Feeding ecology of Eurasian otters (Lutra lutra) in freshwater habitats: Preliminary results of a stable isotope approach

The aim of the present study was to investigate the feeding ecology of an omnivorous bird, the Ring-billed Gull (Larus delawarensis Ord, 1815), breeding in a highly urbanized and heterogeneous landscape (Montréal area, Quebec, Canada). We used gastrointestinal (G.I.) tract content analysis, GPS-based tracking information, and stable isotope profiles of carbon (δ13C) and nitrogen (δ15N) in selected tissues and major food items. Based on GPS tracking data (1–3 days), Ring-billed Gulls were categorized according to their use of three main foraging habitats: agricultural, St. Lawrence River, and anthropogenic (comprising urban areas, landfills, and wastewater treatment plant basins). Ring-billed Gulls that foraged predominantly in anthropogenic habitats exhibited significantly lower δ15N in blood cells and higher total C to N ratios (C:N) in liver. These lower δ15N and higher C:N ratios were characteristic of profiles determined in food items consumed by Ring-billed Gulls at these urbanized sites (e.g., processed foods). The strong positive correlations between δ13C and δ15N in Ring-billed Gull tissues (plasma, blood cells, and liver) that differed in isotopic turnover times, as well as the strong positive correlations in both δ13C and δ15N between tissue pairs, indicated that Ring-billed Gulls exhibited conserved dietary habits throughout the nesting period. This study demonstrates that combining conventional dietary examination, tissue stable isotope analysis, and fine-scale GPS tracking information may improve our understanding of the large intrapopulation variations in foraging behaviour (and isotopic profiles) commonly observed in omnivorous birds.

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Feeding ecology of shallow water meiofauna: insights from a stable isotope tracer experiment in Potter Cove, King George Island, Antarctica

Polar Biology ◽

10.1007/s00300-012-1203-6 ◽

2012 ◽

Vol 35 (11) ◽

pp. 1629-1640 ◽

Cited By ~ 13

Author(s):

Francesca Pasotti ◽

Marleen De Troch ◽

Maarten Raes ◽

Ann Vanreusel

Keyword(s):

Stable Isotope ◽

Shallow Water ◽

Feeding Ecology ◽

Tracer Experiment ◽

King George Island ◽

Potter Cove ◽

Stable Isotope Tracer ◽

Isotope Tracer

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Analysis of the feeding ecology of earthworms (Megascolecidae) in Japanese forests using gut content fractionation and and stable isotope natural abundances

Applied Soil Ecology ◽

10.1016/j.apsoil.2004.04.003 ◽

2004 ◽

Vol 27 (2) ◽

pp. 153-163 ◽

Cited By ~ 39

Author(s):

T. Uchida ◽

N. Kaneko ◽

M.T. Ito ◽

K. Futagami ◽

T. Sasaki ◽

...

Keyword(s):

Stable Isotope ◽

Feeding Ecology ◽

Gut Content

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Stable isotope geochemistry of the metamorphic rocks at larderello geothermal field: Preliminary results

Chemical Geology ◽

10.1016/0009-2541(88)90680-8 ◽

1988 ◽

Vol 70 (1-2) ◽

pp. 164

Author(s):

E. Petrucci ◽

B. Turi ◽

S.M.F. Sheppard

Keyword(s):

Stable Isotope ◽

Isotope Geochemistry ◽

Geothermal Field ◽

Metamorphic Rocks ◽

Stable Isotope Geochemistry ◽

Preliminary Results

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Feeding Ecology of Elusive Caribbean Killer Whales Inferred From Bayesian Stable Isotope Mixing Models and Whalers’ Ecological Knowledge

Frontiers in Marine Science ◽

10.3389/fmars.2021.648421 ◽

2021 ◽

Vol 8 ◽

Author(s):

Jeremy J. Kiszka ◽

Michelle Caputo ◽

Paula Méndez-Fernandez ◽

Russell Fielding

Keyword(s):

