KOALA
4.1 Capture and physical restraint
Capture and retrieval of koalas in managed care is relatively straightforward because most are docile and trees or enclosure furnishings are generally low in height.
It is accomplished by encouraging the koala to back down the tree by placing a hand or object on top of its head. Koalas that are out of reach can be ‘flagged’ down, using a pole with a cloth tied to the end and waved over or touched against the animal’s head. Docile koalas can then have their forefeet unhooked from the tree and be pulled slowly downwards and away from the tree to disengage their hindfeet, before placing them into a sack or transport box. Alternatively, as the koala descends it can be backed into a hessian sack held open against the tree trunk. Less tractable koalas can be managed similarly; however, they can be very aggressive and may bite and/or scratch (Blanshard and Bodley 2008).The capture of free-ranging koalas is more complex and is discussed in Chapter 36. Free-ranging koalas have also been captured from trees by darting (Lynch and Martin 2003). Capture of free-ranging koalas in extreme weather conditions must be avoided. Cold, wet conditions must be avoided as handling disrupts the insulative properties of the fur, resulting in hypothermia. Hyperthermia may occur under hot conditions (NHMRC 2014)
Physical restraint options for koalas vary according to the procedure and the animal’s temperament and habituation to handling. Docile koalas can be picked up from behind by placing a hand under the rump and grasping the fur on the back of the neck. Smaller animals can be picked up by grasping the upper forelimbs from behind. Some can be held with minimal restraint for sample collection, brief examination, injections or mask induction of gaseous anaesthesia. Brief examination and some sample collection (e.g.
fur samples, venipuncture from the cephalic vein and IM injections) can be accomplished without restraint if the animal is sitting quietly or asleep in a tree fork. Towels, blankets and sacks can facilitate handling and restraint of less tractable koalas. Venipuncture, other sample collection, injections and mask induction of anaesthesia can be performed with the koala restrained in a sack (Blanshard and Bodley 2008; NHMRC 2014).4.2 Chemical restraint
Pre-anaesthetic fasting requirements are provided in Table 9.1. Anaesthesia is generally straightforward; however, periods of apnoea and bradycardia, and in unintubated animals, respiratory stridor caused by the long soft palate, are relatively common. Drugs and dose regimens are provided in Appendix 3.
Sedation is rarely required. Diazepam is a useful sedative to facilitate examination and minor procedures (e.g. sample collection). Alfaxalone given IM or IV is useful for induction of heavy sedation or light anaesthesia for short, non-invasive procedures or before supplementation and maintenance with gaseous anaesthesia via mask or endotracheal tube. Induction is smooth, provides good muscle relaxation and recovery is smooth and rapid. For most koalas the IM dose volume is not large and can be given quickly via a 21G needle while the animal is sitting quietly in the fork of a tree branch, while being physically restrained or in a bag. Tiletamine/zolazepam IM or IV provides poorer muscle relaxation, causes mild salivation and recovery can be prolonged. Tiletamine/zolazepam plus medetomidine delivered via dart in free-ranging koalas has been used, resulting in variable levels of
| Table 9.3. Methods used to capture wombats (NHMRC 2014; Bryant and Reiss 2008) | |
| Method | Technique |
| Hand capture | Approach from behind, quickly grasping the wombat just behind the front legs with both arms, lifting it off the ground in a 'bear hug'. The wombat should be held firmly against the handler's chest. Depending on the procedure, it is often more comfortable if the handler sits down once the animal has been restrained |
| Large robust hoop net | In open habitat where wombats are relatively habituated to people, they can be stalked and captured. For less habituated animals, a team of 4-6 people may be required to surround the animal to facilitate net capture |
| Large cage traps | Trap set and secured at a burrow entrance. Wombats are innately 'trap-shy' and may not exit a burrow with a trap at the entrance. Once trapped, chemical restraint is often required to extract the wombat. Traps are not recommended to be left set for more than 2-3 consecutive nights (NHMRC 2014); trap design and deployment strategy refinements for capture of northern hairy-nosed wombats (Lasiorhinuskrefftii) have led to improvements in trap success (Molyneux etal. 2022). Contemporary designs are made from lightweight weld mesh with powder coating and work best when placed at water stations or, if alternative entrances are blocked off, at burrows. |
| Stunning | Southern hairy-nosed wombats (LasiorhinusIatifrons) in open habitat have been captured by 'stunning' (Taggart etal. 2003). The wombat is 'held' in a spotlight beam, a sonic boom is then created by an experienced marksman firing a high-velocity bullet just above the wombat's head. This 'stuns' the wombat while a team of catchers run and capture it in a hand net. Once restrained, it can immediately be placed in a large sack or chemically restrained |
| Walk-through cagetunnel traps | Set at burrow entrances or gate opening in fence lines. These are activated when the wombat trips a nylon fishing line strung across the trap 50 mm above the floor. This causes doors at each end of the trap to fall down, trapping the wombat (Horsup 1998). Once trapped, chemical restraint is often required to extract the wombat |
sedation and anaesthesia (Lynch and Martin 2003; Blan- shard and Bodley 2008).
Isoflurane or sevoflurane in oxygen are commonly used for induction and/or maintenance of anaesthesia. For induction, gradually increasing the isoflurane concentration from 0.5% until anaesthesia is achieved provides a smoother and more stable anaesthesia. This is suitable for docile or sick koalas; however, induction with alfaxalone before supplementation or maintenance with gaseous anaesthesia is preferred.
Intubation can be difficult because of the narrow gape, dental arcades and oropharyngeal opening, the long soft palate and the substantial distance from the oral opening to the larynx, all making visualisation of the glottis difficult. Size 3.0-5.5-mm endotracheal tubes are suitable for most adult koalas. The methods used are similar to those described for macropods (see section 3.2.3) and are described in detail in Blanshard and Bodley (2008). A hand-held rigid endoscope inserted through the endotracheal tube is ideal for intubating koalas (Fig. 9.6).
Standard small domestic animal anaesthetic monitoring equipment can be used. Perianaesthetic hypotension in comparison with other mammalian species is anecdotally a common occurrence in koalas under volatile anaesthesia (E McConnell pers. comm.). The consequences of anaesthesia-related hypotension in koalas are not known; however, reduced perfusion of vital organs could be expected. There are no published reports of normal blood pressure ranges for conscious or anaesthetised koalas. Cumming and Martinez-Taboada (2021) describe the management of hypotension in two koalas. They concluded that dopamine and dobutamine are ineffective in increasing blood pressure in anaesthetised koalas, while non-catecholamine phenylephrine may be more successful. They advise that until more rigorous investigations suggest otherwise, phenylephrine should be used to manage hypotension in anaesthetised koalas.
5.