Jason P. Marshal

Jason P. Marshal
University of the Witwatersrand | wits · School of Animal, Plant and Environmental Sciences

PhD

About

48
Publications
9,018
Reads
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719
Citations
Additional affiliations
May 2013 - present
University of the Witwatersrand
Position
  • Associate Professor of Ecology
August 1999 - September 2005
The University of Arizona
Position
  • Graduate Research Associate

Publications

Publications (48)
Article
Predator avoidance strategies vary across the ungulate guild. Population-level responses to the presence of large predators to a large extent depend on how well ecological conditions suit the particular predator avoidance strategies of a species. Predation risk from ambush predators, e.g. lions negatively correlates with distance from surface water...
Article
Geographic gradients in plant productivity can present foraging large herbivores with varying resource levels across the range of a population, to which individuals can demonstrate varying intensity of selection. To investigate individually-specific responses of nyala antelopes (Tragelaphus angasii) to vegetation greenness, we monitored the landsca...
Article
Transformed landscapes caused by human activity leave remnant patches of natural habitat for wildlife. The persistence of species in the face of such transformation depends on individuals’ ability to adapt to novel habitat, and to secure resources and reproductive opportunities despite habitat alterations. The leopard, Panthera pardus, is the last...
Article
Transformed landscapes caused by human activity leave remnant patches of natural habitat for wildlife. The persistence of species in the face of such transformation depends on individuals’ ability to adapt to novel habitat, and to secure resources and reproductive opportunities despite habitat alterations. The leopard, Panthera pardus, is the last...
Article
Characterising species-landscape associations is relevant for conservation planning and management in response to environmental transformation. The occurrence of reptiles is linked to landscape structure that allows for thermoregulation, shelter and feeding, but the relative importance of these factors is unknown for many tropical and subtropical s...
Article
en Habitat loss is one of largest threats to the persistence of large carnivore populations. However, because most large carnivores are long‐lived, cryptic and wide‐ranging, few studies examine the demographic consequences of habitat loss, and the resultant crowding that ensues, on these species. We used long‐term data to examine the demographic re...
Article
Full-text available
The coexistence of a large herbivore community depends on the degree of overlap in the resource used by the different species composing it. We investigated the role of grass greenness, height, biomass and feeding patch status on feeding patch selection by ruminant black and blue wildebeest (Connochaetes gnou, Connochaetes taurinus), red hartebeest...
Article
Across southern Africa, many populations of the highly-mobile common eland (Tragelaphus oryx) are limited to small, fenced protected areas. We studied such a population at Kgaswane Mountain Reserve (KMR), South Africa, using radio-collared animals to better understand eland range use in a landscape with restricted movement. Placement of home ranges...
Article
Full-text available
In fenced protected areas with limited opportunities to disperse, resources and constraints vary in space and time, affecting herbivore behaviour. The distribution, availability and quality of resources, burnt areas, and potential inter-specific competition all play a role in sustaining populations of large sympatric African herbivores. We investig...
Article
Full-text available
Inaccurate estimates of animal populations may lead to flawed management interventions, therefore, it is essential to understand the status and population trend of a species in order to plan its management efficiently. Aerial surveys are considered a useful method for estimating the population size of large conspicuous animals inhabiting large area...
Article
Full-text available
Long-term growth rates of ungulate populations can be affected where disproportionate mortality occurs to adult females through predation. To investigate differences between lions (Panthera leo) and wild dogs (Lycaon pictus) in relative selection for female prey, we analysed ranger records for impala (Aepyceros melampus) and kudu (Strepsiceros zamb...
Article
en Large‐scale environmental changes create challenges for conservation of wildlife, particularly in fenced, insular protected areas where many wildlife populations persist. Moreover, large mammalian herbivores inhabiting spatially and temporally heterogeneous environments face the challenge of securing highly variable forage resources. Mixed feede...
Article
Carnivores that exhibit fission–fusion social organization can adapt group sizes to prevailing social and ecological conditions. This study focuses on social organization of African lions (Panthera leo) in the Okavango Delta, a seasonally flooded wetland. We used generalized estimating equations and generalized linear mixed models to estimate the e...
Article
Nutritional ecology forms the interface between environmental variability and large herbivore behaviour, life history characteristics, and population dynamics. Forage conditions in arid and semi-arid regions are driven by unpredictable spatial and temporal patterns in rainfall. Diet selection by herbivores should be directed towards overcoming the...
