIONALE Stable isotope analysis (SIA) of whiskers has been used to identify temporal feeding habits, intra-population diet variation, as well as individual dietary specialisation of marine and terrestrial carnivores. However, the potential of the method to disclose such dietary information for large wild felids is hampered by lack of information on species-specific whisker growth rates, whisker growth patterns and whisker-diet trophic discrimination factors (TDFs). METHODS Whisker growth rates and growth patterns were measured for four lions (Panthera leo) and one leopard (Panthera pardus) held at the National Zoological Gardens, Pretoria, South Africa. Actively growing whiskers of the felids were 'marked' four times over 185 days using 13 C-depleted, C3 -based giraffe (Giraffa camelopardalis) meat. The periods with low δ13 C values, identified following serial sectioning of the regrown whiskers at 1 mm intervals and isotopic analysis, were then correlated to specific giraffe meat feeding bouts and hence growth periods. δ13 C and δ15 N whisker-diet TDFs were estimated for five lions whose diet remained consistent over multiple years. RESULTS The whisker growth rates of three lionesses and the leopard were similar (mean = 0.65 mm day-1 ), despite species, sex and age differences. There was a decrease in whisker growth rate over time, suggesting a non-linear whisker growth pattern. However, linear and non-linear growth simulations showed slight differences between the two growth patterns for the proximal ~50 mm of whiskers. δ13 C and δ15 N lion whisker-diet TDFs were also similar amongst individuals (mean = 2.7 ± 0.12 ‰ for δ13 C values and 2.5 ± 0.08 ‰ for δ15 N values), irrespective of age and sex. CONCLUSIONS The whisker growth rate and δ13 C and δ15 N lion whisker-diet TDFs obtained in this study can be applied in future studies to assign dietary information contained in analysed felid whiskers to the correct time period and improve deductions of prey species consumed by wild felids.
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Affiliation(s)
- Ruwimbo Mutirwara
- Department of Conservation and Marine Sciences, Cape Peninsula University of Technology, PO Box 652, Cape Town, 8000, South Africa
| | - Frans G T Radloff
- Department of Conservation and Marine Sciences, Cape Peninsula University of Technology, PO Box 652, Cape Town, 8000, South Africa
| | - Daryl Codron
- Florisbad Quaternary Research Department, National Museum, PO Box 266, Bloemfontein, 9300, South Africa
- Centre for Environmental Management, University of the Free State, PO Box 339, Bloemfontein, 9300, South Africa
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Turner Tomaszewicz CN, Seminoff JA, Price M, Kurle CM. Stable isotope discrimination factors and between-tissue isotope comparisons for bone and skin from captive and wild green sea turtles (Chelonia mydas). RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2017; 31:1903-1914. [PMID: 28857312 PMCID: PMC5653449 DOI: 10.1002/rcm.7974] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 08/21/2017] [Accepted: 08/23/2017] [Indexed: 06/07/2023]
Abstract
RATIONALE The ecological application of stable isotope analysis (SIA) relies on taxa- and tissue-specific stable carbon (Δ13 C) and nitrogen (Δ15 N) isotope discrimination factors, determined with captive animals reared on known diets for sufficient time to reflect dietary isotope ratios. However, captive studies often prohibit lethal sampling, are difficult with endangered species, and reflect conditions not experienced in the wild. METHODS We overcame these constraints and determined the Δ13 C and Δ15 N values for skin and cortical bone from green sea turtles (Chelonia mydas) that died in captivity and evaluated the utility of a mathematical approach to predict discrimination factors. Using stable carbon (δ13 C values) and nitrogen (δ15 N values) isotope ratios from captive and wild turtles, we established relationships between bone stable isotope (SI) ratios and those from skin, a non-lethally sampled tissue, to facilitate comparisons of SI ratios among studies using multiple tissues. RESULTS The mean (±SD) Δ13 C and Δ15 N values (‰) between skin and bone from captive turtles and their diet (non-lipid-extracted) were 2.3 ± 0.3 and 4.1 ± 0.4 and 2.1 ± 0.6 and 5.1 ± 1.1, respectively. The mathematically predicted Δ13 C and Δ15 N values were similar (to within 1‰) to the experimentally derived values. The mean δ15 N values from bone were higher than those from skin for captive (+1.0 ± 0.9‰) and wild (+0.8 ± 1.0‰) turtles; the mean δ13 C values from bone were lower than those from skin for wild turtles (-0.6 ± 0.9‰), but the same as for captive turtles. We used linear regression equations to describe bone vs skin relationships and create bone-to-skin isotope conversion equations. CONCLUSIONS For sea turtles, we provide the first (a) bone-diet SI discrimination factors, (b) comparison of SI ratios from individual-specific bone and skin, and (c) evaluation of the application of a mathematical approach to predict stable isotope discrimination factors. Our approach opens the door for future studies comparing different tissues, and relating SI ratios of captive to wild animals.
