Seasonal paleoecological records from antler collagen δ¹³C and δ¹⁵N

Abstract

Cervids living in high latitudes have evolved to thrive in ecosystems that experience dramatic seasonal changes. Understanding these seasonal adaptations is important for reconstructing cervid life histories, ecosystem dynamics, and responses in the distant and not-so-distant past to changing seasonality caused by climate change. Cervid antlers provide a rare opportunity for insight into faunal seasonal ecology, as they are grown and shed each year. Stable isotopes of carbon and nitrogen measured directly from antlers have the potential to provide seasonal dietary data for individuals. If the isotopic signals in bone and antler are controlled by the same metabolic processes, then the stable carbon and nitrogen isotope compositions of collagen (δ13CColl and δ15NColl) from incrementally grown antler tissue provide time-constrained dietary signals from the spring and summer growth season. Bone, by comparison, provides an average signal over several years. The amino acid (glutamate and phenylalanine) δ15N in antlers from modern captive caribou showed similar trophic discrimination factors to earlier results for other collagenous tissues (bone, tooth dentin, and cementum). Hence, growth rate was not the primary control on the stable isotope composition of antler collagen. We applied this knowledge to assess seasonal shifts in Quaternary fossils of three Cervidae species: elk (Cervus elaphus), moose (Alces alces), and caribou (Rangifer tarandus). Paired antler–bone δ13CColl and δ15NColl from the same individual were used to identify differences between summer and annual diet and ecology. Intra-antler isotopic variability from serially sampled antlers was used to examine seasonal dietary shifts and specialization.

Spatial ecology of moose in Sweden: Combined Sr-O-C isotope analyses of bone and antler

“…Strontium, oxygen and carbon data are shown in Fig 2(A)–2(E) . Since bone and antler represent different time averages (i.e., several years and a few months, respectively) [ 69 , 140 ] we decided to present bone and antler data separately.…”

“…We first note that the isotopic values of bones (mainly cranial bone) represent a mean of several years of life of the individual. On the other hand, the antlers provide an isotopic signal corresponding to their growing season (between spring and summer) [ 69 , 152 , 153 ]. In the present study, antlers were sampled close to the base, thus likely reflecting ∼1 month of life in spring.…”

“…Other key aspects of moose ecology, feeding habits and habitat selection, can be revealed by carbon stable isotopes [ 67 , 69 ]. The mean δ 13 C VPDB values (corrected for the ‘Suess effect’) of the carbonate portion of bioapatite of our moose samples was -14.9‰ (±1.1‰) and -16.2‰ (±1.1‰) for antlers and bones, respectively.…”

C3 plant isotopic variability in a boreal mixed woodland: implications for bison and other herbivores

“…), which may be more important variables for interpreting herbivore isotopic compositions than plant type. Studies that compare herbivore isotopic compositions in ancient C 3 ecosystems to a plant baseline organized by plant type (e.g., Schwartz-Narbonne et al, 2019;Schwartz-Narbonne et al, 2021) presuppose that type is the most important predictor of a plant's isotopic compositions. An alternative approach is to put equal or greater emphasis on major environmental factors that influence plant isotopic compositions, such as the canopy effect (e.g., Drucker et al, 2008;Hofman-Kami nska et al, 2018) or ecosystem changes (e.g., Drucker et al, 2011;Metcalfe & Longstaffe, 2014).…”

Variation in stable carbon (δ13C) and nitrogen (δ15N) isotope compositions along antlers of Qamanirjuaq caribou (Rangifer tarandus groenlandicus)

“…Variation in stable isotopes in relation to changes in diet and migration has been demonstrated with tooth enamel, often reflecting the first 6–12 months of an individual's life (Drucker et al., 2012 ; Fraser et al., 2021 ; Kohn, 2004 ; Passey et al., 2002 ). Antler tissue shows similar finite growth and may therefore record the seasonal dietary changes and migration in a comparable manner (Koch, 2008 ; Schwartz‐Narbonne et al., 2021 ).…”