Bandicoots and bilbies are small to medium sized (150–2500 g) omnivorous marsupials found only in Australia, New Guinea and surrounding islands. They are usually nocturnal and their appearance is characterised by a pointed nose that is used in foraging for ground-living invertebrates and other food items. They are opportunistic species, exploit a wide range of food items, have a rapid reproductive rate, grow quickly and are not long-lived. There are 21 recognised species of which 11 are found in Australia. However, since European settlement the Australian species have suffered severe contractions of their natural ranges and three of the 11 species are now extinct. Overgrazing by sheep, cattle and rabbits has reduced the ground cover needed by bandicoots for nesting and increased their susceptibility to predation by foxes and cats. The Australian bandicoots and bilbies can be divided into three Families (Peramelidae, Chaeropodidae and Thylacomyidae) within the Order Peramelemorphia. Although all species of the Order Peramelemorphia can be termed bandicoots, members of the Family Thylacomyidae are known as bilbies. The Family Peramelidae contains eight species in three Genera, Perameles (long-nosed bandicoots), Isoodon (short-nosed bandicoots) and Echymipera. The extinct pig-footed bandicoot (Chaeropus ecaudatus) is now classified into a separate family, the Chaeropodidae (Tyndale-Biscoe 2005). The Family Thylacomyidae comprises a single genus, Macrotis, containing two species—the lesser bilby (Macrotis leucura), now extinct, and the greater bilby (Macrotis lagotis), commonly referred to as ‘the bilby’. Table 13.1 lists the species of Australian bandicoots. The long-nosed bandicoot (Perameles nasuta) is still relatively common along the eastern coast of Australia, but the ranges of the other two extant long-nosed bandicoots (eastern barred bandicoot, Perameles gunnii, and western barred bandicoot, Perameles bougainville) have dramatically reduced. The desert bandicoot, Perameles eremiana, once occupied central and western arid regions but is now extinct. The eastern barred bandicoot is still common in Tasmania but the mainland population consists of a remnant wild population in eastern Victoria and three small populations in the Victorian grasslands that are the result of captive breeding and release. The western barred bandicoot was once widespread over arid central and southern Australia but is now free-ranging only on two islands off the coast of Western Australia (Dorre and Bernier Islands). Conservation efforts are currently directed at maintaining the free-ranging populations and captive breeding and release of animals into predator-proofed areas in Western Australia and South Australia.
The Australian bandicoots and bilbies can be divided into three Families (Peramelidae, Chaeropodidae and Thylacomyidae) within the Order Peramelemorphia. Although all species of the Order Peramelemorphia can be termed bandicoots, members of the Family Thylacomyidae are known as bilbies.
The Family Peramelidae contains eight species in three Genera, Perameles (long-nosed bandicoots), Isoodon (short-nosed bandicoots) and Echymipera. The extinct pig-footed bandicoot (Chaeropus ecaudatus) is now classified into a separate family, the Chaeropodidae (Tyndale-Biscoe 2005). The Family Thylacomyidae comprises a single genus, Macrotis, containing two species—the lesser bilby (Macrotis leucura), now extinct, and the greater bilby (Macrotis lagotis), commonly referred to as ‘the bilby’. Table 13.1 lists the species of Australian bandicoots.
The long-nosed bandicoot (Perameles nasuta) is still relatively common along the eastern coast of Australia, but the ranges of the other two extant long-nosed bandicoots (eastern barred bandicoot, Perameles gunnii, and western barred bandicoot, Perameles bougainville) have dramatically reduced. The desert bandicoot, Perameles eremiana, once occupied central and western arid regions but is now extinct. The eastern barred bandicoot is still common in Tasmania but the mainland population consists of a remnant wild population in eastern Victoria and three small populations in the Victorian grasslands that are the result of captive breeding and release. The western barred bandicoot was once widespread over arid central and southern Australia but is now free-ranging only on two islands off the coast of Western Australia (Dorre and Bernier Islands). Conservation efforts are currently directed at maintaining the free-ranging populations and captive breeding and release of animals into predator-proofed areas in Western Australia and South Australia.
