Michael E. Byrne

Using dynamic Brownian bridge movement modelling to measure temporal patterns of habitat selection.

Accurately describing animal space use is vital to understanding how wildlife use habitat. Improvements in GPS technology continue to facilitate collection of telemetry data at high spatial and temporal resolutions. Application of the recently introduced dynamic Brownian bridge movement model (dBBMM) to such data is promising as the method explicitly incorporates the behavioural heterogeneity of a movement path into the estimated utilization distribution (UD). Utilization distributions defining space use are normally estimated for time-scales ranging from weeks to months, obscuring much of the fine-scale information available from high-volume GPS data sets. By accounting for movement heterogeneity, the dBBMM provides a rigorous, behaviourally based estimate of space use between each set of relocations. Focusing on UDs generated between individual sets of locations allows us to quantify fine-scale circadian variation in habitat use. We used the dBBMM to estimate UDs bounding individual time steps for three terrestrial species with different life histories to illustrate how the method can be used to identify fine-scale variations in habitat use. We also demonstrate how dBBMMs can be used to characterize circadian patterns of habitat selection and link fine-scale patterns of habitat use to behaviour. We observed circadian patterns of habitat use that varied seasonally for a white-tailed deer (Odocoileus virginianus) and coyote (Canis latrans). We found seasonal patterns in selection by the white-tailed deer and were able to link use of conifer forests and agricultural fields to behavioural state of the coyote. Additionally, we were able to quantify the date in which a Rio Grande wild turkey (Meleagris gallopavo intermedia) initiated laying as well as when during the day, she was most likely to visit the nest site to deposit eggs. The ability to quantify circadian patterns of habitat use may have important implications for research and management of wildlife. Additionally, the ability to link such patterns to behaviour may aid in the development of mechanistic models of habitat selection.

Nesting Ecology of Wild Turkeys in a Bottomland Hardwood Forest

Abstract Although extensively studied in upland landscapes, little has been published regarding Eastern Wild Turkey (Meleagris gallopavo silvestris) nest site selection and reproductive ecology in bottomland systems. Wild Turkeys in these systems face unique conditions, such as persistent flooding, so facets of nesting ecology observed in primarily upland landscapes may not apply directly to Wild Turkeys in bottomland systems. We studied nesting ecology of radio-marked female Wild Turkeys during six nesting seasons (2002–2004, 2008–2010) in a bottomland hardwood system in south-central Louisiana. We studied landscape level nest site selection at three spatial scales (200 m, 400 m, and 800 m) and found Wild Turkeys selected nesting locations in areas that offered greater proportions of nonflooded bottomland forests and higher forest edge density than generally available across the study site at all scales. At smaller spatial scales, forest openings were also important to nest site selection, while at large scales, nest location was negatively related to landscape diversity. All nests were located in dry higher elevation forests (n  =  35) or forest openings (n  =  6). These habitats were likely selected because they offered protection from flood-related nest mortality and access to brood-rearing habitat. At the micro habitat scale, ground level cover was important to nest site selection, and likely provided protection from ground predators. Nests were often associated with small recent breaks in the canopy, presumably as a response to the resulting growth in understory cover. Wild Turkeys avoided nesting in managed forest stands with large areas of open canopy, likely because rapid successional growth in these areas made understory growth too dense. Nest predation was the greatest cause of nest failure (55%). Nesting rates (60%) and female success rates (24%) were among the lowest reported for the species, whereas nest success (39%) was near the range wide average. Reproductive performance may have been hampered by a scarcity of quality nesting habitat due to flooding and generally sparse understory vegetation, which left nests vulnerable to predation. Despite low nesting rates and female success, there was no evidence of a declining population on our study area. We suspect this may be a result of either high poult survival due to high quality brood-rearing habitat or because high female survival rates allow individual birds multiple chances to successfully reproduce.

Seasonal Space Use and Habitat Selection of Adult Raccoons (Procyon lotor) in a Louisiana Bottomland Hardwood Forest

Abstract Raccoon ecology is poorly understood in bottomland hardwood systems, despite the fact that bottomland forests are considered high-quality raccoon habitat. We radio-marked 41 raccoons during 2008–2009 and estimated seasonal space use and habitat selection in a bottomland hardwood forest located within the Atchafalaya floodway system in Louisiana. Space use varied seasonally, with home ranges and core areas largest during the breeding season. Forest openings were important when configuring seasonal home ranges, whereas habitat selection within home ranges varied seasonally. The composition of habitats within core use areas was similar to that of home ranges. We concluded that home range size was influenced by reproductive behaviors and seasonal food availability, whereas habitat selection was most influenced by spatio-temporal changes in seasonal food abundance. Raccoons used all available habitat types and landscape heterogeneity is likely important to raccoons when establishing home ranges in bottomland hardwood forest systems.

Quantifying the spatial and temporal variation in dose from external exposure to radiation: a new tool for use on free-ranging wildlife.

