Occupancy

About: Occupancy is a research topic. Over the lifetime, 2757 publications have been published within this topic receiving 68288 citations.

The effects of survey protocol on detection probabilities and site occupancy estimates of summer breeding anurans

Abstract: Recent declines in amphibian populations have created an urgent need for large-scale, long- term monitoring efforts and many anuran monitoring programs have been established that utilize calling surveys. Calling surveys can be effective monitoring tools; however, differences among survey protocols may bias survey results. Failure to take into account detection probabilities when monitoring anurans can lead to inaccurate inferences about site occupancy, since non-detections in survey data do not necessarily mean that a species is absent unless the probability of detection is 1. We used a likelihood-based method, in the form of the computer program PRESENCE, to estimate detection probabilities and site occupancy rates for summer-breeding anurans in the Western Piedmont of North Carolina. Using detection data from calling surveys, we evaluated how detectability and site occupancy for five anuran species were influenced by 1) time spent listening at each site, 2) number of surveys per site, and 3) sample- and site-specific covariates. We found considerable variation among species with regards to detection probability and site occupancy across survey duration and sampling occasion. Although 13% of all species detection occurred after 3 min, longer surveys did not significantly increase detectability of individual species. We found that detectability varied more with sampling occasion than with survey duration for each species. Covariates had differing effects on occupancy and detectability among individual species. Multiple surveys per site within a season are necessary to eliminate biased detection probabilities, but we found that 3- or 5-min surveys were adequate for detecting all species breeding at the time of the survey.

Building occupancy and energy consumption: Case studies across building types

Abstract: Past research has shown that occupancy information can be used to reduce building energy consumption through occupant-based controls and by mitigating wasteful occupant behavior. In this study, we investigate the dynamic relationship between WiFi connection counts (as a proxy to occupancy) and building electricity consumption across four building typologies (office, lab, health center, and library). Our findings based on one year of data show a strong positive linear correlation between electricity consumption and WiFi count across all four building when the building is in operation. The data exploration also indicates higher interactions between occupants with the plug and lighting loads in office and lab space types as compared to in a health center and a library. Next, using principal component analysis (PCA) for feature extraction followed by Density-based spatial clustering of applications with noise (DBSCAN), we show that distinct clusters could be generated, characterized by an increase in the between-cluster variance and smaller within-cluster variation. Lastly, we apply linear regression to manifest how the clustering results can be used to better model the variables.

Detecting pest and prey responses to fox control across the landscape using remote cameras

Abstract: Context The red fox (Vulpes vulpes) is a widespread pest in southern Australia and is subject to control over large areas using poison baits to protect both agricultural and ecological assets. Foxes and their prey are often cryptic or in low densities, making it difficult to quantify the efficacy of control programs. Aims We explore the use of remote cameras to estimate the activity and spatial occupancy of foxes and potential mammalian and avian prey species before and after poison baiting in the Goonoo region, central New South Wales. Methods In the first of two studies, we set camera traps at 48 sites in forest and cleared areas, on and off tracks, during autumn 2009. In the second study, we placed camera traps in forest and cleared areas, on tracks only, at 100 sites covering an area of ~441 500 ha during winter 2009. We examined camera-trap rates of all species detected and the activity and site occupancy of a selected subset of species before and after poison baiting. Key results Camera traps indicated greater levels of fox activity on vehicular tracks than off them, with this difference being more marked in forest than in cleared agricultural land. Fox activity and occupancy were greater in agricultural land than in forest, with no effect of baiting detected at the landscape scale. Thirty-five other mammal and bird species were identified from photos, with activity for most being greater on than off tracks. Conclusions No clear effects of fox-baiting were detected on foxes or potential prey species in either study by either activity or occupancy. The lack of a baiting effect may reflect rapid recolonisation by foxes from unbaited areas, as bait placement is generally clustered in agricultural land, or the ready availability of alternative food (lambs or lamb carcasses) in some cleared areas. Implications Our results demonstrate that remote cameras provide a simple means of monitoring changes in fox activity and occupancy at the landscape level, and that these measures have great potential to quantify the success or otherwise of fox-control campaigns on both pest and prey species.

Optimizing presence-absence surveys for detecting population trends

Abstract: Presence–absence surveys are a commonly used method for monitoring broad-scale changes in wildlife distributions. However, the lack of power of these surveys for detecting population trends is problematic for their application in wildlife management. Options for improving power include increasing the sampling effort or arbitrarily relaxing the type I error rate. We present an alternative, whereby targeted sampling of particular habitats in the landscape using information from a habitat model increases power. The advantage of this approach is that it does not require a trade-off with either cost or the Pr{type I error} to achieve greater power. We use a demographic model of koala (Phascolarctos cinereus) population dynamics and simulations of the monitoring process to estimate the power to detect a trend in occupancy for a range of strategies, thereby demonstrating that targeting particular habitat qualities can improve power substantially. If the objective is to detect a decline in occupancy, the optimal strategy is to sample high-quality habitats. Alternatively, if the objective is to detect an increase in occupancy, the optimal strategy is to sample intermediate-quality habitats. The strategies with the highest power remained the same under a range of parameter assumptions, although observation error had a strong influence on the optimal strategy. Our approach specifically applies to monitoring for detecting long-term trends in occupancy or abundance. This is a common and important monitoring objective for wildlife managers, and we provide guidelines for more effectively achieving it.

Salamander occupancy in headwater stream networks

Abstract: Summary 1. Stream ecosystems exhibit a highly consistent dendritic geometry in which linear habitat units intersect to create a hierarchical network of connected branches. 2. Ecological and life history traits of species living in streams, such as the potential for overland movement, may interact with this architecture to shape patterns of occupancy and response to disturbance. Specifically, large-scale habitat alteration that fragments stream networks and reduces connectivity may reduce the probability a stream is occupied by sensitive species, such as stream salamanders. 3. We collected habitat occupancy data on four species of stream salamanders in first-order (i.e. headwater) streams in undeveloped and urbanised regions of the eastern U.S.A. We then used an information–theoretic approach to test alternative models of salamander occupancy based on a priori predictions of the effects of network configuration, region and salamander life history. 4. Across all four species, we found that streams connected to other first-order streams had higher occupancy than those flowing directly into larger streams and rivers. For three of the four species, occupancy was lower in the urbanised region than in the undeveloped region. 5. These results demonstrate that the spatial configuration of stream networks within protected areas affects the occurrences of stream salamander species. We strongly encourage preservation of network connections between first-order streams in conservation planning and management decisions that may affect stream species.