Calibration of position and angular data from a magnetic tracking device

This paper describes a method for calibrating data from a magnetic tracking device. Position and orientation data were collected in a 1. 6x0.8x1.4m(3) volume using a Polhemus Fastrak((R)) in conjunction with both a long-range and standard transmitter. Position and orientation data were calibrated using a locally linear model based on the position of the measurement. After calibration, the average position and angular errors were less than 1.8cm and 1.2 degrees up to 1.8m from the transmitter for the long-range transmitter. For the standard transmitter, even after calibration, errors increased sharply when the sensor was more than 1.2m from the transmitter. Up to that distance, post-calibration errors were less than 1.2cm and 1. 2 degrees, while up to 1.8m they were below 5cm and 4 degrees. These errors could be further reduced by noise filtering. However, use of the standard transmitter is not recommended at distance greater than 1.2m due to orientation-based effects. It was concluded that for the volume investigated, tracking devices could provide similar three-dimensional accuracy to video systems.     

The BAARA (Biological AutomAted RAdiotracking) System: A New Approach in Ecological Field Studies

Radiotracking is an important and often the only possible method to explore specific habits and the behaviour of animals, but it has proven to be very demanding and time-consuming, especially when frequent positioning of a large group is required. Our aim was to address this issue by making the process partially automated, to mitigate the demands and related costs. This paper presents a novel automated tracking system that consists of a network of automated tracking stations deployed within the target area. Each station reads the signals from telemetry transmitters, estimates the bearing and distance of the tagged animals and records their position. The station is capable of tracking a theoretically unlimited number of transmitters on different frequency channels with the period of 5–15 seconds per single channel. An ordinary transmitter that fits within the supported frequency band might be used with BAARA (Biological AutomAted RAdiotracking); an extra option is the use of a custom-programmable transmitter with configurable operational parameters, such as the precise frequency channel or the transmission parameters. This new approach to a tracking system was tested for its applicability in a series of field and laboratory tests. BAARA has been tested within fieldwork explorations of Rousettus aegyptiacus during field trips to Dakhla oasis in Egypt. The results illustrate the novel perspective which automated radiotracking opens for the study of spatial behaviour, particularly in addressing topics in the domain of population ecology.     

The use of telemetry to study light synchronization with feeding and gill ventilation rates in Salmo trutta

A technique is described whereby the electromyogram of the m. adductor mandibulae of brown trout is detected by implanted extracellular electrodes and used as the input signal for an ultrasonic transmitter attached externally to the fish. The periodic electrical activity of the muscle during ventilation is relayed by the transmitter using an analogue pulse system.
As the ventilatory electromyogram occurs in discrete rhythmic trains, it follows that alterations to this rhythm can be used to telemeter, instantaneously, single feeding events from a free swimming fish. Laboratory tests have shown that the feeding act is unequivocally distinct electromyographically from other manoeuvres such as 'coughing'.
Four adult brown trout have been equipped with this transmitter system and released in Airthrey Loch, Stirling. Using a tracking facility, feeding activity and ventilatory rhythms have been recorded for extended periods.
The results indicate the presence of three daily peaks of feeding activity, which is discussed in relation to changes in light levels. The telemetry records indicate that night feeding is a common occurrence in brown trout. In addition, ventilatory rates were found to be at or near resting levels.     

Impact implantation of a transmitter on Sarpa salpa behaviour: study with a computerized video tracking system

Two transmitter masses (2 and 6% of the fish's mass) were selected to examine the interference of tags with the behaviour of Sarpa salpa using a computerized video tracking system based on digital imaging techniques. The study demonstrated that light transmitters had no effect on the behavioural variables studied, and a substantial bias in behaviour is introduced if heavier (6%) tags are used.     

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

Determining the detailed movements of individual animals often requires them to carry tracking devices, but tracking broad-scale movement of small bats (<30 g) 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 such as fatalities at wind turbines and diseases. 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. GPS tags and data loggers were sutured to 17 bats in this study. Three tagged bats were recaptured 7 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. 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.     

