Macropus Rufogriseus Research Articles

Electric Fencing for the Control of Wallaby Movement.

Captive colonies of 2 wallaby species, Bennett's wallaby (Macropus rufogriseus) and the Tasmanian pademelon (Thylogale billardieri) were used to evaluate a range of electric fence designs, and the 2 most effective of these were tested in the field in Tasmania. Over a 3-year period, a 10-wire electric fence reduced counts of faecal pellets from M. rufogriseus to 1% and pellets from T. billardieri to 20% of the number in a control plot surrounded with a 7-wire stock fence. Similarly, a 9-wire fence including an outrigger reduced faecal pellets from M. rufogriseus to 12.7% and pellets from T. billardieri to 46.5% of those in the control. In the same period, 5.6% of pasture grown inside the first fence, 16.0% of that in the second and 83.0% of that in the control was eaten.

Electrophoretic comparison of Rugopharynx longibursaris Kung and R. omega Beveridge (Nematoda: Strongyloidea), with the description of R. sigma n. sp. from pademelons, Thylogale spp. (Marsupialia: Macropodidae)

An electrophoretic comparison of the nematodes Rugopharynx longibursaris and R. omega, both from Macropus rufogriseus in south-eastern Australia, revealed fixed genetic differences at 4.5% of the 23 enzyme loci examined. The electrophoretic data do not therefore reject the null hypothesis that the two taxa are conspecific. R. longibursaris was found in Tasmania and in the western mainland population of M. rufogriseus, while R. omega occurred only in the eastern mainland population. Implications for the taxonomic status of the western host population are considered. Specimens formerly assigned to R. omega, from Thylogale stigmatica from Queensland, were found to differ at 45.0% of enzyme loci from specimens from M. rufogriseus. Morphological examination revealed differences in the shape of the buccal capsule, the position of the deirid, the morphology of the spicule tip and the presence of a gubernaculum. A new species, R. sigma, is erected for specimens from T. stigmatica, T. thetis and T. calabyi.

NMR studies of diffusional water permeability of red blood cells from macropodid marsupials (kangaroos and wallabies)

1. 1. The water permeabilities of the red blood cell (RBC) membranes of five species of macropodid marsupials were monitored by using a Mn 2+-doping 1H nuclear magnetic resonance (NMR) technique. 2. 2. Since this appears to be the first time that this type of measurement at 400 MHz for 1H has been reported, an analysis of instrumental parameters influencing the estimated value of the water exchange time ( T e ), and of the diffusional water permeability ( P d ), was performed on samples of human RBC. 3. 3. It was found that a short interpulse delay in the Carr-Purcell-Meiboom-Gill pulse sequence had to be used (around 100 μsec) to avoid an underestimation of the relaxation times, that occurred as the result of molecular diffusion through non-uniform local magnetic fields in and around the cells. 4. 4. There were no significant differences, in the water permeabilities of the RBC membranes, between the five species ( Macropus rufogriseus, M. parma, M. eugenii, M. parryi and Wallabia bicolor). 5. 5. There were also no significant differences between various colonies of M. eugenii living in different habitats. 6. 6. The average values of P d were 9.1 × 10 −3 cm/sec at 24.6°C, 10.4 × 10 −3 cm/sec at 30°C, 12.6 × 10 −3 cm/sec at 37°C, and 14.7 × 10 −3 cm/sec at 42.1°C; these were more than twice as high as those for human RBC. 7. 7. In agreement with the high water permeability the RBC of macropodids displayed a relatively low activation energy of water diffusion across their membranes, ~21 kJ/mol compared with 25kJ/mol for human RBC.