Northern brown bandicoot
Southern brown bandicoot
Western barred bandicoot
Eastern barred bandicoot
Rufous spiny bandicoot
a Extinct species.
Source: Adapted from Seebeck et al. (1990).
Two of the three short-nosed bandicoots: the southern brown bandicoot (Isoodon obesulus) and the northern brown bandicoot (Isoodon macrouras) still occupy a substantial part of their former distribution. However, the golden bandicoot (Isoodon auratus), once distributed over a vast area in arid and tropical Australia, has undergone a huge contraction in range. It is now found only on a few islands off the northern coast of Western Australia. The cause of the rapid and dramatic decline of bandicoot and bilbies inhabiting the central part of Australia is unclear. Grazing by cattle and the introduction of foxes and rabbits may have contributed to the decline of these species. However, it appears that the major impact was the change in land burning patterns caused by movement of Aboriginal people away from their traditional nomadic life and onto cattle stations and missions. The pig-footed bandicoot formerly occurred over a wide area in central and southern Australia and is believed to have become extinct sometime in the 1950s. The rufous spiny bandicoot (Echymipera rufescens) is still relatively common in the rainforest areas of Cape York.
Bilbies were once distributed over most of Australia’s arid zone. However, the greater bilby is now found only in an isolated area in south-west Queensland and in the northern deserts of the Northern Territory and Western Australia. Bilbies have been reintroduced to the Peron peninsula (WA) and to smaller fenced reserves in the south-west of Western Australia and the Roxby Downs area of South Australia.
2 ANATOMY AND PHYSIOLOGY
The evolutionary ancestry of bandicoots and bilbies is not clearly resolved because they share anatomical characteristics with both the other major groups of Australian marsupials. Like the dasyurids they have polyprotodont dentition possessing three or more pairs of incisors in the top and bottom jaw. However, they also display syndactyly of the second and third digits of their hind feet, a characteristic shared with kangaroos and possums. Based on analysis of mitochondrial DNA, there is general agreement that bandicoots and bilbies are a very ancient and separate group from the dasyurid or diprotodont marsupials of Australasia. The divergence of the bandicoots and bilbies from other Australian marsupials is estimated to have occurred about 60 million years ago (Tyndale-Biscoe 2005).
With the exception of the pig-footed bandicoot, bandicoots and bilbies all possess subauricular or interauricular cephalic skin gland complexes (Stoddart 1980). The copious watery secretion they produce conveys a pungent odour highly characteristic of some bandicoot and bilby species. The glandular complex increases in activity markedly during breeding periods in both sexes, but particularly in males. In bilbies the complex is located between the ears and measures 25X18 mm in the adult animal. Its presence can be readily palpated. Bilbies have unusual structures of a glandular appearance located at the mouth commissures (Fig. 13.1). The histological structure and function of these masses is undescribed.
Figure 13.1 Gland-like structures in the commisures of the mouth of the greater bilby. Photo: Larry Vogelnest.
Tedman (1990) described anatomical features of the northern brown bandicoot and noted that the oral cavity receives saliva from relatively small parotid but large mandibular (submaxillary) glands. Saliva produced from the mandibular glands is of a mucoid type. Bandicoots and bilbies have a simple oval stomach and the small intestine is not clearly demarcated into different regions. The size of the caecum varies between species. In the northern brown bandicoot and long-nosed bandicoot it is of moderate size but in Permales spp. it is only about 2 cm in length. The caecal length of the extinct pig-footed bandicoot was reported to be 10 cm (Parsons 1903), suggesting that the species consumed a significant amount of plant material. In most bandicoot species the colon is short relative to the small intestine (26% of tract length in the northern brown bandicoot) but in the bilby the distal colon is much longer, presumably to maximise the resorption of water for this arid-zone species (Hume 1999).
