Very High Frequency Telemetry Research Articles

Distributing transmitters to maximize population-level representativeness in automated radio telemetry studies of animal movement

Telemetry is a powerful and indispensable tool for evaluating wildlife movement and distribution patterns, particularly in systems where opportunities for direct observation are limited. However, the effort and expense required to track individuals often results in small sample sizes, which can lead to biased results if the sample of tracked individuals does not fully capture spatial, temporal, and individual variability within the target population. To better understand the influence of sampling design on results of automated radio telemetry studies, we conducted a retrospective power analysis of very high frequency (VHF) radio telemetry data from the Motus Wildlife Tracking System for two species of birds along the United States Atlantic coast: a shorebird, the piping plover (Charadrius melodus), and a nearshore seabird, the common tern (Sterna hirundo). We found that ~ 100–150 tracked individuals were required to identify 90% of locations known to be used by the tracked population, with 40–50 additional individuals required to include 95% of used locations. For any number of individuals, the percentage of stations included in the sample was higher for common terns than for piping plovers when tags were deployed within a single site and year. Percentages of stations included increased for piping plovers when birds were tagged over multiple sites and, to a lesser extent, years, and increased with average length of the tracking period. The probability that any given receiver station used by the population would be included in a subsample increased with the number of birds tracked, station proximity to a migratory stopover or staging site, number of receiving antennas per station, and percentage of the tracked population present. Our results provide general guidance for the number and distribution of tagged birds required to obtain representative VHF telemetry data, while also highlighting the importance of accounting for station network configuration and species-specific differences in behavior when designing automated radio telemetry studies to address specific research questions. Our results have broad applications to remotely track movements of small-bodied migratory wildlife in inaccessible habitats, including predicting and monitoring effects of offshore wind energy development.

Reptiles on the wrong track? Moving beyond traditional estimators with dynamic Brownian Bridge Movement Models

BackgroundAnimal movement expressed through home ranges or space-use can offer insights into spatial and habitat requirements. However, different classes of estimation methods are currently instinctively applied to answer home range, space-use or movement-based research questions regardless of their widely varying outputs, directly impacting conclusions. Recent technological advances in animal tracking (GPS and satellite tags), have enabled new methods to quantify animal space-use and movement pathways, but so far have primarily targeted mammal and avian species.MethodsMost reptile spatial ecology studies only make use of two older home range estimation methods: Minimum Convex Polygons (MCP) and Kernel Density Estimators (KDE), particularly with the Least Squares Cross Validation (LSCV) and reference (href) bandwidth selection algorithms. These methods are frequently applied to answer space-use and movement-based questions. Reptile movement patterns are unique (e.g., low movement frequency, long stop-over periods), prompting investigation into whether newer movement-based methods –such as dynamic Brownian Bridge Movement Models (dBBMMs)– apply to Very High Frequency (VHF) radio-telemetry tracking data. We simulated movement data for three archetypical reptile species: a highly mobile active hunter, an ambush predator with long-distance moves and long-term sheltering periods, and an ambush predator with short-distance moves and short-term sheltering periods. We compared traditionally used estimators, MCP and KDE, with dBBMMs, across eight feasible VHF field sampling regimes for reptiles, varying from one data point every four daylight hours, to once per month.ResultsAlthough originally designed for GPS tracking studies, dBBMMs outperformed MCPs and KDE href across all tracking regimes in accurately revealing movement pathways, with only KDE LSCV performing comparably at some higher frequency sampling regimes. However, the LSCV algorithm failed to converge with these high-frequency regimes due to high site fidelity, and was unstable across sampling regimes, making its use problematic for species exhibiting long-term sheltering behaviours. We found that dBBMMs minimized the effect of individual variation, maintained low error rates balanced between omission (false negative) and commission (false positive), and performed comparatively well even under low frequency sampling regimes (e.g., once a month).ConclusionsWe recommend dBBMMs as a valuable alternative to MCP and KDE methods for reptile VHF telemetry data, for research questions associated with space-use and movement behaviours within the study period: they work under contemporary tracking protocols and provide more stable estimates. We demonstrate for the first time that dBBMMs can be applied confidently to low-resolution tracking data, while improving comparisons across regimes, individuals, and species.

Benefits and biases of VHF and GPS telemetry: A case study of American alligator spatial ecology

ABSTRACTAmerican alligators (Alligator mississippiensis) historically occupied freshwater habitats such as isolated wetlands, lakes, rivers, bottomland swamps, and floodplains in coastal and inland sites. As a result of loss of aquatic habitats, alligators have adapted to inhabiting human‐made lagoons on golf courses and aquatic habitats in close proximity to developed areas. We conducted a telemetry study of adult (>1.8‐m) male alligators between July 2012 and September 2014 on Jekyll Island, Georgia, USA. Our objective was to compare the efficacy of using very‐high‐frequency (VHF) and Global Positioning System (GPS) telemetry in the framework of understanding the spatial ecology of American alligators in a developed landscape. We present both benefits and biases of using these technologies in studies with large, semiaquatic vertebrates. Global Positioning System telemetry produced larger 100% minimum convex polygon home range sizes (range = 67.0–1,094.0 ha) when compared with VHF telemetry (range = 27.5–596.0 ha). Data collected using a prototype GPS technology custom developed by Advanced Telemetry Systems (ATS, Isanti, MN, USA) allowed for the construction of larger, more biologically accurate home ranges. However, VHF telemetry allowed alligators to be detected in underground habitats where they could not be detected with GPS telemetry and yielded more information on behavior and microhabitat through direct observation. We recommend the use of traditional VHF telemetry to allow researchers to directly observe animal behaviors such as reproduction and foraging in conjunction with GPS telemetry to capture previously unavailable locational data. These data highlight the importance of choosing the appropriate telemetry technology based on habitat type, species, and research objectives. © 2016 The Wildlife Society.

