Dasyurus Viverrinus Research Articles

NICHE DIFFERENTIATION AMONG SYMPATRIC AUSTRALIAN DASYURID CARNIVORES

Niche differentiation occurred on 3 dimensions in a size-structured guild of marsupial carnivores (Marsupialia: Dasyuridae) that included the Tasmanian devil (Sarcophilus laniarius), spotted-tailed quoll (Dasyurus maculatus), and eastern quoll (D. viverrinus). Diet was partitioned on a body size-prey size axis, but substantial overlap occurred between adjacent species. Complementary niche differentiation also occurred on horizontal (vegetation type and structure) and vertical (arboreal) habitat dimensions. Eastern quolls separated completely by using grasslands more than the other 2 species. Spotted-tailed quolls were distinguished by a greater degree of arboreal activity that reflected a large proportion of arboreal prey species in their diet. A strong relationship was found between body size, arboreal activity, and morphologic adaptations for climbing between predators and prey. Coevolution in phenotype among predators and prey and consequent constraint on performance in different habitat types were the most easily measured explanations for habitat differentiation among these species, particularly between spotted-tailed quolls and devils. The ghost of competition past is an alternative and nonexclusive explanation that can equally explain arboreal habitat use by spotted-tailed quolls and separation between the eastern quoll and the spotted-tailed quoll. Risk of predation and prey availability also may be important factors.

Linstowinema, Smales, 1997 (Nematoda : Seuratidae) from dasyurids (Marsupialia : Dasyuridae) from Australia.

Linstowinema edmondsi (Echinonematinae) from Dasyurus hallucatus (Dasyuridae) is redescribed. It can be differentiated from all species of Linstowinema occurring in bandicoots (Peramelidae) in having the first row of cephalic hooks as long as or longer than the second row. L. gracile n. sp. is described from Phascogale tapoatafa and Dasycercus cristicauda, and can be distinguished from all previously described species of Linstowinema in not having a cuticular dilation of the oesophageal region of the body. L. rosamondae n. sp. from Dasykaluta rosamondae, described from females, also lacks the cuticular dilation of the oesophageal region and can be distinguished from L. gracile in having 18-19 rows of body hooks compared with 15. Other Linstowinema spp. for which there is presently insufficient material available for a full description include a single female occurring in Dasyurus viverrinus from Sydney, New South Wales, a single male occurring in Parantechinus bilarni from Kakadu National Park, Northern Territory and three damaged immature males occurring in Sminthopsis leucopus from Timbillica State Forest, New South Wales. Fourth stage larvae of Linstowinema have three rows of cephalic hooks but no body hooks, only spines. Fourth-stage larvae moulting to fifth-stage have body hooks however. This suggests that the genus Linstowinema, with body hooks, may have been derived from the echinomatine genus Inglechina which does not have body hooks.

The function of vigilance in sympatric marsupial carnivores: the eastern quoll and the Tasmanian devil

Sympatric marsupial carnivore (Marsupialia: Dasyuridae) species experience different levels of risk of predation and competition as a consequence of different body size and feeding adaptations. The small eastern quoll,Dasyurus viverrinus, is preyed upon by owls and is aggressively displaced from carcasses by its larger competitor and potential predator, the Tasmanian devil,Sarcophilus laniarius. Devils have no known predators but this specialized scavenger experiences intense intraspecific competition. I studied the vigilance behaviour of individuals of these species feeding on carcasses. (1) Eastern quolls were more vigilant in the presence than in the absence of devils, suggesting that their vigilance functions to detect predators/competitors. (2) Devils showed a decrease in vigilance with increasing body size and age, and a trend towards a decrease with increasing group size. These are the same patterns expected if vigilance was in response to predation risk, although devils have no predators. Vigilance behaviour did not change in the presence of eastern quolls, suggesting that vigilance is not directed towards interspecific competitors. (3) As expected from their greater risk of predation and injury from a larger competitor, eastern quolls appeared to invest more in vigilance than devils did: they used vigilance postures that gave better visibility but disrupted feeding more.

