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.
Highlights
Based on the adage that “you are what you eat”, researchers have widely used stable carbon and nitrogen isotope analysis of animal tissues to address a wide variety of topics related to wildlife management, including trophic interactions, animal movement and migration, and diet composition and habitat use in many species (e.g. [1,2,3,4])
The stable isotope ratios of carbon (13C/12C, reported as δ13C) and nitrogen (15N/14N, reported as δ15N) in animal tissues reflect the isotopic signature of diet and can be used to determine the relative contributions of isotopically distinct food sources to an animal’s diet [5,6,7,8]
The trophic discrimination factor (TDF) is typically expressed as Δ13C for C and Δ15N for N, where Δ represents the difference in isotopic composition between the diet and an animal’s tissue [22]
Summary
The TDF is typically expressed as Δ13C for C and Δ15N for N, where Δ represents the difference in isotopic composition between the diet and an animal’s tissue [22] These TDFs may vary depending upon many factors, including the studied species, trophic level, type of tissue analyzed, growth rate, differential digestibility, and diet quality Dietary inferences based on stable isotope analysis of tissues of wild animals are often unreliable, because researchers rely on generalized, fixed, and not experimentally derived TDFs from the literature without taking into account the species under study, tissue analyzed, or the type of diet [27, 29, 30]. We determined stable carbon and nitrogen isotope discrimination factors in hair samples of four 3-year old captive wild boar (Sus scrofa) fed with a controlled diet of corn (Zea mays) over a 4-month period. In order to facilitate future derivations of the temporal dietary record from isotopic signatures along hair length units, we calculated the average growth rate (mm/day) of wild boar hair
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