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Affiliation(s)
- Calandra N. Turner Tomaszewicz
- Division of Biological Sciences, Ecology, Behavior, and Evolution Section, University of California, San Diego, La Jolla, California 92093-0116, USA
- Southwest Fisheries Science Center, NOAA, National Marine Fisheries Service, La Jolla, California 92037, USA
| | - Jeffrey A. Seminoff
- Southwest Fisheries Science Center, NOAA, National Marine Fisheries Service, La Jolla, California 92037, USA
| | - Mike Price
- SeaWorld San Diego, San Diego, California 92109, USA
| | - Carolyn M. Kurle
- Division of Biological Sciences, Ecology, Behavior, and Evolution Section, University of California, San Diego, La Jolla, California 92093-0116, USA
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Free-ranging domestic cats (Felis catus) on public lands: estimating density, activity, and diet in the Florida Keys. Biol Invasions 2017. [DOI: 10.1007/s10530-017-1534-x] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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HAN H, WEI W, NIE Y, ZHOU W, HU Y, WU Q, WEI F. Distinctive diet-tissue isotopic discrimination factors derived from the exclusive bamboo-eating giant panda. Integr Zool 2016; 11:447-456. [DOI: 10.1111/1749-4877.12208] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Han HAN
- Key Laboratory of Animal Ecology and Conservational Biology, Institute of Zoology; Chinese Academy of Sciences; Beijing China
- University of Chinese Academy of Sciences; Beijing China
| | - Wei WEI
- Key Laboratory of Animal Ecology and Conservational Biology, Institute of Zoology; Chinese Academy of Sciences; Beijing China
| | - Yonggang NIE
- Key Laboratory of Animal Ecology and Conservational Biology, Institute of Zoology; Chinese Academy of Sciences; Beijing China
| | - Wenliang ZHOU
- Key Laboratory of Animal Ecology and Conservational Biology, Institute of Zoology; Chinese Academy of Sciences; Beijing China
| | - Yibo HU
- Key Laboratory of Animal Ecology and Conservational Biology, Institute of Zoology; Chinese Academy of Sciences; Beijing China
| | - Qi WU
- Key Laboratory of Animal Ecology and Conservational Biology, Institute of Zoology; Chinese Academy of Sciences; Beijing China
| | - Fuwen WEI
- Key Laboratory of Animal Ecology and Conservational Biology, Institute of Zoology; Chinese Academy of Sciences; Beijing China
- University of Chinese Academy of Sciences; Beijing China
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Rode KD, Stricker CA, Erlenbach J, Robbins CT, Cherry SG, Newsome SD, Cutting A, Jensen S, Stenhouse G, Brooks M, Hash A, Nicassio N. Isotopic Incorporation and the Effects of Fasting and Dietary Lipid Content on Isotopic Discrimination in Large Carnivorous Mammals. Physiol Biochem Zool 2016; 89:182-97. [DOI: 10.1086/686490] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Steinitz R, Lemm JM, Pasachnik SA, Kurle CM. Diet-tissue stable isotope (Δ(13)C and Δ(15)N) discrimination factors for multiple tissues from terrestrial reptiles. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:9-21. [PMID: 26661966 DOI: 10.1002/rcm.7410] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 09/04/2015] [Accepted: 09/28/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE Stable isotope analysis is a powerful tool for reconstructing trophic interactions to better understand drivers of community ecology. Taxon-specific stable isotope discrimination factors contribute to the best use of this tool. We determined the first Δ(13)C and Δ(15)N values for Rock Iguanas (Cyclura spp.) to better understand isotopic fractionation and estimate wild reptile foraging ecology. METHODS The Δ(13)C and Δ(15)N values between diet and skin, blood, and scat were determined from juvenile and adult iguanas held for 1 year on a known diet. We measured relationships between iguana discrimination factors and size/age and quantified effects of lipid extraction and acid treatment on stable isotope values from iguana tissues. Isotopic and elemental compositions were determined by Dumas combustion using an elemental analyzer coupled to an isotope ratio mass spectrometer using standards of known composition. RESULTS The Δ(13)C and Δ(15)N values ranged from -2.5 to +6.5‰ and +2.2 to +7.5‰, respectively, with