Geology topics

Paul M. Cryan

Publications and source records attributed to Paul M. Cryan.

At least 37 records · Page 2Linked to original sources

USGS2016

Evaluating the effectiveness of wildlife detection and observation technologies at a solar power tower facility

Solar power towers produce electrical energy from sunlight at an industrial scale. Little is known about the effects of this technology on flying animals and few methods exist for automatically detecting or observing wildlife at solar towers and other tall anthropogenic structures. Smoking objects are sometimes observed co-occurring with reflected, concentrated light (“solar flux”) in the airspace around solar towers, but the identity and origins of such objects can be difficult to determine. In this observational pilot study at the world’s largest solar tower facility, we assessed the efficacy of using radar, surveillance video, and insect trapping to detect and observe animals flying near the towers. During site visits in May and September 2014, we monitored the airspace surrounding towers and observed insects, birds, and bats under a variety of environmental and operational conditions. We detected and broadly differentiated animals or objects moving through the airspace generally using radar and near solar towers using several video imaging methods. Video revealed what appeared to be mostly small insects burning in the solar flux. Also, we occasionally detected birds flying in the solar flux but could not accurately identify birds to species or the types of insects and small objects composing the vast majority of smoking targets. Insect trapping on the ground was somewhat effective at sampling smaller insects around the tower, and presence and abundance of insects in the traps generally trended with radar and video observations. Traps did not tend to sample the larger insects we sometimes observed flying in the solar flux or found dead on the ground beneath the towers. Some of the methods we tested (e.g., video surveillance) could be further assessed and potentially used to automatically detect and observe flying animals in the vicinity of solar towers to advance understanding about their effects on wildlife.

California↗

USGS2016

Multiple mortality events in bats: a global review

Despite conservation concerns for many species of bats, factors causing mortality in bats have not been reviewed since 1970. Here, we review and qualitatively describe trends in the occurrence and apparent causes of multiple mortality events (MMEs) in bats around the world. We compiled a database of MMEs, defined as cases in which ≥ 10 dead bats were counted or estimated at a specific location within a maximum timescale of a year, and more typically within a few days or a season. We tabulated 1180 MMEs within nine categories. Prior to 2000, intentional killing by humans caused the greatest proportion of MMEs in bats. In North America and Europe, people typically killed bats because they were perceived as nuisances. Intentional killing occurred in South America for vampire bat control, in Asia and Australia for fruit depredation control, and in Africa and Asia for human food. Biotic factors, accidents, and natural abiotic factors were also important historically. Chemical contaminants were confirmed causes of MMEs in North America, Europe, and in islands. Viral and bacterial diseases ranked low as causes of MMEs in bats. Two factors led to a major shift in causes of MMEs in bats at around 2000: the global increase of industrial wind-power facilities and the outbreak of white-nose syndrome in North America. Collisions with wind turbines and white-nose syndrome are now the leading causes of reported MMEs in bats. Collectively, over half of all reported MMEs were of anthropogenic origin. The documented occurrence of MMEs in bats due to abiotic factors such as intense storms, flooding, heat waves, and drought is likely to increase in the future with climate change. Coupled with the chronic threats of roosting and foraging habitat loss, increasing mortality through MMEs is unlikely to be compensated for, given the need for high survival in the dynamics of bat populations.

Mammal Review↗

USGS2016

Environment, host, and fungal traits predict continental-scale white-nose syndrome in bats

White-nose syndrome is a fungal disease killing bats in eastern North America, but disease is not seen in European bats and is less severe in some North American species. We show that how bats use energy during hibernation and fungal growth rates under different environmental conditions can explain how some bats are able to survive winter with infection and others are not. Our study shows how simple but nonlinear interactions between fungal growth and bat energetics result in decreased survival times at more humid hibernation sites; however, differences between species such as body size and metabolic rates determine the impact of fungal infection on bat survival, allowing European bat species to survive, whereas North American species can experience dramatic decline.

