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Reid REB, Crowley BE, Haupt RJ. The prospects of poop: a review of past achievements and future possibilities in faecal isotope analysis. Biol Rev Camb Philos Soc 2023; 98:2091-2113. [PMID: 37438959 DOI: 10.1111/brv.12996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 06/29/2023] [Accepted: 06/30/2023] [Indexed: 07/14/2023]
Abstract
What can the stable isotope values of human and animal faeces tell us? This often under-appreciated waste product is gaining recognition across a variety of disciplines. Faecal isotopes provide a means of monitoring diet, resource partitioning, landscape use, tracking nutrient inputs and cycling, and reconstructing past climate and environment. Here, we review what faeces are composed of, their temporal resolution, and how these factors may be impacted by digestive physiology and efficiency. As faeces are often used to explore diet, we clarify how isotopic offsets between diet and faeces can be calculated, as well as some differences among commonly used calculations that can lead to confusion. Generally, faecal carbon isotope (δ13 C) values are lower than those of the diet, while faecal nitrogen isotope values (δ15 N) values are higher than in the diet. However, there is considerable variability both within and among species. We explore the role of study design and how limitations stemming from a variety of factors can affect both the reliability and interpretability of faecal isotope data sets. Finally, we summarise the various ways in which faecal isotopes have been applied to date and provide some suggestions for future research. Despite remaining challenges, faecal isotope data are poised to continue to contribute meaningfully to a variety of fields.
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Affiliation(s)
- Rachel E B Reid
- Department of Geosciences, Virginia Tech, 4044 Derring Hall, 926 West Campus Dr, Blacksburg, VA, 24061, USA
| | - Brooke Erin Crowley
- Department of Geosciences, University of Cincinnati, 500 Geology Physics Building, 345 Clifton Court, Cincinnati, OH, 45221-0013, USA
- Department of Anthropology, University of Cincinnati, 481 Braunstein Hall, Cincinnati, OH, 45221-0380, USA
| | - Ryan J Haupt
- National Youth Science Foundation, PO Box 3387, Charleston, WV, 25333-3387, USA
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2
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Navarro-Castilla Á, Hernández MC, Barja I. An Experimental Study in Wild Wood Mice Testing Elemental and Isotope Analysis in Faeces to Determine Variations in Food Intake Amount. Animals (Basel) 2023; 13:ani13071176. [PMID: 37048432 PMCID: PMC10093285 DOI: 10.3390/ani13071176] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 03/16/2023] [Accepted: 03/24/2023] [Indexed: 03/30/2023] Open
Abstract
The analysis of carbon and nitrogen elemental (C, N) and isotopic compositions (δ13C, δ15N) in faeces are considered reliable methodologies for the study of diet in wildlife. Here, we tested the suitability of these techniques to detect variations in the amount of food intake. We captured wild wood mice (Apodemus sylvaticus) with Sherman live traps where bait access was initially free, and later it was experimentally limited inside by four different devices to cause intended variations in the amount ingested. The total C and N (%) and stable δ13C and δ15N isotopic values were determined for the bait and in mice faecal samples. Faecal values were lower than bait ones except for N, likely due to animal matter ingested before capture. No significant differences in total C, N and δ13C were found due to individual traits. However, breeding males showed higher δ15N values than breeding females, probably due to differences in energy and protein demands between both sexes during the breeding season. Only δ13C detected food intake variations (≥2 g). Despite further research being needed, these results initially support the potential of δ13C to provide information on the amount ingested, thus being useful to complement trophic ecology studies.