Studies of the passage of food particles through the gut of the northern brown bandicoot and long-nosed bandicoot suggest that bandicoots maximise their use of plant material by selectively retaining small particles in the caecum and proximal colon (Hume 1999). Possession of a digestive tract that is more differentiated than that of carnivores, together with selective retention of digesta in the hindgut, allows bandicoots and bilbies to switch between plant, animal and fungal material according to the relative abundance of each food type.
A number of anatomical features of the bandicoot and bilby urogenital tract are distinctive among marsupials. The female tract of the eastern barred bandicoot is represented in Figure 13.2. The bladder is quite cranially placed, therefore the urethra is quite long. The remarkable features of the reproductive tract are the expansive vaginal caeca, very long lateral vaginae and the short median vaginal cul de sac, which terminates a considerable distance from the cranial end of the short urogenital sinus. Dissection of the reproductive tract of a multiparous eastern barred bandicoot revealed that the lateral vaginae open into the vaginal caecae and that each caeca connects with the median vagina. The uterine horns are separate and each has a single caudal opening into the median vagina. The median vagina is divided by a central septum. McCracken (1990) found the same anatomical relationships and external appearance of the urogenital tract in the greater bilby. The anatomy of the urogenital tract has been described in three other bandicoot species (Hill 1899; Tedman 1990) and they differ from the bilby and eastern barred bandicoot in two respects. The vaginal caecae of the northern brown bandicoot, southern brown bandicoot and long-nosed bandicoot share a median partition wall and so have an externally undivided bilobed appearance. Additionally, in the northern brown bandicoot the septum that divides the median vagina is reported present only in nulliparous individuals (Tedman 1990).
Male bandicoots have a large prostate and bulbourethral glands in relation to their body size (Tedman 1990) and these organs are usually easily palpated in the abdomen of breeding males.
Figure 13.2 Urogenital anatomy of the female eastern barred bandicoot. 1) Ventral aspect of urogenital tract 2) Ventral aspect with bladder and vaginal caecae reflected forwards 3) dorsal aspect of urogenital tract. a) Kidney b) Vaginal caeca c) Urinary bladder d) Urethra e) Lateral vaginae f) Uterine horns g) Median vagina h) Ovary
A number of bandicoot and bilby species occupy arid habitats and have behavioural and physiological adaptations that enable them to survive in such environments. Studies of the golden bandicoot showed that it can maintain rates of water and electrolyte turnover under conditions of extreme aridity (Bradshaw et al. 1994). Its field metabolic rate was extremely low under drought conditions and increased markedly after rain, and the volume of water required to maintain hygric balance was lower than that required by temperate-zone bandicoots (Withers 1992; Bradshaw et al. 1994). Bilbies also require less water than the predicted amount for a marsupial of their size (Gibson & Hume 2000). Arid-zone insectivorous animals often store fat in their tails because of inevitable short-term food shortages (Hume 1999). However, it appears that only one extant bandicoot species, the western barred bandicoot, has developed this capacity (Gordon & Hall 1995).
Bandicoot and bilby reproductive characteristics are such that, with favourable environmental conditions, they can achieve rates of reproduction greater than any other marsupial group. All species are polyoestrus and capable of breeding throughout the year, but within their natural ranges breeding activity is influenced by food availability and climatic factors (Heinsohn 1966; Gemmell 1990; Reimer & Hindell 1996).
The oestrous cycle of bandicoots and bilbies is relatively short, from 12 d to 37 d. The length of gestation is also extremely short, ranging from 12 d to 16 d (Jackson 2003). Despite the short gestation period, bandicoot and bilby young are born in a relatively advanced stage compared to other marsupials because of the nutrient exchange efficiency of their placental structure (Tyndale-Biscoe 2005). Bandicoots and bilbies are unique among marsupials in that they form a chorioallantoic placenta, where there is very intimate contact between maternal and foetal tissue (Renfree 1982). In all other marsupial groups the allantois remains enfolded by the wall of the yolk sac and never reaches the chorion. Eutherian (placental) mammals all have a chorioallantoic placenta yet bandicoots and bilbies are true marsupials, i.e. their embryonic young are born and nurtured in a well-developed pouch.