Excavations at Mackintosh 90/1 in western Tasmania: a discussion of stratigraphy, chronology and site formation

AbstractMackintosh 90/1 is a limestone cave situated on the edge of Lake Mackintosh in western Tasmania. It contains a moderate density of archaeological debris in a narrow band of organic rich sandy silts that accumulated over a 2,000 year time span immediately following the last glacial maximum. It thus provides a rare opportunity to investigate the composition and structure of a palimpsest of material debris with very fine temporal resolution. Preliminary analyses indicate that both marsupial carnivores and humans contributed to the faunal remains that accumulated at this site and that Bennett's wallaby and wombat are the only two items of human prey included in the assemblage. Preliminary analyses also indicate that the artefact assemblage recovered from Mackintosh 90/1 is broadly similar to those recovered from Pleistocene sites in south‐west Tasmania, in terms of the raw materials being worked and the type of flaking debris being discarded.

Class I Major Histocompatibility Complex Genes of the Red-Necked Wallaby, Macropus rufogriseus

Marsupials are one of three main evolutionary lineages in mammals, the other two being the monotremes and the placental mammals. The marsupial and the placental lineages separated between 120 and 156 million years ago. In this communication, we provide the first molecular description of class I major histocompatibility complex ( Mhc) genes in a representative of the marsupial lineage, the red-necked wallaby, Macropus rufogriseus. Three different, nearly full-length class I Mhc sequences were identified in the cDNA library prepared from spleen mRNA of a single wallaby. The three sequences identify at least two loci. Under the assumption that two of the identified sequences are alleles, we designate the three wallaby genes Maru-Mhc-UA*01, Maru-Mhc-UA*02, and Maru-Mhc-UB*01. The three Maru sequences share several codon deletions and insertions not found in the class I genes of placental mammals. Comparisons of genetic distances among the known class I genes suggest that the Maru genes arose from one ancestral element, whereas the class I genes of the placental mammals arose from another, different ancestral element. The absence of an identifiable defect in the three Maru sequences suggests that the genes from which they were derived are functional. Hence, as in placental mammals, there appear to be two functional class I Mhc loci in the marsupials as well.

The Play Associations of Red‐necked Wallabies (Macropus rufogriseus banksianus) and Relation to Other Social Contexts

AbstractThe partner preferences of a captive group of red‐necked wallabies (Macropus rufogriseus banksianus) during playfights were determined and the patterns of social relations formed compared to those in other social contexts. Wallabies preferred play‐partners of the same sex and of similar age and dominance status. Young males were most likely to initiate play. Females engaged in play almost exclusively with subadult males and, in particular, their male offspring. Play between females was not recorded. In play between males from different age classes, initiation and termination was independent of age. Termination was dependent on who initiated the interaction: initiators were less likely to terminate playfights than were recipients. Wallabies that had recently vacated the pouch were not the focus of social play in the colony.Agonistic interactions also occurred most often between wallabies of the same sex and similar age and dominance but older males were most likely to initiate interactions. Initiation and termination of agonistic interactions was age‐dependent: older wallabies almost always initiated and won encounters with younger partners. There was no correlation among male dyads between their rates of play and agonistic encounters, dominance reversals were more common in play than in agonism, and the patterns of wins and losses in play and agonism were not correlated. There was some suggestive, but inconclusive evidence that the proportion of time males spent in close proximity at food and water troughs was positively correlated with their rates of play and negatively with their rates of agonistic interactions. There was also some evidence that males that played together often had more frequent affiliative interactions than those that did not. However, there was no correlation between rate of play by males and the proportion of time they spent resting together. These results suggest that the function of social play in the wallabies was motor training and not socialization. In addition, they indicate that play and agonism are causally‐distinct categories of behaviour. Based on this interpretation, the relationship between play and serious fighting in macropods and in eutherian mammals is discussed.

