Browsing by Author "Kniowski, Andrew B."
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- Dataset for: Roosting and foraging social structure of the endangered Indiana bat (Myotis sodalis)Kniowski, Andrew B.; Gehrt, Stanley D. (2014-03-04)Social dynamics are an important but poorly understood aspect of bat ecology. We used these data in a combination of graph theoretic and spatial approaches to describe the roost and social network characteristics and foraging associations of an Indiana bat (Myotis sodalis) maternity colony in an agricultural landscape in Ohio, USA.
- Deriving Habitat Models for Northern Long-Eared Bats from Historical Detection Data: A Case Study Using the Fernow Experimental ForestFord, W. Mark; Silvis, Alexander; Rodrigue, Jane L.; Kniowski, Andrew B.; Johnson, Joshua B. (2016-06)The listing of the northern long-eared bat (Myotis septentrionalis) as federally threatened under the Endangered Species Act following severe population declines from white-nose syndrome presents considerable challenges to natural resource managers. Because the northern long-eared bat is a forest habitat generalist, development of effective conservation measures will depend on appropriate understanding of its habitat relationships at individual locations. However, severely reduced population sizes make gathering data for such models difficult. As a result, historical data may be essential in development of habitat models. To date, there has been little evaluation of how effective historical bat presence data, such as data derived from mist-net captures, acoustic detection, and day-roost locations, may be in developing habitat models, nor is it clear how models created using different data sources may differ. We explored this issue by creating presence probability models for the northern long-eared bat on the Fernow Experimental Forest in the central Appalachian Mountains of West Virginia using a historical, presence-only data set. Each presence data type produced outputs that were dissimilar but that still corresponded with known traits of the northern long-eared bat or are easily explained in the context of the particular data collection protocol. However, our results also highlight potential limitations of individual data types. For example, models from mist-net capture data only showed high probability of presence along the dendritic network of riparian areas, an obvious artifact of sampling methodology. Development of ecological niche and presence models for northern long-eared bat populations could be highly valuable for resource managers going forward with this species. We caution, however, that efforts to create such models should consider the substantial limitations of models derived from historical data, and address model assumptions.
- Predicting intensity of white-tailed deer herbivory in the Central Appalachian MountainsKniowski, Andrew B.; Ford, W. Mark (2018-05)In eastern North America, white-tailed deer (Odocoileus virginianus) can have profound influences on forest biodiversity and forest successional processes. Moderate to high deer populations in the central Appalachians have resulted in lower forest biodiversity. Legacy effects in some areas persist even following deer population reductions or declines. This has prompted managers to consider deer population management goals in light of policies designed to support conservation of biodiversity and forest regeneration while continuing to support ample recreational hunting opportunities. However, despite known relationships between herbivory intensity and biodiversity impact, little information exists on the predictability of herbivory intensity across the varied and spatially diverse habitat conditions of the central Appalachians. We examined the predictability of browsing rates across central Appalachian landscapes at four environmental scales: vegetative community characteristics, physical environment, habitat configuration, and local human and deer population demographics. In an information-theoretic approach, we found that a model fitting the number of stems browsed relative to local vegetation characteristics received most (62%) of the overall support of all tested models assessing herbivory impact. Our data suggest that deer herbivory responded most predictably to differences in vegetation quantity and type. No other spatial factors or demographic factors consistently affected browsing intensity. Because herbivory, vegetation communities, and productivity vary spatially, we suggest that effective broad-scale herbivory impact assessment should include spatially-balanced vegetation monitoring that accounts for regional differences in deer forage preference. Effective monitoring is necessary to avoid biodiversity impacts and deleterious changes in vegetation community composition that are difficult to reverse and/or may not be detected using traditional deer-density based management goals.
