Veterinary Aspects of Hand-Rearing Orphaned Marsupials

1 MARSUPIAL NEONATAL BIOLOGY AND PHYSIOLOGY: CONSIDERATIONS FOR HAND-REARING


The hand-rearing of any young animal should mimic the natural situation as closely as possible to optimise its chance of normal health, growth rate and assimilation into a social group of its own species. It is therefore important to have a good knowledge of the development, growth, environment, diet and parental care of the young animal in the natural rearing situation.


1.1 Development of marsupial neonates


The characteristic of marsupials that most clearly distinguishes them from eutherian mammals is the immaturity of their young at birth (Tyndale-Biscoe & Janssens 1988). Gestation is very short in marsupials, ranging from 11–35 d (Tyndale-Biscoe & Renfree 1987) and the young are born at an early embryonic stage, weighing from 3–6 mg in the honey possum (Tarsipes rostratus) to approximately 900 mg in the larger kangaroos. The neonate climbs from its mother’s cloaca towards her mammary gland where it attaches to a teat and completes embryonic development and growth (Russell 1982; Merchant 1989). In most marsupial species, the teats are enclosed within a bag-like pouch that supports the young as it grows, providing an environment with stable temperature and humidity. Many small dasyurid species and the numbat (Myrmecobius fasciatus), however, have no pouch. In some of these dasyurids, lateral folds of skin develop during gestation and progressively cover the young after attachment, partially enclosing them. As they grow, the young become exposed and hang from the mother’s ventrum, supported by the ilio-marsupialis muscle that extends into the mammary gland and each teat. Larger dasyurids, bandicoots, wombats, marsupial moles, the koala (Phascolarctos cinereus), yellow-bellied glider (Petaurus australis), musky rat-kangaroo (Hypsiprymnodon moschatus) and greater bilby (Macrotis lagotis) all have permanent enveloping pouches that open caudally. All other macropods, possums and gliders have deep permanent forward-opening pouches. These permanent pouches may be closed and opened by contraction and relaxation of the underlying muscle, the panniculus carnosus. The number of teats varies between species, ranging from two to twelve. In many species the normal litter size is less than the number of teats and newly born young will attach to teats that were not used by the preceding offspring (Tyndale-Biscoe 2005). In dasyurids, particularly the smaller species, it has been observed that some species give birth to more young than can be accommodated on the teats (see Chapter 10).


The newborn marsupial is a unique composite of embryonic structures and precociously developed functional organs. The head, shoulders and fore limbs are relatively large and well-developed, enabling it to make its way to the teats unaided, whereas the hind limbs are vestigial at this stage. The neonate has closed eyes and the lips of the mouth are fused laterally, leaving only a small rostral opening. The buccal cavity, however, is large and the tongue is well-developed and muscular, allowing the young to firmly attach to a teat and commence suckling. The pinnae of the ears are fused forwards to the skin of the head. The stomach, duodenum and pancreas are in an advanced stage of development at birth, permitting digestion of milk and absorption of nutrients, but the remaining intestinal tract is poorly developed at this stage (Russell 1982; Tyndale-Biscoe 2005). The neonatal kidneys cannot concentrate urine, but water loss is compensated by the continuous suckling of the mother’s dilute early-stage milk. The newborn marsupial is bright red with prominent subcutaneous blood vessels and a moist skin. While it has functional lungs, cutaneous respiration also plays a role in oxygenation during the initial climb to the pouch and in the early days of pouch life (Tyndale-Biscoe 2005). The pouch young (PY) has a form of haemoglobin adapted to the air in the pouch that is lower in oxygen and higher in carbon dioxide concentrations than ambient levels (Baudinette et al. 1985). The early PY is hairless and thyroid function is not yet developed, hence it is completely ectothermic, relying on the stable temperature of the pouch for thermoregulation (Russell 1982; Tyndale-Biscoe 2005).


