History of Animals using Isotope Records (HAIR): A 6-year dietary history of one family of African elephants

Abstract

The dietary and movement history of individual animals can be studied using stable isotope records in animal tissues, providing insight into long-term ecological dynamics and a species niche. We provide a 6-year history of elephant diet by examining tail hair collected from 4 elephants in the same social family unit in northern Kenya. Sequential measurements of carbon, nitrogen, and hydrogen isotope rations in hair provide a weekly record of diet and water resources. Carbon isotope ratios were well correlated with satellite-based measurements of the normalized difference vegetation index (NDVI) of the region occupied by the elephants as recorded by the global positioning system (GPS) movement record; the absolute amount of C4 grass consumption is well correlated with the maximum value of NDVI during individual wet seasons. Changes in hydrogen isotope ratios coincided very closely in time with seasonal fluctuations in rainfall and NDVI whereas diet shifts to relatively high proportions of grass lagged seasonal increases in NDVI by Ϸ2 weeks. The peak probability of conception in the population occurred Ϸ3 weeks after peak grazing. Spatial and temporal patterns of resource use show that the only period of pure browsing by the focal elephants was located in an over-grazed, communally managed region outside the protected area. The ability to extract time-specific longitudinal records on animal diets, and therefore the ecological history of an organism and its environment, provides an avenue for understanding the impact of climate dynamics and land-use change on animal foraging behavior and habitat relations.C4 photosynthesis ͉ carbon-13 ͉ stable isotopes ͉ wildlife conservation V ariation in temporal and spatial resource quality and abundance can have strong affects on animal ecology and community resource partitioning (1). In particular, changes in species composition and abundance at seasonal and longer time scales strongly influences diet and, as a result, community dynamics and the life history of animals (2, 3). Quantifying and dating fine scale foraging behaviors is difficult, typically causing foraging studies to focus on averages compiled from observations and measurements collected from multiple, and often unknown, individuals (e.g., refs. 4-6); such dietary data are difficult to relate to spatially or temporally explicit resource changes. Quantifying the long-term diets of a single individual requires continuous observation, often in the face of cryptic life stages or range shifts and seasonal migration. As such, detailed dietary monitoring through observations is intractable for many species, although the importance of quantifying climate or human mediated diet changes that many species are experiencing is more critical than ever (7). Recent developments in stable isotope ecology enable the derivation of temporally explicit diet records, offering a means by which foraging decisions and the effect of ecological shifts on species can be recorded and compared over time.Stable isotopes in animal tissues record...

Isotopic paleoecology of Clovis mammoths from Arizona

“…We propose that Clovis mammoths sought new C 4 plant growth farther from the river during the summer rainy season and remained closer to the river, foraging on mixed C 3 -C 4 plants, during the winter. A similar pattern of seasonal foraging occurs among modern elephants (21,22,47). Such predictable seasonal behaviors could have made SPV mammoths particularly easy for human hunters to track, even before the Clovis drought.…”

“…However, little else is known about seasonality in the Late Pleistocene SPV or how it affected mammoth ecology. Climate exerts a strong influence on modern elephant diet and migration patterns (21)(22)(23)(24), and the same was likely true for mammoths.…”

“…It has been suggested that mammoths weakened during the drought clustered around water sources in the SPV, making them easier targets for Clovis hunters and ultimately contributing to their extinction (24,41). During droughts, modern African elephants constrict their feeding ranges to areas with permanent water and increase their reliance on woody vegetation, as a result of decreased grass availability (21,42).…”

Individual specialists in a generalist population: results from a long-term stable isotope series

“…Nitrogen isotopes typically indicate trophic position (Post 2002), while carbon isotopes reflect variation in baseline producers or habitat (DeNiro & Epstein 1978). Tissues that are created over time and remain inert after synthesis, such as hair, otoliths and baleen, reflect resource use at the time of formation (Hobson 1999) and allow longitudinal sampling with stable isotope analysis of successive microlayers (Cerling et al 2009;Cherel et al 2009). Sea turtles have such a tissue-scutewhich is a keratinized epidermis covering the bony shell of most chelonians.…”

A feather‐precipitation hydrogen isoscape model for New Zealand: implications for eco‐forensics

“…This may allow one to better rank the suitability of individual bird species as geographical locators. The addition of other stable isotopes in feathers covariates in future work, such as 13 C (aridity/biome/dietary source), 15 N (trophic position) and 34 S (distance from sea), would likely strengthen the resolution of geospatial assignments (Hobson and Wassenaar 1997, Herbert and Wassenaar 2005, Cerling et al 2009, Valenzuela et al 2011.…”