Playfighting in Captive Red-Necked Wallabies, Macropus Rufogriseus Banksianus

The structure and development of playfighting in captive red-necked wallabies, Macropus rufogriseus banksianus, was studied over a 2.5 year period. An ethogram of 21 acts was established. Playfighting involved acts from agonistic, affiliative and sexual contexts. The sequential organisation of acts was highly non-random in both intra- and inter-individual structure. Sequence analysis grouped acts into 3 subsystems : those associated with high (central act: Spar) and low (central act: Paw) intensity bouts of fighting; and those associated with initiation, termination or interbout behaviour. Wallabies playfought at varying intensities ranging from high intensity Sparring matches to low intensity bouts of Pawing coupled with frequent and prolonged periods of affiliative interactions. A third type of playfighting, refusal playfights, was of short duration and was probably failed playfight initiations. There was considerable repetition of acts and sequences of acts, and play-partners interacted in a highly mutual manner. Some acts (Skip, side and chest Autogroom, and Shake) were performed in an apparently exaggerated manner and may have had a communicative function. There was noticable restraint used in the performance of Kicking during playfights compared to that seen in serious fights. The goal of playfighting was either to gain unrestricted grooming access to an opponent's throat or to force an opponent off-balance causing it to retreat. Males of any age playfought more often than females; playfighting in females was very rare. Wallabies engaged in playfights soon after they first began to leave their mother's pouch. Three phases of playfight development in males were identified. The first was an early phase of vigorous play that ended about the time wallabies were weaned. The second phase commenced after weaning and continued until after sexual maturity. It was a transitional period of increasing instability in playfight relations manifested as shorter playfights and more refusal playfights. The final phase was characterised by low intensity playfighting and was typical of older adult males. The design of playfighting and age/sex differences in its performance were used to consider the relative importance of motor training, socialisation and assessment of fighting skills as benefits of playfighting. Most evidence favours motor training as the most important benefit, particularly for high intensity playfighting. For low intensity playfights motor training was not completely satisfactory as the main benefit. It was possible that low intensity playfights gave a different type of motor training than high intensity playfights. Developmental changes in the type of playfighting performed also suggest that either the motor training benefits a wallaby required from play changes with age, or there were age-related changes in the function of playfighting. Neither socialisation or assessment of fighting skills seem to be major benefits of playfighting in the wallabies. The similarities between playfighting in the wallabies and play in better studied taxa (i.e. eutherians), and between wallaby playfighting and the descriptions given in the macropodid literature of prolonged, resource-unrelated serious fights are considered. It was concluded that at least some of the fights of macropodids reported in the literature were misclassed playfights.

Purification, partial characterization, and radioimmunoassay of prolactin and growth hormone from the Bennett's wallaby

Bennett's wallaby prolactin (wPRL) and growth hormone (wGH) were purified from an aqueous extract of pituitary glands. The extract from 202 glands (6.5 g wet wt) was processed by gel filtration on Sephadex G-100, gel filtration on Sephadex G-100 SF, and then anion-exchange chromatography on DEAE-Sepharose CL-6B. The yields of wPRL and wGH were 5.2 and 15.7 mg, respectively. Since recovery of wPRL from the anion exchange column was 10%, anion exchange was performed in the presence of 20% acetonitrile in a subsequent purification. Recovery from this column was markedly increased to 42%. The purified hormones each gave a single vand on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a molecular weight under reducing conditions of 21,000 and 23,000 for GH and PRL, respectively. Each hormone was positively identified by its N-terminal amino acid sequence, which showed high sequence identity with the equivalent eutherian hormone. Semianalytical gel filtration of purified hormone was used to demonstrate that each hormone remained as a monomer in aqueous solution. Each purified hormone was tested in the heterologous PRL radioimmunoassay (RIA) which has been used in many earlier studies to measure marsupial PRL. Highly purified wPRL was less potent than ovine prolactin (5.3 compared with 1.5 ng/ml at 50% displacement) and the cross-reaction of wGH was <0.01%. Antibodies were raised against wPRL and wGH and a homologous RIA was developed for each hormone. The sensitivity of the wPRL assay was 0.8 ng/ml which is similar to that of the heterologous PRL assay. Cross-reaction with a number of eutherian pituitary hormones or wGH was <0.07%. The wGH assay detected 0.8 ng/ml, cross-reacted with GH from several eutherian species, and showed low cross-reaction with wPRL (<0.5). In both the wPRL and wGH assays, pituitary homogenates from several species of marsupial diluted in parallel with the wallaby standard, suggesting that these assays will be of use in studies of a number of marsupial species.

