MACROPODS
3.1 Capture and physical restraint
The physical capture and restraint of macropods requires careful planning, preparation and execution to ensure the safety and welfare of both animals and personnel.
When approached, or during capture attempts, macropods often flee and may run aimlessly into obstacles, resulting in significant injury and sometimes death. When restrained, they may react violently and attempts to restrain them further may result in injury to the animal or handler. Females may eject PY. Performing procedures in high ambient temperatures (>30°C) should be avoided. Macropods are susceptible to capture myopathy (Vogel- nest and Portas 2008; NHMRC 2014; Vogelnest 2015). Larger macropods can be dangerous and may attempt to kick, which, together with the sharp nail of digit 4 of the pes and the powerful hindlimbs, can cause serious injury. Capture from the front of the animal should never be attempted. They will also bite. Restraint of large macropods can be physically demanding.There is considerable species variation in response to capture and restraint. Some are relatively tolerant (including free-ranging animals), while others are intolerant and require the judicious use of sedatives, tranquillisers or anaesthetic agents.
A range of methods and equipment can be used to capture and restrain macropods (Table 9.2). Regardless of the method chosen, careful planning is required, long pursuits must be avoided and alternate options, including willingness to abort the capture, must be available.
3.2 Chemical restraint
Injectable agents can be given IV or IM. Oral administration of sedatives or tranquillisers is rarely used as efficacy is unpredictable and unreliable. Trazodone has been used to calm macropods in various scenarios and could be used prior to a planned anaesthetic procedure (see Appendix 4). Accessible veins in macropods are listed in Appendix 2.
IM injections are best given in the large thigh muscles, by hand, pole syringe or projectile dart. If chemical restraint is to be used after physical capture, larger animals can be held momentarily by the tail and allowed to hop on the spot while they are hand injected or the animal can be lifted off the ground with one hand holding the base of the tail and the other arm placed around the animal’s abdomen with it facing away from you, while a second person hand injects the animal (Vogelnest and Portas 2008). Animals can also be readily injected IM through the material of a net or bag. The success and quality of anaesthesia relies on animals being calm before and during induction.3.2.1 Remote chemical capture and restraint
The remote chemical capture (darting) and restraint of free-ranging macropods is generally limited to the larger species and should only be attempted by experienced operators with appropriate equipment. Darting macropods in managed care to facilitate capture and restraint is frequently used in species ranging from 3 to 90 kg. Light-weight darts with short needles should be used in smaller species. A sound understanding of macropod behaviour is required in
Table 9.2. Methods and equipment used to capture and restrain free-ranging macropods and those in managed care (Vogelnest and Portas 2008; NHMRC 2014)
| Method | Technique |
| Hand capture | Catch by the base of the tail; take care not to hold the tail too distally as this may result in injury to the tail; should be avoided in small macropods (e.g. bettongs, potoroos), as coccygeal vertebral injury may occur, and large individuals because of the degree of difficulty and risk |
| Long-handled hoop nets with flexible hoops | Size of hoop and depth of the net must be appropriate to size of animal; animals can be made to run along a fence line or be cornered and rapidly scooped up in the net as they run past |
| Funnels and capture yards | Funnels can be erected along a fence line or in the corner of an enclosure; run animals down the funnel, which is constructed with material that provides a visual barrier and then hand or net capture. For large-scale capture, free-ranging kangaroos have been herded into purpose-built capture yards for darting (Colgan et al. 2019) |
| Enclosure traps | Large, fenced (height and construction appropriate to species) enclosure with one-way gates with or without a herding funnel or chute; baited to attract the animals or enclosing a watering point; once trapped, hand or net capture within the enclosure or after herding down a funnel; monitor set traps frequently; or dark enclosed area where macropods are encouraged to enter to feed and then in subdued lighting dart, net or hand capture (W Boardman pers. comm.) |