Susceptibility of the tiger quoll, Dasyurus maculatus, and the eastern quoll, D. viverrinus, to 1080-poisoned baits in control programmes for vertebrate pests in eastern Australia

Captive trials were undertaken to determine whether tiger quolls and eastern quolls could detect baits that were either buried or covered with soil following the methods employed in normal buried-poisoned-bait programmes. Both tiger quolls and eastern quolls detected, dug up and consumed buried FOXOFF baits. Consumption trials showed that tiger quolls were capable of consuming 2–3 FOXOFF baits in a single meal and more than three baits overnight. Eastern quolls could consume up to 1.5 baits in a single meal. Field trials were undertaken to investigate whether tiger quolls in the wild could also detect and consume buried baits. Trials with both fresh meat and FOXOFF baits were undertaken at a site near a tiger quoll latrine, using a remote camera to record visits to the site and bait uptake. The results confirmed that tiger quolls in the wild can detect and consume both fresh meat and FOXOFF baits that have been buried or placed on the surface and covered with soil to a depth of 5–8 cm. The results indicate that the buried-bait technique is not specific for introduced predators, and free- feeding may not preclude non-target species from taking buried baits. Reliance on the identification of the species visiting bait stations from tracks may also be unreliable as foxes dug up bait stations searching for baits, even after the bait had been removed, potentially obliterating other tracks.

CHARACTER DISPLACEMENT IN AUSTRALIAN DASYURID CARNIVORES: SIZE RELATIONSHIPS AND PREY SIZE PATTERNS

The four different assemblages of marsupial dasyuroid carnivores in Australia, comprising four species on the island of Tasmania and three different two-species assemblages on the mainland of Australia, present an ideal opportunity to test the theories of competitively based morphological character displacement. With males and females treated as separate morphospecies, four trophic characters that relate to killing and feeding behavior and skull length, as a measure of body size, were examined for evidence of morphological patterning, latitudinal size variation, and sexual dimorphism. The competitive basis for character displacement in intra- and interspecific variation in prey size was sought from dietary analysis at a field site. Even spacing in canine strength, but not in other characters, was found among species and sexes of quolls (Dasyurus viverrinus and D. maculatus), but not including the devil (Sarcophilus laniarius) or the thylacine (Thylacinus cynocephalus), in Tasmania. Even spacing was found in temporalis muscle size for all combinations of the four Tasmanian species. Canine breaking strength and muscle strength driving the canines can be construed as the most important trophic characters involved in prey capture, and therefore in determining the upper size of prey that can be handled. Even spacing was found in Tasmania, where there are two larger species in the guild, but not in any of the three mainland assemblages where the larger species of carnivores have been absent for many generations. The basis for the observed morphological patterning in killing behavior, evidence for even spacing in prey size, and partial character release on the mainland are consistent with the hypothesis of competitive character displacement. These size relationships result from a complex interplay of factors. Latitudinally correlated size variation has influenced an increase in body size and canine strength in D. viverrinus and an increase in body size in D. maculatus in Tasmania. This is countered by decreased canine strength in D. maculatus in Tasmania resulting from competitive character displacement. The result is character convergence. Sexual selection also influences size relationships.

Character Displacement in Australian Dasyurid Carnivores: Size Relationships and Prey Size Patterns

The four different assemblages of marsupial dasyuroid carnivores in Australia, comprising four species on the island of Tasmania and three different two-species assemblages on the mainland of Australia, present an ideal opportunity to test the theories of competitively based morphological character displacement. With males and females treated as separate morphospecies, four trophic characters that relate to killing and feeding behavior and skull length, as a measure of body size, were examined for evidence of morphological patterning, latitudinal size variation, and sexual dimorphism. The competitive basis for character displacement in intra- and interspecific variation in prey size was sought from dietary analysis at a field site. Even spacing in canine strength, but not in other characters, was found among species and sexes of quolls (Dasyurus viverrinus and D. maculatus), but not including the devil (Sarcophilus laniarius) or the thylacine (Thylacinus cynocephalus), in Tasmania. Even spacing was found in temporalis muscle size for all combinations of the four Tasmanian species. Canine breaking strength and muscle strength driving the canines can be construed as the most important trophic characters involved in prey capture, and therefore in determining the upper size of prey that can be handled. Even spacing was found in Tasmania, where there are two larger species in the guild, but not in any of the three mainland assemblages where the larger species of carnivores have been absent for many generations. The basis for the observed morphological patterning in killing behavior, evidence for even spacing in prey size, and partial character release on the mainland are consistent with the hypothesis of competitive character displacement. These size relationships result from a complex interplay of factors. Latitudinally correlated size variation has influenced an increase in body size and canine strength in D. viverrinus and an increase in body size in D. maculatus in Tasmania. This is countered by decreased canine strength in D. maculatus in Tasmania resulting from competitive character displacement. The result is character convergence. Sexual selection also influences size relationships.