Inadequate dosimetry is often the fundamental problem in much of the controversial research dealing with radiation effects on free-ranging wildlife. Such research is difficult because of the need to measure dose from several potential pathways of exposure (i.e., internal contamination, external irradiation, and inhalation). Difficulties in quantifying external exposures can contribute significantly to the uncertainties of dose-effect relationships. Quantifying an animals external exposure due to spatial-temporal use of habitats that can vary by orders of magnitude in radiation levels is particularly challenging. Historically, wildlife dosimetry studies have largely ignored or been unable to accurately quantify variability in external dose because of technological limitations. The difficulties of quantifying the temporal-spatial aspects of external irradiation prompted us to develop a new dosimetry instrument for field research. We merged two existing technologies [Global Positioning Systems (GPS) and electronic dosimeters] to accommodate the restrictive conditions of having a combined unit small enough to be unobtrusively worn on the neck of a free-ranging animal, and sufficiently robust to withstand harsh environmental conditions. The GPS-dosimeter quantifies the spatial and temporal variation in external dose as wildlife traverse radioactively contaminated habitats and sends, via satellites, an animals location and short term integrated dose to the researcher at a user-defined interval. Herein we describe: (1) the GPS-dosimeters; (2) tests to compare their uniformity of response to external irradiation under laboratory conditions; (3) field tests of their durability when worn on wildlife under natural conditions; and (4) a field application of the new technology at a radioactively contaminated site. Use of coupled GPS-dosimetry will allow, for the first time, researchers to better understand the relationship of animals to their contaminated habitats and better assess animal responses to the stress of radiological exposures.

Fine-scale assessment of home ranges and activity patterns for resident black vultures ( Coragyps atratus ) and turkey vultures ( Cathartes aura )

Knowledge of black vulture (Coragyps atratus) and turkey vulture (Cathartes aura) spatial ecology is surprisingly limited despite their vital ecological roles. Fine-scale assessments of space use patterns and resource selection are particularly lacking, although development of tracking technologies has allowed data collection at finer temporal and spatial resolution. Objectives of this study were to conduct the first assessment of monthly home range and core area sizes of resident black and turkey vultures with consideration to sex, as well as elucidate differences in monthly, seasonal, and annual activity patterns based on fine-scale movement data analyses. We collected 2.8-million locations for 9 black and 9 turkey vultures from June 2013 –August 2015 using solar-powered GSM/GPS transmitters. We quantified home ranges and core areas using the dynamic Brownian bridge movement model and evaluated differences as a function of species, sex, and month. Mean monthly home ranges for turkey vultures were ~50% larger than those of black vultures, although mean core area sizes did not differ between species. Turkey vulture home ranges varied little across months, with exception to a notable reduction in space-use in May, which corresponds with timing of chick-rearing activities. Black vulture home ranges and core areas as well as turkey vulture core areas were larger in breeding season months (January–April). Comparison of space use between male and female vultures was only possible for black vultures, and space use was only slightly larger for females during breeding months (February–May). Analysis of activity patterns revealed turkey vultures spend more time in flight and switch motion states (between flight and stationary) more frequently than black vultures across temporal scales. This study reveals substantive variability in space use and activity rates between sympatric black and turkey vultures, providing insights into potential behavioral mechanisms contributing to niche differentiation between these species.

A behaviorally-explicit approach for delivering vaccine baits to mesopredators to control epizootics in fragmented landscapes.

Despite the widespread use of aerial baiting to manage epizootics among free-ranging populations, particularly in rabies management, bait acceptance and seroconversion rates often are lower than required to eliminate spread of disease. Our objectives in this study, therefore, were to evaluate the performance of stratified bait distribution models derived from resource selection functions (RSF) on uptake of placebo rabies baits by raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana), as well as the probability of bait uptake as a function of proximity to bait distribution areas in fragmented agricultural ecosystems. Among 478 raccoons and 108 opossums evaluated for presence of Rhodamine B (RB) across 8 sites, only 26% of raccoons and 20% of opossums exhibited marking consistent with bait consumption 14–24 days post-baiting. The effective area treated, based on 90% kernel density estimators of marked individuals, ranged from 99–240 ha larger than bait distribution zones, with RB marked individuals captured up to 753m beyond the bait zone. Despite incorporation of RSF data into bait distribution models, no differences in uptake rates were observed between treatment and control sites. These data likely reflect the underlying constraints imposed by the loss and fragmentation of habitat on animal movement in heterogeneous landscapes, forcing individuals to optimize movements at coarse (i.e., patch-level) rather than fine spatial scales in highly fragmented environments. Our data also confirm that the probability of bait acceptance decreases with increasing distance from bait zone interiors, even within the zone itself. Thus, although bait acceptance was confirmed beyond bait zone boundaries, the proportion of vaccinated individuals may comprise a small minority of the population at increasing distances from baiting interiors. These data suggest focal baiting creates a buffered area of treated individuals around bait zones or bait stations, but repeated treatments may be needed to achieve sufficient uptake to eradicate disease.

