Macropus Giganteus Research Articles

Experimental manipulation of fertility reveals potential lactation costs in a free-ranging marsupial

Lactation is the most energetically expensive component of reproduction in mammals. Theory predicts that reproducing females will adjust their behaviour to compensate for increased nutritional demands. However, experimental tests are required, since comparisons of the behaviour of naturally reproducing and non-reproducing females cannot distinguish between true costs of reproduction, individual differences or seasonal variation. We experimentally manipulated reproduction in free-ranging, eastern grey kangaroos (Macropus giganteus), using a fertility control agent. Our novel field experiment revealed that females altered their behaviour in direct response to the energetic demands of reproduction: reproducing females increased bite rates, and thus food intake, when the energetic demands of lactation were highest. Reproducing females did not reduce the time spent on vigilance for predators, but increased their forage intake on faecal-contaminated pasture, thereby increasing the risk of infection by gastrointestinal parasites-a largely unrecognized potential cost of reproduction.

Bone fluoride concentrations of eastern grey kangaroos (Macropus giganteus) resident near an aluminium smelter in south-eastern Australia

Lesions of skeletal and dental fluorosis have been described recently in eastern grey kangaroos (Macropus giganteus). The present study further examined the epidemiology of skeletal fluorosis in this species. Bone fluoride concentrations were obtained from a range of skeletal sites of animals from a high (Portland Aluminium) and a low (Cape Bridgewater) fluoride environment in Victoria, Australia. Age, but not sex, affected the mean bone fluoride concentration of kangaroos. For a given age, bone fluoride concentrations were significantly higher in kangaroos from Portland than Cape Bridgewater. Concentrations varied between skeletal sites examined, with samples containing cancellous bone having higher fluoride concentrations than those containing only cortical bone.

Experimental reduction of native vertebrate grazing and addition of logs benefit beetle diversity at multiple scales

Summary 1. High densities of vertebrate herbivores can be a significant barrier to ecological restoration in many parts of the world because of their impact on vegetation biomass. A common method for managing vertebrate herbivores is the use of exclosure fences, but very few studies have examined how small-scale structural refugia (e.g. logs) can mitigate grazing impacts. We examined how beetles responded to experimentally manipulated kangaroo Macropus giganteus grazing levels using both exclosure fences and addition of logs over a 16-month period. 2. We analysed beetle responses across (a) one-hectare sites, by focusing on the interaction between grazing level and log volume, and (b) microhabitats, by focusing on the interaction between grazing level and microhabitat structure (in open ground or at experimental logs). 3. At the site scale, we detected significant negative effects of grazing and positive effects of logs on beetle abundance and species richness. Beetle trophic groups responded in the same direction across grazing levels with herbivores, detritivores and predators all having higher abundance and species richness at low grazing levels. Logs applied at 20 t ha−1 in clumped arrangements had the largest positive effect on beetles at low grazing levels. At the microhabitat scale, beetles sampled adjacent to experimental logs showed an increase in abundance and species richness compared with beetles sampled from open ground, indicating logs are acting as microhabitat buffers from grazing. 4. Synthesis and applications. A reduction in grazing level had benefits for the abundance and species richness of beetles at the site scale. Further benefits were achieved at both site and microhabitat scales when logs are used in combination with exclosure fencing. For ecological restoration, exclosure fences and logs can be used to manage the impacts of vertebrate herbivores at different spatial scales. The rapid response of beetles suggests there may be potential for cascading effects on other biota as a consequence of reduced grazing, including increased food availability for insectivorous vertebrates.