Seasonal and lactational effects on the prolactin response to a dopamine antagonist and TRH in the Bennett's wallaby ( Macropus rufogriseus rufogriseus)

In the Bennett's wallaby prolactin is thought to maintain lactational and seasonal quiescence and is essential for early lactation. However, plasma prolactin concentrations determined in daily or weekly samples at these times are unchanged. In the present study, female Bennett's wallabies were blood sampled at 2-hr intervals over a 24-hr period during seasonal quiescence on either natural or artificial photoperiods to determine whether a diurnal rise of prolactin occurs at this time. Prolactin concentrations did not exhibit a diurnal change. Further experiments were aimed at determining whether there was an increase in the prolactin response to a dopamine antagonist or TRH during the transition to seasonal quiescence. Nonlactating and lactating female Bennett's wallabies were treated with saline, 0.5, 1, and 2 mg of the dopamine antagonist domperidone and 100 μg TRH in October, December, February, and April. In both groups there was a significant elevation in plasma prolactin concentration in response to domperidone with an increasing response at each successive month. In early (October and December) and peak (April) lactation the prolactin response was greater in lactating animals. There was no significant prolactin response to TRH in lactating animals. In nonlactating wallabies, the prolactin response to TRH was increased in February. At peak lactation (April), the response to 1 mg domperidone was blocked when the dose was administered 2 hr after temporary removal of pouch young (RPY). With either larger doses (20 mg) or a 1-mg dose injected 8 hr after RPY, a significant prolactin response was observed. These data support the hypothesis that the transition from lactational to seasonal quiescence is associated with an increase in prolactin secretion, although we failed to demonstrate a change in diurnal profile. Further, in late lactation, when basal prolactin concentrations are elevated, suppression of prolactin by removal of the sucking stimulus is due to a marked, but temporary, increase in dopamine secretion into the portal blood.

Characterization of 2-[ 125i]iodomelatonin binding sites in the brain of a marsupial, bennett's wallaby ( macropus rufogriseus rufogriseus)

1. 1. Specific high affinity binding of 2-[ 125I]iodomelatonin was detected in the brain of the pouch young of a marsupial, Bennett's wallaby. 2. 2. Binding was rapid, stable, saturable and reversible. 3. 3. Scatchard analysis indicated a single class of high affinity binding sites with an equilibrium dissociation constant (Ay of 68 ± 13 pM, a maximal number of binding sites (β max) of 0.7 ±0.1 fmol/mg protein and a Hill coefficient ( n H) of 1.12 ± 0.10. 4. 4. Specific binding was inhibited by GTP (1 mM) indicating that the melatonin receptor is coupled to a guanine nucleotide binding protein, and by melatonin and closely related analogues with a potency order identical to that reported previously in the brain of eutherian mammals, birds and a reptile. 5. 5. These studies suggest that the melatonin receptor is well-conserved through evolution.

Scanning electron microscopy of red blood cells from eleven species of marsupial

Samples of red of blood cells (RBC), washed free of plasma, from eleven marsupial species were examined in a Jeol JSM-6300 F scanning electron microscope. The diameters of the RBC, lying completely flat or exactly on edge, were measured on photographs using a binocular enlarging optical system with a calibrated eye piece. RBC from the following species were studied: bandicoot (Isoodon macrourus), bilby (Macrotis lagotis sagitta), Bennett's wallaby (Macropus rufogriseus), Goodfellow's tree kangaroo (Dendrolagus goodfellowi), koala (Phascolarctos cinereus), parma wallaby (Macropus parma), red kangaroo (Macropus rufus), swamp wallaby (Wallabia bicolor), Tammar wallaby (Macropus eugenii), Tasmanian devil (Sarcophilus harrish) and whiptail wallaby (Macropus parryi). In all species the RBC were biconcave discs. The major morphological difference was in the size of the cells. Taking the human RBC as a reference (with a diameter of 8.0 μm), the RBC of the Tasmanian devil, bilby, bandicoot and Goodfellow's tree kangaroo were ∼7 μm in diameter, whereas those of the other marsupials ranged from 7.8 to 8.6 μm.

