The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Terence J. Robinson - One of the best experts on this subject based on the ideXlab platform.
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Genetic divergence in south african Wildebeest: Analysis of Allozyme variabilty
The Journal of heredity, 1994Co-Authors: S. W. Corbet, W. S. Grant, Terence J. RobinsonAbstract:Genetic variability within the blue (Connochaetes taurinus) and black (C. gnou) Wildebeests in South Africa was estimated from allozyme frequencies at 31 protein-encoding loci. Seven loci, Ak-1, Alb, Est-D, Icdh-1, Mpi-1, Pgm-1, and Tf, were polymorphic in the blue Wildebeest, but only two loci, Est-D and Tf, were variable in its congener. Average gene diversity was H = 0.018 +/- 0.013 in the black Wildebeest and was significantly smaller than that, H = 0.081 +/- 0.030, in the blue Wildebeest. The reduced level of heterozygosity in black Wildebeest is most likely due to a bottleneck in population size in the early 1900s. The genetic distance between the two species was 0.059 +/- 0.027, which is consistent with an estimate of low mtDNA sequence divergence found previously.
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Genetic Divergence in South African Wildebeest: Comparative Cytogenetics and Analysis of Mitochodrial DNA
The Journal of heredity, 1991Co-Authors: S. W. Corbet, Terence J. RobinsonAbstract:The blue and the black Wildebeest, Connochaetes taurinus and C. gnou, are currently classified as congeneric, but previous reports have placed C. taurinus in its own genus, Gorgon. To further clarify the evolutionary relationship between these two species, we examined and compared their mitotic chromosomes and mitochondrial DNA (mtDNA). No species-specific G-banded or C-banded chromosomal markers were found, and we conclude that the karyotypes are invariant at the level of resolution obtained. An evolutionary divergence time of approximately 1 million years was calculated from mtDNA restriction fragment data, indicating a close phylogenetic relationship for the two Wildebeest species. The low nucleotide diversity detected within the black Wildebeest (0.09%) is thought to reflect the recent population bottleneck to which the species has been subjected. In contrast, the limited heterogeneity (0.02%) within the South African blue Wildebeest herds sampled in this study was surprising, and we argue that for many populations, especially those on smaller reserves, this may reflect common descent from a small number of animals through management-controlled translocations.
Jared A. Stabach - One of the best experts on this subject based on the ideXlab platform.
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Wildebeest migration in East Africa: Status, threats and conservation measures
2019Co-Authors: F.u. Msoffe, Joseph O. Ogutu, Mohammed Yahya Said, S.c. Kifugo, De Leeuw J, Van Gardingen P, Robin S. Reid, Jared A. Stabach, Randall B. BooneAbstract:Abstract Migration of ungulates is under pressure worldwide from range contraction, habitat loss and degradation, anthropogenic barriers and poaching. Here, we synthesize and compare the extent of historical migrations of the white-bearded Wildebeest (Connochaetes taurinus) to their contemporary status, in five premier East African ecosystems, namely the Serengeti-Mara, Masai Mara, Athi-Kaputiei, Amboseli and Tarangire-Manyara. The current status, threats to migration, migratory ranges and routes for Wildebeest were characterized using colonial-era maps, literature reviews, GIS and aerial survey databases, GPS collared animals and interviews with long-term researchers. Interference with Wildebeest migratory routes and dispersal ranges has stopped or severely threatens continuation of the historical migration patterns in all but the Serengeti-Mara ecosystem where the threat level is relatively lower. Wildebeest migration has collapsed in Athi-Kaputiei ecosystem and is facing enormous pressures from land subdivision, settlements and fences in Amboseli and Mara ecosystems and from cultivation in Tarangire-Manyara ecosystem. Land use change, primarily expansion in agriculture, roads, settlements and fencing, increasingly restrict migratory Wildebeest from accessing traditional grazing resources in unprotected lands. Privatization of land tenure in group ranches in Kenya and settlement policy (villagization) in Tanzania have accelerated land subdivision, fencing and growth in permanent settlements, leading to loss of key Wildebeest habitats including their migratory routes and wet season calving and feeding grounds. These processes, coupled with increasing human population pressures and climatic variability, are exerting tremendous pressures on Wildebeest migrations. Urgent conservation interventions are necessary to conserve and protect the critical Wildebeest habitats and migration routes in East Africa.