| Cage treadle traps (hard wire mesh, soft-sided) | Suitable for wallabies and potoroids; set overnight; checked overnight and early morning; stabilise and secure with pegs in the ground, weights or tied to rocks or trees to prevent the trap rolling over with animal inside; cover with waterproof sheeting to shelter trapped animals in rain; a visual barrier (e.g. shade cloth) over most of the wire mesh trap allows handlers to approach the trap without being seen, minimising stress and self-harm to the trapped animal; padding the internal roof to minimise head trauma; traps can be baited or unbaited if set along fence lines or natural runways; a range of baits can be used; a period of free feeding from traps before setting improves trapping success; traps left unmonitored when not in use must be locked to avoid tampering and setting by unauthorised people; animal can be removed by encouraging it into a bag placed over the trap entrance (Fig. 9.3) |
| Drawstring traps | Used to capture kangaroos where they habitually move through fences; consists of a tunnel of netting suspended from a steel mesh frame, with drawstring closures at each end; operator closes the trap by hand from a nearby hide and then subdues the kangaroo in the trap; high risk to animal and personnel (Coulson et al. 2003) |
| Cloth bag or sack (burlap, hessian, calico) | Once captured, transfer to bag or sack; generally remain calm providing head is covered; macropods can be comfortably held or transported in tied bags suspended off the ground (ventilation and ambient temperature are important) (Fig. 9.4); heavily sedated or anaesthetised animals should not be hung in bags as they may suffocate if the muzzle gets wedged in a corner of the bag or the neck becomes flexed; animals can be weighed using hanging scales, briefly examined, blood sampled or hand injected with chemical restraint or other drugs |
| Chemical capture | Remote injection devices: • Pole syringe: useful for managed care or free-ranging habituated macropods that can be approached without fleeing; commercial or customised poles; lightweight extendable poles up to 4.85 m have been used (King et al. 2011) • Dart propelled by blowpipe, pistol or rifle: suitable for wallabies and kangaroos in open areas (Cracknell 2013) |
order to approach within an appropriate darting distance. Depending on the species and the circumstances, some habituated macropods can be closely approached on foot while others tolerate close approach by vehicle. Some species are more readily darted at night; however, maintaining visual contact with animals once darted can be challenging. Several projection systems that are suitable for the remote chemical capture of macropods are available in Australia. Both Dan-Inject (DAN-INJECT ApS, Sellerup Skovvej, Denmark) and Pneu-Dart (Pneu-Dart Inc., Williamsport, PA, USA) manufacture compressed gas projectors suitable for darting free-ranging macropods and those in managed care. Pneu-Dart makes light-weight, single-use, 1 mL plastic darts with short (12.7 mm) needles that allow for accurate darting at distances of up to 50 m with minimal risk of trauma (T Portas pers. comm.).
Macropods have a relatively small target area (the caudal thigh muscles) and poorly placed projectile darts
Fig. 9.3. Cage treadle traps suitable for wallabies and potoroids. (a) Thomas trap (collapsible soft trap, flat packs to make freight and hiking into remote areas cheaper and easier; Sheffield Animal Traps, Welshpool, WA, Australia), (b) soft-sided treadle trap, (c) a brush-tailed rockwallaby (Petrogalepenicillata) in a wire treadle trap (note the reflector hanging from the tree (arrow), which facilitates locating traps at night) and (d) a brush-tailed rock-wallaby being transferred from the trap into a canvas bag. Photos: (a) and (b) Deb Ashworth, (c) and (d) Larry Vogelnest
may penetrate the thoracic and abdominal cavities injuring viscera or fracturing long bones, particularly the femur and tibia, resulting in significant morbidity or mortality. Accurate placement of projectile darts and appropriate pressure settings to ensure minimal impact trauma are key factors in achieving a successful and humane outcome. Use of a range finder to measure darting distance is useful to ensure appropriate pressure settings. Once recumbent, anaesthetised macropods should be blindfolded and have a folded towel or sack placed under the neck to angle the nose and mouth downwards to allow saliva and any food material to drain away from the trachea (Fig. 9.5) (T Portas pers. comm.). When working in the field in colder climates a tarpaulin and/or foam rubber matting should be placed under the macropod to minimise heat loss while it is recumbent. Long inductions and high ambient temperatures may result in hyperthermia; water and shade should be available for cooling.