Science Advances↗

USGS2015

Seasonally-dynamic presence-only species distribution models for a cryptic migratory bat impacted by wind energy development

Understanding seasonal distribution and movement patterns of animals that migrate long distances is an essential part of monitoring and conserving their populations. Compared to migratory birds and other more conspicuous migrants, we know very little about the movement patterns of many migratory bats. Hoary bats ( Lasiurus cinereus ), a cryptic, wide-ranging, long-distance migrant, comprise a substantial proportion of the tens to hundreds of thousands of bat fatalities estimated to occur each year at wind turbines in North America. We created seasonally-dynamic species distribution models (SDMs) from 2,753 museum occurrence records collected over five decades in North America to better understand the seasonal geographic distributions of hoary bats. We used 5 SDM approaches: logistic regression, multivariate adaptive regression splines, boosted regression trees, random forest, and maximum entropy and consolidated outputs to generate ensemble maps. These maps represent the first formal hypotheses for sex- and season-specific hoary bat distributions. Our results suggest that North American hoary bats winter in regions with relatively long growing seasons where temperatures are moderated by proximity to oceans, and then move to the continental interior for the summer. SDMs suggested that hoary bats are most broadly distributed in autumn—the season when they are most susceptible to mortality from wind turbines; this season contains the greatest overlap between potentially suitable habitat and wind energy facilities. Comparing wind-turbine fatality data to model outputs could test many predictions, such as ‘risk from turbines is highest in habitats between hoary bat summering and wintering grounds’. Although future field studies are needed to validate the SDMs, this study generated well-justified and testable hypotheses of hoary bat migration patterns and seasonal distribution.

PLoS ONE↗

USGS2015

Using sutures to attach miniature tracking tags to small bats for multimonth movement and behavioral studies

1. Determining the detailed movements of individual animals often requires them to carry tracking devices, but tracking broad-scale movement of small bats (< 30g) has been limited by transmitter technology and long-term attachment methods. This limitation inhibits our understanding of bat dispersal and migration, particularly in the context of emerging conservation issues like fatalities at wind turbines and diseases. 2. We tested a novel method of attaching lightweight global positioning system (GPS) tags and geolocating data loggers to small bats. We used monofilament, synthetic, absorbable sutures to secure GPS tags and data loggers to the skin of anesthetized big brown bats (Eptesicus fuscus) in Colorado and hoary bats (Lasiurus cinereus) in California. 3. GPS tags and data loggers were sutured to 17 bats in this study. Three tagged bats were recaptured seven months after initial deployment, with tags still attached; none of these bats showed ill effects from the tag. No severe injuries were apparent upon recapture of 6 additional bats that carried tags up to 26 days after attachment, however one of the bats exhibited skin chafing. 4. Use of absorbable sutures to affix small tracking devices seems to be a safe, effective method for studying movements of bats over multiple months, although additional testing is warranted. This new attachment method has the potential to quickly advance our understanding of small bats, particularly as more-sophisticated miniature tracking devices (e.g., satellite tags) become available.

Ecology and Evolution↗

USGS2015

Book review: Bats: A world of science and mystery.

This book has something for everyone, from casual seekers of fascinating eye candy to professional scientists interested in the latest discoveries. Without losing sight of how mysterious bats remain despite decades of research, the authors deftly introduce readers to bats and the people who study them. The book is nice to look at, easy to understand, and interesting in many ways. These stories stick in the reader's memory long after being read—a sign of great scientific communication. Review info: Bats: A world of science and mystery. By M. Brock Fenton, Nancy B. Simmons (Eds.), 2015. ISBN 978-0226065120, 240 pp.

Biological Conservation↗

USGS2015

Not to put too fine a point on it - does increasing precision of geographic referencing improve species distribution models for a wide-ranging migratory bat?

