Context This paper explores the morphology of spermatozoa in Australian hydromyine rodents, specifically focusing on the plains mouse (Pseudomys australis ), and examines the interactions between sperm and eggs at time of fertilisation. Aims The aim of this study is to provide an overview of sperm morphology of hydromyine rodents, comparing its morphology across the different species and to investigate the interactions between the gametes at fertilisation in the plains mouse. Methods We summarise the sperm head morphology of the hydromyine rodents across the six divisions, with emphasis on the structure in the plains mouse and its interactions with the zona pellucida during fertilisation. Key results Most hydromyine rodents, including the plains mouse, exhibit a highly complex sperm head morphology with two prominent ventral processes in addition to the apical hook. These processes primarily contain filamentous actin with some species of the New Guinea Pogonomys Division having a nuclear extension into the lower process. Nevertheless three species in the Pogonomys Division and a few in the Pseudomys Division have derived sperm heads which lack the ventral processes which in the plains mouse bind the sperm to the zona pellucida around the ovulated oocyte. This may stabilise the sperm head at this time and facilitate zona pellucida penetration and fusion with the oolemma at this time. Conclusion The complex sperm head morphology in most of the hydromyine rodents is likely to date back over one million years with, in the plains mouse, interaction between sperm and egg during fertilisation involving sperm head stabilisation and zona pellucida attachment. Implications These findings suggest in hydromyine rodents valuable insights into the evolutionary development of sperm morphology and sperm-egg interactions during fertilisation, and in particular that the role of the ventral processes may be critical for successful fertilisation in this group. Understanding these processes could give insight into broader studies on reproductive strategies and evolutionary biology in rodents.

It remains unclear how variation in the intensity of sperm competition shapes phenotypic and molecular evolution across clades. Mice and rats in the subfamily Murinae are a rapid radiation exhibiting incredible diversity in sperm morphology and production. We combined phenotypic and genomic data to perform phylogenetic comparisons of male reproductive traits and genes across 78 murine species. We identified several shifts towards smaller relative testes mass (RTM), presumably reflecting reduced sperm competition. Several sperm traits were associated with RTM, suggesting that mating system evolution selects for convergent suites of traits related to sperm competitive ability. We predicted that sperm competition would also drive more rapid molecular divergence in species with large testes. Contrary to this, we found that many spermatogenesis genes evolved more rapidly in species with smaller RTM due to relaxed purifying selection. While some reproductive genes evolved rapidly under recurrent positive selection, relaxed selection played a greater role in underlying rapid evolution in small testes species. Our work demonstrates that postcopulatory sexual selection can impose strong purifying selection shaping the evolution of male reproduction and that broad patterns of molecular evolution may help identify genes that contribute to male fertility.

Phylogeographic studies of continental clades, especially when combined with palaeoclimate modelling, provide powerful insight into how environment drives speciation across climatic contexts. Australia, a continent characterized by disparate modern biomes and dynamic climate change, provides diverse opportunity to reconstruct the impact of past and present environments on diversification. Here, we use genomic-scale data (1310 exons and whole mitogenomes from 111 samples) to investigate Pleistocene diversification, cryptic diversity, and secondary contact in the Australian delicate mice (Hydromyini: Pseudomys), a recent radiation spanning almost all Australian environments. Across northern Australia, we find no evidence for introgression between cryptic lineages within Pseudomys delicatulus sensu lato, with palaeoclimate models supporting contraction and expansion of suitable habitat since the last glacial maximum. Despite multiple contact zones, we also find little evidence of introgression at a continental scale, with the exception of a potential hybrid zone in the mesic biome. In the arid zone, combined insights from genetic data and palaeomodels support a recent expansion in the arid specialist P. hermannsburgensis and contraction in the semi-arid P. bolami. In the face of repeated secondary contact, differences in sperm morphology and chromosomal rearrangements are potential mechanisms that maintain species boundaries in these recently diverged species. Additionally, we describe the western delicate mouse as a new species and recommend taxonomic reinstatement of the eastern delicate mouse. Overall, we show that speciation in an evolutionarily young and widespread clade has been driven by environmental change, and potentially maintained by divergence in reproductive morphology and chromosome rearrangements.