some differences among tissues and between juveniles and adults. The Δ(13)C values from blood and skin differed among species, but not the Δ(15)N values. The Δ(13)C values from blood and skin and Δ(15)N values from blood were positively correlated with size/age. The Δ(13)C values from scat were negatively correlated with size (not age). Treatment with HCl (scat) and lipid extraction (skin) did not affect the isotope values. CONCLUSIONS These results should aid in the understanding of processes driving stable carbon and nitrogen isotope discrimination factors in reptiles. We provide estimates of Δ(13)C and Δ(15)N values and linear relationships between iguana size/age and discrimination factors for the best interpretation of wild reptile foraging ecology.
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Affiliation(s)
- Ronnie Steinitz
- Division of Biological Sciences, Ecology, Behavior, and Evolution Section, University of California, San Diego, La Jolla, CA, 92093-0116, USA
| | - Jeffrey M Lemm
- San Diego Zoo Institute for Conservation Research, Behavioral Ecology Division, Escondido, CA, 92027-7000, USA
| | - Stesha A Pasachnik
- San Diego Zoo Institute for Conservation Research, Behavioral Ecology Division, Escondido, CA, 92027-7000, USA
| | - Carolyn M Kurle
- Division of Biological Sciences, Ecology, Behavior, and Evolution Section, University of California, San Diego, La Jolla, CA, 92093-0116, USA
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Moss WE, Alldredge MW, Pauli JN. Quantifying risk and resource use for a large carnivore in an expanding urban-wildland interface. J Appl Ecol 2015. [DOI: 10.1111/1365-2664.12563] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Wynne E. Moss
- Department of Forest & Wildlife Ecology; College of Agricultural and Life Sciences; University of Wisconsin; 1630 Linden Dr. Madison WI 53706 USA
| | | | - Jonathan N. Pauli
- Department of Forest & Wildlife Ecology; College of Agricultural and Life Sciences; University of Wisconsin; 1630 Linden Dr. Madison WI 53706 USA
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Tomaszewicz CT, Seminoff JA, Ramirez MD, Kurle CM. Effects of demineralization on the stable isotope analysis of bone samples. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:1879-1888. [PMID: 26411509 PMCID: PMC4606465 DOI: 10.1002/rcm.7295] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 07/27/2015] [Accepted: 07/28/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE The sampling of sequential, annually formed bone growth layers for stable carbon (δ(13)C values) and nitrogen (δ(15)N values) isotope analysis (SIA) can provide a time series of foraging ecology data. To date, no standard protocol exists for the pre-SIA treatment of cortical samples taken from fresh, modern, bones. METHODS Based on the SIA of historical bone, it is assumed that fresh bone samples must be pre-treated with acid prior to SIA. Using an elemental analyzer coupled to an isotope ratio mass spectrometer to measure stable carbon and nitrogen ratios, we tested the need to acidify cortical bone powder with 0.25 M HCl prior to SIA to isolate bone collagen for the determination of δ(13)C and δ(15)N values. We also examined the need for lipid extraction to remove potential biases related to δ(13)C analysis, based on a C:N ratio threshold of 3.5. RESULTS It was found that acidification of micromilled cortical bone samples from marine turtles does not affect their δ(15)N values, and the small effect acidification has on δ(13)C values can be mathematically corrected for, thus eliminating the need for pre-SIA acidification of cortical bone. The lipid content of the cortical bone samples was low, as measured by their C:N ratios, indicating that lipid extracting cortical bone samples from modern marine turtles is unnecessary. CONCLUSIONS We present a standard protocol for testing fresh, modern cortical bone samples prior to SIA, facilitating direct comparison of future studies. Based on the results obtained from marine turtle bones, pre-acidification and lipid removal of cortical bone are not recommended. This is especially useful as there is frequently not enough bone material removed via micromilling of sequential growth layers to accommodate both acid treatment and SIA.