Haemorheology of the eastern grey kangaroo and the Tasmanian devil

The blood of two Australian marsupials, the eastern grey kangaroo (Macropus giganteus) and the Tasmanian devil (Sarcophilus harrisii), has been reported to have greater oxygen-carrying capacity (i.e. haemoglobin content) when compared with that of placental mammals. We investigated whether alterations of blood rheological properties are associated with the increased oxygen-carrying capacity of these marsupials. Eastern grey kangaroos (n = 6) and Tasmanian devils (n = 4) were anaesthetised for blood sampling; human blood (n = 6) was also sampled for comparison. Laboratory measurements included blood and plasma viscosity, red blood cell (RBC) deformability, RBC aggregation and the intrinsic tendency of RBC to aggregate, RBC surface charge and haematological parameters. Scanning electron micrographs of RBC from each species provided morphological information. High-shear blood viscosity at native haematocrit was highest for the Tasmanian devil. When haematocrit was adjusted to 0.4 L L–1, lower-shear blood viscosity was highest for the eastern grey kangaroo. RBC deformability was greatly reduced for the Tasmanian devil. Eastern grey kangaroo blood had the highest RBC aggregation, whereas Tasmanian devil RBC did not aggregate. The surface charge of RBC for marsupials was ~15% lower than that of humans. The dependence of oxygen-delivery effectiveness on haemoglobin concentration (i.e. oxygen content) and blood viscosity was quantitated by calculating the haematocrit to blood viscosity ratio and was 15–25% lower for marsupials compared with humans. Our results suggest that environmental pressures since the marsupial–monotreme divergence have influenced the development of vastly different strategies to maintain a match between oxygen demand and delivery.

Gammaherpesvirus infection in a free‐ranging eastern grey kangaroo (Macropus giganteus)

A gammaherpesvirus was detected by polymerase chain reaction (PCR) in ocular, nasal and oropharyngeal swab samples collected from an adult free-ranging male eastern grey kangaroo (Macropus giganteus) with clinical signs of severe respiratory disease. This is the first time a gammaherpesvirus has been detected in a free-ranging macropod in Australia. The nucleotide sequence of a conserved region of the DNA polymerase gene of the detected virus showed a high degree of identity to a gammaherpesvirus recently detected in a zoological collection of eastern grey kangaroos in North America. The detection of this gammaherpesvirus in a free-ranging, native eastern grey kangaroo provides evidence that this species is a natural host.

A capture technique for free-ranging eastern grey kangaroos (Macropus giganteus) habituated to humans

Available methods to capture free-ranging kangaroos differ in ease of use, selectivity, risk of injury and suitability to specific environments. We describe a simple technique involving the syringe from a ‘jabstick’ attached to an extendable, aluminium pole. We also examine responses of eastern grey kangaroos (Macropus giganteus) to a range of doses of Zoletil®. We captured 307 eastern grey kangaroos that were habituated to humans in Victoria, Australia, from November 2007 to October 2009. We approached kangaroos on foot, and injected the hind limb muscle mass with the pole syringe extended up to 4.85 m. We used Zoletil® 100 at a dose rate of 4.1 ± 1.3 mg kg–1 (mean ± s.d., n = 274). Induction was rapid (4.3 ± 2.0 min, n = 185) and only weakly related to dose (r2 = 0.06). There was no clear relationship between age, sex or body condition and induction time. This pole syringe technique can be successfully and safely used wherever animals can be approached closely, regardless of body condition. The technique provides an effective means to immobilise habituated kangaroos for research and management.

Differential resistance of mammalian sperm chromatin to oxidative stress as assessed by a two-tailed comet assay

Protamines of eutherian species are cysteine-rich molecules that become cross-linked by disulfide bonds during epididymal transit, whereas the protamines of most marsupial species lack cysteine residuals. The present study made use of the differences in protamine structure between eutherian and metatherian mammal spermatozoa to examine the comparative resistance of sperm DNA to oxidative damage in three eutherian species (Mus musculus, Homo sapiens, Sus domesticus) and three metatherian species (Vombatus ursinus, Phascolarctos cinereus, Macropus giganteus). Sperm DNA fragmentation of samples exposed to increasing concentrations of hydrogen peroxide was assessed by means of the two-tailed comet assay. The sperm DNA of the marsupial species studied were significantly more sensitive to oxidative stress than the spermatozoa of eutherian species. Such susceptibility is consistent with the lack of disulfide cross-linking in marsupial sperm chromatin and suggests that the oxidation of thiols to disulfides for chromatin condensation during epididymal transit in eutherian mammals is likely to be important in order to provide stability and protect these cells from the genotoxic effects of adverse environments.

