Greater Bilby Macrotis Lagotis Research Articles

Does litter decomposition vary between the foraging pits of two soil‐disturbing mammal species?

AbstractSoil‐disturbing animals play a critical role in many ecosystem processes. The loss of native soil‐foraging mammals (e.g. greater bilby Macrotis lagotis; burrowing bettong, Bettongia lesueur) throughout vast areas of Australia has altered fundamental soil processes such as decomposition. Little is known about whether surviving native soil‐disturbing animals (e.g. short‐beaked echidna, Tachyglossus aculeatus) produce soil disturbances that are functionally equivalent to those of locally‐extinct native animals. We used a litter bag study to compare abiotic and biotic mechanisms of decomposition within the foraging pits of two native mammal species. We compared decomposition rates between landforms, which we used as a surrogate for soil texture; grass species Austrostipa scabra subsp. scabra and Triodia scariosa subsp. scariosa, which we used as our substrates; and the effects of chemically excluding fungi and/or termites. There were initial differences in the organic mass loss between echidna and bilby/bettong foraging pits, with bilby/bettong pits losing more over 30 days, and echidnas losing more over 63 days. However, over 396 days there was no significant difference between the two pit types. Landform (soil texture) and chemical exclusion of termites and fungi did not affect our measures of decomposition until the final stage of the study. The two grass species lost significantly different amounts of organic material at each collection interval, with Austrostipa losing more at 30, 63 and 130 days and Triodia losing more at the final 396 day collection. This provided the most consistent effect on decomposition. Our results highlight the temporal idiosyncrasies in the various drivers of decomposition in this dune‐swale system. Overall, this study provides evidence that the foraging pits of the short‐beaked echidna do not differ markedly from those of the locally extinct greater bilby and burrowing bettong in terms of their capacity to maintain rates of decomposition at an annual scale. Copyright © 2015 John Wiley & Sons, Ltd.

Studies of Male Reproduction in the Greater BilbyMacrotis lagotis

Despite its vulnerable conservation status there is scant information on male Greater Bilby Macrotis lagotis reproduction. Observations of gross anatomy revealed a testis to body weight ratio of 0.08 - 0.17% (n = 4), the presence of a carrot shaped prostate with an oblique coronal segmentation of ventral and dorsal orientated prostatic tissue, an elongated membranous urethra, two bulbourethral glands and a bifurcated urethra in the glans penis (n = I).The testis contained a high proportion of Leydig tissue (37.5 ± 2.7%) and a seminiferous epithelial cell cycle (8 stages identified) with a predominance of pre-meiotic stages (61.4%) and Sertoli cells with unusually large nuclei. A GnRH stimulation test conducted on four different intact sexually mature Bilbies using 2μg Buserelin resulted in maximal plasma androgen secretion 30 to 60 mins after injection. While steps of M. lagotis spermiogenesis were similar to those described in peramelid marsupials, the morphology of the Bilby spermatozoan at spermiation,was radically different to that of the bandicoot sperm cell. Similar to the bandicoot, M. lagotis spermatozoa in the corpus epididymidis dislocated their neck insertion from the primary implantation fossa, so that by the time the sperm cell had reached the cauda epididymidis, the acetabulum had migrated cranially Into a secondary implantation fossa and the nucleus had become streamlined with respect to the flagellum.This study reports the first description of large crystalloid inclusions in the principal cells of the caput epididymidal epithelium, the significance of which remains unknown. Male Bilby reproduction reported in this study supports the present taxonomic position of the Thylacomyidae.

Foraging animals create fertile patches in an Australian desert shrubland

Fertile patches are created and maintained by a combination of physical and biologically‐mediated processes including soil disturbance by animals. We examined the creation of fertile patches by 4 vertebrates, the greater bilbyMacrotis lagotis, burrowing bettongBettongia lesueur, European rabbitOryctolagus cuniculus, and Gould's sand goannaVaranus gouldiiwithin dunes, ecotones, and swales in a dunefield in arid South Australia. These animals all create pits when foraging for subterranean food resources. We hypothesized that 1) the effect of pits on litter capture would vary among landscapes and animal species, 2) larger pits would trap more litter and seed, 3) pits would contain more viable seed than the surrounding matrix, and 4) the effect of pits on soil chemistry would vary among animal species, and be greater in landscapes with more finely textured soils. We found that litter was restricted almost exclusively to the pits, and was greater in pits with larger openings. Litter capture was greater in ecotones and dunes than in swales. A total of 1307 seedlings from 46 genera germinated from litter samples taken from the pits, but no seedlings emerged from samples taken from soil surrounding the pits. Foraging pits contained significantly higher levels of total C and N than surrounding soil, and total C and N concentrations were greatest in swales and lowest in dunes. Pits contained ca 55% more mineralisable N that surface soils, and pits constructed by bilbies and bettongs contained half the concentration of mineralisable N as those of rabbits and goannas. Concentrations of mineral N and mineralisable N were also greatest in the swales. Our results demonstrate the importance of animal‐created pits as nutrient sinks and sites for seedling establishment, and suggest that changes in the composition of arid zone vertebrates may have resulted in profound changes to nutrient and soil dynamics in arid Australia.

The diet of the re-introduced greater bilbyMacrotis lagotisin the mallee woodlands of western New South Wales

The greater bilby Macrotis lagotis once occupied about 70% of the Australian mainland but is now restricted in occurrence to just 20% of its former range. It is classified as Extinct in New South Wales. We assessed the major components of the diet of a recently re-introduced population of bilbies at Scotia Sanctuary, in western New South Wales, from faecal material collected over a period of 13 months. Animals consumed more invertebrates than green plant material and seeds throughout the study, although there was temporal variation in the presence of these food categories. Five orders of invertebrates were identified, with Coleoptera (beetles) occurring in more than 80% of faecal samples and Isoptera (termites) and Formicidae (ants) in 48% and 40%, respectively. These results identify key components of the diet of the first population of bilbies in New South Wales since the early 20th century and, combined with detailed studies of habitat requirements and prey abundance, should assist with selection of ad...

Pupillary mobility in four species of marsupials with differing lifestyles

AbstractThe pupillary response to the onset of bright light (10 000 lx) and darkness (4 lx) is compared in four species of Australian marsupials with different activity patterns. Maximal and minimal pupil width in relation to eye width was measured and the rate of change assessed. In the arrhythmic fat‐tailed dunnart Sminthopsis crassicaudata, there were marked changes in pupil size with the range of pupil width to eye width of 0.73–0.10; constriction was rapid (54% s−1) and dilatation slower at 10% s−1. The crepuscular honey possum Tarsipes rostratus had a small range of pupil size at 0.56–0.46, with constriction and dilatation being slow at 4% s−1 and 3% s−1, respectively. The strictly nocturnal burrowing bettong Bettongia lesueur had a small pupil with a limited size range of 0.21–0.12; constriction at 25% s−1 outstripped dilatation at 7% s−1. The greater bilby Macrotis lagotis, also strictly nocturnal, had a small and immobile pupil with a fixed pupil width to eye width ratio of 0.08. In conclusion, contrary to most previous assumptions, pupil size is not fixed in marsupials, and not all nocturnal animals possess a wide pupil. Moreover, as a regulatory process, pupillary mobility reflects more than a differentiation between diurnal or nocturnal condition, and seems to correlate with specific visual requirements. The results of this study are discussed in relation to the lifestyle of the species and the associated illumination levels, and as a method of predicting the marsupials' periods of activity in the field.