Lactational Energetics of a Marsupial Carnivore, the Eastern Quoll (Dasyurus viverrinus)

The rates of milk consumption by young of the eastern quoll (Dasyurus viverrinus), a polytocous medium- sized marsupial carnivore, were estimated by means of the 22Na-turnover technique. The mean individual daily rate of milk consumption at seven weeks of age was 0·6 mL, which increased to a peak of 16 mL at about 14 weeks, when the young weighed 130 g. The total amount of milk energy delivered to each young from birth to the commencement of weaning was 4·1 MJ. The digestible energy intake of lactating quolls (± s.d.), 740 ± 117 kJ kg-1 day-1, was nearly double that of non-lactating quolls, 333 ± 75 kJ kg-1 day-1. With such high energy demands during lacation, it is unlikely that a complete litter of six could be successfully reared unless prey are abundant.

Body temperatures and activity patterns of Tasmanian devils (Sarcophilus harrisii) and eastern quolls (Dasyurus viverrinus) through a subalpine winter.

During a field study of carnivorous dasyurid marsupials in subalpine Tasmania, the trapping success for Tasmanian devils (Sarcophilus harrisii), but not for spotted-tailed quolls (Dasyurus maculatus) or eastern quolls (Dasyurus viverrinus), was significantly lower when winter weather conditions turned to sleet or snow or when deep snow lay on the ground. This field study was instigated to determine if devils and eastern quolls spend more time in burrows in severe weather conditions and if they enter torpor. Torpor is known to occur in eutherian mammals as large as devils and in a similar-sized congeneric marsupial, the western quoll (Dasyurus geoffroyi). Using radiotelemetry, body temperatures of Tasmanian devils and eastern quolls ranging freely in their natural habitat were monitored throughout winter. Neither species was observed in torpor, even under prolonged severe weather conditions, and the number of hours spent active not did differ between summer and winter or between moderate and severe winter weather conditions. Body temperatures averaged 36.5 degrees C (SD = 0.079, range of 33.5 degrees-38.6 degrees C) for the three male eastern quolls and 35.7 degrees C (SD = 0.575, range of 31.3 degrees-37.5 degrees C) for the four (male and female) devils. A diel cycle in body temperature occurred in both species; temperatures rose each evening when animals became active, remained high throughout the night despite ambient temperatures falling to the diel minima, and were lower during the day when the individuals were inactive in dens. The amplitude of this cycle was greater in eastern quolls (1.1 degrees C, SD = 0.142) than in devils (0.6 degree C, SD = 0.252).

Reconstructing the Evolutionary Radiation of Dasyurine Marsupials with Cytochrome b, 12S rRNA, and Protamine P1 Gene Trees

We report complete sequences of the cytochrome b, 12S rRNA, and protamine P1 genes from 18 of the 21 extant species of dasyurine marsupials (family Dasyuridae). Partial sequences are included for Pseudantechinus ningbing, but no data are available for Ps. mimulus or Phascolosorex doriae. Phylogenetic analyses of these sequences yield compatible gene trees with limited resolution. Simultaneous parsimony analysis of all three genes suggests the following: (a) a basal polytomy of eight lineages; (b) a sister-group relationship between “phascolosoricine” genera (Neophascogale and Phascolosorex, which are monophyletic) and Dasyums + Sarcophilus; (c) monophyly of Dasyurus viverrinus, D. albopunctatus, D. geoffroii, and D. spartacus apart from other quolls and Sarcophilus; and (d) sister-pairing of D. geoffroii and D. spartacus Previous attempts at unraveling the phylogenetic history of dasyurines have produced strikingly inconsistent results, due in part to differences in character systems examined, interpretations of character homology and independence, and analytical methods employed. We provide some evidence that the basal polytomy is the result of rapid cladogenesis and suggest that this episode of dasyurine evolution is temporally correlated with the onset of aridification following the New Guinean uplift of 15 million years ago.