Article
Full-text available
Similar to declines in antelope species across African conservation areas, sable (Hippotragus niger) at Kgaswane Mountain Reserve, South Africa, has exhibited a negative trend in abundance since 2000. To investigate the cause of decline, we assessed three hypotheses: seasonal forage abundance, habitat conditions and interspecific competition. We co...
Article
Adult survival is a primary determinant of abundance and dynamics of large herbivore populations. For species that are inconspicuous, however, accurate survival estimation depends on accommodating low detection probability. For species with individually recognizable markings, photographic capture-recapture (CR) provides an approach to estimate popu...
Article
Full-text available
While African leopard populations are considered to be continuous as demonstrated by their high genetic variation, the southernmost leopard population exists in the Eastern and Western Cape, South Africa, where anthropogenic activities may be affecting this population's structure. Little is known about the elusive, last free-roaming top predator in...
Article
Full-text available
Continued persistence of black rhinoceros (Diceros bicornis) will likely depend on the cooperation of many reserves and the application of metapopulation models to manage across reserves. The suitability of any reserve, however, depends on factors that promote and constrain occupancy. Constraining factors, particularly human disturbance, are of con...
Article
Full-text available
There has recently been a spate of manuscripts submitted to South African Journal of Wildlife Research that have lacked animal ethics approvals. Clearly this is a serious concern - not only from the chance that unethical research practices have occurred but also that there are no checks and balances to ensure this is the case. In several of those c...
Article
Full-text available
The physiological condition of animals connects resources in the environment to demographic responses through reproduction, survival and abundance,and it provides critical information for conservation and management of wildlife populations.We used archived data (early-wet season 1987, late-wet and early-dry season 1988) from culls of impala (Aepyce...
Article
The factors that affect resource selection by a foraging herbivore can vary according to the resources or conditions associated with particular levels of organization in the environment, and to the scales over which the herbivore perceives and responds to those resources and conditions. To investigate the role of forage in this hierarchical process...
Article
Full-text available
We studied use of habitats and diets of mule deer (Odocoileus hemionus) and feral asses (Equus asinus) by comparing vegetation (i.e., normalized-difference-vegetation index, normalized-difference-vegetation-index rate), elevation, slope, and distances to water-catchments, roads, rivers and canals, and washes used by each species. Distribution was s...
Conference Paper
Full-text available
Background/Question/Methods Herbivores can be divided into three general groups: grazers, browsers and mixed feeders. Mixed feeders switch between grazing and browsing throughout the year, mostly due to changes in environmental conditions. Most studies investigating resource partitioning and the browser/grazer continuum in mammalian herbivores ha...
Article
Full-text available
Foraging behaviour and habitat selection occur as hierarchical processes. Understanding the factors that govern foraging and habitat selection thus requires investigation of those processes over the scales at which they occur. We investigated patterns of habitat use by African elephants (Loxodonta africana) in relation to vegetation greenness to in...
Article
Our understanding of large-scale climatic phenomena and dynamics of large herbivore populations comes principally from research in northern regions with temperate, seasonal climate and animal communities with relatively low species diversity. To assess the generality of that perspective, we investigated effects of El Niño–Southern Oscillation (ENSO...
Article
Full-text available
A growing body of research has demonstrated relationships between population dynamics of large herbivores and large-scale climatic phenomena. We investigated gradients in the effects of one such phenomenon, El Niño Southern Oscillation (ENSO), to look for evidence of its influence on mule deer (Odocoileus hemionus) harvest. Based on the Southern Os...
Article
Full-text available
Provision of surface water has been a long-standing management strategy to enhance habitat for large mammals in southwestern North America. In this paper, we use a resource selection function (RSF) developed from telemetered mountain sheep (Ovis canadensis) in three occupied mountain ranges in the Sonoran Desert, California, USA, to examine the eff...
Chapter
Red deer on RumSoay sheep on HirtaRoe deer in FranceBighorn sheep in AlbertaKudu in KrugerWildebeest in SerengetiMoose on Isle RoyaleElk in North YellowstoneOverviewAcknowledgmentsReferences
Article
We evaluated the relative importance of intrinsic (density-dependent) and extrinsic (density-independent) sources of resource variability in the dynamics of bighorn sheep (Ovis canadensis Shaw, 1804) populations in southwestern USA. We tested the hypothesis that populations experiencing greater variation in forage availability are less likely to be...
Article
Full-text available