Paternity exclusion and dominance in captive Red-necked Wallabies, Macropus rufogriseus (Marsupialia: Macropodidae).

The relationship between dominance rank and paternity was examined in a captive group of Red-necked Wallabies, Macropus rufogriseus. Blood samples were collected from 15 wallabies surviving to the young-at-foot stage as well as from their mothers and all their potential fathers. The alleles present for two polymorphic plasma proteins, albumin and phosphoglucose isomerase, were determined electrophoretically for all wallabies. Dominance relationships were determined by the outcome of agonistic encounters. Alpha-status alternated between two of the three large males(#I and #3). Because of the small number of proteins examined, it was not possible to identify a single, sexually mature male as the probable father for each of the 15 wallabies surviving to the at-foot stage. The probable father of four of these was identified as#3. For a further two (#24 and n1), the probable father was reduced to one of two (#3 or #7) and one of four (#3, #8, #9 and #10) males. When #1 was the alpha-male he did not father at least 30 % (n = 10) of young surviving to the at-foot stage. While the difference was not significant, #3 fathered a greater proportion of the wallabies surviving to the at-foot stage when he was the alpha-male compared to when he was not ( 40 % vs 20 %, or 60 % vs 30 % if he was assumed to have fathered #24 and n1).

Seasonal prolactin secretion and its role in seasonal reproduction: a review.

The majority of seasonally breeding mammals show a seasonal pattern of prolactin secretion with peak concentrations in spring or summer and a nadir in autumn or winter. Photoperiod influences prolactin secretion via its effects on the secretion of the pineal hormone melatonin. Preliminary evidence suggests that the effects of melatonin on both prolactin and gonadotrophin secretion are via a common target area, possibly within the anterior hypothalamus, and that differences in response to photoperiod may be due to differences in the processing and/or interpretation of the melatonin signal. In contrast to seasonal gonadotrophin secretion, the seasonal changes in prolactin are not due to changes in the sensitivity of a feedback loop and so must be due to direct effects on the hypothalamic pathways that control prolactin secretion. Little else can be said with confidence about the neuroendocrine mechanisms that lead to the seasonal changes in prolactin secretion. Dopamine and noradrenaline turnover in the arcuate nucleus and median eminence decrease under short daylength. If catecholamine turnover in these structures is positively correlated with catecholamine concentrations in the long or short hypophysial portal vessels, it is unlikely that the decrease in prolactin concentration in winter is due to the effects of increased concentrations of dopamine or noradrenaline in the portal vessels. There is, however, evidence for increased pituitary sensitivity to dopamine under short daylength, so increased dopamine concentrations may not be required for suppression of prolactin secretion at this time. In addition to the diminished secretion of prolactin under short daylength, rate of prolactin synthesis and pituitary content of prolactin also decline although the mechanisms that regulate these changes are poorly understood. Although all seasonal breeders show a seasonal change in prolactin secretion, there are continuously breeding species in which prolactin secretion is also under photoperiodic control. It is likely therefore that a seasonal pattern of prolactin secretion is only evidence of neuroendocrine sensitivity to changing photoperiod. Depending upon the species, this sensitivity to the seasonal changes in daylength may or may not be accompanied by seasonal changes in a biological endpoint such as seasonal reproduction or indeed other adaptations. Whether the seasonal change in prolactin secretion is an endocrine mediator of such adaptations remains in contention. Certainly in some species this signal does have a role in reproduction. For example, in species with an obligate seasonal embryonic diapause, the seasonal increase in prolactin can act as a luteotrophin (mink and western spotted skunk) or luteostatin (Bennett's and tammar wallabies.(ABSTRACT TRUNCATED AT 400 WORDS)

MHC class II genes of a marsupial, the red-necked wallaby (Macropus rufogriseus): identification of new gene families.

