Dataset Information

Spotting East African mammals in open savannah from space.

ABSTRACT: Knowledge of population dynamics is essential for managing and conserving wildlife. Traditional methods of counting wild animals such as aerial survey or ground counts not only disturb animals, but also can be labour intensive and costly. New, commercially available very high-resolution satellite images offer great potential for accurate estimates of animal abundance over large open areas. However, little research has been conducted in the area of satellite-aided wildlife census, although computer processing speeds and image analysis algorithms have vastly improved. This paper explores the possibility of detecting large animals in the open savannah of Maasai Mara National Reserve, Kenya from very high-resolution GeoEye-1 satellite images. A hybrid image classification method was employed for this specific purpose by incorporating the advantages of both pixel-based and object-based image classification approaches. This was performed in two steps: firstly, a pixel-based image classification method, i.e., artificial neural network was applied to classify potential targets with similar spectral reflectance at pixel level; and then an object-based image classification method was used to further differentiate animal targets from the surrounding landscapes through the applications of expert knowledge. As a result, the large animals in two pilot study areas were successfully detected with an average count error of 8.2%, omission error of 6.6% and commission error of 13.7%. The results of the study show for the first time that it is feasible to perform automated detection and counting of large wild animals in open savannahs from space, and therefore provide a complementary and alternative approach to the conventional wildlife survey techniques.

SUBMITTER: Yang Z

PROVIDER: S-EPMC4281221 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Spotting East African mammals in open savannah from space.

Yang Zheng Z Wang Tiejun T Skidmore Andrew K AK de Leeuw Jan J Said Mohammed Y MY Freer Jim J

PloS one 20141231 12

Knowledge of population dynamics is essential for managing and conserving wildlife. Traditional methods of counting wild animals such as aerial survey or ground counts not only disturb animals, but also can be labour intensive and costly. New, commercially available very high-resolution satellite images offer great potential for accurate estimates of animal abundance over large open areas. However, little research has been conducted in the area of satellite-aided wildlife census, although comput ...[more]

PMID: 25551561

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Project description:BACKGROUND: Annual Nothobranchius fishes are distributed in East and Southern Africa and inhabit ephemeral pools filled during the monsoon season. Nothobranchius show extreme life-history adaptations: embryos survive by entering diapause and they are the vertebrates with the fastest maturation and the shortest lifespan. The distribution of Nothobranchius overlaps with the East Africa Rift System. The geological and paleoclimatic history of this region is known in detail: in particular, aridification of East Africa and expansion of grassland habitats started 8 Mya and three humid periods between 3 and 1 Mya are superimposed on the longer-term aridification. These climatic oscillations are thought to have shaped evolution of savannah African mammals. We reconstructed the phylogeny of Nothobranchius and dated the different stages of diversification in relation to these paleoclimatic events. RESULTS: We sequenced one mitochondrial locus and five nuclear loci in 63 specimens and obtained a robust phylogeny. Nothobranchius can be divided in four geographically separated clades whose boundaries largely correspond to the East Africa Rift system. Statistical analysis of dispersal and vicariance identifies a Nilo-Sudan origin with southwards dispersion and confirmed that these four clades are the result of vicariance events In the absence of fossil Nothobranchius, molecular clock was calibrated using more distant outgroups (secondary calibration). This method estimates the age of the Nothobranchius genus to be 8.3 (6.0 - 10.7) My and the separation of the four clades 4.8 (2.7-7.0) Mya. Diversification within the clades was estimated to have started ~3 Mya and most species pairs were estimated to have an age of 0.5-1 My. CONCLUSIONS: The mechanism of Nothobranchius diversification was allopatric and driven by geographic isolation. We propose a scenario where diversification of Nothobranchius started in rough coincidence with aridification of East Africa, establishment of grassland habitats and the appearance of the typical African bovid fauna of the savannah. Although confidence intervals for the estimated ages of the four Nothobranchius clades are quite large, this scenario is compatible with the biology of extant Nothobranchius that are critically dependent on savannah habitats. Therefore, Nothobranchius diversification might have been shaped by the same paleoclimatic events that shaped African ungulate evolution.

Project description:BackgroundThis study focused on the savannah tsetse species Glossina swynnertoni and G. morsitans centralis, both efficient vectors of human and animal trypanosomiasis in, respectively, East and Central Africa. The aim was to develop long-lasting, practical and cost-effective visually attractive devices that induce the strongest landing responses in these two species for use as insecticide-impregnated tools in population suppression.Methods and findingsTrials were conducted in different seasons and years in Tanzania (G. swynnertoni) and in Angola and the Democratic Republic of the Congo (DRC, G. m. centralis) to measure the performance of traps (pyramidal and epsilon) and targets of different sizes, shapes and colours, with and without chemical baits, at different population densities and under different environmental conditions. Adhesive film was used to catch flies landing on devices at the remote locations to compare tsetse-landing efficiencies. Landing rates by G. m. centralis in both Angola and the DRC were highest on blue-black 1 m2 oblong and 0.5 m2 square and oblong targets but were not significantly different from landings on the pyramidal trap. Landings by G. swynnertoni on 0.5 m2 blue-black oblong targets were likewise not significantly lower than on equivalent 1 m2 square targets. The length of target horizontal edge was closely correlated with landing rate. Blue-black 0.5 m2 targets performed better than equivalents in all-blue for both G. swynnertoni and G. m. centralis, although not consistently. Baiting with chemicals increased the proportion of G. m. centralis entering pyramidal traps.ConclusionsThis study confirms earlier findings on G. swynnertoni that smaller visual targets, down to 0.5 m2, would be as efficient as using 1 m2 targets for population management of this species. This is also the case for G. m. centralis. An insecticide-impregnated pyramidal trap would also constitute an effective control device for G. m. centralis.

Project description:BackgroundIn this paper we review the conservation genetics of African savannah elephants, aiming to understand the spatio-temporal research trends and their underlying factors. As such, we explore three questions associated to the conservation genetics and molecular ecology of these elephants: (1) what are the research trends concerning the conservation genetics of Loxodonta africana? (2) Do richer countries conduct more research on the genetics of African elephants? (3) Which attributes influence where scholars conduct their research?Materials and methodsWe examined available peer-reviewed publications from 1993 to 2014 in complementary online databases, including the ISI/Web of Science (WoS), Scopus and Google Scholar (GS), and searched for publications in scientific journals as well as in the reference section of these publications. We analyzed the annual trend of publications in this field of research, including the number of authors, levels of collaboration among authors, year of publication, publishing journal and the countries from where genetic samples were collected. Additionally, we identified main research clusters, authors, and institutional collaborations, based on co-citation and co-occurrence networks.ResultsWe found that during the study period there was a positive trend in the number of publications and a reduction in the number of authors per paper. Twenty-five countries contributed, with the majority of publications authored by researchers in the USA, Kenya and South Africa. The majority of samples were collected in Kenya, Tanzania and South Africa. Research outputs are associated with the existence of long-term conservation/research projects and research potential as measured by the literacy rate and the number of higher education institutions in a country. Five research clusters were identified, focusing on the origin and evolution of the species, methodological issues and the relatedness among elephant species.ConclusionsResearch in this field should be expanded to additional countries harboring elephant populations to enable a more comprehensive understanding of the population structure and genetic differentiation of the species, and to cope with challenges associated with the conservation of the species such as illegal hunting, habitat fragmentation, species reintroduction and climate change.

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Spotting East African mammals in open savannah from space.

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Spotting East African mammals in open savannah from space.

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