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Variation in habitat selection by white-bearded Wildebeest across different degrees of human disturbance
Ecosphere, 2016Co-Authors: Jared A. Stabach, Robin S. Reid, Randall B. Boone, G. Wittemyer, Jeffrey S. WordenAbstract:Resident white-bearded Wildebeest (Connochaetes taurinus) have experienced widespread population declines across much of their range over the past few decades, the drivers of which are attributed to landscape changes. Despite the ecological significance of this decline, surprisingly little is known about the resource needs and habitat use of these animals. Using global positioning system data collected from 2010 to 2013, we assessed resource selection of Wildebeest inhabiting three study areas in Kenya with varying degrees of natural and anthropogenic disturbance to identify potential behavioral mechanisms underlying potential landscape-driven declines. Wildebeest were observed to consistently avoid anthropogenic features and dense woody cover, irrespective of season, suggestive of avoidance of landscape features that would likely be associated with increased predation risk. Wildebeest also avoided primary roads, particularly across the Athi-Kaputiei Plains where human density and landscape alteration was greatest. The strongest response to normalized difference vegetation index was observed across the Amboseli Basin, the least productive and anthropogenically altered of our three study areas, leading to pronounced seasonal shifts in space use. Selection of natural and anthropogenic features was similar across the Mara and Athi-Kaputiei Plains, with the exception of the response to roads which likely relates to differences in road use. We also observed strong shifts in space use between day and night periods, particularly in relation to anthropogenic features and likely related to human circadian activity patterns. The observed variability in selection provides detailed information to how Wildebeest react to local environmental factors across landscapes, and provides insight to how landscape fragmentation amplifies habitat loss for Wildebeest by driving spatial avoidance, a likely mechanism contributing to population declines in this species. The quantified responses of Wildebeest to landscape features can aid future conservation management efforts and planning to sustain imperiled Wildebeest populations.
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habitat disturbance effects on the physiological stress response in resident kenyan white bearded Wildebeest connochaetes taurinus
Biological Conservation, 2015Co-Authors: Jared A. Stabach, Randall B. Boone, Jeffrey S. Worden, G FlorantAbstract:Abstract Regarded as a keystone species, white-bearded Wildebeest (Connochaetes taurinus) are found across the grassland savannahs of eastern Africa. Over the past 40 years, however, many local populations have become threatened with extinction. This is the first study connecting fecal glucocorticoid metabolites (i.e., stress hormones) in Wildebeest with landscape variables of natural and anthropogenic disturbance. Using a validated technique, fecal samples (n = 168) were collected from Wildebeest over a 3-month study period and across three different study areas in Kenya with varying degrees of disturbance. The stress of sampled populations was similar between study areas, with a seasonal decline in stress hormones found between dry and wet season data collection periods. We used an information-theoretic approach to rank models of fecal glucocorticoid metabolites. Our highest ranking model included an interaction between locally collected plant biomass and disturbance, the number of calves in a group, and ΔNDVI (change in Normalized Difference Vegetation Index). A strong positive effect related to biomass and disturbance suggested that tall/standing biomass and high levels of disturbance contribute to elevated levels of stress in Wildebeest. A strong negative effect related to ΔNDVI was also observed, suggestive that new growth lowers average stress levels. Our research suggests that increased levels of habitat disturbance may have an adverse effect on Wildebeest populations across the region when habitat conditions deteriorate. Wildebeest likely avoid areas of high anthropogenic disturbance which may indirectly lead to lowered fitness.
Jeffrey S. Worden - One of the best experts on this subject based on the ideXlab platform.
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Variation in habitat selection by white-bearded Wildebeest across different degrees of human disturbance
Ecosphere, 2016Co-Authors: Jared A. Stabach, Robin S. Reid, Randall B. Boone, G. Wittemyer, Jeffrey S. WordenAbstract:Resident white-bearded Wildebeest (Connochaetes taurinus) have experienced widespread population declines across much of their range over the past few decades, the drivers of which are attributed to landscape changes. Despite the ecological significance of this decline, surprisingly little is known about the resource needs and habitat use of these animals. Using global positioning system data collected from 2010 to 2013, we assessed resource selection of Wildebeest inhabiting three study areas in Kenya with varying degrees of natural and anthropogenic disturbance to identify potential behavioral mechanisms underlying potential landscape-driven declines. Wildebeest were observed to consistently avoid anthropogenic features and dense woody cover, irrespective of season, suggestive of avoidance of landscape features that would likely be associated with increased predation risk. Wildebeest also avoided primary roads, particularly across the Athi-Kaputiei Plains where human density and landscape alteration was greatest. The strongest response to normalized difference vegetation index was observed across the Amboseli Basin, the least productive and anthropogenically altered of our three study areas, leading to pronounced seasonal shifts in space use. Selection of natural and anthropogenic features was similar across the Mara and Athi-Kaputiei Plains, with the exception of the response to roads which likely relates to differences in road use. We also observed strong shifts in space use between day and night periods, particularly in relation to anthropogenic features and likely related to human circadian activity patterns. The observed variability in selection provides detailed information to how Wildebeest react to local environmental factors across landscapes, and provides insight to how landscape fragmentation amplifies habitat loss for Wildebeest by driving spatial avoidance, a likely mechanism contributing to population declines in this species. The quantified responses of Wildebeest to landscape features can aid future conservation management efforts and planning to sustain imperiled Wildebeest populations.