Candidatus Bartonella antechini: A novel Bartonella species detected in fleas and ticks from the yellow-footed antechinus (Antechinus flavipes), an Australian marsupial

Bartonella are fastidious, Gram-negative, aerobic bacilli belonging to the Alphaproteobacteria group. In the last ten years, the discovery of new Bartonella species from a variety of mammalian hosts, arthropod vectors and geographical areas has increased. More than 20 species of Bartonella have been identified, of which approximately thirteen are associated with disease in humans and animals. Recently, four novel species of Bartonella were isolated from mammalian hosts in Australia: Bartonella australis from eastern grey kangaroos (Macropus giganteus) and Bartonella rattaustraliani, Bartonella queenslandensis and Bartonella coopersplainsensis from rodents. Bartonella-like organisms have also been detected from Ixodes tasmani ticks collected from koalas (Phascolarctos cinereus). However, very little is known about Bartonella spp. in other marsupials in Australia. We report the identification of a novel Bartonella species detected from fleas (Acanthopsylla jordani) and ticks (Ixodes antechini) collected from a small carnivorous marsupial, Antechinus flavipes (Mardos or Yellow-footed antechinus) in the southwest of Western Australia. New nested-PCRs targeting the gltA gene and the ribosomal ITS region were developed as part of the present study. DNA sequencing of the 16S rRNA, gltA, ftsZ and rpoB genes and the ribosomal ITS region revealed that this detection is a distinct Bartonella species and is related to B. australis isolated from kangaroos. This is the first report of two different possible arthropod vectors in Australia (ticks and fleas) being infected with the same species of Bartonella. We propose the name Candidatus Bartonella antechini n. sp. for the recently characterized organism.