A range of concentrated drugs are available providing small volumes suitable for use in projectile darts (see Appendix 3).3.2.2 Sedation and tranquillisation
Macropods are often highly strung and even the most habituated individuals may suffer stress and anxiety when subjected to unusual or noxious stimuli or events, often with dire consequences. The judicious use of sedatives or tranquillisers (see Appendices 3 and 4) when capturing, transporting, introducing, hospitalising or intensively caring for macropods can assist in preventing adverse effects and ensuring positive health and welfare outcomes. Diazepam is a commonly used sedative in
Fig. 9.4. Translocated brush-tailed rock-wallabies (Petrogale penicillata) in bags suspended in trees before release. Photo: Deb Ashworth
macropods. Individual and species responses are variable. Diazepam has a wide safety margin and it is generally preferable to slightly overdose than underdose; however; in all cases a dose appropriate to the temperament and health status of the animal and the circumstances should be chosen. Its anxiolytic and muscle-relaxant properties are useful for the prevention of capture myopathy if given immediately after physical capture. Orally administered diazepam is unreliable and rarely used. Midazolam, used alone or in combination with other agents, is a useful short-acting sedative with similar effects to diazepam. Kragness et al. (2016) used a CRI of midazolam (0.06 mg/ kg per hr IV) to limit activity, yet allow normal consumption of food and water, for 4 d following cervical spinal surgery in a red-necked wallaby (Notamacropus rufogri- seus). Midazolam 1-3 mg/kg per hr CRI titrated to effect, in combination with chlorpromazine (1 mg/kg slow IV q 6 hr) and methocarbamol (50 mg/kg IV q 6 hr as required), continued for 6 d, provided a good level of sedation and muscle relaxation in an adult eastern grey kangaroo (Macropus giganteus) being treated for tetanus, including maintenance of an oesophageal tube (J Weller pers. comm.).
A range of short-, intermediate- and long-acting neuroleptic drugs have been used in macropods (see Appendix 3). They have primarily been used when transporting, introducing or hospitalising macropods. These neuroleptic drugs are 1st-generation antipsychotics that act by blocking dopamine in the CNS. The clinical effect is depression of behavioural responses (so reducing risk of self-injury in situations such as transport for example). They do not however reduce underlying stress, anxiety or fear. If there is high risk of injury in highly reactive individuals during transport, introductions or hospitalisation, then the judicious use of neuroleptics in combination with anxiolytics such trazodone, gabapentin and nonsedative doses of benzodiazepines can be considered (see Appendix 4; D McLelland pers. comm.). Zylkene® (Veto- quinol Australia Pty Ltd, Hamilton Qld) is a milk protein that has clinically proven calming properties. It has been used in a limited number of macropods with apparent beneficial effect in mildly stressful situations in zoo settings (L Vogelnestpers. comm.).
3.2.3 Anaesthesia visualisation of the glottis. Residual food in the oral cavity should be cleared to avoid inadvertent introduction of food particles into the trachea during intubation. A hand-held rigid endoscope inserted through the endotracheal tube is ideal for intubating macropods (Figs 9.6 and 9.7). Alternatively a long narrow-bladed laryngoscope or long curved transilluminator can be used. Long endotracheal tubes are required. A guide stylet can be inserted into the trachea and the endotracheal tube passed over it. The position of the animal’s body (dorsal, lateral or sternolateral) and the manner and position for holding the head are at the preference of the operator. Lateral recumbency, with the forequarters sternal, head elevated and neck extended, and using a rigid endoscope or long-bladed laryngoscope, facilitates intubation in most cases. Blind intubation can be achieved and is easier if the animal is in a deep plane of anaesthesia. In lateral recumbency, the animal’s neck is extended and the tongue is pulled out of the mouth. Grasping the larynx between the thumb and forefinger of one hand, pass the endotracheal tube over the tongue with the other until it touches the glottis. As the animal takes a breath and air is heard rushing through the tube, it is inserted.