Satelliten-Telemetrie eines G?nsegeiers (Gyps fulvus) in Spanien

Summary During the autumn migratory period a juvenile Griffon Vulture was followed by satellite tracking from the breeding grounds in the Pyrenees to the area of Valencia. Satellite tracking was performed on the basis of a Toyocom transmitter connected to the Argos system. The bird could be traced over a two-month period from end of September to end of November 1990. After an initial south-ward movement the bird stayed in an arid lowland close to the Ebro valley for a longer period and later again moved southward to an area near Valencia. Before the transmitter's lifetime ended due to battery insuffiency the bird had turned north into an area where Griffon Vultures are common. The experimental bird may have joined a large group of conspecifics, wintering there. The bird could be traced over a total distance of about 2000 km and the longest stage per day was about 80 km. As in the case of another European pilot study that we have recently carried out on Bewick's Swans, satellite tracking of a Griffon Vulture proved to be a highly promising method to examine in detail migratory movements as well as ecological aspects on route.     

Context‐dependent effects of radio transmitter attachment on a small passerine

Biotelemetry devices provide unprecedented insights into the spatial behaviour and ecology of many animals. Quantifying the potential effects of attaching such devices to animals is essential, but certain effects may appear only in specific or particularly stressful contexts. Here we analyse the effects of radio transmitter attachment on great tits Parus major tagged over three environmentally dissimilar years, as part of a project studying social‐ and communication networks. When we radio‐tagged birds before breeding, only those tagged in the coldest spring tended to be less likely to breed than control birds. Breeding probability was independent of relative transmitter weight (between 5 and 8% bodyweight). When we radio‐tagged both parents during nestling provisioning (transmitter weight between 6 and 8%), tagged parents were more likely than control parents to desert their brood in two out of three years, while in the other year no tagged parents deserted. Tagged parents provisioning larger broods were most likely to desert, especially during lower average temperatures. Video analyses did not reveal any transmitter effects on provisioning behaviour of parents in the year with no desertion. We conclude that radio tagging before breeding did not lead to negative effects, regardless of transmitter weight, but that decisions about radio‐tagging both parents during nestling provisioning need to be made with exceptional care, taking both environmental context and transmitter weight into account. Reporting results from long‐term radio‐tracking studies comprising several environmentally variable years is crucial to understand and predict potential transmitter effects and maximise the tremendous potential of biotelemetry.     

Challenges and prospects in the telemetry of insects

Radio telemetry has been widely used to study the space use and movement behaviour of vertebrates, but transmitter sizes have only recently become small enough to allow tracking of insects under natural field conditions. Here, we review the available literature on insect telemetry using active (battery‐powered) radio transmitters and compare this technology to harmonic radar and radio frequency identification (RFID) which use passive tags (i.e. without a battery). The first radio telemetry studies with insects were published in the late 1980s, and subsequent studies have addressed aspects of insect ecology, behaviour and evolution. Most insect telemetry studies have focused on habitat use and movement, including quantification of movement paths, home range sizes, habitat selection, and movement distances. Fewer studies have addressed foraging behaviour, activity patterns, migratory strategies, or evolutionary aspects. The majority of radio telemetry studies have been conducted outside the tropics, usually with beetles (Coleoptera) and crickets (Orthoptera), but bees (Hymenoptera), dobsonflies (Megaloptera), and dragonflies (Odonata) have also been radio‐tracked. In contrast to the active transmitters used in radio telemetry, the much lower weight of harmonic radar and RFID tags allows them to be used with a broader range of insect taxa. However, the fixed detection zone of a stationary radar unit (< 1 km diameter) and the restricted detection distance of RFID tags (usually < 1–5 m) constitute major constraints of these technologies compared to radio telemetry. Most of the active transmitters in radio telemetry have been applied to insects with a body mass exceeding 1 g, but smaller species in the range 0.2–0.5 g (e.g. bumblebees and orchid bees) have now also been tracked. Current challenges of radio‐tracking insects in the field are related to the constraints of a small transmitter, including short battery life (7–21 days), limited tracking range on the ground (100–500 m), and a transmitter weight that sometimes approaches the weight of a given insect (the ratio of tag mass to body mass varies from 2 to 100%). The attachment of radio transmitters may constrain insect behaviour and incur significant energetic costs, but few studies have addressed this in detail. Future radio telemetry studies should address (i) a larger number of species from different insect families and functional groups, (ii) a better coverage of tropical regions, (iii) intraspecific variability between sexes, ages, castes, and individuals, and (iv) a larger tracking range via aerial surveys with helicopters and aeroplanes equipped with external antennae. Furthermore, field and laboratory studies, including observational and experimental approaches as well as theoretical modelling, could help to clarify the behavioural and energetic consequences of transmitter attachment. Finally, the development of commercially available systems for automated tracking and potential future options of insect telemetry from space will provide exciting new avenues for quantifying movement and space use of insects from local to global spatial scales.     