Degenerative leukoencephalopathy and myelopathy in dasyurids.

From June 1985 to November 1992 eight eastern quolls (Dasyurus viverrinus) and six Tasmanian devils (Sarcophilus harrisii), held at institutions in Australia and Canada, developed progressive blindness and posterior paresis progressing to paralysis. All were aged individuals. At necropsy white matter tracts, particularly in the spinal cord, optic tracts, and cerebellum, contained evidence of severe axon degeneration with vacuolation and macrophage infiltration. The surrounding tissue had evidence of gliosis. The etiology of the condition is unknown but may be a form of age-related degeneration.

Central cardiovascular shunts in the perinatal marsupial

Marsupials are born at an early stage of development after a short period of gestation. In this study the nature and timing of closure of the central cardiovascular shunts was investigated. Light and scanning electron microscopy were used to determine changes in central cardiovascular shunts in eight marsupial species with gestation periods of between 12.5 and 36.5 days and birth weights ranging from 12.5 mg to 740 mg. Laboratory mice with a birth weight of about 1,000 mg and a gestation period of 21 days were included for comparison. Marsupials have a ductus arteriosus and an interatrial communication. The former closes rapidly after birth in the marsupial; however the interatrial communication is in the form of a fenestrated septum, which closes as a result of tissue proliferation over a period of days after birth. An additional central shunt, an interventricular foramen, was found to persist in three species for a short time after birth. In one species, the eastern native cat, Dasyurus viverrinus, which has a gestation period of about 19 days and low birth weight of about 12.5 mg, in addition to the two common shunts there was a large interventricular communication and septation of the outflow tract was incomplete. In adapting from intra-uterine life, it seems that marsupials have adopted different, but equally effective strategies, with regard to the circulatory system.

The Blood of Carnivorous Marsupials: Low Hemoglobin Oxygen Affinity

We examined the blood of four dasyurid marsupials, all small, active insectivores and/or carnivores, to establish if there were any specializations in oxygen transport. All four species had hemoglobins with a low affinity for oxygen. This was demonstrated by high P50's (the partialpressure of oxygen [PO₂] at which the hemoglobin is half-saturated with oxygen) of the whole blood (means of 38.3-59.8 mmHg) and of red cells suspended in a physiological buffer (means of 41.6-49.0 mmHg) at a CO₂ tension of 43 mmHg. There was a strong correlation betuween increase in body mass over three orders of magnitude and increase in the oxygen affinity of the whole blood. The effects of changing CO₂ tensions on the oxygen affinity of whole blood were measured as △log P50/Δlog PCO₂; mean values ranged from 0.25 to 0.373. Values for △log P50/ΔpH wuere measured for red-cell suspensions; means values ranged from -0.40 to -0.481. The introduction of 2,3-diphosphoglycerate significantly decreased the oxygen affinity, of the hemoglobin of Dasyuroides byrnei. The blood of D. byrnei and Dasyurus viverrinus had high hematocrits and high concentrations of hemoglobin. We conclude that hemoglobins with a low affinity for oxygen, an adaptation to an active lifestyle, are a characteristic of dasyurid marsupials generally.

Neodiplostomum spratti n. sp. (Digenea: Diplostomidae) from Antechinus spp. (Marsupialia: Dasyuridae) in Australia, with notes on other diplostomids from Australian mammals

Neodiplostomum spratti n. sp. is described from Antechinus stuartii and A. swainsonii (Marsupialia: Dasyuridae). The status of Neodiplostomum minor, N. flabelliformis, N. intermedius, N. sarcophilus, N. diaboli and Pharyngostomoides dasyuri is reviewed. New hosts records for N. intermedius are Rattus lutreolus, R. leucopus, R. rattus (all Rodentia: Muridae) and Dasyurus maculatus (Dasyuridae). The following undescribed species are recorded: Neodiplostomum spp. from Dasyurus maculatus from Victoria, Dasyurus viverrinus from Tasmania, Perameles nasuta (Marsupialia: Peramelidae) from New South Wales, Sminthopsis leucopus (Dasyuridae) from New South Wales, and a diplostomulum from the lung of Perameles nasuta from New South Wales. The validity of Fibricola is reconsidered and it is proposed that it be considered a synonym of Neodiplostomum. The new combinations Neodiplostomum minor (Dubois, 1936), N. sarcophilus (Sandars, 1957) and N. flabelliformis (Pearson & Dubois, 1985) are proposed: all three were previously attributed to Fibricola.