Wildlife-associatedCryptosporidium fayeriin Human, Australia

To the Editor: Molecular tools are essential for Cryptosporidium spp. identification, taxonomy, and epidemiology because of morphologic similarities between species within this genus. Molecular analyses have now identified 22 Cryptosporidium spp. and >40 cryptic species (i.e., genotypes) across all vertebrate classes (1). The myriad of potential Cryptosporidium spp. hosts, in conjunction with the robustness of the infectious stage (oocyst), means diverse Cryptosporidium spp. constantly circulate through the environment. This circulation increases the potential for disease from a diversity of contamination sources. Human cryptosporidiosis is a global problem causing illness in young, elderly, immunocompromised, and immunocompetent persons in both industrialized and developing nations. The 2 most common etiologic agents, responsible for 90% of reported human infections, are C. hominis and C. parvum (2,3). Additional species identified as human pathogens are C. meleagridis, C. canis, C. felis, and the Cryptosporidium rabbit genotype (4). Each of these species was once thought to be specific for turkeys, dogs, cats, and rabbits, respectively. Incidental findings of C. muris, C. andersoni, C. suis, C. hominis monkey genotype, C. parvum mouse genotype, and Cryptosporidium cervine (W4), chipmunk I (W17), skunk, and horse genotypes have also been reported in humans (4). The pathogenicity of these zoonotic species and genotypes to humans remains unclear. In July 2009, a 29-year-old woman who sought care because of prolonged gastrointestinal illness had a fecal test positive for Cryptosporidium spp. by the Remel ProSpecT Giardia/Cryptosporidium microplate assay (Thermo Fisher Scientific, Lenexa, KS, USA). Oocysts were purified from the specimen (5) and stained with the Cryptosporidium spp.–specific antibody CRY104 labeled with fluorescein isothiocyanate (Biotech Frontiers, North Ryde, Australia) for enumeration. A parasite load of 1.34 × 106 oocysts/g feces was determined by using epifluorescence microscopy at 400× magnification. To identify Cryptosporidium spp., DNA was extracted (5), and a diagnostic fragment of the small subunit (SSU) rRNA) was amplified (6). Clones were screened to identify species and determine the possibility of mixed infection. Plasmids from 50 clones were recovered and digested with the enzyme SspI (New England Biolabs, Beverly, MA, USA) (6). Two different restriction profiles were visualized. The sequence from each of the restriction types was determined; profile 1 contained SspI fragment sizes of 33, 109, 247, and 441 bp; profile 2 had fragments of 33, 254, and 540bp. A BLAST search (www.ncbi.nlm.nih.gov/blast) confirmed the sequences as C. fayeri type 1 and type 2. These 2 sequences correspond to known heterogeneity within the SSU rRNA of C. fayeri (7). The identification of C. fayeri by SSU rRNA was confirmed by the sequence of the actin gene (8), showing 99.8% similarity to C. fayeri (GenBank accession no. {type:entrez-nucleotide,attrs:{text:AF112570,term_id:5714417,term_text:AF112570}}AF112570). Further analysis at the 60-kDa glycoprotein (gp60) locus was used to determine the Cryptosporidium subtype family (5). The MQ1022 gp60 sequence was 98% similar to C. fayeri subtype family IVa (9). Analysis of the microsatellite region further characterized isolate MQ1022 to C. fayeri subtype IVaA9G4T1R1. The nucleotide sequences generated in this study were submitted to GenBank under accession nos. {type:entrez-nucleotide-range,attrs:{text:HQ008932-HQ008934,start_term:HQ008932,end_term:HQ008934,start_term_id:313506256,end_term_id:313506259}}HQ008932-HQ008934. Because the patient was imunocompetent, the disease was believed to be self-limiting, and she was lost to follow-up. The patient resided in a national forest on the east coast of New South Wales, Australia, an area where marsupials are abundant. She had frequent contact with partially domesticated marsupials. Notably, C. fayeri has been identified in 6 Australian marsupial species. Identification of C. fayeri in a human patient is a concern for water catchment authorities in the Sydney region. The main water supply for Sydney, Warragamba Dam, covers 9,050 km2 and is surrounded by national forest inhabited by diverse and abundant marsupials. A previous study that investigated Cryptosporidium spp. in a wild eastern gray kangaroo (Macropus giganteus) population reported a prevalence of 6.7% (10). Oocyst shedding ranged from 20/g feces to 2.0 × 106/g feces (10). Subtype IVaA9G4T1R1 identified from the patient in this study has been characterized from eastern gray kangaroos in Warragamba Dam (9). Throughout the year, large groups of eastern gray kangaroos graze within riparian zones in the catchment. Such close proximity to the water presents a high possibility that the dam’s water is contaminated with oocysts from these animals. The Cryptosporidium genus is diverse, both in species and suitable hosts. The mechanisms of host specificity remain unknown, but the frequency of Cryptosporidium spp. crossing the host barrier and becoming zoonoses is increasing. This increase indicates that Cryptosporidium spp. host specificity is not as stringent as previously thought.

Bennett’s wallaby ( Macropus rufogriseus) marrow quality vs quantity: evaluating human decision-making and seasonal occupation in late Pleistocene Tasmania