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Affiliation(s)
- Álvaro Navarro-Castilla
- Eco- and Ethophysiology Lab, Departamento de Biología, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Centro de Investigación en Biodiversidad y Cambio Global (CIBC-UAM), Universidad Autónoma de Madrid, C. Darwin 2, 28049 Madrid, Spain
- Correspondence:
| | - M. Carmen Hernández
- Eco- and Ethophysiology Lab, Departamento de Biología, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Isabel Barja
- Eco- and Ethophysiology Lab, Departamento de Biología, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Centro de Investigación en Biodiversidad y Cambio Global (CIBC-UAM), Universidad Autónoma de Madrid, C. Darwin 2, 28049 Madrid, Spain
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3
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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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4
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Reevaluating trophic discrimination factors (
Δδ
13
C
and
Δδ
15
N
) for diet reconstruction. ECOL MONOGR 2022. [DOI: 10.1002/ecm.1525] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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5
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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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6
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Rogers MC, Hilderbrand GV, Gustine DD, Joly K, Leacock WB, Mangipane BA, Welker JM. Splitting hairs: dietary niche breadth modelling using stable isotope analysis of a sequentially grown tissue. ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES 2020; 56:358-369. [PMID: 32631088 DOI: 10.1080/10256016.2020.1787404] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 05/23/2020] [Indexed: 06/11/2023]
Abstract
Stable isotope data from durable, sequentially grown tissues (e.g. hair, claw, and baleen) is commonly used for modelling dietary niche breadth. The use of tissues grown over multiple months to years, however, has the potential to complicate isotopic niche breadth modelling, as time-averaged stable isotope signals from whole tissues may obscure information available from chronologically resolved stable isotope signals in serially sectioned tissues. We determined if whole samples of brown bear guard hair produced different isotopic niche breadth estimates than those produced from subsampled, serially sectioned samples of the same tissue from the same set of individuals. We sampled guard hair from brown bears (Ursus arctos) in four regions of Alaska with disparate biogeographies and dietary resource availability. Whole hair and serially sectioned hair samples were used to produce paired isotopic dietary niche breadth estimates for each region in the SIBER Bayesian model framework in R. Isotopic data from serially sectioned hair consistently produced larger estimates of isotopic dietary niche breadth than isotope data from whole hair samples. Serial sampling captures finer-scale changes in diet and when cumulatively used to estimate isotopic niche breadth, the serially sampled isotope data more fully captures dietary variability and true isotopic niche breadth.
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Affiliation(s)
- Matthew C Rogers
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, USA
- NOAA Alaska Fisheries Science Center, Auke Bay Laboratories, Juneau, AK, USA
| | | | - David D Gustine
- National Park Service, Grand Teton National Park, Moose, WY, USA
| | - Kyle Joly
- National Park Service, Gates of the Arctic National Park and Preserve, Fairbanks, AK, USA
| | - William B Leacock
- US Fish and Wildlife Service, Kodiak National Wildlife Refuge, Kodiak, AK, USA
| | - Buck A Mangipane
- National Park Service, Lake Clark National Park and Preserve, Port Alsworth, AK, USA
| | - Jeffrey M Welker
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK, USA
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7
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Stanek A, Wolf N, Welker J, Jensen S. Experimentally derived incorporation rates and diet-to-tissue discrimination values for carbon and nitrogen stable isotopes in gray wolves (Canis lupus) fed a marine diet. CAN J ZOOL 2019. [DOI: 10.1139/cjz-2019-0049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent studies have noted the differential effects of marine versus terrestrial diets on the carbon and nitrogen stable isotope (13C and 15N, respectively) diet-to-tissue discrimination values and incorporation rates for omnivorous and carnivorous mammals. Inaccurate estimates of these parameters may result in misrepresentation of diet composition or in the timing of diet shifts. Here, we present the results of a diet-switch experiment designed to estimate diet-to-tissue discrimination values and incorporation rates for tissues of gray wolves (Canis lupus Linnaeus, 1758) fed a diet of Pacific salmon (genus Oncorhynchus Suckley, 1861). Our results demonstrate substantial differences in both parameters between wolves maintained on a marine (salmon) diet and wolves maintained on terrestrially sourced prey (beef, Bos taurus Linnaeus, 1758). Increased awareness of the significance of marine resources to omnivorous and carnivorous consumers, like wolves, highlights the importance of phenomenological and mechanistic understandings of the effects of fish and other marine prey on dietary investigations based on stable isotopes.