Bat specimens held in natural history museum collections can provide insights into the distribution of species. However, there are several important sources of spatial error associated with natural history specimens that may influence the analysis and mapping of bat species distributions. We analyzed the importance of geographic referencing and error correction in species distribution modeling (SDM) using occurrence records of hoary bats ( Lasiurus cinereus ). This species is known to migrate long distances and is a species of increasing concern due to fatalities documented at wind energy facilities in North America. We used 3,215 museum occurrence records collected from 1950–2000 for hoary bats in North America. We compared SDM performance using five approaches: generalized linear models, multivariate adaptive regression splines, boosted regression trees, random forest, and maximum entropy models. We evaluated results using three SDM performance metrics (AUC, sensitivity, and specificity) and two data sets: one comprised of the original occurrence data, and a second data set consisting of these same records after the locations were adjusted to correct for identifiable spatial errors. The increase in precision improved the mean estimated spatial error associated with hoary bat records from 5.11 km to 1.58 km, and this reduction in error resulted in a slight increase in all three SDM performance metrics. These results provide insights into the importance of geographic referencing and the value of correcting spatial errors in modeling the distribution of a wide-ranging bat species. We conclude that the considerable time and effort invested in carefully increasing the precision of the occurrence locations in this data set was not worth the marginal gains in improved SDM performance, and it seems likely that gains would be similar for other bat species that range across large areas of the continent, migrate, and are habitat generalists.

Acta Chiropterologica↗

USGS2015

Ultraviolet vision may be widespread in bats

Insectivorous bats are well known for their abilities to find and pursue flying insect prey at close range using echolocation, but they also rely heavily on vision. For example, at night bats use vision to orient across landscapes, avoid large obstacles, and locate roosts. Although lacking sharp visual acuity, the eyes of bats evolved to function at very low levels of illumination. Recent evidence based on genetics, immunohistochemistry, and laboratory behavioral trials indicated that many bats can see ultraviolet light (UV), at least at illumination levels similar to or brighter than those before twilight. Despite this growing evidence for potentially widespread UV vision in bats, the prevalence of UV vision among bats remains unknown and has not been studied outside of the laboratory. We used a Y-maze to test whether wild-caught bats could see reflected UV light and whether such UV vision functions at the dim lighting conditions typically experienced by night-flying bats. Seven insectivorous species of bats, representing five genera and three families, showed a statistically significant ‘escape-toward-the-light’ behavior when placed in the Y-maze. Our results provide compelling evidence of widespread dim-light UV vision in bats.

Arizona, Colorado↗

USGS2015

Dim ultraviolet light as a means of deterring activity by the Hawaiian hoary bat Lasiurus cinereus semotus

Widespread bat fatalities at industrial wind turbines are a conservation issue with the potential to inhibit efficient use of an abundant source of energy. Bat fatalities can be reduced by altering turbine operations, but such curtailment decreases turbine efficiency. If additional ways of reducing bat fatalities at wind turbines were available such tradeoffs might not be needed. Based on the facts that bats perceive distant objects primarily through vision and can see in very dim lighting conditions, and the possibility that bats might interact with turbines after approaching them as they would trees, we propose a novel method of reducing bat activity at wind turbines: illumination of the structure with dim light. As a first step toward assessing this approach, we illuminated trees with dim flickering ultraviolet (UV) light in areas frequented by Hawaiian hoary bats Lasiurus cinereus semotus , an endangered subspecies affected by wind turbines. We used a repeated-measures design to quantify bat activity near trees with acoustic detectors and thermal video cameras in the presence and absence of UV illumination, while concurrently monitoring insect numbers. Results indicate that dim UV reduces bat activity despite an increase in insect numbers. Experimental treatment did not completely inhibit bat activity near trees, nor did all measures of bat activity show statistically significant differences due to high variance in bat activity among sites. However, the observed decreases in bat activity with dim UV illumination justify further testing of this method as a means to reduce bat fatalities at wind turbines.

Hawaii↗

USGS2015

Behavior of the Hawaiian Hawaiian Hoary Bat (Lasiurus cinereus semotus) at wind turbines and its distribution across the North Ko'olau Mountains, O'ahu