Differences in evaluation of three different approaches in home range sizes of red deer Cervus elaphus in Western Carpathians / Rozdiely vo vyhodnotení veľkosti domovských okrskov jeleňa lesného Cervus elaphus v Západných Karpatoch tromi rôznymi prístupmi

Abstract The aim of this study was to evaluate differences using three different approaches in home range sizes of selected male individuals of red deer (Cervus elaphus). This study was conducted in the Kremnica Mountains (the Western Carpathians) located in central Slovakia. The study included data from three individuals, collared and tracked by using the VHF (Very High Frequency) telemetry. The data were evaluated within three different seasons (winter, summer and rut). For the measuring of home range sizes three methods were used: Minimum Convex Polygon (MCP), Kernel Home Range (KHR) and Local Convex Hull (LoCoH). The seasonal effect on home range size was analyzed by using the analysis of variance (ANOVA) two and three main effects. The study showed differences in home range sizes and core areas in red deer population. The migrant individual had a lager home range size with used methods. The differences occurred between total seasonal home ranges, but statistically not significant. The home range created by Local Convex Hull was significantly smaller than the home range created by Kernel Home Range.

Home range use by the European hare (Lepus europaeus) in a structurally diverse agricultural landscape analysed at a fine temporal scale

An animal’s home range use is influenced by the landscape type. European hare (Lepus europaeus) home ranging behaviour has been studied only in agricultural areas with medium to large fields. In agricultural areas with small fields, European hares’ locomotor behaviour is expected to be more localised. We tracked nine European hares by means of global positioning system (GPS) and very high-frequency (VHF) collars during summer in an agricultural area with small fields in Lower Austria. In particular, we analysed the hares’ space use at a fine temporal scale, such as when they were active and resting within single 24-h periods. Furthermore, we compared data (day–day distances and day–night distances travelled) calculated from GPS and VHF telemetry. Home ranges were smaller, and the distances between areas used for activity and inactivity were shorter, in this agricultural area with small fields than has ever been measured in other agricultural areas with larger fields. Both active and inactive European hares expressed a preference for areas near field edges. Our findings suggest that with GPS, it is possible to distinguish between the movement path and the relative location of distinctly used areas within an animal’s home range, whereas with VHF these two parameters may be difficult to separate. In conclusion, our results show that in areas where resources are easily accessible, such as in agricultural areas with small fields, the European hare is able to reduce its home range size to almost half of the minimum size that has been recorded so far in other habitats. As small home ranges involve less energy expenditure for movement, our results suggest that animals living in agro-ecosystems may benefit from small fields.

Molt Migration by Giant Canada Geese in Eastern South Dakota

We captured giant Canada geese (Branta canadensis maxima) in 7 counties in eastern South Dakota during the summer molting period, 2000–2003. We attached very high frequency (VHF) transmitters to 150 adult female geese with brood patches, and leg bands to 3,839 geese. We documented molt migrations using VHF telemetry and indirect band recovery at locations north of South Dakota. Telemetry of radio-collared female geese during the breeding season indicated that 56% of nonbreeders, 81% of unsuccessful breeders, and 19% of successful female breeders embarked on a molt migration. Five of 34 geese that underwent molt migrations moved to northeast South Dakota, and the other twenty-nine migrated north of South Dakota. Eighty-six of 647 indirect band recoveries were from north of South Dakota (46o N latitude), suggesting that the geese were molting north of South Dakota. The percentage of indirect recoveries (13%) that occurred north of 46° N latitude was significantly greater (χ1 = 160.6, P < 0.001) than northern indirect recoveries (3.5%) reported by Gleason (1997) for giant Canada geese banded in eastern South Dakota from 1955 to 1995. We believe it is likely that 50 to 60% of eastern South Dakota’s population of giant Canada geese undergo molt migrations. These movements affect management strategies in nesting areas, as well as in molting areas. Any management technique, such as egg addling in nesting areas, may reduce local crop damage but increase problems in areas where geese molt. Harvest strategies for molt migrants should involve coordination with state and provincial agencies. Further studies incorporating satellite telemetry are needed to document specifically the molting locations of South Dakota geese.