As the PY grows, it undergoes a series of physical changes. The rate of growth and length of pouch life varies greatly between marsupial species, but the sequence of development of these changes is similar for all species. This development has been best studied in the tammar wallaby (Macropus eugenii) and the sequence in this species is indicative of the general marsupial pattern. After a gestation period of 28 d, the tammar wallaby is born at a weight of 0.3–0.4 g. On arrival in the pouch the neonate attaches to one of four teats. If the mother has been recently suckling a previous offspring, only three teats are available to the neonate, as the suckled teat is too large and elongated. For the first 100 d of pouch life, the PY remains continuously attached to that teat. There will be no milk production from the remaining teats from two days post partum, hence transfer to another teat later in lactation is not possible. During this first 100 d, the pinnae become detached from the head and change to pointing backwards. The upper and lower lips gradually separate from each other so the mouth opening becomes progressively larger. The skin gradually becomes pigmented and whiskers develop. At approximately 100 d the PY weighs 100 g, its lips are fully separated and it relinquishes the teat for the first time. Thereafter, it is intermittently attached until weaning and the process of dental eruption commences. At about 140 d, the eyes open and a fine layer of fur has formed over the body. By day 160, the kidneys are fully developed and the PY can produce concentrated urine. By day 180, the fur has thickened, thyroid function has fully developed and the PY has become endothermic (Tyndale-Biscoe & Janssens 1988; Tyndale-Biscoe 2005).


At this stage, the young marsupial is considered roughly equivalent developmentally to the newborn eutherian. In most species, this is the time of first exit from the pouch (Maynes 1976; Russell 1982). The preferred body temperature of the newly endothermic PY is several degrees lower than the temperature inside the closed pouch as this expends the least amount of energy and oxygen. It therefore needs to dissipate heat and achieves this by occasionally putting the head out of the pouch, and in some species begins to nibble grass or leaves at these times. The tammar wallaby first leaves the pouch at approximately 200 d and begins to hop around, intermittently returning to the pouch until it exits permanently at about 250 d. Herbage progressively forms a greater proportion of the young’s diet between days 200 and 250 but it continues to drink milk, with peak milk intake occurring at day 240. Significant digestive physiological changes occur at this time as the diet gradually transitions from high-fat milk to grass and herbs. The gastrointestinal tracts of young herbivorous marsupials require inoculation with appropriate bacteria and protozoa to facilitate fermentation of ingesta in the forestomach in some species and caecum in others. Macropods likely acquire this microflora by grazing on herbage among the faeces of adult conspecifics and by licking saliva from their mother’s lips (Tyndale-Biscoe 2005). Young common wombats (Vombatus ursinus) at the age of first emergence from the burrow have been observed to eat small moist faecal pellets from adults which differ from the normal dry faecal cubes (Triggs 1996; Boer 1998). The young koala feeds on a semi-liquid substance termed ‘pap’ produced from its mother’s cloaca soon after it commences putting its head out of the pouch (see Chapter 8). Pap is unlike normal koala faeces and microbially resembles the contents of the caecum (Osawa et al. 1993).


Most young marsupials continue to suckle occasionally following permanent pouch exit. In the tammar wallaby, suckling ceases between days 300 to 350 (Tyndale-Biscoe & Janssens 1988). The period following initial pouch exit is one of accelerated growth in all species. The body weight of the young tammar wallaby increases from 500 g at 200 d to 2 kg at 300 d, then to 3 kg at 360 d (Janssens et al. 1997). Female marsupials reach sexual maturity shortly after weaning in most species. Males generally mature at a later age.


