Wildlife tracking technologies

In 1997-1998, biologists discovered 5000 dead Swainson's hawks at roosting sites in southern Argentina—nine of them wearing leg bands that originated in western Canada. The find proved a vital clue in solving the mystery of why the number of breeding hawks in Alberta and Saskatchewan was declining.

Autopsies revealed that the birds had ingested the pesticide monocrotophos by eating contaminated grasshoppers. To determine the scope of the threat, biologists at Environment Canada's Canadian Wildlife Service outfitted six hawks the following year with special satellite tracking devices before they departed for their annual 13,000-kilometre journey south. Their discovery that individual hawks roamed throughout the region in winter contributed to the nationwide ban of the pesticide in Argentina, and was instrumental in eliminating this significant threat to the species' survival.

Satellite telemetry and banding are just two technologies biologists use to determine when and where populations move. This information is vital because it enables them to detect causes of population decline, assess potential threats, and monitor habitat quality throughout a species' range. The data gathered through tracking are used in wildlife management and conservation programs, to set game bird hunting regulations, in recovery plans for endangered species, and to address issues ranging from disease to environmental contamination.

Before the 1960s, the primary method of tracking wildlife was to capture and mark individuals with an identifying tag or band, and then to either observe them in the wild or recover them through recapture or by finding deceased remains. From these studies, scientists are able to determine individual longevity and cause of mortality, the age structure of populations, and limited information on movement and fidelity to certain sites.

Since 1904, over 59 million birds have been banded in North America—and close to 250,000 birds are still banded annually in Canada. Metal leg bands carry a unique identification number that corresponds to a file of information about the date and location of capture and other vital statistics about the bird. Information is collected when game birds are shot by hunters, or when birds are found dead or recaptured. The problem with bands is that fewer than one per cent of those attached to songbirds and fewer than 10 per cent attached to game birds are ever recovered. Coloured plastic leg bands, streamers, nasal disks, wing tags and collars are also used to identify individual birds and members, and can be spotted from several hundred metres away using a telescope. They can yield information about survival rates and breeding success for birds that return to identified breeding, molting or winter sites each year. But the lives of fartherranging species that spend their time in unobservable or remote regions remain a mystery.

During World War II, radar operators began to realize that some of the blips on their screens were flocks of birds passing through their range. Scientists at Environment Canada have used this technology to learn more about the direction and form of migrations and the movement of local concentrations of birds between their roosting and feeding areas—particularly where they pose a hazard to aircraft. Although radar can't distinguish between species, scientists are experimenting with toothpick-sized transponders that could be attached to individual birds to identify the flights of specific flocks.

The first big breakthrough in tracking technology took place in the early 1960s with the advent of radio telemetry. Like satellite telemeters, radio telemeters consist of a transmitter, antenna and power cell that are attached to the subject by a variety of means. For large animals, a harness or collar is the most common method, while glue, subcutaneous prongs and surgical implants are used in cases where harnesses are too much of an impediment—as with diving ducks. Although larger packages have a longer range and lifespan, small animals will only be fitted with transmitters not exceeding six per cent of their body weight and for birds, less than three per cent, to ensure their welfare. The smallest radio transmitters—which have been used to study toads, bats and songbirds—are the size of a dime and weigh just one gram each.

An Environment Canada scientist fits a tranquilized polar bear with a collar equipped with a satellite transmitter.

Signals emitted by the transmitters are detected using receivers—either by homing toward the signal and observing the subject, or by using triangulation. In the latter case, a directional bearing is taken from two or more receiver positions at precisely the same time. These bearings are then drawn on a map, with the point at which the directional lines intersect marking the location of the animal. Receivers can be operated on foot or in cars, boats or small aircraft. Computer-based remote tracking systems can also be programmed to run independently.

Because its signals have a limited range, radio telemetry tends to be used for localized studies on populations in a well defined and accessible area. Environment Canada has used radio collars to study a variety of mammals, including elk, caribou and timber wolves. Radio telemetry has revealed important information on territorial boundaries, interaction among different populations, breeding locations and rates, food consumption and other behaviours by making it possible to locate and observe individual animals.

Radio telemetry is also used to study the movements of birds—although rarely over a large area. This technology has revealed much about the behaviour of species, including the fact that prairie falcons in southern Alberta travel up to 25 kilometres from their nesting sites on riverside cliffs to catch ground squirrels on range land. It has shown that approximately half of endangered burrowing owls die between the time they leave their nest and migrate south, and provided the first clues to their winter range when three transmitter-carrying owls were detected in southern Texas. Telemetry also helped to confirmed that the world's only tree-nesting seabird, the marbled murrelet, nests in British Columbia's oldgrowth forests, which are under severe pressure from the lumber industry.

The first satellite telemeter used in wildlife tracking was a bulky five-kilogram unit attached to a grizzly bear in the mid-1970s. Since then, the miniaturization of the electronics in the platform transmitter terminal (PTT) and the addition of on-board sensors to collect data on movement, temperature, altitude, humidity, heart rate and other factors have revolutionized conservation ornithology. In 1993, PTTs weighing 28 grams—about the size of a disposable lighter—were attached to peregrine falcons to test the PTTs' capabilities on far-ranging species. In just two years, satellite studies revealed more about the falcon's range and critical breeding, migratory and wintering habitats in North and South America than 25 years of conventional field studies and banding returns. For example, although peregrines inhabit very small areas during winter, during migration they travel long distances very quickly—one subject making the flight from northern Alberta to Veracruz, Mexico, in just 23 days.