We studied the landscape distribution of endemic Hawaiian hoary bats (Lasiurus cinereus semotus ) on the north Ko‘olau Mountains of O‘ahu, Hawai‘i, from May 2013 to May 2014, while simultaneously studying their behavior at wind turbines within the broader landscape. This research aimed to assess the risk that wind turbines pose to bats on the island and integrated a variety of methods, including acoustic monitoring, thermal videography, and fatality searches.Our findings indicate that hoary bats were acoustically cryptic and occurred sparsely in the region. Overall site occupancy rate was 55% during the 1-year period of acoustic monitoring at 23 sites, and there was only an 8% chance of acoustically detecting a bat on a given night if it was present. We detected bats less frequently in windward northern parts of the study area and at windy, lower-elevation sites with rough terrain. Bats were detected more frequently in leeward southern parts of the study area and at wind-sheltered, higher-elevation sites with flat ridgetops. Acoustic detections were consistently low from October through February and increased at most sites to peak in April through August. However, meteorological conditions were not found to be associated with the acoustic prevalence of bats on a night-to-night basis. We observed more than three thousand events involving bats during six months of nightly video surveillance at four wind turbines. Video monitoring revealed several links to weather at the local scale, despite acoustic detections not clearly relating to weather in our broader landscape analysis. Video demonstrated bats occurring near turbines more often on nights with little rain, warmer temperatures, moderate wind speeds, low humidity, and the low but rising barometric pressures indicative of fair weather and improved foraging conditions. Video monitoring also demonstrated that the presence of bats near turbines strongly correlates with insect presence. We detected bats on video rather infrequently, averaging only one to two passes per hour. Most detections were brief (median = 4.0 sec) and involved single bats (97%), with the amount of time during which bats were observed totaling to only 0.10% of the video analyzed (about 3.8 hours of 3,847 total hours). Bats frequently foraged in the airspace near turbines. These results differ from a recent similar study on the mainland (continental North America) and may indicate that Hawaiian hoary bats spend less time closely approaching wind turbines and show less interest in them than their more-migratory mainland conspecifics. We speculate that the Hawaiian hoary bats we observed were locally resident and frequenting high-quality habitat near familiar structures. In contrast, hoary bats observed at wind facilities on the mainland appear to approach and investigate unfamiliar landscape structures that they mistake for trees as they migrate long distances. Consequently, Hawaiian hoary bats may be less susceptible to fatality at wind turbines on a per-encounter basis than hoary bats in North America. Only one bat carcass was found at the four turbines searched daily for six months. The relatively high probability of finding carcasses provided strong assurance that few carcasses were likely missed—there was less than a 10% chance that total fatality at the four turbines monitored for half a year exceeded three bats.

Hawaii↗

USGS2014

White-nose syndrome initiates a cascade of physiologic disturbances in the hibernating bat host

Background The physiological effects of white-nose syndrome (WNS) in hibernating bats and ultimate causes of mortality from infection with Pseudogymnoascus (formerly Geomyces ) destructans are not fully understood. Increased frequency of arousal from torpor described among hibernating bats with late-stage WNS is thought to accelerate depletion of fat reserves, but the physiological mechanisms that lead to these alterations in hibernation behavior have not been elucidated. We used the doubly labeled water (DLW) method and clinical chemistry to evaluate energy use, body composition changes, and blood chemistry perturbations in hibernating little brown bats ( Myotis lucifugus ) experimentally infected with P. destructans to better understand the physiological processes that underlie mortality from WNS. Results These data indicated that fat energy utilization, as demonstrated by changes in body composition, was two-fold higher for bats with WNS compared to negative controls. These differences were apparent in early stages of infection when torpor-arousal patterns were equivalent between infected and non-infected animals, suggesting that P. destructans has complex physiological impacts on its host prior to onset of clinical signs indicative of late-stage infections. Additionally, bats with mild to moderate skin lesions associated with early-stage WNS demonstrated a chronic respiratory acidosis characterized by significantly elevated dissolved carbon dioxide, acidemia, and elevated bicarbonate. Potassium concentrations were also significantly higher among infected bats, but sodium, chloride, and other hydration parameters were equivalent to controls. Conclusions Integrating these novel findings on the physiological changes that occur in early-stage WNS with those previously documented in late-stage infections, we propose a multi-stage disease progression model that mechanistically describes the pathologic and physiologic effects underlying mortality of WNS in hibernating bats. This model identifies testable hypotheses for better understanding this disease, knowledge that will be critical for defining effective disease mitigation strategies aimed at reducing morbidity and mortality that results from WNS.