In placental mammals, the class II region of the major histocompatibility complex (Mhc) consists of several gene families which show orthologous relationships in the different species. As these families are not orthologous with the Mhc class II beta-chain-encoding gene families of birds, the different mammalian families must have diverged after the separation of birds and mammals approximately 250 Mya but before the radiation of placental mammals (60-80 Mya). To obtain further information about the origin of the class II genes in mammals, we studied the beta-chain-encoding genes of the wallaby as a representative of marsupials, which split from placental mammals approximately 125 Mya. Three beta-chain-encoding genes were isolated from a red-necked wallaby (Macropus rufogriseus) cDNA library by using a chimpanzee DRB probe, and their nucleotide sequences were determined. The genes are not orthologous to any of the genes in mammals studied thus far but belong to two new families which we designated Maru-DAB and Maru-DBB. One of the three sequences (DAB2) seems to be derived from a transcribed pseudogene; it lacks the codons specifying the first 51 amino acid residues of the beta 2 domain. The fact that the DAB and DBB families have thus far not been found in placental mammals and that none of the DOB, DPB, DQB, or DRB genes seems to be expressed in the one representative marsupial species can be interpreted as suggesting that class II gene families of eutherian and metatherian mammals evolved from different ancestral genes.

Severe haemolytic anaemia and disseminated intravascular coagulation in a wallaby (Macropus rufogriseus)

Severe haemolytic anaemia and diffuse intravascular coagulation were identified in a red-necked wallaby which was also suffering from necrobacillosis. Since no other cause of the haemolysis could be identified, the anaemia was probably due to haemolysins produced by the anaerobic organisms of the necrobacillosis lesion.

Seasonal changes in the reproductive organs and plasma and pituitary hormone content of the male Bennett's wallaby (Macropus rufogriseus vufogriseus)

In a number of species of seasonally breeding marsupial, the male is fertile throughout the year but there is a marked seasonal change in weight of the accessory sexual glands. In this study, body weight, prostate, epididymis and testis weights and plasma concentrations of testosterone, LH and prolactin and pituitary content of LH and prolactin were determined in male Bennett's wallabies shot at 1–2 month intervals over a period of 17 months. There was a highly significant increase in prostate weight which was coincident with the breeding season for this species. A small but significant increase in testis weight was also observed but epididymis weight remained unchanged. Plasma testosterone concentrations were significantly increased at a time coincident with the increase in prostate weight. Plasma prolactin and LH concentrations were low in most animals and remained unchanged during the study. In contrast, pituitary prolactin and LH contents showed highly significant changes, with increasing and peak hormone content preceding maximum prostate weight and plasma testosterone concentrations by several months. While these latter results suggest a role for prolactin and LH in the seasonal control of the reproductive organs in the male wallaby, a more intensive study of the pattern of secretion of these hormones and possibly more sensitive hormone assays are required to understand their relative roles in regulating the annual cycle of prostate growth.

Melatonin implants prevent the onset of seasonal quiescence and suppress the release of prolactin in response to a dopamine antagonist in the Bennett's wallaby (Macropus rufogriseus rufogriseus)

Three groups of adult female wallabies were maintained out of doors under conditions of natural photoperiod and temperature from late December to mid-August. One group (M1; N = 6) received Silastic elastomer melatonin implants on 14 December, a second group (M2; N = 5) were given implants on 16 February and a third group (C; N = 7) were unimplanted controls. Group C animals had all ceased cycling by 15 March and the subsequent breeding season commenced on 5 July +/- 6.9 days. Group M1 wallabies continued to cycle throughout the experimental period and did not exhibit ovarian quiescence. In Group M2, 2/5 animals continued to undergo repeated oestrous cycles and 3/5 ceased cycling between 14 December and 27 January and began again after the insertion of melatonin implants on 16 February. The prolactin response 30 min after s.c. administration of the dopamine antagonist domperidone was determined approximately every 4 weeks. In Group C, peak responses were high during the period of seasonal quiescence (January-June; mean range 14.2-19.6 ng/ml) and fell significantly (P less than 0.02) at the beginning of the breeding season in early July to 7.4 +/- 3.1 ng/ml. In Group M1, prolactin levels remained low (2.8-8.2 ng/ml) throughout the course of the experiment while in Group M2, response to domperidone fell following the insertion of the implants and subsequently remained at levels similar to those in Group M1. Our data support the hypothesis that photoperiod-induced changes in the secretion of melatonin after the winter solstice drive this species into seasonal quiescence by influencing the dopaminergic control of prolactin secretion.