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Affiliation(s)
- Calandra Turner Tomaszewicz
- Division of Biological Sciences, Ecology, Behavior, and Evolution Section, University of California, San Diego, La Jolla, California 92093-0116, USA
- Southwest Fisheries Science Center, NOAA, National Marine Fisheries Service, La Jolla, California 92037, USA
| | - Jeffrey A. Seminoff
- Southwest Fisheries Science Center, NOAA, National Marine Fisheries Service, La Jolla, California 92037, USA
| | - Matthew D. Ramirez
- Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon 97330, USA
| | - Carolyn M. Kurle
- Division of Biological Sciences, Ecology, Behavior, and Evolution Section, University of California, San Diego, La Jolla, California 92093-0116, USA
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18
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McLaren AAD, Crawshaw GJ, Patterson BR. Carbon and nitrogen discrimination factors of wolves and accuracy of diet inferences using stable isotope analysis. WILDLIFE SOC B 2015. [DOI: 10.1002/wsb.599] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Ashley A. D. McLaren
- Ontario Ministry of Natural Resources and Forestry; Wildlife Research and Monitoring Section, Trent University, DNA Building; 2140 East Bank Drive Peterborough ON K9J 7B8 Canada
| | | | - Brent R. Patterson
- Ontario Ministry of Natural Resources and Forestry; Wildlife Research and Monitoring Section, Trent University, DNA Building; 2140 East Bank Drive Peterborough ON K9J 7B8 Canada
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Wolf N, Newsome SD, Peters J, Fogel ML. Variability in the routing of dietary proteins and lipids to consumer tissues influences tissue-specific isotopic discrimination. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:1448-1456. [PMID: 26147485 DOI: 10.1002/rcm.7239] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 04/27/2015] [Accepted: 05/26/2015] [Indexed: 06/04/2023]
Abstract
RATIONALE The eco-physiological mechanisms that govern the incorporation and routing of macronutrients from dietary sources into consumer tissues determine the efficacy of stable isotope analysis (SIA) for studying animal foraging ecology. We document how changes in the relative amounts of dietary proteins and lipids affect the metabolic routing of these macronutrients and the consequent effects on tissue-specific discrimination factors in domestic mice using SIA. We also examine the effects of dietary macromolecular content on a commonly used methodological approach: lipid extraction of potential food sources. METHODS We used carbon ((13) C) and nitrogen ((15) N) isotopes to examine the routing of carbon from dietary proteins and lipids that were used by mice to biosynthesize hair, blood, muscle, and liver. Growing mice were fed one of four diet treatments in which the total dietary content of C4 -based lipids (δ(13) C = -14.5‰) and C(3) -based proteins (δ(13) C = -27‰) varied inversely between 5% and 40%. RESULTS The δ(13) C values of mouse tissues increased by approximately 2-6‰ with increasing dietary lipid content. The difference in δ(13) C values between mouse tissues and bulk diet ranged from 0.1 ± 1.5‰ to 2.3 ± 0.6‰ for all diet treatments. The mean (±SD) difference between the δ(13) C values of mouse tissues and dietary protein varied systematically among tissues and ranged from 3.1 ± 0.1‰ to 4.5 ± 0.6‰ for low fat diets and from 5.4 ± 0.4‰ to 10.5 ± 7.3‰ for high fat diets. CONCLUSIONS Mice used some fraction of their dietary lipid carbon to synthesize tissue proteins, suggesting flexibility in the routing of dietary macromolecules to consumer tissues based on dietary macromolecular availability. Consequently, all constituent dietary macromolecules, not just protein, should be considered when determining the relationship between diets and consumer tissues using SIA. In addition, in cases where animals consume diets with high lipid contents, non lipid-extracted prey samples should be analyzed to estimate diets using SIA.