The lactation period of bandicoots and bilbies is extremely short. Weaning occurs at approximately 55–75 d in bandicoots and around 3 mo in the greater bilby (Heinsohn 1966; Hall 1990; McCracken 1990). This rapid growth is possible because their milk is very energy-dense, more so than any other mammal group except the seals (Tyndale-Biscoe 2005). If conditions are favourable, females return to oestrus during late lactation so that they give birth to a new litter as the older litter is weaned. Sexual maturity in female bandicoots usually occurs around 3 mo of age, although this may be delayed depending on seasonal food availability (Lyne 1964; Gemmell 1986; Jackson 2003). Female bilbies reach sexual maturity around 5–7 mo (McCracken 1990; Southgate et al. 2000). In captivity, bandicoots and bilbies breed well if held in favourable nutritional and social conditions, and in enclosures designed to minimise stress.
The growth and development of the northern brown bandicoot has been described by Hall (1990) and is presented in Table 13.2. This species has a gestation period of 12.5 d and a pouch life of 50 ± 7 d. McCracken (1990) studied the development rate of the greater bilby from pouch life to sexual maturity (see Table 13.3).
The life-span of bandicoot species is relatively short compared with many other Australian mammals. In a study of wild southern brown bandicoots in Victoria no animal was found to live beyond 3.5 yr (Lobert & Lee 1990). A similar longevity was found in wild eastern barred bandicoots (M Watson pers. comm.). In captivity the usual longevity of these species is 4–5 yr. Captive bilbies usually live to 7–10 yr; the average life expectancy in one wild population was 4 yr (Southgate et al. 2000).
Deciduous claws on digits 2, 3 and 4 of fore limbs lost
Prominent ear bulge
Pouch present in females
Scrotum present in males
Teats present in female pouch
Claws appearing on hind limb digits
Facial vibrissae appear
Righting reflex present
All vibrissae present
Pelage pigment shows on dorsum
Short fur all over body
Eyes commence to open
Detaching from teat
Eyes fully open
Young leave pouch but are not fully weaned
Source: Adapted from Hall (1990) and Bach (1998).
Ears unfused and turned backwards
Facial vibrissae appear
Pelage pigment appears
Pelage pigment complete
Mouth fully open
Eyes fully open
Short fur all over body
Young leave pouch but are not fully weaned
Source: Adapted from McCracken (1990).
The captive management of all wild animals is greatly assisted by knowledge of their natural habitat preferences, diet and behaviour. The wide distribution of bandicoots and bilbies in Australia prior to European settlement meant that they occurred in a wide variety of habitat types ranging from tussock grasslands and heaths to open forest. They adjust their behaviour to exploit altered habitats such as regenerating grasslands after fire, and cleared pasture, as both provide an abundance of insect larvae. All Australian bandicoots and bilbies are nocturnal in behaviour. Most of the bandicoot species rest in shallow grass nests during the day, although the northern brown bandicoot uses hollow logs for daytime shelter. Bilbies construct burrows up to a few metres long for shelter during daylight hours.
4.1 Housing and husbandry
In captivity, bandicoot species are best housed in enclosures with a 10–20 cm sand or soil floor, with areas of leaf litter to allow the animals to florage and dig grass nests. Galvanised wire mesh of 10 × 10 mm must be laid under the substrate to prevent animals digging out of the enclosure. Enclosures should be planted with tussock grasses and/or small shrubs and contain branches and hollow logs. Plywood panels leaning at an angle against enclosure walls and filled with straw bedding provide additional shelter. The walls of the enclosure should be smooth-sided up to 1.5 m to prevent animals from catching their nails in mesh when jumping or climbing. At least one-third of the enclosure should be covered to protect animals from excessive rain and sun.
