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

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.

Stable isotopes, morphology, and body condition metrics suggest similarity in the trophic level and diversity in the carbon sources of freshwater and early marine diets of Chinook salmon

“…Had the fish in this study engaged in a recent diet switch or more temporally diverse dietary habits, we would not expect the level of congruency in cross-tissue stable isotope values we observed. We note that the lack of covariation between the two isotopes observed within tissues is not unique to our study, and similar findings have been previously documented in a variety of taxonomic groups (e.g., deVries et al 2015;Stanek et al 2019).…”

Svalbard reindeer winter diets: Long‐term dietary shifts to graminoids in response to a changing climate

“…Still, our results support the findings of previous studies, in that they suggest that intrinsic processes, such as pregnancy, and nutritional status (mobilization of body stores) have small contrasting effects on serum δ 13 C and δ 15 N values. Dietary supplies of energy and N are the largest contributors to the stable isotope pool in serum (Ben‐David & Flaherty, 2012 ; Fry, 2006 ; Rogers et al, 2015 , 2020 ; Stanek et al, 2017 , 2019 ), consequently, shifts in the serum δ 13 C and δ 15 N values are most likely due to increased utilization of δ 15 N enriched and δ 13 C depleted graminoids in late winter. Ultimately, we propose that the main extrinsic environmental drivers of Svalbard reindeer serum δ 13 C and δ 15 N values—population density, summer temperature, and ROS—have acted collectively to increase the utilization of graminoids in later winter.…”

“…Still, our results support the findings of previous studies, in that they suggest that intrinsic processes, such as pregnancy, and nutritional status (mobilization of body stores) have small contrasting effects on serum δ 13 C and δ 15 N values. Dietary supplies of energy and N are the largest contributors to the stable isotope pool in serum (Ben-David & Flaherty, 2012;Fry, 2006;Rogers et al, 2015Rogers et al, , 2020Stanek et al, 2017Stanek et al, , 2019…”

“…Dietary information at different temporal scales can be effectively inferred using stable isotope analysis (SIA) of different tissues (Ben‐David & Flaherty, 2012 ; Fry, 2006 ; Rogers et al, 2015 , 2020 ; Stanek et al, 2017 , 2019 ). Progressive shifts in a herbivore's stable isotope (δ 13 C and δ 15 N) values reflect dietary changes as a result of differential tissue growth and turnover rates: from serum at 1–2 weeks → red blood cells at 2–3 months → muscle at 6–9 months → → bone over the lifetime (Dalerum & Angerbjörn, 2005 ; Libby et al, 1967 ; Tieszen et al, 1983 ).…”

Dietary reconstructions of Magdalenian canids from SW-Germany do not indicate that the area was a centre of early European wolf domestication

“…It may also be useful to consider what the known spread in measured isotopic signatures of wolves can be. Different studies have determined different TEFs for the different tissues of wolves [17,18,19,20] , but here we consider collagen for the Magdalenian specimens and hairs for modern wolves. A classical study on wolves from coastal British Columbia [21] analysed the isotopic signatures of hairs of wolves in three distinct regions (mainland, inner islands adjacent to the coast, outer islands).…”