AVHRR monitoring of savanna primary production in Senegal, West Africa: 1987-1988

Diallo, Oumar; Diouf, Alioune; Hanan, Niall P.; Ndiaye, Aminata; Prévost, Y.

doi:10.1080/01431169108929725

Cited by 129 publications

(74 citation statements)

References 17 publications

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“…1C); during these intervals, B1013 had similar C 4 grass consumption as the other six elephants. The single exception is the highest C 4 consumption peak, which occurred during the dry season between June 18 and August 16,2001. By comparison, the other six elephants had a low fraction of C 4 grass consumption during this dry season.…”

Section: Resultsmentioning

confidence: 99%

“…In this study, we used 10-day composite normalized differential vegetation index (NDVI) data, available through Satellite Probatoire d'Observation de la Terre (SPOT), to determine changes in season across the study area. NDVI is a remote sensing index value calculated as the ratio between red and near infrared reflection that is highly correlated with green (photosynthetically active) biomass (15,16). Remotely sensed data provide a direct measure of photosynthetic activity over large spatial regions, offering advantages over the classically used point-sampled rainfall data in areas, like the study region, where weather stations are sparse.…”

Section: Methodsmentioning

confidence: 99%

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Stable isotopes in elephant hair document migration patterns and diet changes

Cerling

Wittemyer

Rasmussen

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

195

152

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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...

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Stable isotopes in elephant hair document migration patterns and diet changes

Cerling

Wittemyer

Rasmussen

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

195

152

View full text Add to dashboard Cite

show abstract

“…We used 10-day composite NDVI data available through Satellite Probatoire d'Observation de la Terre (SPOT) to determine NPP changes in season across the study area. NDVI is a remote sensing index value calculated as the ratio between red and near infrared reflection that is highly correlated with green (photosynthetically active) biomass (50,51). Remotely sensed data provides a direct measure of photosynthetic activity over large spatial regions, offering advantages over the classically-used point sampled rainfall data in areas, like the study region, where weather stations are sparse (39).…”

Section: Methodsmentioning

confidence: 99%

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

Cerling¹,

Wittemyer

Ehleringer³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

113

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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...

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“…Although, there has been a number of studies on migration and desertifi cation in SubSaharan Africa related to global warming (Thornton et al, 2006;Brooks, 2004;Gado, 1998;Chouiki, 1997;Traoré, 1997;Diop-Maes, 1997;Oucho, 1995;Diallo, O., A. Diouf et al, 1991;Justice et al, 1991;Tucker, 1991;Ayiemba, 1990;Diallo, 1981) as well as unexpected snow in Johannesburg (South Africa) and an unusual fl ooding during an extended raining season in forefront Sub-Saharan countries in 2007, it emerges from this literature review that no quantitative study has been done to determine whether global warming increases ruralurban migration and net emigration in forefront Sub-Saharan countries. This paper attempts to fi ll this gap in the literature.…”

Section: Atmospheric Concentration Of Carbon Dioxidementioning

confidence: 99%

Impact of Global Warming on Rural-Urban Migration and Net Emigration in Forefront Sub-Saharan Countries

Bouare

2009

SSRN Journal

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Global warming has recently raised a lot of concerns about the future of our planet in terms of inhabitability. These concerns focus particularly on the possible increase in the migration toward more hospitable urban areas within a country or toward more hospitable countries. However, to our knowledge, there is no quantitative study to assess the impact of global warming on migration in Sub-Saharan Africa. Therefore, this paper attempts to determine whether global warming increases rural-urban migration and net emigration (i.e. emigration of nationals out of a country minus immigration of foreigners into the country) over the period 2000-2005 in six forefront Sub-Saharan countries, namely Burkina Faso, Chad, Mali, Mauritania, Niger and Senegal. We found that global warming alone is insignifi cantly related to rural-urban migration and net emigration. However, when associated with other independent variables or cofactors such as population growth rate and gross domestic product growth rate, global warming increases both rural-urban migration and net emigration.

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AVHRR monitoring of savanna primary production in Senegal, West Africa: 1987-1988

Cited by 129 publications

References 17 publications

Stable isotopes in elephant hair document migration patterns and diet changes

Stable isotopes in elephant hair document migration patterns and diet changes

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

Impact of Global Warming on Rural-Urban Migration and Net Emigration in Forefront Sub-Saharan Countries

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