The history of wildlife tracking technology involves the evolution of technologies that have been used to monitor, track, and locate many different types of wildlife. Many individuals have an interest in tracking wildlife, including biologists, scientific researchers, and conservationists. Biotelemetry is "the instrumental technique for gaining and transmitting information from a living organism and its environment to a remote observer".Slater, L. E. 1965. Introduction (special issue on telemetry). Bioscience 15(2):81–82.
1800s
Bird banding
John James Audubon, a French American naturalist, ornithologist, and painter was the first person that attempted to paint and describe all the birds of America. In 1803, he conducted the first known bird banding experiment in North America and tied strings around the legs of Eastern Phoebes. He observed that the birds would return to the same nesting site every year, demonstrating philopatry.
Bird banding was used in 1890 by Hans Christian C. Mortensen, a Danish biologist. Birds can be captured by hand, using mist-nets, cannon-nets, or cage traps. A band that is typically made out of aluminum, or coloured plastic is attached to the leg of the bird. Each band has a unique identification code so that when birds are later recaptured, individuals can be identified.Cleminson A, Nebel S. 2012. Bird Banding. Nature Education Knowledge. 3(8): 1. Mist-nets became widely available in the early 1950s, which dramatically increased the recovery of marked birds.
Early 1930s
Scale clipping The first scientific paper on scale clipping was published in 1933.Blanchard, F. N. and E. B. Finster. 1933. A method of marking living snakes for future recognition, with a discussion of some problems and results. Ecology 14:334-347. Sharp dissecting or microsurgical scissors are used to clip specific ventrals on snakes. A serial enumeration system is used so that individuals can be identified based on the scarring pattern.Brown WS and Parker WS. 1976. A Ventral Scale Clipping System for Permanently Marking Snakes (Reptilia, Serpentes). J Herpetol. 10(3): 247-249.
1940s
Radar During World War II, birds that were migrating caused "phantom signals" or "radar angels" to appear on radar screens.Harper, W.G. 1958. Detection of Bird Migration by Centimetric Radar-- a Cause of Radar 'Angels'. Proceedings of the Royal Society of London. Series B, Biological Sciences. 149(937): 484-502. Since then, radar has become a widely used method for studying migrating organisms. Early radar technologies, such as WSR-57 (Weather Surveillance Radar - 1957), have been replaced by the Next Generation Weather Radar program (NEXRAD) which was installed in segments during the 1990s. Also known as WSR-88D (Weather Surveillance Radar 88 Doppler), NEXRAD is a Doppler system that replaced older non-Doppler meteorological radars. NEXRAD can determine both the direction and speed of migrating individuals that are traveling both toward and away from the radar.Russell, K. R. & Gauthreaux, Jr., S. A. Use of weather radar to characterize movements of roosting purple martins. Wildlife Society Bulletin 26, 5-16 (1998).
Isotope analysis Isotope analysis is based on the principle that most elements exist in two or more forms, known as isotopes. Isotopes have the same number of protons but differ in their number of neutrons, resulting in different masses. This variation in the relative abundance of stable isotopes results from tiny mass differences that cause the isotopes to act differently in chemical reactions and physical processes. Different environments are often characterized by predictable isotopic signatures, meaning that organism's unique isotopic signatures can be traced to unique environments containing the same isotope signatures.West, J. B. et al. Stable isotopes as one of nature's ecological recorders. Trends in Ecology & Evolution 21, 408-414 (2006). The fundamental design of isotope ratio mass spectrometers, a tool used for analyzing isotopes, has not changed since the 1940s. Stable-isotope analysis (SIA) is frequently used with birds since only one capture is needed to determine its breeding origin. SIA is based on the principle that birds will retain isotopic information in their tissues that are based on the isotopic landscapes they inhabited in the recent past. Isotopic information is obtained mostly from feathers, since the keratin in feathers is metabolically inert. For various bird species tested, their feathers' elemental turnover rate is positively correlated with their metabolic rate. A problem with SIA occurs if birds undergo protein catabolism during migration and their isotopic information is subsequently lost as a result of blood-cell replacement. SIA is difficult to employ on birds that switch their diets seasonally due to the difficulty of separating isotopic changes due to location change from isotopic changes due to diet change. The elements that are primarily analyzed for SIA are: carbon, nitrogen, oxygen, hydrogen, and sulphur. Isotopic variation among plants is largely based on differences in photosynthetic pathways. The method is beneficial since it relies on capturing an individual only once. Important information can be obtained from something as simple as a birds' feather, which is relatively easily and painlessly extracted.