Small terrestrial mammals and bats of Melaleuca and Claytons, southwestern Tasmania

A survey of small terrestrial mammals and bats was undertaken in two areas of southwestern Tasmania: around Melaleuca, in sedgeland, scrub and woodland communities, and at Claytons in mixed forest. The density of bats was extremely low in comparison with populations in eastern Tasmania. The densities of Rattus lutreolusand Antechinus minimuswere greatest in sedgeland/scrub with a dense undergrowth. Pseudomys higginsi was only captured in mixed forest but is also present around Deny King's garden. Dasyurus viverrinus was most abundant in young sedgeland. Cercartetus nanus was present at both Clay tons and Melaleuca. No introduced rodents were trapped, but an outbreak of Rattus rattus had occurred previous to our study. No Mastacomys fuscus were trapped but they have been recorded in a previous study. Fire has an important influence on the composition and structure of the vegetation which, in turn, influences the composition and density of the mammal community.

Testosterone-LH response and episodic secretion in the male marsupial, Dasyurus viverrinus

The pattern of testosterone-LH secretion, feedback mechanism, and periodicity of release were investigated in the male marsupial eastern quoll. Testosterone secretion is controlled directly by LH and in the wild, the secretion of both are synchronous and show a major peak at breeding time. An inverse relationship between the secretion of LH and testosterone occurs after castration which supports the hypothesis that a negative feedback mechanism exists between the gonads and the pituitary gland as in other mammals. These hormones fluctuate in a cyclic manner over 24 hr.

The brachylaimidae (Trematoda: Digenea) of Australian native mammals and birds, including descriptions of Dasyurotrema n. g. and four new species of Brachylaima

The Brachylaimidae of Australian native animals are revised. Brachylaima dasyuri (Johnston, 1913) is redescribed from Dasyurus viverrinus, Phascogale tapoatafa and Isoodon macrourus. B. simile (Johnston, 1913) is removed from synonymy with B. dasyuri, reinstated as a valid species and redescribed from Perameles nasuta, Isoodon obesulus and Antechinus stuartii. B. antechini Peisley & Howell, 1975 is reduced to synonymy with B. simile. B. brindabellensis n. sp. is described from Rattus fuscipes. B. walterae n. sp. is described from Antechinus swainsonii and A. stuartii. B. delecta n. sp. is described from Antechinus flavipes. B. sandarsae n. sp. is described from Antechinus godmani. B. pulchellum (Johnston, 1917) is redescribed from Leucosarcia melanoleuca. An unnamed Brachylaima species is described from Isoodon macrourus. New host records are Brachylaima dasyuri from Phascogale tapoatafa and B. simile from Perameles nasuta. Dasyurotrema mascomai n. g., n. sp. is described from Antechinus swainsonii. The new genus is placed in the Panopistinae. It differs from the existing genera by having a single loop of the uterus passing anterior to the ventral sucker and the genital pore posterior to the posterior testis but still distinctly ventral. A second species of Dasyurotrema is recorded, but not described, from Antechinus stuartii. Brachylaimid metacercariae are described from Rhytida capillacea, Helicarion virens, H. mastersi and Vercularion strangei. In no case was a host species found to harbour more than one species from any brachylaimid genus at a single geographical site.

Temporal Decline of 1080 Within Meat Baits Used for Control of Wild Dogs in New South Wales.