BMC Physiology↗

USGS2014

Behavior of bats at wind turbines

Wind turbines are causing unprecedented numbers of bat fatalities. Many fatalities involve tree-roosting bats, but reasons for this higher susceptibility remain unknown. To better understand behaviors associated with risk, we monitored bats at three experimentally manipulated wind turbines in Indiana, United States, from July 29 to October 1, 2012, using thermal cameras and other methods. We observed bats on 993 occasions and saw many behaviors, including close approaches, flight loops and dives, hovering, and chases. Most bats altered course toward turbines during observation. Based on these new observations, we tested the hypotheses that wind speed and blade rotation speed influenced the way that bats interacted with turbines. We found that bats were detected more frequently at lower wind speeds and typically approached turbines on the leeward (downwind) side. The proportion of leeward approaches increased with wind speed when blades were prevented from turning, yet decreased when blades could turn. Bats were observed more frequently at turbines on moonlit nights. Taken together, these observations suggest that bats may orient toward turbines by sensing air currents and using vision, and that air turbulence caused by fast-moving blades creates conditions that are less attractive to bats passing in close proximity. Tree bats may respond to streams of air flowing downwind from trees at night while searching for roosts, conspecifics, and nocturnal insect prey that could accumulate in such flows. Fatalities of tree bats at turbines may be the consequence of behaviors that evolved to provide selective advantages when elicited by tall trees, but are now maladaptive when elicited by wind turbines.

Indiana↗

USGS2014

Optimizing conservation strategies for Mexican freetailed bats: a population viability and ecosystem services approach

Conservation planning can be challenging due to the need to balance biological concerns about population viability with social concerns about the benefits biodiversity provide to society, often while operating under a limited budget. Methods and tools that help prioritize conservation actions are critical for the management of at-risk species. Here, we use a multi-attribute utility function to assess the optimal maternity roosts to conserve for maintaining the population viability and the ecosystem services of a single species, the Mexican free-tailed bat ( Tadarida brasiliensis mexicana ). Mexican free-tailed bats provide ecosystem services such as insect pest-suppression in agricultural areas and recreational viewing opportunities, and may be threatened by climate change and development of wind energy. We evaluated each roost based on five attributes: the maternity roost’s contribution to population viability, the pest suppression ecosystem services to the surrounding area provided by the bats residing in the roost, the ecotourism value of the roost, the risks posed to each roost structure, and the risks posed to the population of bats residing in each roost. We compared several scenarios that prioritized these attributes differently, hypothesizing that the set of roosts with the highest rankings would vary according to the conservation scenario. Our results indicate that placing higher values on different roost attributes (e.g. population importance over ecosystem service value) altered the roost rankings. We determined that the values placed on various conservation objectives are an important determinant of habitat planning.

Biodiversity and Conservation↗

USGS2014

Market forces and technological substitutes cause fluctuations in the value of bat pest-control services for cotton

Critics of the market-based, ecosystem services approach to biodiversity conservation worry that volatile market conditions and technological substitutes will diminish the value of ecosystem services and obviate the “economic benefits” arguments for conservation. To explore the effects of market forces and substitutes on service values, we assessed how the value of the pest-control services provided by Mexican free-tailed bats (Tadarida brasiliensis mexicana) to cotton production in the southwestern U.S. has changed over time. We calculated service values each year from 1990 through 2008 by estimating the value of avoided crop damage and the reduced social and private costs of insecticide use in the presence of bats. Over this period, the ecosystem service value declined by 79% ($19.09 million U.S. dollars) due to the introduction and widespread adoption of Bt (Bacillus thuringiensis) cotton transgenically modified to express its own pesticide, falling global cotton prices and the reduction in the number of hectares in the U.S. planted with cotton. Our results demonstrate that fluctuations in market conditions can cause temporal variation in ecosystem service values even when ecosystem function – in this case bat population numbers – is held constant. Evidence is accumulating, however, of the evolution of pest resistance to Bt cotton, suggesting that the value of bat pest-control services may increase again. This gives rise to an economic option value argument for conserving Mexican free-tailed bat populations. We anticipate that these results will spur discussion about the role of ecosystem services in biodiversity conservation in general, and bat conservation in particular.

