Collar attachment

A jaguar wearing a tracking collar

Lioness with a tracking collar, South Luangwa National Park, Zambia

Collar attachment is the primary technique where the subject has a suitable body type and behaviour. Tracking collars are typically used on the animal's neck (assuming the head has a larger circumference than the neck)^[4] but also on a limb, perhaps around an ankle. Suitable animals for neck attachment include primates, large cats, some bears, etc. Limb attachment works well in animals such as kiwi, where the foot is much larger than the ankle.

Harness attachment

Harness attachments may be used when collar attachment is unsuitable, such as for animals whose neck diameter may exceed that of the head. Examples of this type of animal may include pigs, Tasmanian devils, etc. Large, long-necked birds such as the greylag goose may also need to be fitted with a harness to prevent the removal of the tag by the subject.^[5]

Direct attachment

Direct attachment is used on animals where a collar cannot be used, such as birds, reptiles, and marine mammals.

In the case of birds, the GPS unit must be very lightweight to avoid interfering with the bird's ability to fly or swim. The device is usually attached by gluing or, for short deployments, taping^[6] to the bird. The unit will then naturally fall off when the bird subsequently moults.

In the case of reptiles such as crocodiles and turtles, gluing the unit onto the animal's skin or carapace using epoxy (or similar material) is the most common method and minimises discomfort.^[7]

In deployments on marine mammals such as phocids or otariids, the device would be glued to the fur and fall off during the annual moult. Units used with turtles or marine animals have to resist the corrosive effects of seawater and be waterproof to pressures of up to 200bar.

Other attachment methods

Other applications include rhinoceros tracking, for which a hole may be drilled in the animal's horn and a device implanted. Compared to other methods, implanted transmitters may suffer from a reduced range as the large mass of the animal's body can absorb some transmitted power.

There are also GPS implants for large snakes, such as ones offered by Telemetry Solutions.

Embedded

Duty Cycle Scheduling - GPS devices typically record data about the animal's exact location and store readings at pre-set intervals known as duty cycles. By setting the interval between readings, the researcher can determine the device's lifespan - persistent readings drain battery power more rapidly. In contrast, longer intervals between readings might provide lower resolution over a more extended deployment.^[8]

Release Timers - Some devices can be programmed to drop off at a set time/date rather than requiring recapture and manual retrieval. Some may also be fitted with a low-power radio receiver allowing a remote signal to trigger the automatic release.

Analytical

Locational data provided by GPS devices can be displayed using Geographic information system (GIS) packages such as the open-source GRASS or plotted and prepared for display on the World Wide Web using packages such as Generic Mapping Tools (GMT), FollowDem (developed by Ecrins National Park to track ibex) or Maptool.

Statistical software such as R can be used to display and examine data and may reveal behavioural patterns or trends.

Argos

GPS tracking devices have been linked to an Argos Platform Transmitter Terminal (PTT), enabling them to transmit data via the Argos System, a scientific satellite system that has been in use since 1978. Users can download their data directly from Argos via telnet and process the raw data to extract their transmitted information.^[9]

Where satellite uplink fails due to antenna damage, it may be possible to intercept the underpowered transmission locally using a satellite uplink receiver.^[10]

GSM

GPS location data can be transmitted via the GSM mobile/cell phone network, using SMS messages or internet protocols over a GPRS session.^[11] The EPASTO GPS is dedicated to follow and locate cow.

UHF/VHF

GPS data may be transmitted via short-range radio signals and decoded using a custom receiver.

Effects on animals

It was believed that GPS collars used on animals affected their behavior. This theory was tested on elephants that lived in a zoo in the United States. They studied how the elephants behaved with and without the collars simultaneously for both scenarios and saw no change in behavior.^[12] A study was done with mantled howler monkeys to see if GPS Ball and Chain collars affected the monkeys behavior. The study involved observing a group of collared and uncollared female howler monkeys. There was no significant difference in the collared and uncollared behavior, but when the study was over, it was discovered that the monkeys had injuries. The collars had caused damage to the necks of the monkeys; one had minor scratches and some swelling, while four other monkeys had deep cuts from the collar. Two of the monkeys with the lacerations had their tissue healing over the collar.^[13]

Tracking technology and battery life

There is a need for Internet-enabled tracking collars for animals to be designed with a multiple-year lifespan to avoid interference with the animals. Satellite tracking devices are deployed in ultra-remote areas. To preserve battery power, the device only powers on when required. GSM or cellular technology is widely deployed where connectivity is available - however, GSM is also highly intensive on battery power. Devices either have a large battery or are only powered on when required. Sigfox or LoRa are new technologies powering the Internet of Things connectivity. These technologies are beginning to be deployed in remote areas due to their ease of deployment and incredibly long range. The advantages of these technologies for an animal tracking collar are that the device form size can be minimised, and the battery life is considerably extended. Sigfox has already covered large parts of the Kruger National Park in South Africa, allowing rangers to track smaller forms of wildlife better.^[14]