A pilot study on the fatty acid composition of the bone marrow, brain tissue and muscle (flesh) of the medium-sized marsupial the Bennett’s wallaby ( Macropus rufogriseus), aimed to explore the mechanisms behind the dominance of this human prey species in late Pleistocene southwest Tasmania. In particular it was designed to investigate why humans frequently selected and transported the wallaby hindquarters, breaking open their longbones and metatarsals to expose the marrow cavity, when these animals could easily have been transported whole. Initial results indicated that the percentage of unsaturated fatty acids particularly palmitoleic acid (C 16:1) and oleic acid (C 18:1) in the bone marrow increased distally away from the body core temperature or the heart, towards the hands and feet. There is a corresponding decrease in the percentage of the saturated fatty acids, particularly palmitic acid (C 16:0) and stearic acid (C 18:0). This is similar to the pattern identified in placental artiodactyls (even-toed ungulates) and rodents. The preliminary study was then expanded to a year-long seasonal experiment involving wallabies from different Tasmanian environmental and climatic zones to see if this can better help explain the apparent seasonal occupation of caves indicated from recent Bennett’s wallaby teeth annuli (Skeletochronological studies). It was found that the Bennett’s wallaby remained a relatively stable and dependable resource throughout the year, with environmental, altitudinal and seasonal variability having only a minor effect on the fatty acid composition or nutritional quality of their bone marrow, muscle and brain tissue. Interestingly, the animals had increased desirable unsaturated fatty acids in their marrow, muscle and brain during the winter and spring with decreased amounts during the summer and autumn. This lends support to an earlier Kidney Fat Index (KFI) analysis for the Bennett’s wallaby which recorded significant seasonal differences within and between regions, indicating an environmental effect on overall body condition. Fatty acid analysis of the Common wombat Vombatus ursinus, the Tasmanian pademelon Thylogale billardierii, and the Forester or Eastern Grey kangaroo Macropus giganteus were also included to ascertain why these animals remained constant, although minor, prey species throughout the late Pleistocene. While the results from these animals were similar to the Bennett’s wallaby, there were some unexpected and surprising patterns that require further investigation. All of these fatty acid analyses have important implications for understanding human decision-making and occupation of southwest Tasmania during the Last Glacial Maximum, for modern dietary and palaeodietary benefits, and for understanding the physiology of these unique Australian marsupials.

Pest Responses to Odors From Predators Fed a Diet of Target Species Conspecifics and Heterospecifics

ABSTRACT Research into the use of predator‐odor‐based repellents as a management tool has gained momentum during the past 30 years. Some studies have suggested that odors from a predator whose diet includes the target species are more effective than odors from a predator that does not consume the species. To evaluate this management tool in the Australian context and to determine the effect, if any, of predator diet on odor repellence, we tested eutherian and metatherian, predator fecal odors on phylogenetically separated pest species that currently occur in Australia. We evaluated fecal odors from tigers (Panthera tigris) and Tasmanian devils (Sarcophilus harrisii) as repellents for goats (Capra hircus) and eastern grey kangaroos (Macropus giganteus). We fed tigers and Tasmanian devils 2 diets: one of goat and one of eastern grey kangaroo. The test fecal odors were more effective than a control odor of carrier material and solvent at deterring goats (P < 0.001) and kangaroos (P = 0.02) from food. Tiger fecal odor was more effective than Tasmanian devil odor in deterring both goats (P = 0.001)and kangaroos (P = 0.03). We observed a decrease in the number of feeding events for goats when they were exposed to the odor from a tiger fed goat compared with all other predator‐diet combinations (P < 0.001). We also observed a decrease in feeding events for kangaroos when exposed to the odor from a tiger fed kangaroo compared with all other predator‐diet combinations. We observed signs of desensitization to the test odors in goats and habituation to the test odors in kangaroos over the experimental period. A better understanding of the factors involved in desensitization and habituation may increase the effectiveness of fecal odor‐based repellents as a humane and nonlethal management tool for managers.

Use of a Sustained Release Chlorhexidine Varnish as Treatment of Oral Necrobacillosis in Macropus spp.

Oral necrobacillosis or lumpy jaw is a common cause of morbidity and mortality affecting captive macropods. This article describes several cases of a new treatment regimen using a sustained release chlorhexidine varnish applied locally to the teeth and the gingivae of two Macropus species, eastern grey kangaroos (Macropus gigantus) from Gan-Garoo Australian Park and a red-necked wallaby (Macropus rufogriseus fruticus) from The Tisch Family Zoological Gardens in Jerusalem. The varnish was applied using a horsehair paint brush as three 1- to 2-mm thick layers. The active ingredient in the varnish was the disinfectant chlorhexidine. Results indicated that use of an intraoral sustained release varnish significantly shortens the treatment time and may prevent recurrence.

