Tobler M.W.,Institute for Conservation Research |
Powell G.V.N.,World Wildlife Fund
Biological Conservation | Year: 2013
Camera traps have become the main method for estimating jaguar (Panthera onca) densities. Over 74 studies have been carried out throughout the species range following standard design recommendations. We reviewed the study designs used by these studies and the results obtained. Using simulated data we evaluated the performance of different statistical methods for estimating density from camera trap data including the closed-population capture-recapture models Mo and Mh with a buffer of 1/2 and the full mean maximum distance moved (MMDM) and spatially explicit capture-recapture (SECR) models under different study designs and scenarios. We found that for the studies reviewed density estimates were negatively correlated with camera polygon size and MMDM estimates were positively correlated. The simulations showed that for camera polygons that were smaller than approximately one home range density estimates for all methods had a positive bias. For large polygons the Mh MMDM and SECR model produced the most accurate results and elongated polygons can improve estimates with the SECR model. When encounter rates and home range sizes varied by sex, estimates had a negative bias for models that did not include sex as a covariate. Based on the simulations we concluded that the majority of jaguar camera trap studies did not meet the requirements necessary to produce unbiased density estimates and likely overestimated true densities. We make clear recommendations for future study designs with respect to camera layout, number of cameras, study length, and camera placement. Our findings directly apply to camera trap studies of other large carnivores. © 2012 Elsevier Ltd.
Andersen K.M.,Smithsonian Tropical Research Institute |
Andersen K.M.,Institute for Conservation Research |
Turner B.L.,Smithsonian Tropical Research Institute
Journal of Ecology | Year: 2013
Soil nitrogen (N) occurs in a range of chemical forms from simple inorganic compounds, such as nitrate (NO3 -) and ammonium (NH4 +), to organic compounds, such as amino acids. Plants differ in their capacity to use these various forms, which might influence the distribution of species across environmental nutrient gradients. We tested the hypothesis that the distribution of understorey palm species along a soil N gradient in a tropical montane forest in Panama is related to preferences for different chemical forms of N. We conducted a field experiment using 15N-labelled ammonium, nitrate and glycine to examine whether tropical plants show preferences for, or are flexible in, their use of chemical forms of soil N. All species used N from inorganic and organic sources and showed no preference for chemical forms of N. However, across all species, the overall N acquisition pattern was glycine ≥ nitrate ≥ ammonium. Species from low-nutrient sites dominated by ammonium and organic N forms had inherently slow N uptake rates. Synthesis. Patterns in the distribution of understorey palms were related to nitrogen (N) uptake rates rather than preferences for N chemical forms. Down-regulation of N uptake rates may be an important adaptation for plant species associated with low-N soils, with plasticity in N acquisition patterns from various N sources important in alleviating competition for soil N. We found that patterns in the distribution of understorey palms were related to nitrogen (N) uptake rates rather than preferences for N chemical forms. Down-regulation of N uptake rates may be an important adaptation for plant species associated with low N soils, with plasticity in N acquisition patterns from various N sources important in alleviating competition for soil N. © 2013 The Authors. Journal of Ecology © 2013 British Ecological Society.
Pekin B.K.,Institute for Conservation Research
Conservation Biology | Year: 2013
Although agricultural intensification is thought to pose a significant threat to species, little is known about its role in driving biodiversity loss at regional scales. I assessed the effects of a major component of agricultural intensification, agricultural chemical use, and land-cover and climatic variables on butterfly diversity across 81 provinces in Turkey, where agriculture is practiced extensively but with varying degrees of intensity. I determined butterfly species presence in each province from data on known butterfly distributions and calculated agricultural chemical use as the proportion of agricultural households that use chemical fertilizers and pesticides. I used constrained correspondence analyses and regression-based multimodel inference to determine the effect of environmental variables on species composition and richness, respectively. The variation in butterfly species composition across the provinces was largely explained (78%) by the combination of agricultural chemical use, particularly pesticides, and climatic and land-cover variables. Although overall butterfly richness was primarily explained by climatic and land-cover variables, such as the area of natural vegetation cover, threatened butterfly richness and the relative number of threatened butterfly species decreased substantially as the proportion of agricultural households using pesticides increased. These findings suggest that widespread use of agricultural chemicals, or other components of agricultural intensification that may be collinear with pesticide use, pose an imminent threat to the biodiversity of Turkey. Accordingly, policies that mitigate agricultural intensification and promote low-input farming practices are crucial for protecting threatened species from extinction in rapidly industrializing nations such as Turkey. © 2013 Society for Conservation Biology.
Pekin B.K.,Institute for Conservation Research
Land Use Policy | Year: 2016
Natural vegetation enhances the value of agricultural landscapes for people and wildlife. However, the role of anthropogenic versus topographic factors in driving the extent of natural vegetation cover within agricultural lands at large spatial scales remains unexplored. I assessed the influence of anthropogenic and topographic variables on the extent of agricultural mosaics with high natural vegetation cover in the country of Turkey where a large extent of natural and semi-natural vegetation is maintained by traditional agriculture. GIS layers depicting human land use, elevation, slope, roads and population data were obtained and summarized at two spatial scales, within provinces and for 100 km2 grid cells covering the country's entire agricultural land area. Average farm size was also obtained at province level. Hierarchical Partitioning was conducted to determine the independent effect of anthropogenic and topographic variables on the variation in agriculture with high natural vegetation. Slope had the largest independent effect on the variation in the proportion of agricultural mosaic with high natural vegetation cover. The extent of agricultural and settlement area also explained much of the variation in natural vegetation across both grid cells and provinces. The proportion of natural vegetation increased as human population and road density decreased across grid cells and as average farm size decreased across provinces. These results suggest that while topography is the primary driver of natural vegetation cover within agricultural mosaics in Turkey, the pressures associated with urban development and agricultural industrialization may also influence the cultural and wildlife value of agricultural landscapes. © 2016 Elsevier Ltd.
Miller L.J.,Institute for Conservation Research
Zoo Biology | Year: 2012
Many publications within the field of zoo animal welfare have stated the importance of decreasing stereotypic behavior (e.g., pacing) to help ensure a positive visitor experience. The idea behind these statements is that visitors want to see animals engaged in natural behavior. Additionally, it is thought that watching an animal exhibit species-appropriate behavior could help increase a visitor's connection to wildlife and ultimately their interest in conservation. However, until recently, no information was available to validate such statements. The purpose of this research was to examine people's reaction to viewing an animal engaged in pacing behavior. Participants were randomly selected to fill out a survey after watching a short video of either a tiger pacing or resting (control). Results indicate that having viewed a tiger pacing significantly decreases people's perception of the level of care animals receive at that facility. In addition, people's interest in supporting zoos decreased as a result of viewing this behavior. Results are discussed from an animal welfare, business, and conservation perspective. © 2011 Wiley Periodicals, Inc.