Bandicoots often display aggression when more than two animals are kept in areas that are too small. This is especially true if males are housed together; therefore bandicoots are often kept as individuals or male/female pairs. The breeding male bandicoot is not removed from the female while she has young in the pouch or at foot but it is important to remove independent young swiftly. Adult bandicoots often injure young animals left with them past the time of independence. A suitably sized enclosure for a pair of bandicoots is about 6 × 3.5 m, although animals are often successfully kept in smaller areas. More animals can be kept in larger enclosures, but aggression between males may be a problem. It was observed that free-ranging eastern barred bandicoots actively defended foraging areas, and that the mean home range of males was 12.94 ha and of females was 2.38 ha (Dufty 1991).
In contrast, bilbies are less aggressive towards other individuals and can more easily be kept in pairs or small groups. A study of captive bilbies suggested that there is a rigid dominance hierarchy among males, but they can be maintained without destructive fighting (Johnson & Johnson 1983). Bilby pairs can be successfully housed and bred in enclosures as small as 2.5 × 2.5 m but ideally should be housed in larger areas (J Butcher pers. comm.). An enclosure size of 8 × 5 m can be used to house a pair of animals or a single male and two females. Animals housed in small enclosures should be provided with a nest box that is accessed via an artificial tunnel of plastic pipe 15 cm in diameter and a few metres in length. Bilbies are usually housed on sand at least 20 cm deep, which must be kept clean and dry to prevent the development of foot problems.
Like the bandicoots, bilbies are nocturnal and shelter in cool burrows during the day. Enclosures for captive bilbies require a means of cooling when the ambient temperature approaches or exceeds 33°C. This can be achieved via overhead fans and mist sprinklers turned on for short periods so the sand substrate does not become excessively moist. Outdoor enclosures for bilbies should have solid sides up to 1 m and be meshed above that height. Bilbies displayed in nocturnal exhibits can be adequately housed in areas separated by solid smooth partitions at least 75 cm high as bilbies tend to climb rather than jump.
Sick or injured bandicoots and bilbies can be temporarily housed as solitary animals in smaller enclosures. If their medical condition contraindicates the use of enclosures with sand or dirt substrates they can be housed on a non-abrasive surface such as epoxy flooring, butcher’s paper, newspaper or clean towels if a softer substrate is required. These should be changed daily. Animals should be provided with a nest box so they can take refuge during the daylight hours. Animals can be kept in such enclosures for lengthy periods while under treatment but may become stressed by frequent handling for medical treatments. Twice daily handling for short periods is usually well-tolerated.
4.2 Individual marking and identification techniques
Passive integrated transponders are commonly used to identify bandicoots and bilbies. The devices are easily inserted under the skin of the interscapular area, usually without the need for anaesthesia in suitably restrained animals. However, the skin on long-nosed bandicoots is very fragile and tears easily as the implanting needle is inserted. In this species it is preferable to have the animal anaesthetised and a stab incision made with a scalpel blade, through which the implanting needle is inserted (L Vogelnest pers. comm.). Skin holes made by implanting needles or stab incisions can be closed with tissue glue. Ear tattoos are a useful method to apply a permanent external identifying mark in bandicoots and bilbies. Tattoos can be applied by the use of pliers containing needle blocks or a tattoo gun. Because of the delicate nature of the pinnae in most bandicoot species, care must be taken when using tattoo guns not to over-apply them in one area. Doing so can quickly result in a full-thickness laceration of the pinna.
Bandicoots and bilbies are best transported in calico bags placed within an adequately ventilated transport box. The bag should be large enough to give the animal some freedom of movement and cushioned with grass bedding or a thick towel. The transport of bilbies in boxes without additional containment within sacks has resulted in nail damage because animals try to dig out of the box (J Butcher pers. comm.). It has been observed that bilbies become more agitated when transported during night-time hours when they would normally be active. This has resulted in some animals suffering nasal abrasions even when contained within a sack (J Butcher pers. comm.). Bandicoot species can be transported in darkened boxes without sacks as long as adequate bedding material such as grass hay is provided. This method of transport is useful when the animal is destined for field release. In that situation transport boxes can simply be opened at the field site, allowing the bandicoot to vacate when it chooses.