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Affiliation(s)
- Nathan Wolf
- Fairweather Science LLC, Anchorage, AK, 99515, USA
| | - Seth D Newsome
- University of New Mexico, Department of Biology, Albuquerque, NM, 87131, USA
| | - Jacob Peters
- Harvard University, Organismic and Evolutionary Biology, Cambridge, MA, 02138, USA
| | - Marilyn L Fogel
- University of California Merced, Environmental Sciences, Merced, CA, 95343, USA
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Montanari S, Amato G. Discrimination factors of carbon and nitrogen stable isotopes from diet to hair and scat in captive tigers (Panthera tigris) and snow leopards (Uncia uncia). RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:1062-1068. [PMID: 26044274 DOI: 10.1002/rcm.7194] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 03/04/2015] [Accepted: 03/06/2015] [Indexed: 06/04/2023]
Abstract
RATIONALE In order to use stable isotope ratio values obtained from wild animal tissues, we must accurately calculate the differences in isotope ratios between diet and consumer (δtissue - δdiet). These values, called trophic discrimination factors (TDFs, denoted with ∆), are necessary for stable isotope ecology studies and are best calculated in controlled environments. METHODS Scat, hair, and diet samples were collected from captive tigers (n = 8) and snow leopards (n = 10) at the Bronx Zoo. The isotope ratios of carbon and nitrogen, the two most commonly used in ecological studies, of the samples were measured by continuous-flow isotope ratio mass spectrometry. The trophic discrimination factors were calculated for both carbon (δ(13)C values) and nitrogen (δ(15)N values). RESULTS It was found that the only significant TDFs in this study were diet-hair, ∆(13)CHair, for snow leopards (5.97 ± 1.25‰) and tigers (6.45 ± 0.54‰), and diet-scat, ∆(15)NScat, in snow leopards (2.49 ± 1.30‰). The other mean isotope ratios were not significantly different from that of the premixed feline diet. The ∆(15)NHair values for both species were unusually low, potentially due to the protein content and quality of the feline diet. CONCLUSIONS The discrimination factors of the stable isotopes of carbon and nitrogen calculated in this study can be applied to ecological studies of wild, non-captive terrestrial mammals. The effect of protein quality in isotope discrimination is also worthy of further investigation to better understand variation in TDFs. Carnivore scat is shown to be a valuable material for isotopic analysis.
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Affiliation(s)
- Shaena Montanari
- Columbia University, Department of Ecology, Evolution, and Environmental Biology, 1200 Amsterdam Avenue, New York, NY, 10027, USA
- Sackler Institute for Comparative Genomics, American Museum of Natural History, Central Park West at 79th Street, New York, NY, 10024, USA
| | - George Amato
- Columbia University, Department of Ecology, Evolution, and Environmental Biology, 1200 Amsterdam Avenue, New York, NY, 10027, USA
- Sackler Institute for Comparative Genomics, American Museum of Natural History, Central Park West at 79th Street, New York, NY, 10024, USA
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Holá M, Ježek M, Kušta T, Košatová M. Trophic discrimination factors of stable carbon and nitrogen isotopes in hair of corn fed wild boar. PLoS One 2015; 10:e0125042. [PMID: 25915400 PMCID: PMC4411150 DOI: 10.1371/journal.pone.0125042] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 03/09/2015] [Indexed: 11/24/2022] Open
Abstract
Stable isotope measurements are increasingly being used to gain insights into the nutritional ecology of many wildlife species and their role in ecosystem structure and function. Such studies require estimations of trophic discrimination factors (i.e. differences in the isotopic ratio between the consumer and its diet). Although trophic discrimination factors are tissue- and species- specific, researchers often rely on generalized, and fixed trophic discrimination factors that have not been experimentally derived. In this experimental study, captive wild boar (Sus scrofa) were fed a controlled diet of corn (Zea mays), a popular and increasingly dominant food source for wild boar in the Czech Republic and elsewhere in Europe, and trophic discrimination factors for stable carbon (Δ13C) and nitrogen (Δ15N) isotopes were determined from hair samples. The mean Δ13C and Δ15N in wild boar hair were –2.3 ‰ and +3.5 ‰, respectively. Also, in order to facilitate future derivations of isotopic measurements along wild boar hair, we calculated the average hair growth rate to be 1.1 mm d-1. Our results serve as a baseline for interpreting isotopic patterns of free-ranging wild boar in current European agricultural landscapes. However, future research is needed in order to provide a broader understanding of the processes underlying the variation in trophic discrimination factors of carbon and nitrogen across of variety of diet types.
