Use of stable isotopes to identify dietary differences across subpopulations and sex for a free-ranging generalist herbivore.
Carbon and nitrogen isotopes in tissues can be used to understand plants consumed by various taxa, but can they provide additional information about consumers? Values of δ(13)C and δ(15)N were assessed from tissue of free-ranging elk (Cervus elaphus) occupying disparate habitats of mixed prairie-oak savannah that contained C3 agricultural crops in a C4-dominated landscape and in key plants consumed by elk. Muscle and hoof samples were collected from female and male elk in two subpopulations (forested land and grassland) from private land and one subpopulation from the Wichita Mountains Wildlife Refuge (refuge) in 2001-2006. Previous research identified differences between mean muscle δ(13)C and δ(15)N and mean hoof δ(13)C and δ(15)N indicating that isotopes differed between tissues of varying metabolic activity. Mean δ(13)C in hoof of elk on forested land and grassland were lower than hoof δ(13)C from elk in the refuge indicating greater long-term consumption of C3 plants by elk on forested land and grassland subpopulations. The δ(15)N in hoof was greater for elk outside the refuge than that for elk in the refuge. Interaction of sex and subpopulation only occurred for hoof δ(15)N suggesting that factors such as tissue type, sex, and habitat need to be considered to understand free-ranging ecology of generalist herbivores using stable isotopes. Availability of C3 agricultural crops high in percent nitrogen on a nearly annual basis in a C4-dominated landscape was likely driving differences in tissue δ(13)C and δ(15)N among subpopulations of free-ranging elk. An increase in tissue δ(15)N resulted from an increase in the consumption of higher δ(15)N in forage for sexes and subpopulations of a free-ranging ungulate in North America but δ(15)N should be further evaluated as an index of nutrition for subpopulations of generalist herbivores.
a U.S. Geological Survey, Pennsylvania Cooperative Fish and Wildlife Research Unit , Pennsylvania State University, University Park , PA , USA.
W David
WD
Walter
D000818:Animals; D002247:Carbon Isotopes / Q000378:metabolism; D003670:Deer / Q000378:metabolism*; D017753:Ecosystem; D005247:Feeding Behavior; D005260:Female; D006724:Hoof and Claw / Q000737:chemistry; D008297:Male; D013058:Mass Spectrometry; D018482:Muscle, Skeletal / Q000737:chemistry; D009587:Nitrogen Isotopes / Q000378:metabolism; D009825:Oklahoma; D010944:Plants / Q000378:metabolism; D012727:Sex Characteristics
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes
Cervus elaphus; animals; carbon-13; elk; isotope ecology; nitrogen-15; nutrition; sexual segregation; subpopulation tissue