Bandicoots and bilbies are omnivorous and consume a diet of insects and other invertebrates, hypogeal fungal fruiting bodies, seeds, grasses and plant bulbs. They occasionally consume small reptiles (Norman 1991). They can be considered to be opportunistic feeders in that they adjust their dietary intake depending on seasonal availability of food items. In a study of bilbies in south-western Queensland, it was found that the plant component of their diet consisted mostly of seeds and did not vary greatly across seasons. In contrast, the consumption of invertebrates varied seasonally when availability increased over summer; the favoured food items were termites and ants (Gibson 2001). Ants and termites were also found to make up a substantial portion of the diet of golden bandicoots studied on Marchinbar Island (NT) (Southgate et al. 1996). It is not surprising that bandicoots and bilbies in Australia’s arid and semiarid zones exploit these invertebrate food items, given the abundance of ants and termites in those areas. Additionally, the colonial habits of ants and termites offer a concentrated food source, minimising required foraging times and maximising rates of prey intake.
Studies of the natural diet of temperate-zone bandicoots indicate that they are opportunistic omnivores (Hume 1999). In a mixture of open pasture and eucalypt forest habitat in southern Tasmania, eastern barred bandicoots were found to have a marked variation in the seasonal consumption of invertebrates, correlating with a spring breeding peak (Reimer & Hindell 1996). The study found that the proportion of plant and fungal material in the diet was highest (58%) in autumn, equal to that of insects in winter and lowest (28%) in spring. Claridge (1991) compared the diets of southern brown bandicoots and long-nosed bandicoots in eucalypt forest in south-east New South Wales. Both species fed mainly on ants, cockroaches, beetle larvae and plant material, but with varying proportions consumed seasonally (presumably dependent on availability). It was noted that the southern brown bandicoot consumed a significant amount of hypogeal fungi in all seasons.
It is likely that a significant amount of the water needs of bandicoots are met by water contained in food items or by intake of dew on consumed plant material. Free-ranging golden bandicoots were able to maintain water and electrolyte balance despite loss of body condition during conditions of severe drought (Bradshaw et al. 1994). Nagy et al. (1991) studied the physiology of free-ranging southern brown bandicoots and concluded that the animals did not drink from water bodies in their environment. Regardless of these findings, bandicoots and bilbies in captivity should be provided with fresh water.
5.1 Diet of captive animals
Diets fed to captive animals usually consist of food items similar to those consumed by their wild counterparts, or at least approximating the nutritional composition (percentage of protein, fat etc.) of the natural diet. The approach to nutrition of captive bandicoots and bilbies in Australia has been the former—there have been no studies aimed at establishing the nutritional composition of natural diets and the actual nutritional requirements of bandicoots and bilbies are unknown. Diets fed to captive animals tend not to vary seasonally, whereas it is well-known that the diet of free-ranging animals often vary widely over the course of a year.
Diets fed to captive bandicoots and bilbies consist of a mixture of commercial dried dog kibble, seeds, insects, invertebrates, vegetables and small amounts of fruit. Some examples of bandicoot and bilby diets used in Australian facilities are reported in Jackson (2003) and the diet fed to eastern barred bandicoots at Melbourne Zoo is presented in Table 13.4. Recently captured wild bandicoots can be encouraged to eat by providing extra invertebrate food items and adding aromatic food items such as canned cat food or highly palatable supplements (e.g. Nutrigel, Troy Laboratories) to the standard diet. These dietary modifications are beneficial in animals debilitated by illness.