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Affiliation(s)
- A.E. Stanek
- Department of Biological Sciences, University of Alaska Anchorage, 3211 Providence Drive, Anchorage, AK 99508, USA
| | - N. Wolf
- Department of Biological Sciences, University of Alaska Anchorage, 3211 Providence Drive, Anchorage, AK 99508, USA
| | - J.M. Welker
- Department of Biological Sciences, University of Alaska Anchorage, 3211 Providence Drive, Anchorage, AK 99508, USA
- Ecology and Genetics Research Unit, University of Oulu, Finland 90014, and UArctic Research Chair
| | - S. Jensen
- The Alaska Zoo, 4731 O’Malley Road, Anchorage, AK 99507, USA
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8
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Crowley BE, Wultsch C, Kelly MJ. Does faecal matter reflect location? An initial assessment of isotopic variability between consumed prey remains and faecal matter for wild jaguars . ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES 2019; 55:478-498. [PMID: 31402710 DOI: 10.1080/10256016.2019.1648263] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2018] [Accepted: 07/01/2019] [Indexed: 06/10/2023]
Abstract
Faecal isotopic analysis may complement other non-invasive wildlife survey tools for monitoring landscape use by carnivores, such as motion-detecting cameras and non-invasive genetic sampling. We analysed carbon, nitrogen, and strontium isotopes in faecal matter produced by jaguars (Panthera onca) as well as bones from consumed prey at the Mountain Pine Ridge Forest Reserve (MPR) in Belize, Central America. The MPR is ideally suited for a spatial isotope study as vegetation and geology both vary considerably. The isotopic composition of faecal matter should reflect the habitat and geology where consumed prey lived. We used bone from consumed prey recovered from jaguar scats as a proxy for diet. Faecal matter and bone showed comparable spatial isotopic trends, suggesting that the isotopic composition of jaguar faeces can be used to detect foraging in different habitats (pine forest versus broadleaf forest) or on different geologies (Mesozoic carbonates; Palaeozoic granite, contact metamorphics, and metasediments). This result is reassuring as bones are not always present in carnivore scats. Studying landscape use by cryptic and wide-ranging carnivore species like jaguars remains challenging. Isotopic analysis of faecal matter complements the existing array of non-invasive spatial monitoring tools.
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Affiliation(s)
- Brooke E Crowley
- Department of Geology, University of Cincinnati , Cincinnati , OH , USA
- Department of Anthropology, University of Cincinnati , Cincinnati , OH , USA
| | - Claudia Wultsch
- Bioinformatics and Computational Genomics Laboratory, Hunter College, City University of New York , New York , NY , USA
- Sackler Institute for Comparative Genomics, American Museum of Natural History , New York , NY , USA
- Department of Fish and Wildlife Conservation, Virginia Tech , Blacksburg , VA , USA
| | - Marcella J Kelly
- Department of Fish and Wildlife Conservation, Virginia Tech , Blacksburg , VA , USA
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9
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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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10
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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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11
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Abstract
Stable isotope analysis of feces can provide a non-invasive method for tracking the dietary habits of nearly any mammalian species. While fecal samples are often collected for macroscopic and genetic study, stable isotope analysis can also be applied to expand the knowledge of species-specific dietary ecology. It is somewhat unclear how digestion changes the isotope ratios of animals' diets, so more controlled diet studies are needed. To date, most diet-to-feces controlled stable isotope experiments have been performed on herbivores, so in this study I analyzed the carbon and nitrogen stable isotope ratios in the diet and feces of the meerkat (Suricata suricatta), a small omnivorous mammal. The carbon trophic discrimination factor between diet and feces (Δ13Cfeces) is calculated to be 0.1 ± 1.5‰, which is not significantly different from zero, and in turn, not different than the dietary input. On the other hand, the nitrogen trophic discrimination factor (Δ15Nfeces) is 1.5 ± 1.1‰, which is significantly different from zero, meaning it is different than the average dietary input. Based on data generated in this experiment and a review of the published literature, carbon isotopes of feces characterize diet, while nitrogen isotope ratios of feces are consistently higher than dietary inputs, meaning a discrimination factor needs to be taken into account. The carbon and nitrogen stable isotope values of feces are an excellent snapshot of diet that can be used in concert with other analytical methods to better understand ecology, diets, and habitat use of mammals.
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Affiliation(s)
- Shaena Montanari
- School of GeoSciences, University of Edinburgh, Edinburgh, United Kingdom
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12
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Reid REB, Koch PL. Isotopic ecology of coyotes from scat and road kill carcasses: A complementary approach to feeding experiments. PLoS One 2017; 12:e0174897. [PMID: 28369133 PMCID: PMC5378380 DOI: 10.1371/journal.pone.0174897] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 03/16/2017] [Indexed: 11/18/2022] Open
Abstract
Scat is frequently used to study animal diets because it is easy to find and collect, but one concern is that gross fecal analysis (GFA) techniques exaggerate the importance of small-bodied prey to mammalian mesopredator diets. To capitalize on the benefits of scat, we suggest the analysis of scat carbon and nitrogen isotope values (δ13C and δ15N). This technique offers researchers a non-invasive method to gather short-term dietary information. We conducted three interrelated studies to validate the use of isotopic values from coyote scat: 1) we determined tissue-to-tissue apparent C and N isotope enrichment factors (ε13* and ε15*) for coyotes from road kill animals (n = 4); 2) we derived diet-to-scat isotope discrimination factors for coyotes; and 3) we used field collected coyote scats (n = 12) to compare estimates of coyote dietary proportions from stable isotope mixing models with estimates from two GFA techniques. Scat consistently had the lowest δ13C and δ15N values among the tissues sampled. We derived a diet-to-scat Δ13C value of -1.5‰ ± 1.6‰ and Δ15N value of 2.3‰ ± 1.3‰ for coyotes. Coyote scat δ13C and δ15N values adjusted for discrimination consistently plot within the isotopic mixing space created by known dietary items. In comparison with GFA results, we found that mixing model estimates of coyote dietary proportions de-emphasize the importance of small-bodied prey. Coyote scat δ13C and δ15N values therefore offer a relatively quick and non-invasive way to gain accurate dietary information.