Satellite Telemetry Reveals Higher Fishing Mortality Rates Than Previously Estimated, Suggesting Overfishing of an Apex Marine Predator

Overfishing is a primary cause of population declines for many shark species of conservation concern. However, means of obtaining information on fishery interactions and mortality, necessary for the development of successful conservation strategies, are often fisheries-dependent and of questionable quality for many species of commercially exploited pelagic sharks. We used satellite telemetry as a fisheries-independent tool to document fisheries interactions, and quantify fishing mortality of the highly migratory shortfin mako shark (Isurus oxyrinchus) in the western North Atlantic Ocean. Forty satellite-tagged shortfin mako sharks tracked over 3 years entered the Exclusive Economic Zones of 19 countries and were harvested in fisheries of five countries, with 30% of tagged sharks harvested. Our tagging-derived estimates of instantaneous fishing mortality rates (F = 0.19–0.56) were 10-fold higher than previous estimates from fisheries-dependent data (approx. 0.015–0.024), suggesting data used in stock assessments may considerably underestimate fishing mortality. Additionally, our estimates of F were greater than those associated with maximum sustainable yield, suggesting a state of overfishing. This information has direct application to evaluations of stock status and for effective management of populations, and thus satellite tagging studies have potential to provide more accurate estimates of fishing mortality and survival than traditional fisheries-dependent methodology.

Spring Excursions of Mature Male White-tailed Deer (Odocoileus virginianus) in North Central Pennsylvania

Abstract During the breeding season, male white-tailed deer (Odocoileus virginianus)have been reported to take excursions outside of their normal home ranges, likely in search of receptive females. However, we documented additional excursive movements by males during spring in north central Pennsylvania. From December 2011 – April 2012, we equipped 13 mature (≥2.5 y old) male white-tailed deer with global positioning system (GPS) collars programmed to record locations hourly. We defined an excursion as any occasion where a male traveled ≥1.6 km outside of its 95% home range boundaries for ≥12 h. Between 6 April and 6 June 2012, nine males (69.2%) made excursions with six making ≥2 excursions. Mean total path distance and duration of excursions was 4.0 km (range  =  1.7-8.0 km) and 22 h (range  =  12–40 h), respectively. Although the reason for spring excursions is obscure, hypotheses such as increased doe aggression before parturition, males returning to natal home ranges, or visitation to mineral sites do not appear tenable based on current observations.

Environmental conditions and animal behavior influence performance of solar-powered GPS-GSM transmitters

ABSTRACT Solar-powered GPS transmitters linked to the GSM cellular transmission system are a powerful new tool for avian research. Data collection can be researcher programmed or use dynamic fix (DF) rates that are automatically adjusted in accordance with battery charge. Lack of prior knowledge of fix (location) collection rates represents an obstacle to designing studies with transmitters that use DF rates. We assessed the quantity and quality of data collected by a commercially available DF transmitter. To assess fix collection rates, factors influencing fix collection rates, GPS accuracy, and the ability of transmitters to differentiate movement from nonmovement, we used a combination of controlled static tests at known locations, deployments on free-ranging Black Vultures (Coragyps atratus) and Turkey Vultures (Cathartes aura), and motion tests. During static testing, transmitters often collected upwards of 500 fixes per day in open habitats with little cloud cover. Hourly fix rates varied, commonly reaching 1 fix min−1 at midday but dropping to 1 fix hr−1 at night. The numbers of daylight fixes collected during vulture deployments were greater on days with little cloud cover, positively correlated with increasing daily movement rates, and positively correlated with available daylight hours, likely due in part to increased solar radiation near the summer solstice. Mean horizontal GPS error was 7.8 m (± 12.2 m SD). Mean vertical error was 4.5 m (± 142 m) above true elevation. Speed records >0 km hr−1 were reliable indicators of movement provided a 3D fix was obtained. Overall, the transmitters that we evaluated provided large volumes of data, but the inability to control data collection schedules may prove problematic for some applications. DF solar-powered transmitters appear best suited for use with active species in open habitats, and least suitable for use with species that inhabit high latitudes year-round or spend considerable time under forest cover.

Horizontal and Vertical Movements of White Marlin, Kajikia albida, Tagged Off the Yucatan Peninsula

Original Article Horizontal and vertical movements of white marlin, Kajikia albida, tagged off the Yucatán Peninsula J. J. Vaudo*, M. E. Byrne, B. M. Wetherbee, G. M. Harvey, A. Mendillo Jr , and M. S. Shivji The Guy Harvey Research Institute, Nova Southeastern University, 8000 North Ocean Drive, Dania Beach, FL 33004, USA Department of Biological Sciences, University of Rhode Island, 120 Flagg Road, Kingston, RI 02881, USA Keen M International, Av Rueda Medina 318, Centro Supmza. 001, Isla Mujeres, Quintana Roo 77400, Mexico *Corresponding author: tel: þ1 (954) 262 3677; fax: þ1 (954) 262 4098; e-mail: jvaudo@nova.edu Current address: School of Natural Resources, University of Missouri, Columbia, MO, USA.