Serologic-based Investigation of Leptospirosis in a Population of Free-ranging Eastern Grey Kangaroos (Macropus giganteus) Indicating the Presence of Leptospira weilii Serovar Topaz

Eastern grey kangaroos (Macropus giganteus) are one of the most abundant large macropodids sharing the landscape with humans. Despite this, little is known about the prevalence of Leptospira carriage within this species and the role that they may partake in the transmission of this disease in Australia. The sera of 87 free-ranging eastern grey kangaroos, captured in the Warragamba Catchment Area, Sydney, Australia, from June 2004 to November 2006, were screened against a reference panel of 22 Leptospira serovars using the microscopic agglutination test (MAT). Leptospiral antibodies were detected in 47% (41 of 87) of serum samples collected. Leptospira weilii Topaz, a newly emergent serovar in Australia, was detected in all seropositive kangaroos (41 of 41; 100%). The sex and tail-fat body condition index of kangaroos appeared to have no significant effect on the exposure to the disease. This serologic-based study is the first reported for L. weilii serovar Topaz in New South Wales, to our knowledge, having previously been isolated only in humans and two other animal species (bovine and long-nosed bandicoot [Perameles nasuta]) in Western Australia and Queensland. The potential role of eastern grey kangaroos in the maintenance and zoonotic spread of the disease to livestock and humans is discussed.

Interactions among social monitoring, anti-predator vigilance and group size in eastern grey kangaroos

Group size is known to affect both the amount of time that prey animals spend in vigilance and the degree to which the vigilance of group members is synchronized. However, the variation in group-size effects reported in the literature is not yet understood. Prey animals exhibit vigilance both to protect themselves against predators and to monitor other group members, and both forms of vigilance presumably influence group-size effects on vigilance. However, our understanding of the patterns of individual investment underlying the time sharing between anti-predator and social vigilance is still limited. We studied patterns of variation in individual vigilance and the synchronization of vigilance with group size in a wild population of eastern grey kangaroos (Macropus giganteus) subject to predation, in particular focusing on peripheral females because we expected that they would exhibit both social and anti-predator vigilance. There was no global effect of group size on individual vigilance. The lack of group-size effect was the result of two compensating effects. The proportion of time individuals spent looking at other group members increased, whereas the proportion of time they spent scanning the environment decreased with group size; as a result, overall vigilance levels did not change with group size. Moreover, a degree of synchrony of vigilance occurred within groups and that degree increased with the proportion of vigilance time peripheral females spent in anti-predator vigilance. Our results highlight the crucial roles of both social and anti-predator components of vigilance in the understanding of the relationship between group size and vigilance, as well as in the synchronization of vigilance among group members.

A novel observation of dingoes (Canis lupus dingo) attacking a swimming eastern grey kangaroo (Macropus giganteus)

The dingo (Canis lupus dingo) is a keystone species in Australian ecosystems. The current study reports four dingoes observed attacking a swimming eastern grey kangaroo (Macropus giganteus) in the Wollondilly River, New South Wales. It is proposed that kangaroos need to stand at a certain depth of water to escape an attack by dingoes. If dingoes can continue attacking from opposing directions without threat of injury from the kangaroo, such as in shallow water where dingoes can stand or deep water where kangaroos cannot stand, then the attack may continue until the predator(s) kill the prey or the prey escapes. Further research on such behaviours is needed to understand the functional role of dingoes and the importance of pack structure in development of hunting strategies.