Evaluation and calibration of an electromagnetic tracking device for biomechanical analysis of lifting tasks.

Electromagnetic motion tracking devices are increasingly used as a kinematic measuring tool. The aim of this study was to evaluate a long-range transmitter in an environment with a conventional force plate present in order to assess its suitability for further biomechanical applications. Using a calibration apparatus developed in our lab and Optotrack measurements, the performances of the Motion Star were evaluated. Positions and orientations were measured in a 140 x 80 x 120 cm(3) space centered on the force plate. Using a mathematical model developed at Queen's University, these data were calibrated. Errors on position and orientation were less than 150 mm and 10 degrees before calibration of the Motion Star, and less than 20mm and 2 degrees after calibration, with no differences between data collected with the force plate switched on/off. These errors did not depend on sensor orientation. Variability of the signal was small indicating minimal noise. Field distortion was the largest source of measurement error, which increased with the distance between the transmitter and the sensor and the proximity of the sensor to the force plate. Before its use for biomechanical analysis of lifting tasks and validation of dynamic models using force plate data, the data from electromagnetic motion tracking devices must be calibrated to decrease the errors due to electromagnetic field distortion.     

Serendipitous re-sighting of a basking shark Cetorhinus maximus reveals inter-annual connectivity between American and European coastal hotspots

Transatlantic stock mixing in basking sharks Cetorhinus maximus is supported by low genetic diversity in populations throughout the Atlantic Ocean. However, despite significant focus on the species' movements; >1500 individual sharks marked for recapture and >150 individuals equipped with remote tracking tags, only a single record of transatlantic movment has been previously recorded. Within this context, the seredipitous re-sighting of a female basking shark fitted with a satellite transmitter at Malin Head, Ireland 993 days later at Cape Cod, USA is noteworthy.     

Detrimental impacts of radiotransmitters on juvenile Louisiana Waterthrushes

ABSTRACT.   The Louisiana Waterthrush (waterthrush; Seiurus motacilla ) is a forest-dwelling, Nearctic-Neotropical migratory passerine that nests along streams. We attached radiotransmitters (0.6–0.8 g) to 12 nestling waterthrushes using snug, elastic loops. At three nests, adult waterthrushes were videotaped removing radio-tagged young from the nest. In addition, we recovered nine radio-backpacks (with two still attached to the carcasses of nestlings) near nests within a few days after attaching transmitters. Only one of 12 radio-tagged young was relocated more than 24 h after attaching the transmitter. Thus, the method of transmitter attachment we used was not effective. Using snug, nonelastic loops (e.g., nylon) for the harness may reduce the loss of transmitters, but may injure the skin as fledglings grow. Other possible alternatives include (1) gluing the transmitter to skin on the back of nestlings, (2) capturing fledglings in mist nets and attaching transmitters a week or more after fledging by which time contour feathers have grown and the likelihood of a parent removing the transmitter may be reduced, or (3) attempting to monitor fledglings without attaching transmitters. The success of the latter two alternatives would likely be enhanced by attaching transmitters to adults and then tracking them to locate their still-dependent fledglings.     

Satellite tracking of elephants in northwestern Namibia

Satellite tracking of elephants was found to be a valuable tool despite numerous technical problems. A local reference beacon is vital for obtaining an adequate number of accurate locations. Two out of ten satellite transmitters failed within two months of deployment, but an average of one location per collar transmitter was obtained every 3.4 days for the period October 1987-May 1988. The study was made in the wet season in northwestern Namibia. Seasonal home ranges of elephants as determined by satellite tracking were larger than recorded elsewhere in Africa (c. 5800-8700km²). Elephants from Etosha National Park moved to within 20 km of the Angolan border, and elephants in the Kaokoveld moved across previous bioclimatic demarcations of populations. The validity of previous classifications of elephants into discrete populations in northwestern Namibia is questioned.     

