Timothy G O'Brien

Timothy G O'Brien
Wildlife Conservation Society | WCS · Center for Global Conservation

PhD

About

158
Publications
120,046
Reads
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8,314
Citations
Additional affiliations
July 1990 - present
The Wildlife Society
Position
  • Senior Scientist and Biometrician

Publications

Publications (158)
Article
Full-text available
Climate change threatens to push species to higher elevations and eventual extinction. Birds, in particular, are shown to be shifting upslope in the Neo-tropics and Southeast Asia. Yet previous studies have lacked the temporal resolution to investigate distributional dynamics over time in relation to climatic fluctuations, especially in the underst...
Article
Forest fires can cause direct mortality to wildlife, and the associated habitat damage can reduce carrying capacity and population densities. However, little is known about long-term responses of animals to fire in the wet tropics. From 2000-2015, we examined siamang ranging patterns in habitat damaged by fire to assess the effects on these arborea...
Article
Full-text available
Activity range ‐ the amount of time spent active per day ‐ is a fundamental aspect contributing to the optimization process by which animals achieve energetic balance. Based on their size and the nature of their diet, theoretical expectations are that larger carnivores need more time active to fulfil their energetic needs than do smaller ones and a...
Article
Full-text available
The understanding of global diversity patterns has benefitted from a focus on functional traits and how they relate to variation in environmental conditions among assemblages. Distant communities in similar environments often share characteristics, and for tropical forest mammals, this functional trait convergence has been demonstrated at coarse sc...
Article
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Bushmeat hunting is widely cited as cause for declines of wildlife populations throughout Africa. Forest duikers (Bovidae, Cephalophinae) are among the most exploited species. Whether current harvest rates imperil duikers is debated because of the difficulty of accurately assessing population trends. To assess population trends, we first reviewed l...
Article
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In order to understand how the effects of land‐use change vary among taxa and environmental contexts, we investigate how three types of land‐use change have influenced phylogenetic diversity (PD) and species composition of three functionally distinct communities: plants, small mammals, and large mammals. We found large mammal communities were by fa...
Article
Identifying the underlying drivers of species’ distributional dynamics is critical for predicting change and managing biological diversity. While anthropogenic factors such as climate change can affect species distributions through time, other naturally occurring ecological processes can also have an influence. Theory predicts that interactions bet...
Article
Identifying optimal sampling designs for detecting population-level declines is critical for optimizing expenditures by research and monitoring programmes. The Tropical Ecology Assessment and Monitoring (TEAM) network is the most extensive tropical camera-trap monitoring programme, but the effectiveness of its sampling protocol has not been rigorou...
Article
Full-text available
When predators are removed or suppressed for generations, prey populations tend to increase and when predators are re-introduced, prey densities should fall back to pre-control levels. In cases of apparent competition where there are alternate abundant and rare prey species, rare species may decline further than expected or disappear altogether. Re...
Data
Hourly movement data. Hourly movement data for African lions, Grevy’s zebras and Plains zebras used in simulations of encounter rates. (XLSX)
Data
Comparison of ecological conditions. The compatibility of temporally disconnected movement data. (DOCX)
Data
Details of lion collar operation. Dates that collars were operational, number of sample days, hourly distance traveled (SD), and daily distance traveled (SD) for female lions, Plains zebra and Grevy's zebra. Lions with numbers were recaptured more than once and collar either changed or repaired during study. (DOCX)
Article
In species where females do not associate spatially with other females, males usually range over an area including the home ranges of multiple females or defend the home range of one female. Nevertheless, social polyandry (multimale–unifemale grouping) occurs in some species. We examine an ecological constraints model relating habitat quality to fa...
Article
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Dromedary camels (Camelus dromedarius) are an important protein source for people in semi-arid and arid regions of Africa. In Kenya, camel populations have grown dramatically in the past few decades resulting in the potential for increased disease transmission between humans and camels. An estimated 4 million Kenyans drink unpasteurised camel milk,...
Article
Full-text available
Camera traps that capture photos of animals are a valuable tool for monitoring biodiversity. The use of camera traps is rapidly increasing and there is an urgent need for standardization to facilitate data management, reporting and data sharing. Here we offer the Camera Trap Metadata Standard as an open data standard for storing and sharing camera t...
Article
Full-text available
INTRODUCTIONThe biodiversity-productivity relationship (BPR; the effect of biodiversity on ecosystem productivity) is foundational to our understanding of the global extinction crisis and its impacts on the functioning of natural ecosystems. The BPR has been a prominent research topic within ecology in recent decades, but it is only recently that w...
Article
Full-text available