1.2 Pouch environment


The marsupial pouch provides the developing young with an environment of high stable humidity and temperature. For the hairless PY, the moist humid environment likely plays a role in cutaneous respiration immediately after birth, and subsequently prevents drying of the skin and dehydration (Fig. 2.1). Pouch temperature has been measured in several species as 34–36°C, slightly lower than marsupial adult body temperature (35.5–37°C) (Tyndale-Biscoe 2005). Young macropods, koalas, wombats and brushtail possums (Trichosurus spp.) will usually be solitary in the pouch, but the young of most other species generally share the pouch with one or two littermates (Russell 1982). When the neonate attaches, the teat is small (1–5 mm long) but it gradually elongates as the PY grows, reaching a length of several centimetres by late lactation, enabling access for suckling by the emerged young. Following weaning, these suckled teats gradually return to their original size, in readiness for attachment by new offspring. The pouch also expands to accommodate the growing young, then involutes following final pouch exit. Thermal intolerance is the main stimulus for the PY to commence leaving the pouch, but it appears that the mother also plays a role in determining the time of permanent emergence, in many cases denying re-entry at the time of birth of the next offspring.


art


Figure 2.1 Pouch of an eastern barred bandicoot, Perameles gunnii, with newborn PY. Note the deep moist pouch interior with a caudally directed opening, characteristic of bandicoots.


1.3 Maternal care


Russell (1982) described three basic patterns of maternal care seen across the range of marsupial species.


Pattern A is seen in species with shallow pouches and large litters, e.g. pygmy possums (Burramyidae) and dasyurids. Initially the PY are well-attached to the teats, but when their lips become fully open and they can release the teat the mother leaves them in a nest when she goes out to feed. At this stage their eyes are closed, they have little fur and are probably unable to thermoregulate. While in the nest, milk is their only food. When their eyes are open and they are well-furred, they begin to leave the nest with their mother, on her back or at foot. Eventually they leave the nest alone to forage, returning occasionally to their mother to suckle, until weaning (Russell 1982).


Pattern B is seen in species that utilise nests or burrows and have deep pouches, e.g. ringtail possums (Pseudocheirus spp.), brushtail possums, gliders, wombats, bandicoots and the greater bilby After they begin to release the teat, the PY remain in the pouch until their eyes are opened, they are well-furred and able to thermoregulate. They leave the pouch for the first time while their mother is in the nest and may return to it at times, although they will generally be left in the nest when their mother goes out to feed. While in the nest, milk is their only food. After a period, the young begin to leave the nest with the mother, on her back or at foot. Eventually they leave the nest alone to forage, returning occasionally to their mother to suckle, until weaning (Russell 1982).


Pattern C is seen in species that have deep pouches and don’t utilise nests, e.g. macropods and the koala. When the PY is well-furred and the eyes are open, it begins to protrude its head out of the pouch occasionally. It then leaves the pouch for brief periods that gradually lengthen until it is permanently out of the pouch. It continues to suckle from the mother and follows her closely until weaning, and in some species beyond that time (Russell 1982).


In all cases, during the pouch-dwelling period, the mother keeps the PY and pouch clean by frequently licking them to remove urine and faeces. It is conjectured that this process may also stimulate the PY to urinate and defecate, hence they may be unable to do this spontaneously in the hand-rearing situation (Russell 1982). This maternal behaviour likely plays an important role in water conservation in arid-dwelling species, as the passing of dilute urine by the PY could otherwise result in severe water loss from the mother–young unit, compromising their survival. It is probable that this behaviour also plays a role in immune protection for the PY against potential pathogens in its immediate environment. Microorganisms ingested by the mother from the pouch and faeces will induce production of specific maternal antibodies that will be transferred to the PY in the immunoglobulins of the milk (Tyndale-Biscoe 2005). The mother continues to groom her young after it leaves the pouch, although it will start self-grooming at this stage (Russell 1982).


Macropods, possums, koalas and wombats, despite the considerable manual dexterity of the three former groups, do not assist young to return to the pouch. Greatest mortality occurs when young are big enough to fall out of the pouch, but not large enough to return to it unaided (Russell 1982).