Short- and long-term trials were conducted to determine the rate of decline of 1080 (sodium fluoroacetate) in meat baits used for poisoning wild dogs. Baits were injected with 0.2 ml of standard 1080 solution (nominal dose of 6.00 mg of pure 1080 per bait) and placed in the field. In the long-term trial, 10 baits were collected at 7 intervals between 3 h and 226 days, and analysed for residual 1080 by liquid chromatography. The recoverable 1080 content declined greatly over the first 48 days, although at 226 days all 10 baits retained some 1080. By 42.4 days the mean residual level of 1080 in the baits was predicted to be less than the theoretical LD99 for wild dogs. At the time of distribution, baits contained less than the LD50 for an average-sized eastern quoll. The LD99 for domestic cattle-dogs was predicted to be still present in baits at 72.9 days. Loss of 1080 from these baits was not correlated with rainfall, temperature or humidity. In the short-term trial, 10 baits were collected at 11 intervals up to 200 h. The recoverable 1080 content decreased by 3.09 mg (61% of the injected dose) within the first hour after injection and declined to a low of 2.70 mg at hour 50. The level of recovered 1080 then rose to 73% of the injected dose at hour 150.

The effect of restricted feeding on the wheel-running activity rhythms of the predatory marsupial Dasyurus viverrinus

The effects of restricted feeding schedules on the circadian rhythms of wheel-running of Dasyurus viverrinus were examined under a light/dark cycle and in constant darkness (experiment 1) and in constant light (experiment 2). The results of the 2 experiments showed that: (1) in contrast to the light/dark cycle, restricted feeding is only a weak zeitgeber for the wheel-running activity rhythms of D. viverrinus; (2) restricted feeding elicits meal anticipatory activity in D. viverrinus comparable to that elicited by restricted feeding in the rat; (3) transient cycles of the anticipatory activity free-run with a period different to that of the main component of activity for several cycles after the termination of restricted feeding; and (4) activity suggestive of beating between 2 oscillators occurs during restricted feeding and after the termination of restricted feeding. Taken together the latter 3 observations suggest that the activity rhythms of D. viverrinus are controlled by at least 2 separate circadian oscillators.

Vascular and Avascular Retinae in Mammals

Intraretinal blood vessels are present in some and absent in other vertebrate species, including the mammals. Among the marsupials, both vascular and avascular retinae are seen. We determined the funduscopic appearance of the eye, investigated the functional aspects of ocular blood flow in both types of retina in marsupials and compared our results with known patterns in placental mammals. The Australian polyprotodont marsupials, the Tasmanian devil, Sarcophilus harrisii, and the quoll, Dasyurus viverrinus, together with an American polyprotodont, the Virginia opossum, Didelphis virginiana, demonstrate variable degrees of tapetal differentiation, pigmentation and a very close parallel course of their intraretinal arteries and veins over considerable distances. Using the technique of fluorescein angiography, we found that retinal blood flow in the 3 vascular Australian species commenced with arterial filling. Early venous was seen next, followed by the capillary blush. This unusual sequence of vascular flow differs from that of the arterial-capillary-venous filling seen in placental mammals. This difference is most likely a consequence of the known looped, end artery organisation found within marsupial nervous systems, of which the retinae are a part. The 2 diprotodont marsupials examined, the brushtail possum, Trichosurus vulpecula, and the sugar glider, Petaurus breviceps, possess avascular retinae. Only a small residual tuft of fluorescein-impermeable vessels projects from the optic disc into the vitreous. Interestingly, the structural complexity of the central visual system in diprotodonts all of whom possess avascular retinae) is commonly accepted as being greater than that of the stem polyprotodont line (which possess vascular retinae). If retinal function matches this internal complexity, then retinal avascularity may, as in birds, be associated with superior vision. However, as the retinae of these mammals clearly lack any nutritive mechanisms directly analogous to those in the retinae of, say, birds or the megachiropteran bats, their retinal nutritive pathways remain enigmatic.

Haematology of the Australian Eastern quoll, Dasyurus viverrinus—II. Red cell enzymes and metabolic intermediates

1. 1. The activity of 21 red cell enzymes and three red cell metabolic intermediates were measured in adult Dasyurus viverrinus and compared with published data on other marsupials. 2. 2. Phosphofructokinase (PFK), glyceraldehyde dehydrogenase (GAPD) and phosphoglycerate kinase (PGK) were elevated in comparison to other marsupials. 3. 3. Enolase (ENO) and 2,3-diphosphoglycerate (2,3 DPG) were lower than in other marsupials.