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Affiliation(s)
- Michaela Holá
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Prague, Czech Republic
- * E-mail:
| | - Miloš Ježek
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Prague, Czech Republic
| | - Tomáš Kušta
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Prague, Czech Republic
| | - Michaela Košatová
- Department of Ecology, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Prague, Czech Republic
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Voigt CC, Thalwitzer S, Melzheimer J, Blanc AS, Jago M, Wachter B. The conflict between cheetahs and humans on Namibian farmland elucidated by stable isotope diet analysis. PLoS One 2014; 9:e101917. [PMID: 25162403 PMCID: PMC4146470 DOI: 10.1371/journal.pone.0101917] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 06/12/2014] [Indexed: 11/18/2022] Open
Abstract
Large areas of Namibia are covered by farmland, which is also used by game and predator species. Because it can cause conflicts with farmers when predators, such as cheetahs (Acinonyx jubatus), hunt livestock, we assessed whether livestock constitutes a significant part of the cheetah diet by analysing the stable isotope composition of blood and tissue samples of cheetahs and their potential prey species. According to isotopic similarities, we defined three isotopic categories of potential prey: members of a C4 food web with high δ15N values (gemsbok, cattle, springhare and guinea fowl) and those with low δ15N values (hartebeest, warthog), and members of a C3 food web, namely browsers (eland, kudu, springbok, steenbok and scrub hare). We quantified the trophic discrimination of heavy isotopes in cheetah muscle in 9 captive individuals and measured an enrichment for 15N (3.2‰) but not for 13C in relation to food. We captured 53 free-ranging cheetahs of which 23 were members of groups. Cheetahs of the same group were isotopically distinct from members of other groups, indicating that group members shared their prey. Solitary males (n = 21) and males in a bachelor groups (n = 11) fed mostly on hartebeest and warthogs, followed by browsers in case of solitary males, and by grazers with high δ15N values in case of bachelor groups. Female cheetahs (n = 9) predominantly fed on browsers and used also hartebeest and warthogs. Mixing models suggested that the isotopic prey category that included cattle was only important, if at all, for males living in bachelor groups. Stable isotope analysis of fur, muscle, red blood cells and blood plasma in 9 free-ranging cheetahs identified most individuals as isotopic specialists, focussing on isotopically distinct prey categories as their food.
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Affiliation(s)
- Christian C. Voigt
- Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
| | - Susanne Thalwitzer
- Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
| | - Jörg Melzheimer
- Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
| | - Anne-Sophie Blanc
- Institute of Zoology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Mark Jago
- The AfriCat Foundation, Farm Okonjima, Otjiwarongo, Otjozondjupa, Namibia
| | - Bettina Wachter
- Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
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Kurle CM, Koch PL, Tershy BR, Croll DA. The effects of sex, tissue type, and dietary components on stable isotope discrimination factors (Δ13C and Δ15N) in mammalian omnivores. ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES 2014; 50:307-321. [PMID: 24787278 DOI: 10.1080/10256016.2014.908872] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We tested the effects of sex, tissue, and diet on stable isotope discrimination factors (Δ(13)C and Δ(15)N) for six tissues from rats fed four diets with varied C and N sources, but comparable protein quality and quantity. The Δ(13)C and Δ(15)N values ranged from 1.7-4.1‰ and 0.4-4.3‰, respectively. Females had higher Δ(15)N values than males because males grew larger, whereas Δ(13)C values did not differ between sexes. Differences in Δ(13)C values among tissue types increased with increasing variability in dietary carbon sources. The Δ(15)N values increased with increasing dietary δ(15)N values for all tissues except liver and serum, which have fast stable isotope turnover times, and differences in Δ(15)N values among tissue types decreased with increasing dietary animal protein. Our results demonstrate that variability in dietary sources can affect Δ(13)C values, protein source affects Δ(15)N values even when protein quality and quantity are controlled, and the isotope turnover rate of a tissue can influence the degree to which diet affects Δ(15)N values.
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Affiliation(s)
- Carolyn M Kurle
- a Division of Biological Sciences , University of California , San Diego, La Jolla , CA , USA
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