1950s
Acoustic telemetry
Acoustic telemetry is based on the principles of sonar, which was developed to detect submarines during World War I. The properties of acoustic systems favour their use in deep waters with high conductivity and low turbulence. The first acoustic telemetry equipment was developed for studying fish in 1956 by the U.S. Bureau of Commercial Fisheries and the Minneapolis-Honeywell Regulator Corporation. Individuals that want to track marine wildlife in salt water face unique challenges. Radio waves are highly absorbed by salt water, making them a poor choice for sending messages through the ocean. Sound waves, on the other hand, are not similarly impeded by seawater. Due to the fact that sound can travel more than 4 times faster in water than in air, this allows for near real-time listening over long distances with proper acoustic telemetry equipment. Acoustic signals are the preferred communication tool for researchers who wish to track fish and wildlife in marine habitats in real time. As with radio, acoustic telemetry requires transmitters to send signals and receivers to hear them. The transmitters are electronic tags that emit a series of sound pulses into the surroundings. They can be surgically implanted or attached externally to an organism. The range of signal reception can vary from a few meters to more than a thousand meters. The signal typically transmits once every minute or two, in order to conserve battery life. Receivers are small, data-logging computers that “listen” for tagged individuals. When a signal is identified, the tag's unique ID code is saved with the date and time. The data from any single receiver provide a record of each signal to that location by a tagged individual. Researchers might deploy many receivers over large regions to understand the movement patterns of tagged individuals. Hydrophones, a type of underwater microphone, receive acoustic signals and then either store or convert them into radio signals for rapid transmission through the air to receivers on shore.
1960s
VHF telemetry VHF (very high frequency) telemetry typically requires a user to acquire VHF transmissions from a VHF transmitter (usually in a collar attached to the animal) using a hand-held antenna. VHF signals are either received by mobile or stationary receivers equipped with directional antennae. The location of the transmitter can then be determined by acquiring the transmissions from three (or more) different locations to triangulate the location of the device. VHF tracking is more commonly known as "radio-tracking."
“Radio-tracking is a revolutionary technique for studying many kinds of free-ranging animals. By March 1979, one of the leading commercial suppliers of radio tracking equipment had sold over 17,500 radio collars. Numerous species, from crayfish through elephants, have been studied with this technique in widespread regions of the world, from pole to pole and in most major countries of the world”.
The idea of using tiny radio transmitters attached to animals to track those creatures occurred to several people in the 1950s when transistors were rapidly replacing vacuum tubes, thus minimizing the size of devices that could produce radio signals. Concurrently, some workers started developing such devices to monitor animal heart rates and respiration while others strove to embed transmitters in collars and harnesses so animal locations could be tracked.Craighead, F. C., Jr., et al., 1963. In L. E. Slater (ed.) Radiotracking of Grizzly Bears. Bio-Telemetry, Proceedings of the Interdisciplinary Conference, New York, March, 1962, pp. 133-148. Pergamon Press, Inc., New York, USAMarshall, W. H., and J. J. Kupa. 1963. Development of radio-telemetry techniques for ruffed grouse studies. Transactions of the North American Wildlife and Natural Resources Conference 28:443-456.
Each of these groups involved wildlife biologists teaming up with electronics engineers or technicians to build the radio-transmitters. Of these electronics experts, William (Bill) W. Cochran, while an undergraduate student with the University of Illinois, had been working on the radio transmitting systems for some of the earliest satellites for the U. S. Army.
George Swenson,Swenson, G. W. Copyright 1994 Institute of Electrical and Electronics Engineers. Reprinted from the IEEE Antennas and Propagation Magazine, vol. 36, no. 2, pp.32-35, April 1994. principal investigator on a NASA-sponsored University of Illinois project to study Sputnik-era radio propagation through the Earth's ionosphere, had this to say about him:
“... [Cochran] had been responsible for building and operating our field stations for a couple of years. He'd demonstrated exceptional skill with transistor circuits. Bill and I decided we could build a couple of satellite payloads, and we started to experiment with circuits and various kinds of batteries.”
“...while he was designing satellite transmitters and receivers, [he] was also moonlighting for wildlife biologists of the Illinois Natural History Survey. They had the idea that small radio transmitters, attached to rabbits, might allow them to track the animals into their burrows, and establish their activity patterns. It worked. Success led to a suggestion from an ornithologist that perhaps birds could be tracked in flight.”
According to Cochran (8/23/19), wildlife biologist Frank Bellrose wished to test the direction in which translocated mallard ducks flew when released into a new area. Cochran built a transmitter to attach to the duck with a light metal band around its chest, and when the duck passed a station where Cochran was monitoring a satellite, he was able to record the signal. Swenson continued: “As [the duck] breathed quietly, the metal band periodically distorted and pulled the frequency, causing a varying beat note from the receiver. An audio-frequency discriminator was available, so the frequency variations could be recorded on a strip chart. When the bird was released into the air, its breathing was recorded on the chart, and in addition, a higher-frequency modulation representing its wing beats. The biologists informed us that we'd made the first measurements of the relation between the wing beats and the breathing of a flying bird, thus answering a long-standing question,” as well as the direction in which the duck flew.
“Of course I was very young and cared little about what ducks do and knew nothing about publishing and didn’t even care if they included me as a co-author,” stated Cochran (8/23/19).