Satellite transmitters operate on an ultra-high frequency, sending out an identification code and other information to satellites that collect data as they pass overhead. Ground-based computers use the Doppler effect—shifts in the frequency of the received signal caused by the satellite's movement—to figure out the animal's location to within several hundred metres. Because they send their signals into space, satellite transmitters require more battery power, and are therefore heavier than radio transmitters. To extend battery life, most units can be programmed to transmit at different rates at different times of year. Transmitters weighing only 15 grams are being tested, but the smallest model currently available is 20 grams—light enough for a duck.

A veterinarian releases a male king eider after surgery to implant a lightweight satellite transmitter.

In the future, small PTTs may carry Global Positioning System (GPS) receivers, which can pinpoint a position anywhere on earth almost instantly and to within 20 metres. Already used to track grizzly bears, these devices are capable of storing data over a period of time and then transmitting them as a single message when a satellite is overhead. Although a 100-gram GPS will likely be on the market soon, the technology is still too heavy for birds.

Because they spend so much time offshore, sea ducks have been a major focus of Environment Canada's satellite telemetry work. In eastern North America, scientists using the technology to study endangered harlequin ducks made the surprising discovery that birds breeding in Quebec were actually two separate populations—one that molted along the Labrador coast and the other that molted in Greenland. Since then, scientists in the two countries have begun meeting to discuss the challenges of managing this species across its range.

Biologists also began using satellite tracking last year to study the declining Atlantic population of the Barrow's goldeneye—one of the few ducks that lays its eggs in the cavities of old trees. The initiative led to the documentation of the first breeding record for eastern North America and identified several important molting sites. A similar initiative to determine why western Canada's king eider population has dropped 50 per cent since 1976 has revealed two key staging areas for males in the eastern Beaufort Sea, molting sites as far west as the Siberian Bering Sea and wintering sites on the Bering Sea and the Gulf of Alaska. Further studies may confirm suspicions that changes in marine habitat conditions at these sites are behind the decline.

While satellite tracking is particularly useful for avian species, Environment Canada scientists have also used satellite collars on female polar bears and their cubs since 1996 to delineate the population and determine how mothers select their dens. The Department is also supporting a study on the habitat use and movements of harbour porpoises off the coast of New Brunswick, where they are threatened by gill net fishing activity.

A new and unobtrusive way to track species that are too small for transmitters was discovered by scientists in Saskatchewan, who determined that continental patterns in hydrogen isotopes in water are translated through the food web to the tissue of animals. Field studies of songbirds and migratory monarch butterflies have proven the method a reliable indicator of the latitude of origin of species that breed in North America.

In recent years, many wildlife tracking projects have taken on the role of virtual science classrooms for thousands of schoolchildren and others who follow the movement on species on special Internet sites. This fall, the Canadian Space Agency and the Canadian Wildlife Service will launch a pilot project to engage students in scientific research on the conservation of three migratory wildlife species: the peregrine falcon, polar bear and leatherback turtle. Students will follow the movement of satellite-tagged subjects on the Internet and conduct research on habitats, weather, and other local conditions in an effort to assess threats to the survival of these species throughout their range.

In the future, lighter, longer-lasting, less obtrusive and more accurate satellite tracking technologies—used in combination with other methods such as banding and colour marking, and radio telemetry—promise to help unlock a wealth of information on the many species whose movements and behaviours remain a mystery to biologists.

Banding and other marking

• inexpensive (about $10 per bird)
• provides essential baseline data on population dynamics
• recovery rate low
• provides no information on movements in unobservable areas, and very little in areas where few people live
• can be used on any size of bird
• observational errors can affect accuracy of data
• useful for determining cause of mortality
• useful to determine long-term data, such as maximum life span
• can be reported anywhere in North America by calling toll-free:
  1-800-327-BAND (2263)

Radio Telemetry

• moderately expensive (transmitters $200, receivers $1,500)
• data collection very labourintensive
• tracking by aircraft expensive and reliant on weather and accessibility
• limited tracking range (up to 30 kilometres from aircraft, 10 on ground)
• accurate to within 100 metres
• smallest package weighs one gram
• large transmitters are relatively long-term (batteries can last up to three years), but small ones may last as little as a week
• transmitter may break, malfunction or fall off

Satellite Telemetry

• expensive (transmitters $5,000, satellite time $2,000 per year per transmitter)
• data collection instantaneous, usually at intervals 1 hr
• unlimited range
• accurate to within several hundred metres
• smallest package weighs 20 grams
• shorter-term (batteries last up to one year for external transmitters and eight months for internal ones)
• transmitter may break, malfunction or fall off

  Home |  Air |  Atmospheric Science |  Climate Change |  Environmental Action |  Habitat |  Pollution |  Species at Risk |  Technology |  Water |  Weather |  Wildlife