Stable isotopes in elephant hair document migration patterns and diet changes

Abstract

We use chronologies of stable isotopes measured from elephant (Loxodonta africana) hair to determine migration patterns and seasonal diet changes in elephants in and near Samburu National Reserve in northern Kenya. Stable carbon isotopes record diet changes, principally enabling differentiation between browse and tropical grasses, which use the C3 and C4 photosynthetic pathways, respectively; stable nitrogen isotopes record regional patterns related to aridity, offering insight into localized ranging behavior. Isotopically identified range shifts were corroborated by global positioning system radio tracking data of the studied individuals. Comparison of the stable isotope record in the hair of one migrant individual with that of a resident population shows important differences in feeding and ranging behavior over time. Our analysis indicates that differences are the result of excursions into mesic environments coupled with intermittent crop raiding by the migrant individual. Variation in diet, quantified by using stable isotopes, can offer insight into diet-related wildlife behavior.13-carbon ͉ 15-nitrogen ͉ chronology ͉ human-elephant conflict T he stable isotope ratios of 13 C͞ 12 C in hair records the diet of mammals (1-4). It is particularly useful in distinguishing diets of C 3 browse versus C 4 grass in tropical regions (5-7) because of the large difference in 13 C͞ 12 C ratios between plants using the C 3 and C 4 photosynthetic pathways, respectively. In tropical regions, the C 3 pathway is used primarily by trees and shrubs, whereas plants using the C 4 pathway are principally grasses (8,9).Hair is a particularly useful indicator of diet change (3, 4) because the isotope turnover of mammal tissues is high enough to resolve short-term diet changes. Recent advances in methodology, progressed through the study of large mammals with controlled diet changes (10, 11), allows detailed reconstruction of the diet history of individual large mammals in wild populations (12,13).In this study, we determine the growth rates and stable 13 C͞ 12 C and 15 N͞ 14 N ratios in elephant hair collected between 2001 and 2004. We focus on the behavior of a resident population of Samburu National Reserve, Northern Kenya, for the time period of 2000 to 2002. We compare stable isotope results of this resident population with a migrant elephant (B1013) that visited Samburu Reserve up to several times each year. Differences in isotope ratios between the resident individuals and the migrant indicate different behaviors, including rapid migration across long distances by the migrant individual and differences in the fraction C 4 biomass in the diet. The latter may be related to seasonal crop raiding, which can be quantified by using stable isotope ratios. Materials and MethodsGlobal Positioning System (GPS) radio collars were fitted to elephants in Samburu National Reserve, Northern Kenya, between 2001 and 2004 (14). Collars were programmed to record positions at hourly intervals, offering detailed records of movement. Tail hairs fro...

Hydrogen and oxygen isotope ratios in human hair are related to geography

“…We asked how well the model could be inverted to predict the isotope ratio of the tap water for the city in which the hair sample originated. For these 65 hair samples, we again achieved 85% and 86% agreement, respectively, between the predicted and observed ''isotopic origins'' of both the ␦ 2 H h and ␦ 18 Hair has been shown to be a sequential recorder of changes in diet (3,12,(32)(33)(34)(35). Similarly, geographic movements by an individual between locations with contrasting tap-water isotope ratios should be detectable.…”

“…T he carbon (␦ 13 C), nitrogen (␦ 15 N), and sulfur (␦ 34 S) isotope ratios of humans, other animals, and microbes are strongly correlated with the isotope ratios of their dietary inputs (1)(2)(3)(4)(5). The adage ''You are what you eat'' reflects the observation that there are limited differences (Յ1‰) between heterotrophic organisms and their diet in either the ␦ 13 C or ␦ 34 S values (6)(7)(8).…”

Incorporating mortality into habitat selection to identify secure and risky habitats for savannah elephants

“…The dry season is the limiting season for this mega-herbivore (Illius, 2006;Trimble et al, 2009), so we consider the dry season best reflects limitations in habitat suitability and ultimately best relates to fitness. Habitat selection patterns are likely to vary in the core wet season (Young et al, 2009), when elephants shift their diet to consume more grasses (Cerling et al, 2006;Codron et al, 2011) and are less dependent on permanent water sources (Harris et al, 2008;Young et al, 2009). Based on our knowledge of elephant use patterns in the area from GPS collar data, we suspect that areas designated as "non-habitat" will be most influenced, particularly in NG-north.…”

Seasonal diet changes in elephant and impala in mopane woodland

“…Elephant and impala have different strategies to cope with changing forage conditions over the seasons. Elephants have a diet dominated by browse in the dry season, but they mainly feed on green, nutritious grasses in the early wet season (Hansen et al 1985;Beekman and Prins 1989;Cerling et al 2006). Relative to their body mass, elephants have a short mean gut retention time, and they can include food items of low digestibility in their diet (Owen-Smith 1988).…”