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Affiliation(s)
- Rachel E. B. Reid
- Earth and Planetary Sciences Department, University of California, Santa Cruz, California, United States of America
- * E-mail:
| | - Paul L. Koch
- Earth and Planetary Sciences Department, University of California, Santa Cruz, California, United States of America
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13
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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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14
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Matley JK, Fisk AT, Tobin AJ, Heupel MR, Simpfendorfer CA. Diet-tissue discrimination factors and turnover of carbon and nitrogen stable isotopes in tissues of an adult predatory coral reef fish, Plectropomus leopardus. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:29-44. [PMID: 26661968 DOI: 10.1002/rcm.7406] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 09/10/2015] [Accepted: 09/22/2015] [Indexed: 05/13/2023]
Abstract
RATIONALE Stable isotope ratios (δ(13)C and δ(15)N values) provide a unique perspective into the ecology of animals because the isotope ratio values of consumers reflect the values in food. Despite the value of stable isotopes in ecological studies, the lack of species-specific experimentally derived diet-tissue discrimination factors (DTDFs) and turnover rates limits their application at a broad scale. Furthermore, most aquatic feeding experiments use temperate, fast-growing fish species and few have considered medium- to large-sized adults with low growth rates from tropical ecosystems. METHODS A controlled-diet stable isotope feeding trial was conducted over a 196-day period for the adult predatory reef fish leopard coralgrouper (Plectropomus leopardus). This study calculated δ(13)C and δ(15)N DTDFs and turnover rates in five tissues (liver, plasma, red blood cells (RBC), fin, and muscle) using a continuous flow isotope ratio mass spectrometer equipped with an elemental analyzer. In addition, the effect of chemical lipid extraction (LE) on stable isotope values was examined for each tissue. RESULTS Turnover was mainly influenced by metabolism (as opposed to growth) with LE δ(15)N half-life values lowest in fin (37 days) and plasma (66 days), and highest in RBC (88 days) and muscle (126 days). The diet-tissue discrimination factors for δ(15)N values in all tissues (Δ(15)N: -0.15 to 1.84‰) were typically lower than commonly reported literature values. Lipid extraction altered both δ(15) N and δ(13)C values compared with untreated samples; however, for the δ(15)N values, the differences were small (mean δ(15)N(LE-Bulk) <0.46‰ in all tissues). CONCLUSIONS This study informs future interpretation of stable isotope data for medium- to large-sized fish and demonstrates that DTDFs developed for temperate fish species, particularly for δ(15)N values, may not apply to tropical species. Sampling of muscle and/or RBC is recommended for a relatively long-term representation of feeding habits, while plasma and/or fin should be used for a more recent indication of diet.
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Affiliation(s)
- J K Matley
- Centre for Sustainable Tropical Fisheries and Aquaculture & College of Marine and Environmental Sciences, James Cook University, Townsville, Qld, 4811, Australia
| | - A T Fisk
- Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, Canada, N9B 3P4
| | - A J Tobin
- Centre for Sustainable Tropical Fisheries and Aquaculture & College of Marine and Environmental Sciences, James Cook University, Townsville, Qld, 4811, Australia
| | - M R Heupel
- Centre for Sustainable Tropical Fisheries and Aquaculture & College of Marine and Environmental Sciences, James Cook University, Townsville, Qld, 4811, Australia
- Australian Institute of Marine Science, PMB No 3, Townsville, Qld, 4810, Australia
| | - C A Simpfendorfer
- Centre for Sustainable Tropical Fisheries and Aquaculture & College of Marine and Environmental Sciences, James Cook University, Townsville, Qld, 4811, Australia
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