PLoS ONE↗

USGS2014

Continental-scale, seasonal movements of a heterothermic migratory tree bat

Long-distance migration evolved independently in bats and unique migration behaviors are likely, but because of their cryptic lifestyles, many details remain unknown. North American hoary bats (Lasiurus cinereus cinereus) roost in trees year-round and probably migrate farther than any other bats, yet we still lack basic information about their migration patterns and wintering locations or strategies. This information is needed to better understand unprecedented fatality of hoary bats at wind turbines during autumn migration and to determine whether the species could be susceptible to an emerging disease affecting hibernating bats. Our aim was to infer probable seasonal movements of individual hoary bats to better understand their migration and seasonal distribution in North America. We analyzed the stable isotope values of non-exchangeable hydrogen in the keratin of bat hair and combined isotopic results with prior distributional information to derive relative probability density surfaces for the geographic origins of individuals. We then mapped probable directions and distances of seasonal movement. Results indicate that hoary bats summer across broad areas. In addition to assumed latitudinal migration, we uncovered evidence of longitudinal movement by hoary bats from inland summering grounds to coastal regions during autumn and winter. Coastal regions with nonfreezing temperatures may be important wintering areas for hoary bats. Hoary bats migrating through any particular area, such as a wind turbine facility in autumn, are likely to have originated from a broad expanse of summering grounds from which they have traveled in no recognizable order. Better characterizing migration patterns and wintering behaviors of hoary bats sheds light on the evolution of migration and provides context for conserving these migrants.

Ecological Applications↗

USGS2014

Bat flight and zoonotic viruses

Bats are sources of high viral diversity and high-profile zoonotic viruses worldwide. Although apparently not pathogenic in their reservoir hosts, some viruses from bats severely affect other mammals, including humans. Examples include severe acute respiratory syndrome coronaviruses, Ebola and Marburg viruses, and Nipah and Hendra viruses. Factors underlying high viral diversity in bats are the subject of speculation. We hypothesize that flight, a factor common to all bats but to no other mammals, provides an intensive selective force for coexistence with viral parasites through a daily cycle that elevates metabolism and body temperature analogous to the febrile response in other mammals. On an evolutionary scale, this host–virus interaction might have resulted in the large diversity of zoonotic viruses in bats, possibly through bat viruses adapting to be more tolerant of the fever response and less virulent to their natural hosts.

Emerging Infectious Diseases↗

USGS2014

Watching the dark: New surveillance cameras are changing bat research

It is, according to an old proverb, “better to light a candle than to curse the darkness.” And those of us trying to discover new insights into the mysterious lives of bats often do a lot of cursing in the darkness. Bats do most things under cover of night, and often in places where humans and most other animals can’t go. This dark inaccessibility is great for bats, but not so great for those of us trying to study them. Successful conservation hinges on understanding bat behaviors and needs, as well as identifying and addressing the things that threaten them in the darkness. But how do we light a candle without scaring the bats away or altering their behavior?

BATS Magazine↗

USGS2013

Moving across the border: Modeling migratory bat populations

The migration of animals across long distances and between multiple habitats presents a major challenge for conservation. For the migratory Mexican free-tailed bat (Tadarida brasiliensis mexicana), these challenges include identifying and protecting migratory routes and critical roosts in two countries, the United States and Mexico. Knowledge and conservation of bat migratory routes is critical in the face of increasing threats from climate change and wind turbines that might decrease migratory survival. We employ a new modeling approach for bat migration, network modeling, to simulate migratory routes between winter habitat in southern Mexico and summer breeding habitat in northern Mexico and the southwestern United States. We use the model to identify key migratory routes and the roosts of greatest conservation value to the overall population. We measure roost importance by the degree to which the overall bat population declined when the roost was removed from the model. The major migratory routes—those with the greatest number of migrants—were between winter habitat in southern Mexico and summer breeding roosts in Texas and the northern Mexican states of Sonora and Nuevo Leon. The summer breeding roosts in Texas, Sonora, and Nuevo Leon were the most important for maintaining population numbers and network structure – these are also the largest roosts. This modeling approach contributes to conservation efforts by identifying the most influential areas for bat populations, and can be used as a tool to improve our understanding of bat migration for other species. We anticipate this approach will help direct coordination of habitat protection across borders.

Ecosphere↗