Abstract
In bone, the spacing between δ13C in collagen and bioapatite carbonate is greater in herbivores than carnivores, with implications for understanding animal dietary ecology from surviving hard tissues. Two explanations have been proposed: varying diet composition or differences in physiology between herbivores and carnivores. We measured the isotopic effects of carnivorous and herbivorous diets on a single species, to test the effect of diet composition alone. Protein δ13C and δ15N and carbonate δ13C were measured on egg and bone from hens on different diets. Herbivorous hens had a +14.3‰ spacing between egg albumen and shell δ13C, compared to +12.4‰ for omnivorous hens, and +11.5‰ for carnivorous hens. The bioapatite–collagen Δ13C spacing was measured as +6.2‰ for herbivorous hens, and calculated as +4.3‰ for omnivorous hens, and +3.4‰ for carnivorous hens—similar to observed mammalian herbivore and carnivore bioapatite–collagen Δ13C differences. We conclude that a shift in diet composition from herbivory to carnivory in a single species does alter the bioapatite–collagen carbon isotopic spacing. Our data strongly suggest that this results from differences in the Δ13Cbioapatite–diet spacing, and not that of Δ13Ccollagen–diet.
Highlights
The relationship between the carbon and nitrogen isotope composition of an individual’s diet and their body tissues is frequently employed as a method of dietary analysis in several different research fields, including ecology, archaeology and physiology (Gannes et al 1998; Lee-Thorp 2008; Boecklen et al 2011)
Hens fed on the wheat diet (A) had a mean Δ13Cshell–albumen spacing of +14.3‰, compared to a mean spacing of +12.4‰ for those hens on a mixed diet (B), and +11.5‰ for those hens fed on beef (C), showing that within a single species, the Δ13Cshell–albumen spacing is affected by the diet composition, and that an herbivorous diet results in a greater spacing between body protein and carbonate δ13C than does a carnivorous diet (Fig. 2)
While shell and albumen δ13C values cannot be directly equated with the δ13C of bone bioapatite carbonate and collagen, the difference between the observed Δ13Cshell–albumen values of the herbivorous and carnivorous hens is 2.8‰ (+14.3‰ versus +11.5‰), very similar to the typical 3‰ difference observed between the Δ13Cap–coll spacings of herbivores and carnivores (Krueger and Sullivan 1984; Lee-Thorp et al 1989; Clementz et al 2009)
Summary
The relationship between the carbon and nitrogen isotope composition of an individual’s diet and their body tissues is frequently employed as a method of dietary analysis in several different research fields, including ecology, archaeology and physiology (Gannes et al 1998; Lee-Thorp 2008; Boecklen et al 2011). An individual’s diet can be inferred from the isotopic signature, which is transferred to and retained in the body during the absorption and incorporation of food. The interpretation of diet is predicated on understanding and accounting for any isotopic fractionation resulting from the incorporation of diet into body tissues. There have been a number of empirical studies aimed at elucidating isotopic fractionation during the body’s metabolism, yet some observed patterns remain puzzling. One such is the offset between the carbon isotopic values of the biomineral and protein components of bone.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