Dominance, body size and internal relatedness influence male reproductive success in eastern grey kangaroos (Macropus giganteus)

Knowledge of the determinants of reproductive success is essential for understanding the adaptive significance of particular traits. The present study examined whether particular behavioural, morphological, physiological or genetic traits were correlated with male dominance and reproductive success using three semi-free-ranging captive populations (n = 98) of the eastern grey kangaroo (Macropus giganteus). The morphological traits measured included bodyweight, head, forearm, tail, pes and leg length, forearm and bicep circumference, and testis size. Blood samples were collected to determine serum testosterone concentrations. All individuals were typed for 10 microsatellite loci and paternity determined for each pouch young. To determine the influence of relatedness and genetic diversity on male reproductive success, internal relatedness, standardised heterozygosity and mean d(2) were calculated. Dominant males sired a significantly higher proportion of offspring than smaller, lower-ranked males and had higher testosterone concentrations. Males that sired offspring were significantly heavier and had larger body size. Sires were significantly more heterozygous and genetically dissimilar to breeding females than non-sires. Despite the wealth of knowledge on the social organisation of kangaroos, this is the first study to assign parentage and male reproductive success using molecular evidence.

Eastern grey kangaroo (Macropus giganteus) myofibres. 2. Characteristics of eight skeletal muscles

The myofibre characteristics of eight skeletal muscles of economic importance, comprising six muscles from the upper hindlimb, one from the lumbar and one from the sacral region, from five eastern grey kangaroos (Macropus giganteus) were determined. Differential staining of myosin heavy chains allowed myofibres to be classified as Types 1 (slow oxidative), 2A (fast oxidative-glycolytic) and 2X/2B (fast glycolytic), as well as the intermediate or transitional Types 2C (Type 1–Type 2A intermediate) and 2AX/B (Type 2A–Type 2X/2B intermediate). The m. psoas minor had a higher area comprising Type 1 myofibres (41.4%) relative to total myofibre area than did any of the other muscles studied (each <5%). This was due to the m. psoas minor having a higher percentage (31.9%) and larger average cross-sectional area (CSA; 4211 µm2) of Type 1 myofibres. Type 2X/2B myofibres comprised over 70% of the relative area in the mm. semimembranosus, semitendinosus and gluteus medius, compared with 34.2% in the m. psoas minor, with the other muscles intermediate. The proportion of Type 2A myofibres ranged from 19.1% (m. gluteus medius) to 34.6% (m. caudal dorsolateral sacrocaudalis) of the relative myofibre area. The m. caudal dorsolateral sacrocaudalis had the largest average myofibre CSA and the m. adductor the smallest (5539 and 2455 µm2, respectively). Among the intermediate myofibre types, Type 2AX/B myofibres were more prevalent (range 4.3%–13.0% of myofibres) than Type 2C myofibres (≤0.5%). Overall, the correlations between carcass weight and the percentage and relative areas of myofibres were positive for Type 2A and negative for Type 2X/2B myofibres. The results provide a detailed characterisation of myofibres in kangaroo skeletal muscles of economic importance. Furthermore, they enhance our understanding of factors influencing kangaroo muscle structure and post-mortem metabolism and provide potential indicators of eating quality of kangaroo meat.

Eastern grey kangaroo (Macropus giganteus) myofibres. 1. A simplified classification method using two commercially available antibodies