Control of Bennett's and Tammar Wallabies in New Zealand Using Compound 1080 Gel on Foliage Baits.

Trials were carried out against Bennett's wallabies (Macropus rufogriseus rufogriseus) and tammar wallabies (M. eugenii) in areas of indigenous forest where browsing is preventing or damaging regeneration. Compound 1080 (sodium monofluoroacetate) in a carbopol gel was spread on the foliage of palatable plants. Numbers of Bennett's wallabies were reduced by 91% and tammar wallabies by 87%. These kill estimates compare favourably with those achieved using aerially sown baits. The costs per hectare of gel poisoning were estimated to be as little as 40% of those for aerial baiting, but the costs of using gel will increase as the control areas become larger, more rugged, and less easily traversed on foot.

Roles of prolactin and the uterus in the control of luteal regression in the Bennett's wallaby (Macropus rufogriseus rufogriseus)

The factors responsible for controlling luteal regression in macropodid marsupials are unclear. Experiments were designed to examine the role of the uterus and the pre-partum prolactin pulse in this process. In experiment 1, two groups of adult female Bennett's wallabies were hysterectomized (n = 3) or sham-hysterectomized (n = 3) on Day 16 of a non-pregnant oestrous cycle and daily peripheral blood samples were collected between Days 10-37. In both groups, circulating progesterone concentrations declined to below 0.96 nmol L-1 at luteolysis on Days 28-33. Circulating prolactin concentrations remained low over the period of luteal regression. In experiment 2, two groups of animals, which were maintained in the presence of a fertile male and synchronized by the removal of pouch young (RPY), were treated on Day 16 after RPY with a single injection of long-acting bromocriptine (Parlodel LA, Sandoz Ltd, Basle, Switzerland; 50 mg per animal n = 5) or vehicle (n = 4). Vehicle-treated animals gave birth on Day 28 (n = 3) or Day 29 (n = 1) with a significant elevation of prolactin on Day 28. In contrast, 4 of the 5 bromocriptine-treated animals failed to give birth and one gave birth on Day 29. No comparable prolactin pulse was detected in any of them. Circulating progesterone concentrations declined later in the bromocriptine-treated group than in the controls. These data suggest that different mechanisms lead to luteolysis in pregnant and non-pregnant animals; in pregnancy the luteolytic signal is prolactin, whereas in the non-pregnant cycle another signal of non-uterine origin is involved.

Habitat separation in the grey kangaroos, Macropus giganteus Shaw and M. filiginosus (Desmarest) (Marsupialia: Macropodidae), in Grampians National Park, western Victoria.

Habitat preferences of sympatric populations of the Eastern Grey Kangaroo, Macropus giganteus, the Western Grey Kangaroo, M. fuliginosus, and the Red-necked Wallaby, M. rufogriseus, were examined in the Grampians National Park , western Victoria. A transect through a range of vegetation types was surveyed from a vehicle at three-hourly intervals over a 24 h period in all seasons. Highest densities of M. giganteus were recorded in Eucalyptus camaldulensis woodland with an understorey of grass, bracken or shrubs. Macropus fuliginosus occurred at highest densities on a grass airfield, and in the surrounding heathland and low heath woodland of E. baxteri and E. aromaphloia, but was never recorded in the habitat favoured by M. giganteus. On the airfield M. fuliginosus exhibited seasonal changes in density and in diel activity. Macropus rufogriseus, the most diurnal species, occurred at comparatively low and uniform densities throughout th e study area.