Stable Isotope ◽

Feeding Ecology ◽

Caribbean Region ◽

Ecological Knowledge ◽

Mixing Models ◽

Physeter Macrocephalus ◽

Potential Prey ◽

Killer Whales ◽

Marine Predators ◽

The Caribbean

Investigating the feeding ecology of marine predators is critical for understanding their roles and functional importance in ecosystems. However, assessing the diet of large and wide-ranging predators can be challenging, particularly in the case of rare and elusive species. Killer whales (Orcinus orca) are large apex predators in global oceans, but very little is known about their feeding ecology in tropical ecosystems, particularly in the Caribbean Sea. Killer whales are distributed throughout the Caribbean, and are a regular target of artisanal whalers in St. Vincent and the Grenadines (West Indies). Here we investigate the feeding ecology of Caribbean killer whales using a combination of stable isotope analysis (δ15N, δ13C) and traditional ecological knowledge (TEK) data from whalers operating from St. Vincent. Potential prey data from the Caribbean region included large pelagic teleosts, sea turtles, oceanic sharks, cetaceans, and oceanic cephalopods. Mixing models suggest that the contribution of odontocete cetaceans to the diet of killer whales is the most important (overall mean contribution: 60.4%), particularly mesopelagic delphinids (Lagenodelphis hosei; 26.4%, SD = 0.14), large teuthophageous odontocetes (Physeter macrocephalus, Globicephala macrorhynchus; 20.0%, SD = 0.14), and epipelagic delphinids (Stenella attenuata; 14%, SD = 0.14). Oceanic sharks (Carcharhinus longimanus) had a contribution of 17.0% of the diet of killer whales (SD = 0.13), and other potential prey had a relatively marginal contribution. TEK data suggest that whalers believe killer whales feed almost exclusively on cetaceans, particularly odontocete species that they hunt (e.g., G. macrorhynchus). Stable isotope and TEK data were consistent to some extent, although TEK data are qualitative and based on a limited number of observations. Despite some limitations (including sample size for both methods), this study highlights the value of combining independent data sources and methodologies to investigate the ecological roles of marine predators in data-poor regions.

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Feeding Ecology of Three Euphausiid Species in the North Pacific Ocean Inferred From 18S V9 Metabarcoding and Stable Isotope Analysis

Frontiers in Marine Science ◽

10.3389/fmars.2021.756067 ◽

2021 ◽

Vol 8 ◽

Author(s):

Fanyu Zhou ◽

Junya Hirai ◽

Koji Hamasaki ◽

Sachiko Horii ◽

Atsushi Tsuda

Keyword(s):

Stable Isotope ◽

Stable Isotope Analysis ◽

Feeding Ecology ◽

North Pacific ◽

Prey Availability ◽

Trophic Position ◽

Isotope Analysis ◽

Trophic Levels ◽

Gut Contents ◽

North Pacific Subtropical Gyre

Euphausiids are abundant micronekton and important links between higher and lower trophic levels in marine ecosystems; however, their detailed diets cannot be fully understood by conventional microscopy, especially in subtropical areas. Here, we report the euphausiid community structure in the California Current (CC) area and the eastern/western North Pacific subtropical gyre (ESG and WSG) and detail the feeding ecology of the dominant species (Euphausia pacifica, E. brevis, and E. hemigibba) in each region using a combined approach of gut content analysis via 18S V9 metabarcoding and stable carbon and nitrogen isotope analysis. A pronounced omnivorous feeding of all studied euphausiid species was supported by both methods: phytoplanktonic taxonomic groups (Dinophyta, Stramenopiles, and Archaeplastida), Copepoda, and Hydrozoa were detected in the gut contents; all the three euphausiid species displayed an intermediate trophic position between the net plankton (0.2–1.0 mm) and the myctophid fish (15.2–85.5 mm). However, Hydrozoa found in euphausiid gut contents likely derived from a potential cod-end feeding, based on isotope analysis. E. pacifica in the CC province ingested more autotrophic prey, including pelagophyte and green algae, due to a greater abundance of Stramenopiles and Archaeplastida in shallow layers of CC water. On the other hand, non-autotrophic prey such as mixotrophic Kareniaceae dinoflagellates, Pontellidae and Clausocalanidae copepods, and Sphaerozoidae rhizarian contributed more to the diets of E. brevis and E. hemigibba because of a lower chlorophyll a concentration or potentially a scarcity of autotrophic prey availability in ESG and WSG. The feeding patterns of dominant euphausiid species conducting filter feeding were thus largely determined by phytoplankton prey availability in the environments. Dietary difference across three species was also indicated by stable isotope analysis, with a lower mean trophic level of E. pacifica (2.32) than E. brevis (2.48) and E. hemigibba (2.57). These results verify direct trophic interactions between euphausiids and primary production and suggest that the omnivorous feeding habit is a favorable character for dominant Euphausia species.

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