Unless relying completely on opportunistic sightings a tool is required to locate animals of interest. The use of tracking collars is probably the most common method of monitoring wild animals. The use of tracking collars allows researchers and managers to collect baseline data like home range sizes, daily movements, behavioural data and diet. Radio tracking involves fitting the study animal with a VHF radio collar.
Caution should always be exercised when fitting younger animals with tracking collars as neck circumference will grow over time to a point where an adult animal can be suffocated by the tracking collar. The weight of radio collars should also always be considered to ensure they are in no way an impediment to the animal being tracked. Given recent technological advances and the capacity of collar manufacturers to produce lightweight products, collars which weigh over 450 g should be avoided on wild dogs. Be sure to ask the manufacturer what the final collar weight will be, particularly if modifications from the standard product are to be made.
The technique that has most revolutionized wildlife research is radio tracking, or wildlife telemetry. Telemetry radio tracking involves fitting the study animal with a VHF radio collar. The collar consists of a radio transmitter (set to transmit a regular VHF signal on a specific, pre-set frequency) and a battery. The specific collar frequency is programmed into a receiver which, if in range, picks up the signal as an audible ‘beep’. Most collars have at least a 2 km line-of-sight range but some brands are stronger and at times more reliable than others. The receiver is attached to a directional aerial which will pick up stronger, louder signal when pointing in the direction of the collared animal. The signal can then be followed until visual of the individual or pack is obtained. The clarity and strength of the signal can be affected by the terrain. Mountainous areas are particularly difficult to track in as signal can be blocked or bounced by the rocks resulting in unreliable signal or a false direction. Flat plains with sandy substrate can also prove difficult to track as signals can appear weaker. An elevated position can help to receive clearer signal over a greater distance. If an aircraft is available and affordable the greater height it provides can boost the collar range to over 30kms. Wild dogs are crepuscular and move almost daily, so independent daily and nightly resting locations can be recorded. For an in depth assessment of telemetry and tracking techniques see Samuel and Fuller (1996).
Advantages: relatively low cost, reasonable accuracy for most purposes, and long lived (the battery of each collar lasts approximately 3 years).
Disadvantages: it is labour-intensive and can be terrain-dependant and weather-dependent if aircraft-based.
Weight: 350 – 450 g
Approximate cost of collar: R3 000 – R5 000 (including delivery)
GPS collars allow for remote detection of the collared animal’s position. The Global Positioning System is used to record the animal’s exact location and store the readings at pre-set intervals. The older GPS collars store the data until collar is retrieved. This is done either by immobilizing the animal or using a device that allows the collar to drop off at a set date. Now, most GPS collars allow the data to be downloaded remotely, either by a radio link or, in areas with GSM mobile phone coverage, by text messages. Some GPS collars can store data which is then downloaded remotely (within several hundred meters) using a handheld UHF device. For further information on GPS tracking see Hulbert (2001).
Advantages: GPS collars have some advantages over VHF collars in that data can be collected at any time of the day or night remotely and, in addition, researchers need to spend much less time in the field as the data can be easily downloaded. Many GPS collars are also fitted with VHF capabilities so animals can still be tracked between times of data transmission.
Disadvantages: A major draw-back of GPS collars is that, if using GSM mobile phone technology, the animal must be in an area of mobile phone reception at the exact time of data download or that data point will be stored until such time as the animal moves into an area of reception. The weight of some brands of GPS collars make them unsuitable for use on wild dogs. The costs of GPS collars can make them prohibitively expensive.
Weight: 450 -500 g
Approximate cost of collar: R20 000 – R35 000
Satellite collars, although considerably more expensive than VHF and GPS collars, are the most effective and efficient way to collect location data. With satellite telemetry, in contrast to GPS telemetry, the animal’s collar unit acts as a transmitter and sends information to satellite receivers, which relay this information to a recording centre on Earth. The collars transmit location data via the Argos system or other network of satellites which collect, process and disseminate the data (using the Doppler Shift method to calculate the actual position of the collar transmitting the data signal). Key variables like latitude and longitude are determined but aspects such as altitude, temperature and activity data can also be transmitted if the collar is programmed to do so during manufacture. The location of the collared animal is collected from Platform Terminal Transmitters and delivered directly to the user’s PC. See Gorman et al. (1992) for more information on satellite tracking of wild dogs.
Advantages: Up to date, current data is constantly available to the subscriber.
Disadvantages: Although recent technological progress has been made, satellite telemetry is less accurate than either conventional VHF radio tracking or GPS radio tracking. Satellite telemetry frequently reports locations whose accuracy varies from within 150 m to many kilometres.
Weight: 450 g
Approximate cost of collar: R20 000 – 40 000
Additional features available on tracking collars
- In order to extend battery life some collars can be programmed to turn on and off at certain times of the day
- Some collars send a variable signal depending on whether an animal is resting or active, known as ‘activity detection’.
- Many collars today can produce a ‘mortality signal’ if the collar does not move for a preset length of time. This allows the collar to be retrieved if it has fallen off or if the animal has died.
- Modified collars with anti-snare plates attached
- Modified collars with remote drop-off mechanisms enable collars to be removed and collected without immobilizing the animal.