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habitat disturbance effects on the physiological stress response in resident kenyan white bearded Wildebeest connochaetes taurinus
Biological Conservation, 2015Co-Authors: Jared A. Stabach, Randall B. Boone, Jeffrey S. Worden, G FlorantAbstract:Abstract Regarded as a keystone species, white-bearded Wildebeest (Connochaetes taurinus) are found across the grassland savannahs of eastern Africa. Over the past 40 years, however, many local populations have become threatened with extinction. This is the first study connecting fecal glucocorticoid metabolites (i.e., stress hormones) in Wildebeest with landscape variables of natural and anthropogenic disturbance. Using a validated technique, fecal samples (n = 168) were collected from Wildebeest over a 3-month study period and across three different study areas in Kenya with varying degrees of disturbance. The stress of sampled populations was similar between study areas, with a seasonal decline in stress hormones found between dry and wet season data collection periods. We used an information-theoretic approach to rank models of fecal glucocorticoid metabolites. Our highest ranking model included an interaction between locally collected plant biomass and disturbance, the number of calves in a group, and ΔNDVI (change in Normalized Difference Vegetation Index). A strong positive effect related to biomass and disturbance suggested that tall/standing biomass and high levels of disturbance contribute to elevated levels of stress in Wildebeest. A strong negative effect related to ΔNDVI was also observed, suggestive that new growth lowers average stress levels. Our research suggests that increased levels of habitat disturbance may have an adverse effect on Wildebeest populations across the region when habitat conditions deteriorate. Wildebeest likely avoid areas of high anthropogenic disturbance which may indirectly lead to lowered fitness.
Randall B. Boone - One of the best experts on this subject based on the ideXlab platform.
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Wildebeest migration in East Africa: Status, threats and conservation measures
2019Co-Authors: F.u. Msoffe, Joseph O. Ogutu, Mohammed Yahya Said, S.c. Kifugo, De Leeuw J, Van Gardingen P, Robin S. Reid, Jared A. Stabach, Randall B. BooneAbstract:Abstract Migration of ungulates is under pressure worldwide from range contraction, habitat loss and degradation, anthropogenic barriers and poaching. Here, we synthesize and compare the extent of historical migrations of the white-bearded Wildebeest (Connochaetes taurinus) to their contemporary status, in five premier East African ecosystems, namely the Serengeti-Mara, Masai Mara, Athi-Kaputiei, Amboseli and Tarangire-Manyara. The current status, threats to migration, migratory ranges and routes for Wildebeest were characterized using colonial-era maps, literature reviews, GIS and aerial survey databases, GPS collared animals and interviews with long-term researchers. Interference with Wildebeest migratory routes and dispersal ranges has stopped or severely threatens continuation of the historical migration patterns in all but the Serengeti-Mara ecosystem where the threat level is relatively lower. Wildebeest migration has collapsed in Athi-Kaputiei ecosystem and is facing enormous pressures from land subdivision, settlements and fences in Amboseli and Mara ecosystems and from cultivation in Tarangire-Manyara ecosystem. Land use change, primarily expansion in agriculture, roads, settlements and fencing, increasingly restrict migratory Wildebeest from accessing traditional grazing resources in unprotected lands. Privatization of land tenure in group ranches in Kenya and settlement policy (villagization) in Tanzania have accelerated land subdivision, fencing and growth in permanent settlements, leading to loss of key Wildebeest habitats including their migratory routes and wet season calving and feeding grounds. These processes, coupled with increasing human population pressures and climatic variability, are exerting tremendous pressures on Wildebeest migrations. Urgent conservation interventions are necessary to conserve and protect the critical Wildebeest habitats and migration routes in East Africa.
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Variation in habitat selection by white-bearded Wildebeest across different degrees of human disturbance
Ecosphere, 2016Co-Authors: Jared A. Stabach, Robin S. Reid, Randall B. Boone, G. Wittemyer, Jeffrey S. WordenAbstract:Resident white-bearded Wildebeest (Connochaetes taurinus) have experienced widespread population declines across much of their range over the past few decades, the drivers of which are attributed to landscape changes. Despite the ecological significance of this decline, surprisingly little is known about the resource needs and habitat use of these animals. Using global positioning system data collected from 2010 to 2013, we assessed resource selection of Wildebeest inhabiting three study areas in Kenya with varying degrees of natural and anthropogenic disturbance to identify potential behavioral mechanisms underlying potential landscape-driven declines. Wildebeest were observed to consistently avoid anthropogenic features and dense woody cover, irrespective of season, suggestive of avoidance of landscape features that would likely be associated with increased predation risk. Wildebeest also avoided primary roads, particularly across the Athi-Kaputiei Plains where human density and landscape alteration was greatest. The strongest response to normalized difference vegetation index was observed across the Amboseli Basin, the least productive and anthropogenically altered of our three study areas, leading to pronounced seasonal shifts in space use. Selection of natural and anthropogenic features was similar across the Mara and Athi-Kaputiei Plains, with the exception of the response to roads which likely relates to differences in road use. We also observed strong shifts in space use between day and night periods, particularly in relation to anthropogenic features and likely related to human circadian activity patterns. The observed variability in selection provides detailed information to how Wildebeest react to local environmental factors across landscapes, and provides insight to how landscape fragmentation amplifies habitat loss for Wildebeest by driving spatial avoidance, a likely mechanism contributing to population declines in this species. The quantified responses of Wildebeest to landscape features can aid future conservation management efforts and planning to sustain imperiled Wildebeest populations.