Fig. 9.5. Field anaesthesia of an eastern grey kangaroo (Macropus giganteus). Note the blindfold, folded sack under the neck to angle the head downwards allowing drainage away from the trachea and rubber matting placed under the animal to minimise heat loss. Photo: Timothy Portas
Pre-anaesthetic fasting requirements are provided in Table 9.1. A wide range of injectable drugs have been used in macropods for pre-medication prior to gaseous induction or as anaesthetic induction agents (see Appendix 3). Inhalation anaesthesia with isoflurane or sevoflurane in oxygen is commonly used. Induction using a face mask while the animal is physically restrained, ideally in a bag, is useful for smaller species, docile individuals and PY. The head can be extracted from the bag for mask placement or through the cloth with the animal’s head in a corner of the bag.
Intubation can be difficult and is not usually necessary unless working on the head, in the oral cavity or for prolonged procedures. The narrow gape and dental arcades and substantial distance from the oral opening to the larynx make visualisation of the glottis difficult. Introduction of an endotracheal tube further obscures
Nasotracheal intubation has been reported in a red kangaroo (Osphranter rufus) with acute facial swelling that prevented the mouth from opening. The kangaroo was intubated blindly using a 7-mm (internal diameter), 60-cm long endotracheal tube. Sterile lubricant was used to assist placement. The tip of the tube was positioned ventrally and the tube advanced slowly, with a finger
Fig. 9.6. Hand-held rigid endoscope inserted inside an endotracheal tube, useful for intubation of macropods, wombats and koalas. Photo: Larry Vogelnest
directing it towards the ventral meatus. The head of the animal was extended and the tube advanced carefully into the trachea (Bauquier and Golder 2010).
Standard monitoring equipment used for small domestic animals can be used. Blood pressure can be monitored non-invasively (oscillometry technique), with a cuff placed at the base of the tail over the coccygeal artery. Management of bradycardia and hypotension if they occur are based on small animal principles (Monticelli et al. 2016). Indirect oscillometric measurements of blood pressure at the tail base of six anaesthetised red-necked wallabies had wide limits of agreement and variable bias when evaluated against direct blood pressure measured in the medial metatarsal artery (Watson et al. 2016). Though not accurate, such indirect measurements can potentially detect trends in blood pressure over time.
Fig. 9.7. Hand-held rigid endoscope being used to intubate a Goodfellow's tree-kangaroo (Dendrolagusgoodfellowi). Photo: Taronga Wildlife Hospital
3.2.4 Locoregional anaesthesia
Locoregional anaesthesia and the judicious use of analgesics are important adjuncts to multimodal pain management in macropods (see Appendix 4). The use of pre- or intraoperative locoregional anaesthesia is likely to have a sparing effect on requirements for intraoperative gaseous anaesthesia and postoperative analgesia such as opioids. Macropods are prone to stress and poorly managed pain is a likely contributing factor. Locoregional anaesthesia is commonly used in veterinary surgery to eliminate pain only in the region of the surgery. Its use and benefits are well recognised in oral, orthopaedic and other surgical procedures. Its use in macropods would minimise stress and improve postsurgical recovery. Locoregional anaesthesia can be facilitated with the use of ultrasound guidance or a transcutaneous electrical nerve stimulator. The successful use of these techniques, however, relies of detailed knowledge of neuroanatomy. Ultrasound-guided femoral and sciatic nerve blocks using ropivacaine in a red-necked wallaby undergoing an orthopaedic procedure have been described (Monticelli et al. 2016). Although the sciatic nerve could be easily visualised, the femoral nerve could not be readily identified. Lignocaine, injected into the spermatic cord on each side proximal to the testes, provides intra- and postoperative analgesia when castrating macropods (and other marsupials).
4.