- Roosting and Foraging Social Structure of the Endangered Indiana Bat (Myotis sodalis)Silvis, Alexander; Kniowski, Andrew B.; Gehrt, Stanley D.; Ford, W. Mark (PLOS, 2014-05-09)Social dynamics are an important but poorly understood aspect of bat ecology. Herein we use a combination of graph theoretic and spatial approaches to describe the roost and social network characteristics and foraging associations of an Indiana bat (Myotis sodalis) maternity colony in an agricultural landscape in Ohio, USA. We tracked 46 bats to 50 roosts (423 total relocations) and collected 2,306 foraging locations for 40 bats during the summers of 2009 and 2010. We found the colony roosting network was highly centralized in both years and that roost and social networks differed significantly from random networks. Roost and social network structure also differed substantially between years. Social network structure appeared to be unrelated to segregation of roosts between age classes. For bats whose individual foraging ranges were calculated, many shared foraging space with at least one other bat. Compared across all possible bat dyads, 47% and 43% of the dyads showed more than expected overlap of foraging areas in 2009 and 2010 respectively. Colony roosting area differed between years, but the roosting area centroid shifted only 332 m. In contrast, whole colony foraging area use was similar between years. Random roost removal simulations suggest that Indiana bat colonies may be robust to loss of a limited number of roosts but may respond differently from year to year. Our study emphasizes the utility of graphic theoretic and spatial approaches for examining the sociality and roosting behavior of bats. Detailed knowledge of the relationships between social and spatial aspects of bat ecology could greatly increase conservation effectiveness by allowing more structured approaches to roost and habitat retention for tree-roosting, socially-aggregating bat species.
- Spatial factors of white-tailed deer herbivory assessment in the central Appalachian MountainsKniowski, Andrew B.; Ford, W. Mark (2018-04)Because moderate to over-abundant white-tailed deer (Odocoileus virginianus) herbivory impacts biodiversity and can alter community function, ecological benchmarks of herbivory impact are needed to assess deer impacts. We evaluated spatial patterns of deer herbivory and their relation to herbivory assessment by evaluating woody vegetation along 20 transects at each of 30 sites spread across a wide range of deer herd densities and vegetative condition throughout the biodiverse Appalachian Mountains of Virginia, USA. Surprisingly, herbivory patterns and the availability of woody forage generally were unchanged among physiographic regions and land use diversity classes. However, some relationships between browsing pattern and vegetation varied with scale. The total quantity of vegetation browsed on a given site and at the transect scale were related positively to the availability of forage, as the proportion of stems browsed decreased as stem density increased. However, this was only true when all stems were considered equally. When stem densities by species were weighted for deer preference, the proportion of stems browsed had no relationship or increased with stem density. Compared to the value from all transects sampled, on average, the mean of >= 3 transects within a site was within 0.1 of the browsing ratio and stem densities were within 0.5 stems m(-2). Our results suggest that one transect per square kilometer with a minimum of three transects may be sufficient for most browsing intensity survey requirements to assess herbivory impacts in the Appalachian region of Virginia. Still, inclusion of spatial factors to help partition variation of deer herbivory potentially may allow for improved precision and accuracy in the design of field herbivory impact assessment methods and improve their application across various landscape contexts.
- Spatial Methods for Broad-Scale Assessment of Deer Browse Impacts in VirginiaKniowski, Andrew B.; Ford, W. Mark (2014)Biodiversity has become a central focus of conservation effort and research over the past several decades. Ungulates are important modifiers in many ecosystems and can significantly alter biodiversity. Throughout the eastern United States, white-tailed deer (Odocoileus virginianus) are the forefront of research and discussion due to chronically high densities in many regions and the resultant impact to ecosystems and human land use activities. Although ecological benchmarks or measures of herbivory impact have become increasingly important metrics to consider in deer population management, current limitations in understanding impede their application across landscapes. For example, few data describe the local and regional spatial variation in impact measures due to inherent geologic and topographic characteristics. Further, little is known regarding the extent anthropogenically altered landscape elements, such as roadways, agriculture, and urban areas influence deer browse impact or how vegetation species respond to herbivory in different landscape contexts. We propose a method to examine deer spatial browse patterns and factors influencing browse intensity and impact measurement across Virginia by implementing a spatially explicit and stratified study design. By examining distinct, spatial aspects of deer herbivory across landscapes, the information gathered may provide critical insight and aid the widespread application of deer impact measurements.