title: Stable isotope series from elephant ivory reveal lifetime histories of a true dietary generalist.
abstract: Longitudinal studies have revealed how variation in resource use within consumer populations can impact their dynamics and functional significance in communities. Here, we investigate multi-decadal diet variations within individuals of a keystone megaherbivore species, the African elephant (Loxodonta africana), using serial stable isotope analysis of tusks from the Kruger National Park, South Africa. These records, representing the longest continuous diet histories documented for any extant species, reveal extensive seasonal and annual variations in isotopic--and hence dietary--niches of individuals, but little variation between them. Lack of niche distinction across individuals contrasts several recent studies, which found relatively high levels of individual niche specialization in various taxa. Our result is consistent with theory that individual mammal herbivores are nutritionally constrained to maintain broad diet niches. Individual diet specialization would also be a costly strategy for large-bodied taxa foraging over wide areas in spatio-temporally heterogeneous environments. High levels of within-individual diet variability occurred within and across seasons, and persisted despite an overall increase in inferred C(4) grass consumption through the twentieth century. We suggest that switching between C(3) browsing and C(4) grazing over extended time scales facilitates elephant survival through environmental change, and could even allow recovery of overused resources.
authors.affiliation: School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa. jacquicodron@gmail.com
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Codron
authors.forename: Daryl
authors.initials: D
authors.lastname: Codron
authors.forename: Matt
authors.initials: M
authors.lastname: Sponheimer
authors.forename: Kevin
authors.initials: K
authors.lastname: Kirkman
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Duffy
authors.forename: Erich J
authors.initials: EJ
authors.lastname: Raubenheimer
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Mélice
authors.forename: Rina
authors.initials: R
authors.lastname: Grant
authors.forename: Marcus
authors.initials: M
authors.lastname: Clauss
authors.forename: Julia A
authors.initials: JA
authors.lastname: Lee-Thorp
mesh_terms: D000220:Adaptation, Biological / Q000502:physiology*; D000366:Age Determination by Teeth / Q000379:methods / Q000662:veterinary; D000818:Animals; D002247:Carbon Isotopes / Q000032:analysis*; D003804:Dentin / Q000737:chemistry; D004032:Diet; D004606:Elephants; D016014:Linear Models; D013058:Mass Spectrometry; D009587:Nitrogen Isotopes / Q000032:analysis*; D010103:Oxygen Isotopes / Q000032:analysis*; D013019:South Africa; D014070:Tooth / Q000033:anatomy & histology / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D010103:Oxygen Isotopes