We investigated which species of waterbirds at Bolivar, a wastewater treatment plant in Metropolitan Adelaide, South Australia, are likely to have been immigrants from the ephemeral wetlands in the arid zone. To do this, we compared the abundance of waterbird species observed at Bolivar during the dry period in the eastern arid zone of late 2018 and 2019 with that during the subsequent wet period 2020–2022. Pink-eared Duck Malacorhynchus membranaceus, Grey Teal Anas gracilis, Australasian Shoveler Spatula rhynchotis, Hardhead Aythya australis and Blue-billed Duck Oxyura australis were all more abundant during the arid-zone dry period. By contrast, Australian Shelduck Tadorna tadornoides, Eurasian Coot Fulica atra and Black Swan Cygnus atratus showed increased abundance in spring and early summer in all years, with no marked differences between the dry and wet periods in the arid zone. Wader species that breed in the Northern Hemisphere – Sharp-tailed Sandpiper Calidris acuminata and Red-necked Stint C. ruficollis – also tended to be more abundant during the arid-zone dry year, as did Red-necked Avocet Recurvirostra novaehollandiae, whereas Pied Stilt Himantopus leucocephalus tended to be more abundant in the arid-zone wet years, with breeding by this species taking place in spring. These data suggest that Bolivar is a critically important conservation site for waterbirds and that various species use this location as a refuge during dry times in the arid zone of eastern Australia.

Remnant natural populations of greater bilbies (Macrotis lagotis) are confined to the Australian arid zone where bilbies construct and shelter in multiple burrows within their home range. We investigated burrow use behaviour of bilbies in a translocated population in temperate southern Australia to determine if behaviour differed in this climatic zone. Over a 12 month period, 43 adult bilbies at Venus Bay Conservation Park were spool-and-line tracked to 118 burrows. Active burrow density was 0.55 per ha, and bilbies at the site used multiple burrows (up to 13 for males and 8 for females) and regularly moved between diurnal burrows. Male bilbies had significantly larger burrow ranges (10.2 ± 5.8 ha, MCP100, mean ± s.d.) than females (2.6 ± 1.8 ha), and were similar in size to those recorded in an arid zone population. Males’ burrow ranges tended to overlap with the burrow range of multiple other males and females. The density of burrows in the current study suggests that bilby burrows were likely to have been a common landscape feature within the southern parts of the species range prior to their local extinction. Further research is needed to determine the impact of the loss of bilby burrows from southern Australia on other burrow commensal species.

CONTEXTSperm morphology varies greatly across mammalian species and this variability is especially evident in murid rodents with both sperm head shape and tail length being sexually selected traits. The Palawan spiny rat, Maxomys panglima has a longer sperm tail than that currently recorded for any other mammalian species.AIMSThe aim of the current study was to determine the sperm morphology of an individual Palawan spiny rat, M. panglima.METHODSLight and transmission electron microscopy were carried out.KEY RESULTSWe found that the sperm tail of M. panglima has an average length of 380μm with the midpiece being approximately 185μm in length with comparatively small mitochondria but very large coarse fibres. Furthermore, the sperm head has a less acutely flexed apical hook than that of most other murid rodents including those of several other Maxomys species.CONCLUSIONSThe Palawan spiny rat has a highly divergent sperm morphology with an extremely long tail. It may turn out to be an important species for testing various hypotheses of sperm form and function in mammals.IMPLICATIONSThese findings suggest markedly different selective pressures may have resulted in this unique sperm morphology, the functional significance of which remains to be determined.

Testis asymmetry, in which the testes in an individual differ in size, has recently been reported in koalas (Phascolarctos cinereus) in the Mount Lofty Ranges population of South Australia. We describe the morphology and histology of both testes from affected individuals in this population (n=56) and the parameters of koalas with normal-sized testes based on age and breeding season (n=56). Morphologic measurements included testis weight, length, width, and volume; histologic parameters included seminiferous tubule diameter, seminiferous epithelial height, and seminiferous tubule (interstitial tissue ratio and presence or absence of spermatozoa). Of the 56 koalas with intraindividual variation in testes size, 47 were classified as asymmetric and nine as microtestes. For koalas with asymmetric testes, all morphologic parameters were significantly decreased in the smaller testes compared with normal-sized testes, but for the histologic parameters, only seminiferous tubule diameter was significantly less. Histopathologic examination of the asymmetric testes showed 38 with normal parenchyma histologically indistinguishable between intraindividual testes, four with degeneration and atrophy, and three with hypoplasia, whereas examination of microtestes showed degeneration and atrophy in seven, hypoplasia in one, and aplasia in one. No association of testis size difference with Chlamydia pecorum infection was found in a subset of animals. For the 56 koalas with normal-sized testes, morphologic parameters were found to increase with age, and juvenile and young adults were found to have smaller seminiferous tubule diameters than adults. No differences were found between testes of koalas in the breeding and nonbreeding season. Overall, these findings indicate that testis asymmetry in koalas from the Mount Lofty Ranges population is common but not associated with decreased function, except where testis malformations such as hypoplasia or aplasia occur or when parenchyma has been disrupted by acquired disease.