1.4 Passive immunity and development of the immune system


Immunology of marsupial PY has been studied in a range of species, with most work being done on the quokka (Setonix brachyurus), common wallaroo (Macropus robustus), tammar wallaby and Virginia opossum (Didelphis virginiana). These studies demonstrated significant differences in the development of the immune systems of marsupials and eutherian mammals. In eutherians, thymus development largely occurs during gestation, and in most species active immune responses are almost mature at the time of birth. In the final stages of immune system maturation, the neonate is protected by a short period of passive transfer of maternal immunoglobulins, either across the placenta, as in the rabbit and human, or from the first milk (colostrum), as in horses and ruminants (Deane & Cooper 1988; Tyndale-Biscoe 2005).


In contrast with eutherians, no lymphoid tissue is present in marsupials at birth, hence the neonate is not immunocompetent (Tyndale-Biscoe 2005). Within the first few days of life lymphocytes appear in the thymus, the first lymphoid tissue to develop. All diprotodont marsupials except wombats (macropods, possums, gliders, koala) differ from most eutherians in that they possess both a cervical and thoracic thymus. Wombats have only a cervical thymus and the polyprotodont marsupials (dasyurids, bandicoots, bilby, marsupial moles) possess only a thoracic thymus. In the species with two thymi, the cervical is the larger and dominant one at all stages of development (Yadav 1973). Within the first week, the first lymph nodes appear and in the next few weeks differentiated lymphoid tissue develops in the spleen. Active immunity commences development at days 7–17 when Hassall’s corpuscles are first evident in the thymus and antibody responses to antigen can be detected. Most species reach immune system maturation at the time of first release of the maternal teat, approximately halfway through pouch life (Basden et al. 1997; Old & Deane 2000).


During the period of lymphoid tissue development, PY are protected by the passive transfer of maternal immunoglobulins, essential for survival in the microbially rich environment of the pouch. Transplacental transfer from the yolk sac fluid has been demonstrated in only one species, the tammar wallaby (Deane et al. 1990). In all species studied, this protection is primarily provided through immunoglobulins secreted into the milk until the PY first relinquishes the teat, and in some cases until the time of first exit from the pouch. The immunoglobulins are absorbed unchanged across the gut epithelium of the PY throughout this period, in contrast with eutherians in which absorption of colostral antibodies is only possible in the first few days after birth. In the quokka, this passively acquired antibody has a half-life of only 8–9 d, and has virtually disappeared from the blood by 4–6 wk after cessation of suckling (Old & Deane 2000; Yadav 1971). It is also believed that secretions from the pouch epithelium and macrophages found in marsupial milk at different stages of lactation may play roles in immunological protection of the PY (Old & Deane 2000).


Hence, throughout most of pouch life the PY has two sources of immunological protection—passively acquired maternal antibodies and its own active responses. Pouch life begins with the young wholly dependent upon maternal protection and ends with it wholly dependent upon its own immune system (Deane & Cooper 1988). Hand-reared PY must be considered at risk from infectious disease because they are no longer receiving passive immunity, they will have lost most maternal immunoglobulins by about 4 wk after separation from the mother, and they are protected only by an underdeveloped active immune system.