Utilizamos el análisis microhistológico de fecas para identificar especies de plantas en la dieta de los venados buras del desierto (Odocoileus hemionus eremicus) en el sureste de California, y para investigar cambios estacionales en el uso de las clases de forraje. Identificamos 34 taxa de plantas, 7 de las cuales no se han registrado previamente...
Article
Full-text available
We studied habitat use by desert mule deer (Odocoileus hemionus eremicus) in the Sonoran Desert to understand the relative importance of vegetation, terrain characteristics, human disturbances, and water sources in determining their distribution. We located 44 radiocollared female mule deer weekly over 5 years. In spring, when water was most scarce...
Article
Full-text available
We investigated associations between rainfall and body condition of desert mule deer (Odocoileus hemionus eremicus) in the Sonoran Desert, California, using two indices of condition based on body fat: a categorical score based on subcutaneous fat and visibility of bones under the skin of free-ranging animals via remote photography, and percent fat...
Article
Full-text available
We studied mountain sheep in the vicinity of three high-wall limestone mines in San Bernardino County, CA, USA to evaluate factors that influenced habitat use and, specifically, to investigate the influence of mining activity on distribution of those specialized ungulates. We used aerial telemetry data to estimate a resource selection function by f...
Article
Full-text available
2008: Evidence for inter-specific competition between feral ass Equus asinus and mountain sheep Ovis canadensis in a desert environment. -Wildl. Biol. 14: 228-236. Different ungulate species that co-occur over evolutionary time have been hypothesized to develop mechanisms to limit the degree to which they directly compete for the same limited resou...
Article
The addition of wildlife water developments (i.e., catchments) to arid areas may concentrate foraging by desert ungulates and decrease forage availability near catchments. We looked for gradients in forage biomass and use by mule deer (Odocoileus hemionus) and bighorn sheep (Ovis canadensis) along dry riparian streams near catchments. We measured f...
Article
Full-text available
We studied habitat use by desert mule deer (Odocoileus hemionus eremicus) in the Sonoran Desert to understand the relative importance of vegetation, terrain characteristics, human disturbances, and water sources in determining their distribution. We located 44 radiocollared female mule deer weekly over 5 years. In spring, when water was most scarce...
Article
Full-text available
The addition of wildlife water developments (i.e., catchments) to arid areas may concentrate foraging by desert ungulates and decrease forage availability near catchments. We looked for gradients in forage biomass and use by mule deer (Odocoileus hemionus) and bighorn sheep (Ovis canadensis) along dry riparian streams near catchments. We measured f...
Article
Full-text available
Desert mule deer, Odocoileus hemionus eremicus, occur at low densities in the Sonoran Desert of southeastern California and consequently are difficult to monitor using standard wildlife techniques. We used radiocollared deer, remote photography at wildlife water developments (i.e., catchments), and mark-recapture techniques to estimate population a...
Article
Full-text available
Forage quality affects physiological condition, population dynamics, habitat use, and distribution of ungulates. We studied how rainfall, temperature, forage biomass, and forage growth are related to water content, crude protein (CP), and in vitro dry-matter digestibility (IVDMD) of some common forage species of desert mule deer (Odocoileus hemionu...
Article
Forage availability for mule deer (Odocoileus hemionus) in the Sonoran Desert depends on plant biomass, which is influenced by rainfall. We determined how rainfall, temperature and plant characteristics affected biomass of deer forage. We measured forage biomass, rainfall and temperature every 3 months from April 2000 to December 2002. Quarterly ra...
Article
The removal of an incisiform tooth to determine age in live cervids has generated disagreement among wildlife professionals, but few data are available to resolve whether or not study animals are affected by that technique. We found no effect of tooth removal on body mass, percent body fat, pregnancy rate, or fetal rate among mule deer (Odocoileus...
Article
We used long-term El Niño southern oscillation (ENSO), rainfall, and deer harvest records to investigate effects of ENSO and rainfall on mule deer (Odocoileus hemionus) population trends in the Sonoran Desert, south-eastern California, USA. We found significant relationships between the southern oscillation index and rainfall (R2 = 0.38, P ≤ 0.001)...
Article
Gray wolf (Canis lupus) predation is density dependent if the proportion of prey killed by wolves increases with prey density. The functional response is 1 component of wolf predation that has an important effect on whether density-dependent predation occurs, and consequently whether wolves have the potential to regulate prey to a low-density equil...
Article
Full-text available
Certain long-term studies on large herbivore populations have made espe- cially influential contributions to current understanding of population dynamics. They are outstanding either for the detailed understanding that they have provided based on individually recognizable animals, or for the windows opened into particular processes from the prolong...

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