TELEMETRY, DATA-LOGGING TAGS AND IMPLANTS
Very high frequency (VHF) telemetry is commonly used for monitoring free-ranging koalas, with most transmitters applied as collars. VHF transmitters as anklets (Fig. 36.1), ear-tags or sutured back-mounted tags are alternatives to collar-mounted telemetry devices.
Anklets are now no longer recommended due to the risk of constrictive injury, but ear-tag and back-mounted methods have lower risk of serious injury (J Loader pers. comm.). They may be used as a sole telemetry device or as a back-up for primary telemetry collar failure or loss. All telemetry devices have the potential to cause injury, discomfort and sometimes death, and therefore pose a risk to animal welfare. The correct use and application of these devices must be clearly understood by researchers and others using them (see below).Many koala tracking projects do not monitor koalas with sufficient frequency to intervene if tag-associated complications develop or to detect death early enough to permit a necropsy examination. Hence, collar-related deaths are probably significantly underdetected and
Fig. 36.1. Free-ranging koala with VHF anklet attached as a back-up telemetry device in the event of primary telemetry collar failure.
therefore underreported. Veterinarians have an important role in monitoring and providing advice on the correct use and application of these devices. In all cases, the use of these devices requires approval from a relevant animal care and ethics committee.
Other devices used to collect data include wireless identification (WID) ear tags (Wild Spy Pty Ltd, Banyo, Qld), GPS collars and increasingly sophisticated biotelemetry collars (Bali and Delaney 1996; Jones et al. 2013; Hanger et al. 2017). Intra-abdominal implants have been used to monitor location (VHF) and core body temperatures in both managed and free-ranging koalas (Adam et al.
2016; see Chapter 10). Subcutaneously implanted data loggers have been used to monitor heart rate (L Vogelnest pers. comm.). Veterinary involvement in projects using these devices is becoming increasingly expected by animal care and ethics committees, because of the animal welfare risks (L Turner pers. comm.).Common injuries associated with telemetry and other tags include rubbing (Fig. 36.2), constriction (Fig. 36.3), hanging and strangulation. Ulceration (superficial or
Fig. 36.2. Severe collar rub injury caused by a GPS collar with a wide band of collar material.
deep), infections and non-healing wounds at tag contact points may occur. Most of these relate to poorly fitted and poorly designed and made (particularly the material used) collars, anklets or tags and environmental factors. Habitat with a high density of Parsonsia vine where koalas have to forcibly push through tangled vines, increases the likelihood of tags, collars or anklets being distorted, dislodged or broken. Prolonged wet weather, particularly when ticks are prevalent (attachment wounds beneath the collar increase rubbing and act as portals for infection), increases the risk of rubbing and bacterial dermatitis. Collar materials must be non-abrasive, narrow (rather than broad) to minimise the trapping of moisture against the skin and must have a break-point to prevent hanging. Relatively innocuous rub injuries can be portals of entry for pathogenic bacteria, resulting in septicaemia and death, particularly during prolonged periods of inclement weather.
A large, 4-yr monitoring program conducted in Qld, during which over 200 koalas were tracked at any given time, used very narrow, low-profile collar material for tag attachment with an integral break-point (K-Tracker, Incyt/LX, Sydney, NSW) (Fig. 36.4). No collar-related deaths or significant injuries in over 200 000 koala-device days were recorded (Hanger et al. 2017). The safety of these devices was attributable to two important features:
Fig. 36.3. Constrictive injury to the hindleg caused by the attachment band of the anklet after swelling of the leg caused by a traumatic injury.
the integral break point, which prevented hanging, and the narrow, low profile of the collar material, preventing abrasion and the trapping of moisture against the skin.
2.