1.5 Marsupial milk


Milk production in eutherian mammals has been studied for a wide range of species. The milk of each species is relatively uniform in composition throughout lactation once it is fully established but there are major differences between species in milk concentration and composition, reflecting the differences in lifestyles, suckling regimes and the production of altricial or precocial young. In contrast, in marsupials, milk composition is relatively uniform between species, reflecting the similarities in development and maternal care across the taxa. Notably, however, because the milk of marsupials must support the young from its embryonic state at birth until it is independent, the composition changes profoundly both quantitatively and qualitatively during the course of lactation (Merchant 1989; Tyndale-Biscoe 2005). Studies have demonstrated that the milks of numerous species show similar sequences of change through lactation (Jackson 2003; Tyndale-Biscoe 2005). These changes in the tammar wallaby and common brushtail (Trichosurus vulpecula) are examples of this marsupial trend (Figs 2.2, 2.3). In these species, there is a gradual increase in the carbohydrate concentration from 4–6% at birth to a peak of 11–13% shortly before first pouch emergence, after which there is a rapid decline to 1% in the tammar wallaby and 4% in the common brushtail. The peak concentration reached is very high compared with the concentration of carbohydrate in the milk of most eutherians. Protein concentration also gradually increases from 3–4% at birth to 7–8% at pouch exit, followed by a slight decrease. Changes in lipid concentration are more variable between species, especially towards the end of lactation, but the general trend is an initial gradual increase from 1–2% at birth, with a sharp rise at the time of pouch emergence up to 9% in the common brushtail and 24% in the tammar wallaby. The net effect of these changes is a gradual increase in the energy content of the milk throughout lactation. In the tammar wallaby the change is from approximately 2500 kJ/L at birth to 5000 kJ/L at day 180, then a rapid increase to 11 000–12 000 kJ/L by days 250–300 (Messer & Walker 1992). These marked changes meet the increasing energetic demands of the growing PY as it gradually becomes more active and develops endothermy.


In eutherians, lactose is the major milk sugar. It is rapidly digested to galactose and glucose by the action of the intestinal lactase, b-galactosidase, located extracellularly in the microvillus brush border of the gut epithelium (Messer et al. 1989). In contrast, marsupial milk has very low levels of lactose. The predominant carbohydrates for most of lactation are oligosaccharides of increasing size, most composed of 1 unit of lactose and 1–8 units of galactose. Since single molecules of oligosaccharides exert the same osmotic pressure regardless of size, these increasingly larger oligosaccharides provide progressively higher levels of carbohydrate to the growing PY while maintaining the milk necessarily isotonic with plasma (Tyndale-Biscoe 2005). In contrast to the eutherian model, these oligosaccharides are transported from the gut lumen into the epithelial cells where they are digested to galactose and glucose by intracellular b-galactosidase. These monosaccharides then enter the circulation, providing the major energy source of the growing PY. Studies in the tammar wallaby suggest that the transport of sugars into the cells may occur via pinocytosis. As this is a relatively slow process, it limits the rate at which artificial formula containing lactose or oligosaccharides may be bottle-fed to hand-reared PY without causing diarrhoea. Mother-reared PY apparently suckle constantly, presumably drinking small volumes very frequently. For practical reasons, hand-reared PY are fed less frequently. Sugar accumulated in the gut lumen, due to a combination of infrequent high-volume feeds and the slow process of pinocytosis, may result in an osmotic diarrhoea (Messer et al. 1989).


art


Figure 2.2 Changes in the mean concentrations of lipids, proteins and carbohydrates in the milk of the tammar wallaby throughout lactation. The pouch exit bar indicates the times of initial and permanent pouch exit. (Source: Adapted from Messer & Walker (1992).)


art


Figure 2.3 Changes in the mean concentrations of lipids, proteins and carbohydrates in the milk of the common brushtail throughout lactation. The pouch exit bar indicates the times of initial and permanent pouch exit. (Source: Adapted from Messer & Walker (1992).)


The rapid decrease in carbohydrate content of marsupial milk that occurs shortly before first pouch emergence is accompanied by a change from large oligosaccharides to more simple sugars, mainly galactose in macropods, and lactose in brushtail and ringtail possums. In addition to intracellular enzyme, brushtail possums have extracellular lactase that increases in activity at the time of pouch emergence (Messer & Walker 1992). These rapid quantitative and qualitative changes in milk carbohydrates occur as the PY is starting to eat solids, and are likely related to the establishment of conditions in the gut suitable for the microbial populations required for the digestion of herbage (Merchant 1989). Hence the function of the alimentary tract is transitioning from the digestion of simple milk sugars to fermentative digestion of complex plant carbohydrates. At the time of this change, the lipid concentration of the milk dramatically increases as it becomes the major energy source, supporting the emerging PY at its time of most rapid growth and highest energetic demands as it develops locomotion and independent thermoregulation (Tyndale-Biscoe 2005).