Average amounts offered to each animal per day
40 g dried dog kibble
20 g mixed vegetables (chosen from carrot, pumpkin, sweet potato, endive, mushroom, sweetcorn, broccoli and beetroot) and apple
15 g insects (e.g. crickets, mealworms)
The diet shown in Table 13.4 provides (on a dry matter basis) 30% crude protein, 16% fat, 0.89% calcium and 0.82% phosphorus. The fat content of the diet is high because insects are a very rich source of fat. The dried dog kibble is a high-protein puppy formulation (Advance Pedigree Puppy Rehydratable, Masterfoods). These food items are used because a substantial proportion of the natural diet of this species is insects and other invertebrates. Protein concentrations in invertebrates are relatively high, ranging from 40–70% on a dry matter basis (Bernard & Allen 1997). Crude fat content is quite variable in insects with species, season and life stage; it ranges between 10% and 58% (Dierenfield & Barker 1995). While fat is an important source of energy for insectivorous animals, the appropriateness of feeding a diet containing 16% fat year-round warrants further investigation.
6 CAPTURE AND RESTRAINT
6.1 Capture and physical restraint
Bandicoots and bilbies are fairly innocuous and tend not to bite or scratch. They are delicate and timid and great care must be taken at all times to avoid injury to the animal. Spring or gravity traps are used to capture free-ranging bandicoots with the animal attracted into the trap using bait such as a mixture of oats, peanut butter and honey. Capture of bandicoots and bilbies from pens is best attempted when they are in a nesting area so that the risk of injury is minimised. If located in a nest box, a calico bag can be easily slipped over and around the animal to scoop it up.
To capture smaller bandicoots from grass nests, a cloth catch net is often used. Mesh netting is not suitable as it will result in a higher rate of minor abrasions. The aim is to position the net at the head end and flush the animal out into the bag. The net is held with its edge on the ground at one end of the nest and a hand gently slipped under the other end of the nest to feel for the animal’s rump. Prolonged attempts to capture fighty animals when they are moving around an enclosure should be avoided as the animal may injure itself while trying to evade capture. Once the animal is in the net it can be transferred to a soft cloth handling bag. This is facilitated by using a cloth net with a drawstring opening which can be placed inside the top of the handling bag.
Figure 13.3 Physical restraint of a juvenile long-nosed bandicoot.
Smaller species can be captured from a nest box or grass nest by hand restraint. When capturing animals by hand from a grass nest, it is wise to have an assistant holding a net against the ground in front of the nest in case the animal evades the restraint. To capture the animal, one hand is used to apply pressure to the top of the nest to discourage the animal exiting while the other hand is introduced to locate the rump of the animal. Once this is achieved, this hand is moved forward in order to restrain the neck. The animal is lifted out with the rump supported by one hand and the other hand on the back of the animal with the neck restrained between the fore and middle fingers (Fig. 13.3). Bilbies are more difficult to restrain in this manner due to their size. If capturing this species by hand it is most appropriate to firmly grasp the tail base and quickly lift them into a handling bag. Bandicoots should not be restrained by grasping the skin alone as in some species hair is easily lost and the skin can be torn. Bandicoot species should never be restrained by grasping the tail due to its fragility.
Simple examinations can be performed on animals when they are in a bag. The best method of doing this is to sit with the bag on the operator’s lap and expose the areas of interest in a sequential manner while keeping most of the animal inside the bag. Small species can be turned over and gently restrained in the bag between the handler’s legs to allow examination of the pouch.
When releasing animals after an examination it is best to shut them in a straw-filled nest box to allow them to settle. When the handler is leaving the enclosure the box is quietly opened to let the animal exit in its own time.
6.2 Chemical restraint
Inhalation anaesthesia using isoflurane in oxygen delivered via a T-piece is the method of choice for the chemical restraint of bandicoots and bilbies. Most species are easily restrained in a soft cloth bag with the nose exposed to allow placement of a face-mask. Alternatively the mask can be placed over the nose while the animal is wedged in a corner of the bag. Bilbies may struggle excessively during mask inductions and for this reason midazolam at 0.1–0.2 mg/kg IM as a premedication is sometimes useful. Diazepam has also been used as a pre-anaesthetic sedative at a dose of 0.5–1.0 mg/kg IM (Vogelnest 1999). Pre-anaesthetic fasting is unnecessary in bandicoots and bilbies as they are not prone to regurgitation. Intubation is generally easily achieved with the aid of a small-bladed laryngoscope. Suitable endotracheal tube sizes are 2 mm (uncuffed) for smaller species and 3.0 mm or 3.5 mm for bilbies.