Estimation and validation of spatio-temporal parameters for sprint running using a radio-based tracking system

Spatio-temporal parameters like step length, step frequency and ground contact time are directly related to sprinting performance. There is still a lack of knowledge, however, on how these parameters interact.Recently, various algorithms for the automatic detection of step parameters during sprint running have been presented which have been based on data from motion capture systems, video cameras, opto-electronic systems or Inertial measurement units. However, all of these methods suffer from at least one of the following shortcomings: they are (a) not applicable for more than one sprinter simultaneously, (b) only capable of capturing a small volume or (c) do not provide accurate spatial parameters. To circumvent these issues, the radio-based local position measurement system RedFIR could be used to obtain spatio-temporal information during sprinting based on lightweight transmitters attached to the athletes. To assess and optimize the accuracy of these parameters 19 100 m sprints of twelve young elite athletes (age: 16.5 ± 2.3 years) were recorded by a radio-based tracking system and a opto-electronic reference instrument. Optimal filter parameters for the step detection algorithm were obtained based on RMSE differences between estimates and reference values on an unseen test set. Attaching a transmitter above the ankle showed the best results.Bland-Altman analysis yielded 95% limits of agreement of [−14.65 cm, 15.05 cm] for step length [−0.016 s, 0.016 s] for step time and [−0.020 s, 0.028 s] for ground contact time, respectively. RMS errors smaller than 2% for step length and step time show the applicability of radio-based tracking systems to provide spatio-temporal parameters. This creates new opportunities for performance analysis that can be applied for any running discipline taking place within a stadium. Since analysis for multiple athletes is available in real-time this allows immediate feedback to coaches, athletes and media.     

Identification of an endogenous glutamatergic transmitter system controlling excitability and conductivity of atrial cardiomyocytes

As an excitatory transmitter system, the glutamatergic transmitter system controls excitability and conductivity of neurons. Since both cardiomyocytes and neurons are excitable cells, we hypothesized that cardiomyocytes may also be regulated by a similar system. Here, we have demonstrated that atrial cardiomyocytes have an intrinsic glutamatergic transmitter system, which regulates the generation and propagation of action potentials. First, there are abundant vesicles containing glutamate beneath the plasma membrane of rat atrial cardiomyocytes. Second, rat atrial cardiomyocytes express key elements of the glutamatergic transmitter system, such as the glutamate metabolic enzyme, ionotropic glutamate receptors (iGluRs), and glutamate transporters. Third, iGluR agonists evoke iGluR-gated currents and decrease the threshold of electrical excitability in rat atrial cardiomyocytes. Fourth, iGluR antagonists strikingly attenuate the conduction velocity of electrical impulses in rat atrial myocardium both in vitro and in vivo. Knockdown of GRIA3 or GRIN1, two highly expressed iGluR subtypes in atria, drastically decreased the excitatory firing rate and slowed down the electrical conduction velocity in cultured human induced pluripotent stem cell (iPSC)-derived atrial cardiomyocyte monolayers. Finally, iGluR antagonists effectively prevent and terminate atrial fibrillation in a rat isolated heart model. In addition, the key elements of the glutamatergic transmitter system are also present and show electrophysiological functions in human atrial cardiomyocytes. In conclusion, our data reveal an intrinsic glutamatergic transmitter system directly modulating excitability and conductivity of atrial cardiomyocytes through controlling iGluR-gated currents. Manipulation of this system may open potential new avenues for therapeutic intervention of cardiac arrhythmias.Subject terms: Cell biology, Molecular biology     

Multichannel subcarrier ECG, respiration, and temperature biotelemetry system.

A three-channel biotelemetry system measuring ECG, respiration, and body temperature is described. The transmitter employs a 6-kHz subcarrier oscillator and is small enough for surgical implantation in animals the size of rats or larger. The frequency modulated 6-kHz tone from the reciver can be demodulated directly or recorded on an inexpensive cassette tape recorder for future analysis. The transmitter cost is approximately $35.00 and measures 3 times 1 cm. A battery life of several weeks and transmitter range of 10-100 m is typical. Transmission is on the FM broadcast band (88-108 MHz) and reception from an inexpensive FM portable receiver is possible.     

An Integrated Vehicle-Mounted Telemetry System for VHF Telemetry Applications

Abstract: We designed and developed a vehicle-mounted very high frequency-based telemetry system that integrated an on-board antenna, receiver, electronic compass, Global Positioning System, computer, and Geographic Information System. The system allows users to accurately and quickly obtain fixes, estimate and confirm locations of radiomarked animals, and immediately record data into an electronic spreadsheet or database. The total cost of materials to build the system was $7,349 (United States currency). Mean error angle of 2.63 ± 12.1° (SD; range = −33.7–42.2°) and mean location error distance of 128 ± 91.3 m (SD; range = 0–408 m) suggested precision and accuracy of our system were comparable to other reported systems. Mean time to record 5 bearings/test transmitter was 6.28 ± 0.24 minutes (SE), which is the most efficient system reported to locate animals in the field. Vehicle-mounted telemetry systems like ours provide additional value to studies that involve tracking highly mobile species because investigators need not take bearings from established receiving stations and because investigators can immediately recognize bounced signals and take additional bearings and optimize accuracy of location estimates.     