Marsupial milk lipid is principally composed of triglycerides. The predominant fatty acid in early lactation is palmitic acid, which may be important in the synthesis of surfactants required for oxygen transport across the lungs. In the second half of lactation oleic acid is predominant, playing a key role in the synthesis of myelin sheaths around developing nerve fibres (Tyndale-Biscoe 2005).


Milk protein has been mainly studied in the tammar wallaby. Marked changes in amino acid composition occur during lactation, notably including a sudden increase in sulphur-containing amino acids, particularly cysteine, during the period of hair follicle development. This may be of significance in hand-rearing as many PY are raised from this stage of development (Messer & Walker 1992).


The concentrations of minerals in marsupial milks are similar to those in eutherians, with a few notable exceptions. Copper and iron concentrations are substantially higher in marsupial milks, particularly in early lactation when the neonatal liver has a limited storage capacity. In the early milk of tammar wallabies, copper and iron concentrations are approximately 5 mg/L and 22 mg/L respectively, compared with 0.1–0.6 mg/L and 0.3–0.5 mg/L respectively in eutherian milk. Calcium and phosphorus concentrations increase throughout lactation, doubling in levels from early to late-stage milk, presumably reflecting the increasing requirements for these elements in the accelerated bone growth of the older PY. Sodium and potassium concentrations also change during lactation, with high concentrations of sodium in early milk decreasing to low levels at the stage of kidney maturation in the pre-emergent PY. Potassium levels follow the opposite trend (Merchant 1989; Tyndale-Biscoe 2005).


In summary, lactation in marsupials is a much more complex and changing process than that of eutherians. A major challenge in hand-rearing marsupials is offering a suitable substitute milk diet that can meet the changing needs of the developing PY.


1.6 Weaning


In species with patterns A and B modes of maternal care, weaning commences when the PY leaves the nest and accompanies its mother when she is foraging. In pattern C species, it commences when the PY first protrudes its head from the pouch, koalas eating pap and macropods nibbling a little grass, although they eat very little until they first fully emerge from the pouch. Weaning results mainly from a gradually increasing lack of co-operation by the mother when the young attempts to suckle (Russell 1982). The natural diets of adult marsupials are described in later chapters.


2 CRITERIA FOR INTERVENTION


Marsupial PY may require hand-rearing for several reasons. In Australia, the majority of hand-rearing cases are wildlife found orphaned after the mother’s death by motor vehicle accident, shooting or predation. A live PY may be found in the pouch of the dead mother or emergent young may be found near the body. In some cases, emergent PY or young-at-heel may stray from the site after the mother is killed, and as they are still partially milk-dependent they will not survive alone. If pouch examination of a dead female reveals a lactating mammary gland and elongated teat, a careful search should be made of the accident scene for the dependent young. For PY at the stage of permanent attachment to the teat, removal must be performed carefully to avoid palatal and lip injuries as the tip of the suckled teat is expanded to fill the oral cavity. Alternatively, the teat may be cut from the pouch and pinned to the inside of the PY’s substitute pouch. The PY will generally release it within 2–3 hr (L Dennis pers. comm.).


Wild PY may be found and hand-reared after they have been thrown from the mother’s pouch or dislodged from her back during pursuit by a predator or in response to other stressful stimuli. It is a survival technique of some marsupial species to jettison PY in such circumstances by the simultaneous relaxation of the pouch sphincter and contraction of the longitudinal subcutaneous muscles of the pouch, effectively causing the pouch to disappear. PY that are still permanently attached to the teat are rarely thrown, as they are not a great burden to the fleeing mother. Emergent young are often safely reunited with their mother following the stressful event. The at-risk animals in these circumstances are the intermittently attached, pre-emergent PY as they are readily ejected but incapable of independently returning to the pouch. They will not survive without intervention (Booth 2002).