Using Subpopulation Structure for Barren-Ground Grizzly Bear Management

Abstract The subpopulation is an intermediate level of organization that is ecologically meaningful for research and management. We used location data (n = 1,235) from 54 barren-ground grizzly bears (Ursus arctos) monitored from 1974–78 (n = 12) using VHF (very high frequency) telemetry and from 2001–06 (n = 42) using GPS (global positioning system) telemetry to delineate subpopulation structure in the Mackenzie Delta region of the Northwest Territories, Canada. We used Ward's cluster analysis to group bears into 4 subpopulations using their geographical position in 4 seasons. We used the fixed-kernel method to bound subpopulation areas and to estimate the relative probability of use by each subpopulation for each geographic information system (GIS) grid cell. The Delta is the starting point for the proposed Mackenzie Valley Pipeline. To demonstrate how subpopulation structure can be used to partition potential anthropogenic disturbance across the population, we estimated the mean probability of use of...

Florida Panther Habitat Selection Analysis of Concurrent GPS and VHF Telemetry Data

Abstract: Florida panthers (Puma concolor coryi) are listed as an endangered subspecies in the United States and they exist in a single Florida population with &lt;100 individuals; all known reproduction occurs south of Lake Okeechobee. Habitat loss is the biggest threat to this small population and previous studies of habitat selection have relied on very high frequency (VHF) telemetry data collected almost exclusively during diurnal periods. We investigated habitat selection of 12 panthers in the northern portion of the breeding range using 1) Global Positioning System (GPS) telemetry data collected during nocturnal and diurnal periods and 2) VHF telemetry data collected only during diurnal periods. Analysis of both types of telemetry data yielded similar results as panthers selected upland (P &lt; 0.001) and wetland (P &lt; 0.001) forested habitat types. Our results indicated that forests are the habitats selected by panthers and generally support the current United States Fish and Wildlife Service panther habitat ranking system. We suggest that future studies with greater numbers of panthers should investigate panther habitat selection using GPS telemetry data collected throughout the range of the Florida panther and with location attempts scheduled more evenly across the diel period. Global Positioning System radiocollars were effective at obtaining previously unavailable nocturnal telemetry data on panthers; however, we recommend that panther researchers continue to collect VHF telemetry data until acquisition rates and durability of GPS collars improve. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):633–639; 2008)

In SituCharacterization of Two Wireless Transmission Schemes for Ingestible Capsules

We report the experimental in situ characterization of 30-40 MHz and 868 MHz wireless transmission schemes for ingestible capsules, in porcine carcasses. This includes a detailed study of the performance of a magnetically coupled near-field very high-frequency (VHF) transmission scheme that requires only one eighth of the volume and one quarter of the power consumption of existing 868-MHz solutions. Our in situ measurements tested the performance of four different capsules specially constructed for this study (two variants of each transmission scheme), in two scenarios. One mimicked the performance of a body-worn receiving coil, while the other allowed the characterization of the direction-dependent signal attenuation due to losses in the surrounding tissue. We found that the magnetically coupled near-field VHF telemetry scheme presents an attractive option for future, miniturized ingestible capsules for medical applications.

Remote-sensing systems and seabirds: their use, abuse and potential for measuring marine environmental variables

We examined how seabirds might be used to study marine environmental variables, which necessitates knowing location and the value of the variable to be studied. Five systems can potentially be used for determination of location: VHF (Very High Frequency) telemetry, PTT (Platform Terminal Transmitters) telemetry, GLS (Global Location Service) geolocation methods, dead reckoning and GPS (Global Positioning System), each with its own advantages with respect to accuracy, potential number of fixes and size. Temperature and light were used to illustrate potential difficulties in recording environmental variables. Systems currently used on seabirds for measurement of temperature respond slowly to environmental changes; thus, they may not measure sea surface temperature adequately when contact periods with water bodies are too short. Light can be easily measured for light extinction studies, but sensor orientation plays a large role in determining recorded values. Both problems can be corrected. The foraging behaviour of seabirds was also examined in order to identify those features which would be useful for determination of marine environmental variables at a variety of spatial and temporal scales. Area coverage by birds is highly dependent on breeding phase and tends to be concentrated in areas where prey acquisition is particularly enhanced. The identification of these sites may be of particular interest to marine biologists. 'Plungers' and 'divers' are potentially most useful for assessment of variables deeper within the water column, with some divers spending up to 90% of their time sub-surface. Few seabirds exploit the water column deeper than 20 m, although some divers regularly exceed 50 m (primarily penguins and auks), while 2 species dive in excess of 300 m. The wide-ranging behaviour of seabirds coupled, in many instances, with their substantial body size makes them potentially excellent carriers of sophisticated environmental measuring technology; however, the ethical question of how much the well-being of birds can, and should, be compromised by such an approach needs to be carefully considered.

Comparison of 3 Methods for Evaluating Activity of Dall's Sheep

Validation of the reliability of remote-sensing data is critical to subsequent analyses, yet is often neglected. Thus, we assessed the efficacy of 3 methods of collecting information on activities of captive and free-ranging Dall's sheep (Ovis dalli) in Alaska. Conventional very high frequency (VHF) radio-telemetry transmitters and platform transmitter terminals that transmit to satellites, eacj wotj motion-sensitive tipswitches, were compared with simultaneous direct observation Both VHF (98% agreement) and satellite telemetry (98% agreement) reliably distinguished active from inactive behaviors for free-ranging females