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habitat disturbance effects on the physiological stress response in resident kenyan white bearded Wildebeest connochaetes taurinus
Biological Conservation, 2015Co-Authors: Jared A. Stabach, Randall B. Boone, Jeffrey S. Worden, G FlorantAbstract:Abstract Regarded as a keystone species, white-bearded Wildebeest (Connochaetes taurinus) are found across the grassland savannahs of eastern Africa. Over the past 40 years, however, many local populations have become threatened with extinction. This is the first study connecting fecal glucocorticoid metabolites (i.e., stress hormones) in Wildebeest with landscape variables of natural and anthropogenic disturbance. Using a validated technique, fecal samples (n = 168) were collected from Wildebeest over a 3-month study period and across three different study areas in Kenya with varying degrees of disturbance. The stress of sampled populations was similar between study areas, with a seasonal decline in stress hormones found between dry and wet season data collection periods. We used an information-theoretic approach to rank models of fecal glucocorticoid metabolites. Our highest ranking model included an interaction between locally collected plant biomass and disturbance, the number of calves in a group, and ΔNDVI (change in Normalized Difference Vegetation Index). A strong positive effect related to biomass and disturbance suggested that tall/standing biomass and high levels of disturbance contribute to elevated levels of stress in Wildebeest. A strong negative effect related to ΔNDVI was also observed, suggestive that new growth lowers average stress levels. Our research suggests that increased levels of habitat disturbance may have an adverse effect on Wildebeest populations across the region when habitat conditions deteriorate. Wildebeest likely avoid areas of high anthropogenic disturbance which may indirectly lead to lowered fitness.
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SERENGETI Wildebeest MIGRATORY PATTERNS MODELED FROM RAINFALL AND NEW VEGETATION GROWTH
Ecology, 2006Co-Authors: Randall B. Boone, Simon Thirgood, J. Grant C. HopcraftAbstract:We used evolutionary programming to model innate migratory pathways of Wildebeest in the Serengeti Mara Ecosystem, Tanzania and Kenya. Wildebeest annually move from the southern short-grass plains of the Serengeti to the northern woodlands of the Mara. We used satellite images to create 12 average monthly and 180 10-day surfaces from 1998 to 2003 of percentage rainfall and new vegetation. The surfaces were combined in five additive and three multiplicative models, with the weightings on rainfall and new vegetation from 0% to 100%. Modeled Wildebeest were first assigned random migration pathways. In simulated generations, animals best able to access rainfall and vegetation were retained, and they produced offspring with similar migratory pathways. Modeling proceeded until the best pathway was stable. In a learning phase, modeling continued with the ten-day images in the objective function. The additive model, influenced 25% by rainfall and 75% by vegetation growth, yielded the best agreement, with a multi-resolution comparison to observed densities yielding 76.8% of blocks in agreement (kappa = 0.32). Agreement was best for dry season and early wet season (kappa = 0.22–0.57), and poorest for the late wet season (0.04). The model suggests that new forage growth is a dominant correlate of Wildebeest migration.
F. H. Bank - One of the best experts on this subject based on the ideXlab platform.
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allozyme divergence among four representatives of the subfamily alcelaphinae family bovidae
Comparative Biochemistry and Physiology B, 1995Co-Authors: J. Paul Grobler, F. H. BankAbstract:Abstract We used protein gel electrophoresis to study genetic diversity within and between blue Wildebeest ( Connochaetes taurinus ), black Wildebeest ( C. gnou ), red hartebeest ( Alcelaphus buselaphus caama ) and blesbok ( Damaliscus dorcas phillipsi ). Twenty-nine protein encoding loci were resolved, average heterozygosity ranged from 3.25-5.36% and between population gene diversity accounted for the major share of the total relative gene diversity (69.34%). Genetic distance values ranged from 0.021 to 0.132 and 0.029 to 0.136, with closest identity between the two Wildebeest species (as expected for congeneric species). The results are discussed with specific reference to taxonomic relationships between species within the subfamily where interbreeding is known to have occurred.