Background Plasmodium knowlesi is a zoonotic pathogen, transmitted among macaques and to humans by anopheline mosquitoes. Information on P. knowlesi malaria is lacking in most regions so the first step to understand the geographical distribution of disease risk is to define the distributions of the reservoir and vector species. Methods We used mac...
Data
Additional file 7: Macaca fascicularis data. Each record of M. fascicularis occurrence is provided with a location and date. Duplicate records within a calendar year have been removed. Locations are classed as points (defined as <25 km2) or polygons (defined as >25 km2). (XLSX 322 kb)
Data
Additional file 10: Relative probability of Macaca fascicularis occurrence. A GeoTIFF raster data layer containing a predicted value (the mean model output) for every 5×5km pixel within SE Asia excluding islands outside the species range. This file can be opened in GIS software (e.g. QGIS, ArcMap, etc) or using the ‘raster’ R package. (TIF 4459 kb)
Data
Additional file 11: Relative probability of Macaca nemestrina occurrence. A GeoTIFF raster data layer containing a predicted value (the mean model output) for every 5×5km pixel within SE Asia excluding islands outside the species range. This file can be opened in GIS software (e.g. QGIS, ArcMap, etc) or using the ‘raster’ R package. (TIF 4090 kb)
Data
Additional file 16: Relative probability of a member of the Leucosphyrus Group occurring. A GeoTIFF raster data layer containing a predicted value (the mean model output) for every 5×5km pixel within SE Asia excluding islands outside the group range. This file can be opened in GIS software (e.g. QGIS, ArcMap, etc) or using the ‘raster’ R package. (...
Data
Full-text available
Additional file 1: Distributions of the model input data in space and time. The spatial distributions of the species occurrence data and background data are shown on a series of maps and their temporal distributions are shown by a series of histograms. (DOCX 1584 kb) Additional file 2: Environmental variables used in the species distribution model...
Data
Additional file 8: Macaca nemestrina data. Each record of M. nemestrina occurrence is provided with a location and date. Duplicate records within a calendar year have been removed. Locations are classed as points (defined as <25 km2) or polygons (defined as >25 km2). (XLSX 130 kb)
Data
Additional file 9: Macaca leonina data. Each record of M. leonina occurrence is provided with a location and date. Duplicate records within a calendar year have been removed. Locations are classed as points (defined as <25 km2) or polygons (defined as >25 km2). (XLSX 63 kb)
Data
Additional file 12: Relative probability of Macaca leonina occurrence. A GeoTIFF raster data layer containing a predicted value (the mean model output) for every 5×5km pixel within SE Asia excluding islands outside the species range. This file can be opened in GIS software (e.g. QGIS, ArcMap, etc) or using the ‘raster’ R package. (TIF 3459 kb)
Data
Additional file 13: Relative probability of Anopheles dirus occurrence. A GeoTIFF raster data layer containing a predicted value (the mean model output) for every 5×5km pixel within SE Asia excluding islands outside the species range. This file can be opened in GIS software (e.g. QGIS, ArcMap, etc) or using the ‘raster’ R package. (TIF 3461 kb)
Data
Additional file 14: Relative probability of a member of the Dirus Complex occurring. A GeoTIFF raster data layer containing a predicted value (the mean model output) for every 5×5km pixel within SE Asia excluding islands outside the complex range. This file can be opened in GIS software (e.g. QGIS, ArcMap, etc) or using the ‘raster’ R package. (TIF...
Data
Additional file 15: Relative probability of a member of the Leucosphyrus Complex occurring. A GeoTIFF raster data layer containing a predicted value (the mean model output) for every 5×5km pixel within SE Asia excluding islands outside the complex range. This file can be opened in GIS software (e.g. QGIS, ArcMap, etc) or using the ‘raster’ R packag...
Article
Full-text available
The conservation of tropical forest carbon stocks offers the opportunity to curb climate 43 change by reducing greenhouse gas emissions from deforestation and simultaneously conserve 44 biodiversity. However, there has been considerable debate about the extent to which carbon 45 storage will provide benefits to biodiversity in part because whether...
Article
Full-text available
Extinction rates in the Anthropocene are three orders of magnitude higher than background and disproportionately occur in the tropics, home of half the world’s species. Despite global efforts to combat tropical species extinctions, lack of high-quality, objective information on mammals and birds, representing 244 species from 15 tropical forest pro...
Data
Population occupancy status. By class (a), IUCN category (b), body mass (c), guild (d), landscape type (e), and hunting status (f). Bar height illustrates the relative frequencies of each occupancy status, and bar width illustrates the sample size. Asterisks indicate a significantly different occupancy status. See S2 Table for numerical data. (TIF)
Data
Occupancy status by TEAM site and guild. The proportion of populations with decreasing (orange), increasing (purple), unknown (gray), or stable (white) occupancy for each guild at each site; n = 511 populations. See S1 Table for site information corresponding to the three-letter site codes. Bar length illustrates the proportion of each occupancy st...
Data
Pairwise relationships between continuous site-level variables. Upper triangular portion of the matrix contains Pearson correlation coefficients, with the font size proportional to the correlation coefficient. Lower triangular portions of the matrix contain pairwise scatter plots to illustrate associations. “PAsize” is the log of the size of the pr...
Data
Summary information for TEAM sites. Including the full site name, site code, country, number of years of camera trap data, number of populations monitored by TEAM, percent of populations for each occupancy status, percent of monitored populations that were reported as hunted or not hunted, landscape connectivity, camera trap sampling area, protecte...
