Photo: This modern wildlife tracker is a Passive Integrated Transponder or PIT tag.
One of the challenging things about studying wild animals is finding a way to uniquely identify individual animals. Over the years, many methods have been used by researchers. Now, as technology advances, animals can be marked quickly, permanently, harmlessly and inexpensively.
Banding birds may be the most often seen tagging or marking method used by wildlife researchers. An aluminum band with a unique letter and number code is placed on one of the legs of the bird. When the bird is recaptured, dead or alive, the identifying band number can be reported to a central clearinghouse, the Bird Banding Laboratory in Patuxent, Maryland.
Some studies also mark birds with colored bands, flags or wing tags with alphanumeric codes that allow a report without the recapture of the bird.
The tagging method used for birds is not a good choice for all animals. Some species are too small, and many species are shy and secretive or have life habits that do not lend themselves to remote viewing.
Some usual methods of marking reptiles involves permanently scarring, without harming, the animal. Toes of lizards are clipped off in a sequence that allows identification upon recapture. The edges of a turtle’s shell are sequentially notched to allow identification.
However, there is now a much preferred method of permanently marking an animal so it is not permanently scarred or burdened—RFID, radio frequency identification. The technology is widely used in wildlife research, and the RFID tag commonly used is called a passive integrated transponder or PIT tag.
Modern RFID technology has been around since the 1970s, and as the cost of using it has decreased, its use has grown. You may already be familiar with RFID tags with barcodes that appear on product labels.
The most common use of RFID involves a microchip attached to an antenna. Another device, a reader, emits radio frequency energy as it is passed over the microchip. This energy enables the microchip to send its stored information through the attached antennae while the reader collects, interprets and displays or stores information.
This is an example of a passive RFID tag. It’s very small and similar in size and shape to a grain of rice, and some tags are as tiny as a grain of sand.
The small RFID tags have distinct advantages.
The tags can contain significantly more information than barcodes. RFID tags do not fade, smear or tear, and they can be placed out of sight since they operate on radio waves that pass through most substances.
When used on animals, the tiny RFID tag is injected and inserted just under the skin of the animal where it harmlessly remains.
Many people have their pets micro-chipped. If their pet is lost, a reader passed over the chip relays information about the pet’s owner. For wildlife research, almost any species studied can be micro-chipped which allows for reliable, and essentially permanent, identification.
Depending on the tagging setup, another advantage of RFID marking technology is the potential for automated tracking. In one case, fish of an endangered species were tagged. By placing the antenna of the reader on the river bottom, the movements of the fish could be automatically tracked year-round.
As RFID is increasingly used, the technology improves and allows for easier and more remote detection.
— By Roger Clay, wildlife biologist, Alabama Division of Wildlife and Freshwater Fisheries
— Photo Courtesy Pacific Northwest National Laboratory