The dynamic organization of postsynaptic proteins: translocating molecules regulate synaptic function

Physiological roles for postsynaptic molecules in synaptogenesis and plasticity are under intense investigation. Recent imaging experiments, including GFP-based and single-particle tracking strategies, reveal rapid movement of synaptic components to and from the postsynaptic sites. Furthermore, specific patterns of neuronal activity and/or activation of specific transmitter receptors trigger selective translocation of postsynaptic components. These emerging dynamic properties of synaptic specializations add another layer of complexity to the signaling mechanisms of CNS synapses.     

Effect of position-fixing interval on estimated swimming speed and movement pattern of fish tracked with a stationary positioning system

Ultrasonic telemetry using stationary positioning systems allows several fish to be tracked simultaneously, but systems that are incapable of sampling multiple frequencies simultaneously can record data from only one transmitter (individual) at a time. Tracking several individuals simultaneously thus results in longer intervals between successive position fixes for each fish. This deficiency leads to loss of detail in the tracking data collected, and may be expected to cause loss of accuracy in estimates of the swimming speeds and movement patterns of the fish tracked. Even systems that track fish on multiple frequencies are not capable of continuous tracking due to technical issues. We determined the swimming speed, area occupied, activity rhythm and movement pattern of cod (Gadus morhua) using a stationary single-channel positioning system, and analysed how estimates of these behavioural parameters were affected by the interval between successive position fixes. Single fish were tracked at a time, and position fixes were eliminated at regular intervals in the original data to generate new data sets, as if they had been collected in the course of tracking several fish (2–16). In comparison with the complete set, these data sets gave 30–70% decreases in estimates of swimming speed depending on the number of fish supposedly being tracked. These results were similar for two individuals of different size and activity level, indicating that they can be employed as correction factors to partly compensate for underestimates of swimming speed when several fish are tracked simultaneously. Tracking `several' fish only slightly affected the estimates of area occupied (1–15%). The diurnal activity rhythm was also similar between the data sets, whereas details in search pattern were not seen when several fish were tracked simultaneously.     

Influence of device accuracy and choice of algorithm for species distribution modelling of seabirds: a case study using black‐browed albatrosses

Species distribution models (SDM) based on tracking data from different devices are used increasingly to explain and predict seabird distributions. However, different tracking methods provide different data resolutions, ranging from < 10 m to > 100 km. To better understand the implications of this variation, we modeled the potential distribution of black‐browed albatrosses Thalassarche melanophris from South Georgia that were simultaneously equipped with a platform terminal transmitter (PTT) (high resolution) and a global location sensor (GLS) logger (coarse resolution), and measured the overlap of the respective potential distribution for a total of nine different SDM algorithms. We found slightly better model fits for the PTT than for GLS data (AUC values 0.958 ± 0.048 vs 0.95 ± 0.05) across all algorithms. The overlaps of the predicted distributions were higher between device types for the same algorithm, than among algorithms for either device type. Uncertainty arising from coarse‐resolution location data is therefore lower than that associated with the modeling technique. Consequently, the choice of an appropriate algorithm appears to be more important than device type when applying SDMs to seabird tracking data. Despite their low accuracy, GLS data appear to be effective for analyzing the habitat preferences and distribution patterns of pelagic species.     

A microampere radiotelemetry transmitter for measurement of temperature from unrestrained subjects

A miniature radiotelemetry transmitter is described suitable for chronic or acute monitoring of temperatures from animal or human subjects. The transmitters can be easily constructed with little or no electronics background from discrete components readily available from any electronics supplier. Transmitters weighed from 2.5-20 g, had volumes of 0.8-3.5 ml, had normal currents of 50-120 muA with potential transmitter lives of 35 h to greater than 1 yr, and transmission ranges of 10-30 m. Transmitters could be implanted, swallowed, or connected to chronically or acutely attached temperature probes. The design of the telemetry system allows for reception on any commercial FM receiver. Depending on mode of decoding the temperature data transmitter signal can be accurate to measure changes of from 0.15 to 0.015 degrees C. Thus with a minimum of expense and little electronics background a temperature-dependent transmitter system can be constructed for monitoring temperatures from unrestrained subjects.