Skeletal muscles from eastern grey kangaroos (Macropus giganteus) were assessed for myofibre contractile and metabolic characteristics using immunocytochemical and histological staining of serial sections. Myofibre classification using monoclonal antibodies that typically bind to mammalian slow (clone WB-MHC), fast (clone MY-32) and Types 1, 2X and 2B (clone S5 8H2) myosin heavy chains was validated using acid- and alkali-preincubated myofibrillar ATPase, NADH and α-glycerophosphate dehydrogenase stains. Myofibres were classified as Type 1 (slow oxidative), Type 2A (fast oxidative-glycolytic), Type 2X/2B (fast glycolytic) or intermediate or transitional myofibre Types 2C (Type 1–Type 2A intermediate) and 2AX/B (Type 2A–Type 2X/2B intermediate). The Type 2 (fast) antibody (clone MY-32) used in the present study did not bind to a subset of fast myofibres in any of the eight kangaroo muscles investigated. These myofibres were identified as Type 2A using clone S5 8H2 and on the basis of the histochemical staining profile. Hence, a simplified immunostaining system using only clones WB-MHC (anti-Type 1) and MY-32 (anti-Type 2X/2B) allowed five myofibre types to be identified based on the staining pattern and intensity of staining for the two antibodies. It is concluded that the myofibres of muscles from kangaroos can be quickly classified into five types using two commercially available antibodies. This method is directly applicable for routine investigations into the myofibre properties of commercially important muscles from the kangaroo musculature and, when combined with enzymatic assays for oxidative and glycolytic activity, will allow for a better understanding of factors influencing the quality of meat from kangaroos.

Toxoplasmosis and genotyping of Toxoplasma gondii in Macropus rufus and Macropus giganteus in Argentina

Toxoplasma gondii infection is frequently asymptomatic; however, it can be severe or even fatal to some hosts. In this study, diagnosis of disseminated toxoplasmosis in one red kangaroo ( Macropus rufus) and one great grey kangaroo ( Macropus giganteus) from the La Plata Zoo, Argentina and the isolation and molecular characterization of T. gondii are reported. Both male kangaroos showed depression and sudden death. Toxoplasma gondii infection was diagnosed by fresh examination, histophatology, immunohistochemistry, PCR and bioassay in mice. During fresh examination many protozoan cysts were observed in diaphragm, heart and hind limb muscles of M. rufus. Cysts were also observed in samples from M. giganteus, although in lower number. Cysts from both kangaroos stained strongly with T. gondii anti-serum by immunohistochemistry. The M. rufus showed more considerable histopathological lesions like non-suppurative meningoencephalitis, myositis and myocarditis. All mice inoculated with tissues from both kangaroos developed IFAT titers to T. gondii (titer ≥800) and brain cysts at necropsy. Both T. gondii isolates were maintained by mice passages and the M. rufus isolate was also maintained in cell culture. Toxoplasma gondii DNA from tissue samples was analyzed by PCR-RFLP analysis using the markers 5′SAG2, 3′SAG2, BTUB, GRA6, SAG3, c22-8, L358, PK1, c29-2 and Apico. Genotyping revealed that the T. gondii isolate from M. rufus was clonal type III and the isolate from M. giganteus was clonal type II. This is the first report of disseminated toxoplasmosis in M. rufus and M. giganteus in Argentina caused by genotypes of T. gondii considered non-virulent in a mouse model.

Foraging efficiency and parasite risk in eastern grey kangaroos (Macropus giganteus)

Large mammalian herbivores must balance foraging efficiency with multiple constraints, including the risk of gastrointestinal parasitism. The costs imposed by gastrointestinal parasites are likely to exert selective pressure on hosts to develop aversion behaviors. Fecal aversion, or the avoidance of foraging patches contaminated by feces, is one mechanism by which herbivores can reduce their exposure to gastrointestinal parasites transmitted through the fecal contamination of foraging grounds. As feces also fertilize the surrounding pasture, herbivores may face a choice between the benefits of increased nutrient intake and an increased risk of parasitism. We investigated fecal aversion in free-ranging eastern grey kangaroos (Macropus giganteus), including the potential conflict between fecal aversion and increased nutrient intake, through a combination of field observations and a field experiment. Kangaroos exhibited fecal aversion by moving through contaminated patches as they were encountered. The experiment revealed that both sward height and fecal contamination affected the kangaroos’ choice of foraging patches: kangaroos preferred taller grass but would not accept a higher risk of parasitism for increased nutrient intake. Key words: eastern grey kangaroo, fecal aversion, foraging behavior, Macropus giganteus, parasitism. [Behav Ecol]