Data
Population occupancy status and monitoring duration. Frequency histogram of population trends based on the number of years of camera trap data (3–4 y [n = 8 sites, 270 populations], 5 y [n = 4 sites, 141 populations], or 6 y or more [n = 3 sites, 100 populations]). While the variance in occupancy trends decreased with additional years of data, the...
Data
Population occupancy over time. Each line depicts the trend of a particular species population monitored by TEAM. Color depicts significantly decreasing (orange), significantly increasing (purple), unknown (gray), or stable (black) occupancy trends. See S2 Table for numerical data. (TIF)
Data
Forest cover and landscape classification. (a) Green represents forest cover and brown represents non-forested cover for the ZOI of each protected area (Materials and Methods). Bold text is the code for each TEAM site. x- and y-axis labels are degrees latitude and longitude, respectively. (b) The UPGMA cluster analysis was based on two measures of...
Data
AIC comparison of univariate logistic regression models. For (a) the proportion of decreasing occupancy status populations per site and (b) the proportion of increasing occupancy status populations per site. For both decreasing and increasing occupancy status proportions, the null models with no covariates performed better (delta AIC > 2) than all...
Data
Monitored populations and associated attribute data. The following attributes are listed for each population: Class, Order, Family, Species, IUCN Red List Status (TH = Threatened, NT = Near Threatened, VU = Vulnerable, LC = Least Concern, DD = Data Deficient), Body Mass, Guild (Omnivore, Carnivore, Herbivore, Insectivore), Occupancy Coefficient Slo...
Article
Full-text available
Cannon et al. report an increase in tree diversity 8 years after selective logging in Borneo (1). These results accord with theoretical expectations (2) and with previous observations in Borneo and elsewhere (3); however, the significance of these findings is debatable.
Article
Reliable assessments of species' status are prerequisites for monitoring the success of conservation programmes. However, survey conditions such as terrain and inaccessibility, compounded by the low densities of many species across Southeast Asia and other parts of the world are considerable barriers to obtaining robust populations estimates. We us...
Article
Full-text available
The conservation of tropical forest carbon stocks offers the opportunity to curb climate change by reducing greenhouse gas emissions from deforestation and simultaneously conserve biodiversity. However, there has been considerable debate about the extent to which carbon storage will provide benefits to biodiversity in part because whether forests t...
Research
Full-text available
Examines long-term trends in livestock and wildlife numbers by land use across Laikipia County using bi-annual aerial survey data from 1981 to 2012.
Research
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report evaluates the effectiveness of aerial surveys in monitoring large African vertebrates at the landscape level.
Article
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Increasingly, the restoration of large carnivores is proposed as a means through which to restore community structure and ecosystem function via trophic cascades. After a decades-long absence, African wild dogs (Lycaon pictus) recolonized the Laikipia Plateau in central Kenya, which we hypothesized would trigger a trophic cascade via suppression of...
Article
Habitat loss and degradation, overexploitation, climate change and the spread of invasive species are drastically depleting the Earth's biological diversity, leading to detrimental impacts on ecosystem services and human well-being. Our ability to monitor the state of biodiversity and the impacts of global environmental change on this natural capi...
Article
We examined (1) the relationships between aboveground tropical forest C storage, biodiversity and environmental drivers and (2) how these relationships inform theory concerning ecosystem function and biodiversity. Experiments have shown that there is a positive relationship between biodiversity and ecosystem functioning, but intense debate exists o...
Article
Full-text available
Camera traps are used by scientists and natural resource managers to acquire ecological data, and the rapidly increasing camera trapping literature highlights how popular this technique has become. Nevertheless, the methodological information reported in camera trap publications can vary widely, making replication of the study difficult. Here we pr...
Article
Full-text available
Two hundred fourteen serosamples were collected from four livestock species across five ranches in Laikipia County, Kenya. Serological analysis for Coxiella burnetii (the causative agent for Q fever) showed a distinct seroprevalence gradient: the lowest in cattle, higher in sheep and goats, and the highest in camels. Laikipia-wide aerial counts sho...
Technical Report
Action oriented literature review of jaguar survey and monitoring techniques and methods with sections on survey designs and statistical analyses, field techniques, population genetics, jaguar capture and handling, ecological factors in human-jaguar conflicts and co-existence
Technical Report
Spanish version of team generated recommendations for survey and monitoring techniques for jaguars in the Mexico-United States Northwestern jaguar Recovery Unit (NRU). Includes descriptions of the NRU, discussions of presence-absence-occupancy, abundance and density, population genetics, demographic parameters, and spatial ecology, data capture and...
Technical Report
Team generated recommendations for survey and monitoring techniques for jaguars in the Mexico-United States Northwestern jaguar Recovery Unit (NRU), with descriptions of the NRU, discussions of presence-absence and occupancy, abundance and density, population genetics, demographic parameters and spatial ecology, data capture and curation in the NRU...