In captive marsupials, PY may require hand-rearing following the death of the mother. They may also be intentionally pulled for hand-rearing for a range of reasons, including failure to thrive, illness of the PY or mother, history of poor maternal care by an individual, and the conditioning of a young animal for display or educational purposes. PY may also be thrown from the pouch in captive animals, most commonly during or following capture and restraint. On these occasions, attempts may be made to return the ejected PY to the mother’s pouch as an alternative to hand-rearing. This is rarely successful with PY at the stage of permanent attachment to the teat—if they have been thrown, it is generally an indication of failure of lactation or poor PY viability. Return to the pouch of pre-emergent, intermittently attached PY is best achieved following anaesthesia of the mother. The PY is warmed and rehydrated if required then returned to the pouch, and several long pieces of adhesive tape placed transversely across the pouch opening. The mother will generally groom off this tape over the next few days. It should be noted that such attempts may be unsuccessful and the PY may be re-thrown, hence it is advisable to alternatively make an immediate decision to hand-rear in the case of valuable individuals. To reduce the risk of ejection of pre-emergent PY following anaesthesia of females, care should be taken throughout the procedure to optimise the viability of the young, maintaining it at normal body temperature by preventing heat loss in the mother and closing the pouch with clothes pegs. If the female’s body temperature drops significantly, a local heat source should be applied to the outside of the pouch, taking care to avoid overheating. It is advisable to tape the pouch closed prior to recovery as described above.


Fostering PY to lactating females of the same or similar species is possible only in limited circumstances and is rarely a viable alternative to hand-rearing. It is, however, utilised as a tool in endangered species breeding programs to increase the reproductive output of valuable individuals by double- and triple-clutching (Chapter 7, section 11.2.7). Several critical criteria must be met to optimise the success of this procedure: the foster mother must be of a species of similar size, pouch-life length and life habits to the PY, she must be at a very similar stage of lactation as the natural mother so that her teat size and milk composition is suitable for the PY, and her own young must be removed prior to cross-fostering (Booth 2002).


3 ASSESSMENT OF THE POUCH YOUNG


PY are very distressed if not enclosed within a pouch. On presentation, they should be immediately placed in a cloth bag, woollen hat or thick sock or wrapped loosely in a blanket. The artificial ‘pouch’ should then be placed in a heated box or against a person’s skin beneath warm clothing until the PY can be examined.


Assessment of history for wild PY must include their exact geographic origin. If the PY is successfully hand-reared for release, most wildlife agencies require that it be released in close proximity to its site of origin. History-taking should include how the PY was orphaned, as this circumstance may influence its condition. It should also include the length of time since the PY was found, and details of its environmental conditions and nutrition since discovery.


A full clinical examination should be performed to assess the viability of the PY (sections 6.2 and 6.3 describe techniques for restraint and clinical examination). Assessment must be made of the animal’s general condition, hydration status and attitude. Many PY present with some degree of hypothermia and dehydration due to a lengthy interval between orphaning and discovery, or because their rescuer did not provide adequate environmental and/or nutritional support. The healthy newly orphaned or ejected PY will wriggle vigorously, resist handling, demonstrate pouch-seeking behaviour and may vocalise loudly. Examine for problems related to the orphaning incident. Victims of vehicular accidents and arboreal species found under trees may have contusions and/or fractures. The most common fractures in macropod PY orphaned by vehicular accidents are of the tail and hind limbs (usually tibias or metatarsals), often occurring in a triad of fractures of both limbs and the tail (Speare 1988). Examine closely for this triad if one fracture is detected. Young possums, particularly ringtails, are frequently victims of cat attack and often present with small puncture wounds that may be difficult to find in their dense fur. Potentially fatal septicaemia is a common sequela to these wounds.

Only gold members can continue reading. Log In or Register to continue

May 28, 2017 | Posted by in GENERAL | Comments Off on Veterinary Aspects of Hand-Rearing Orphaned Marsupials
Premium Wordpress Themes by UFO Themes