Recovery from inhalation anaesthesia is usually rapid and smooth in bandicoots, but bilbies occasionally have slightly prolonged recoveries. Animals should be allowed to recover fully in a nest box before release. If midazolam or diazepam has been used as a premedication, recovery can be aided by the administration of the benzodiazepine antagonist flumazenil at a dose rate of 0.05–0.1 mg per mg of benzodiazepine. This can be delivered by IM or IV injection. Flumazenil can be used during an anaesthetic procedure if it is judged that the midazolam sedation is significantly depressing respiration.
Injectable anaesthetic agents have rarely been used in bandicoots and bilbies as inhalation anaesthesia is simple and safe in all situations.
7 CLINICAL PATHOLOGY
7.1 Haematology and biochemistry
Venipuncture sites most commonly used in bandicoots and bilbies are the femoral vein, the cephalic vein and, in species with a substantial tail, the lateral tail vein. In bilbies, collection of blood is most easily achieved from the jugular vein or lateral tail vein. The jugular vein is also used in the smaller bandicoot species, but more commonly blood is collected from the femoral vein. In many species, the thin skin in the inguinal area means the femoral vein can be visualised. This is particularly true for female animals of most species, where it is visible running inside the pouch. When the femoral vein cannot be directly visualised, its position is located by palpating the femoral artery pulse. The femoral vein runs parallel and just caudal to this artery and a 25 G needle is introduced to the area until blood flashes in the needle hub.
A number of other sites have been used to collect blood from bandicoot species. These include the lateral saphenous vein and medial tibial artery in eastern barred bandicoots (Booth 1994) and the orbital sinus of the northern brown bandicoot (Kemper et al. 1990) and golden bandicoot (Bradshaw et al. 1994). Collection of blood from the orbital sinus of bandicoots is not recommended by this author as other alternatives pose less risk to the animal’s welfare.
7.1.2 Reference ranges and interpretation
Haematology and biochemistry reference ranges have not been established for all species of bandicoot and bilbies. Clarke (2004) presents values derived from small numbers of individuals from a number of bandicoot and bilby species. Wicks (2005) reports on the haematological characteristics of the southern brown bandicoot. Table 13.5 presents blood data collected from captive eastern barred bandicoots and bilbies and from wild southern brown bandicoots. All animals were apparently healthy at the time of blood collection.
Table 13.5 Haematology and biochemistry values (mean ± SD) of the eastern barred bandicoot,1 southern brown bandicoot,2 long-nosed bandicoot3 and greater bilby4
There is no published data on the haematological and biochemical responses of bandicoots and bilbies to various physiological and pathological states. There are also no unique haematological or biochemical features of bandicoots and bilbies. In most cases standard principles of interpretation of results can be applied, however, as is the case in many marsupial species, haematological and biochemical results in bandicoots and bilbies frequently belie the severity of pathological changes.
Bandicoots and bilbies are distinctive among the marsupials in that their young grow and develop very rapidly. Successful hand-rearing of bandicoots and bilbies requires consideration of the milk composition needed to achieve rapid rates of growth. Only three species in this group have had their milk composition studied in detail—the northern brown bandicoot, the eastern barred bandicoot and the southern brown bandicoot (Merchant 1990; Ikonomopoulou et al. 2005; R Rose unpub). These studies showed that the composition of bandicoot milk changes through the lactation period. In the first few days of lactation the milk is very dilute, with total solids measured as 8% (w/w) in the northern brown bandicoot. During lactation the milk of all three species becomes steadily more concentrated. At 3–4 wk of lactation solids have risen to around 28%, and by the end of lactation the milk of the northern brown bandicoot contains 45% solids. Eastern barred bandicoot milk contains 54% solids. Table 13.6