The delicate mouse (Pseudomys delicatulus) ranges from Queensland to northern Western Australia. In this study the morphology of the cellular organisation of the testis and cauda epididymal spermatozoa are compared. Individuals from the mainland of the Northern Territory and Western Australia invariably have only 60–70% of the testes composed of seminiferous tubules with the interstitial tissue between the tubules containing abundant lipid rich Leydig cells, whereas the cauda epididymal sperm have highly polymorphic, often pear-shaped, heads and basally attached tails. In individuals from Queensland the seminiferous tubules make up approximately 80% of the testis, whereas in the cauda epididymides the sperm populations are generally less variable and have bilaterally flattened heads with the tail attached to the lower concave surface. These differences in the morphology of the delicate mouse testis and spermatozoa in these two geographic regions suggest differences in intensity of intermale sperm competition, with individuals from northern Western Australia and the mainland of the Northern Territory exhibiting monogamy whereas those from Queensland may exhibit some degree of intermale sperm competition and hence possibly have a polyandrous or promiscuous mating system. These findings support the suggestion that P. delicatulus, as currently recognised, contains at least one cryptic species.

The wastewater treatment plant at Bolivar in South Australia contains three groups of ponds which provide different managed habitats. Ponds 1, 2 and 3 contain a constant level of water of >1 metre in depth throughout the year, whereas in Ponds 4, 5 and 6 the water level is reduced each year with the result that the ponds become largely dry for several weeks from late summer. The third group of eight ponds, the sludge lagoons, are anaerobic and each year two or three of these ponds gradually dry out. In this study, we compared the abundance of the various species of waterbirds on these three groups of ponds throughout the period from September 2021 until December 2023. We found major differences in abundance of birds between the three groups. Most of the waders, together with Black Swan Cygnus atratus, Hardhead Aythya australis and Eurasian Coot Fulica atra, were largely present on Ponds 4–6, whereas Blue-billed Duck Oxyura australis, dabbling ducks, and three species of cormorants (Phalacrocoracidae) tended to be more abundant on Ponds 1–3, with the sludge lagoons generally having mainly Grey Teal Anas gracilis.

In New Guinea them are around 100 species of native rodents in the family Muridae that are members of two tribes, the Hydromyini and Rattini, and five divisions-the Hydromys, Uromys, Mallomys, Pogonomys, and Rattus divisions. Here we review their basic reproductive biology so far as it can be determined from the material available. We find that females of most species in the Hydromys and Uromys divisions have 4 nipples, most species in the Pogonomys division have 6. whereas in the Mallomys division nipple number across species ranges from 2 to 6, and in the Rattus division from 4 up to 12. The number of fetuses observed in pregnant individuals in species of all of the hydromyine divisions was generally between 1 and 3 but in three species in the Rattus division up to 6, or even occasionally more, occurs. In males, the relative testes mass (RTM) of most species in the Hydromys, Uromys, Mallomys, and Rattus divisions was usually between 1 and 3% of body mass, whereas in the Pogonomys division it varied markedly from only around 0.4% in Hyomys goliath up to 5% in two species of Pogonomys. The spermatozoa of species in the Hydromys and Uromys divisions, like in the Australian species of these divisions, contained a head with an apical hook together and two ventral processes, whereas in the Pogonomys and Mallomys divisions marked interspecific differences occurred with some having a sperm head with an apical hook and ventral processes but in others there were no ventral processes but a long apical hook. Sperm tail length of most species was generally between 90 and 130 um but Chiruromys and Xenuromys had sperm tail lengths of 150-153 gm. Male accessory' sex glands were generally similar across the species except for that of the preputial glands which appeared to be absent in species of Pogonomys and Chiruromys but very large in ilyomys. The findings of large relative testes mass in Pogonomys and long sperm tails in Chiruromys and .Xenuromys suggest selection for high levels of intennale sperm competition and hence multimale breeding systems in these species, whereas the variation in preputial gland size suggest interspecific differences in social organization.

Hopping mice (Genus Notomys ) are a monophyletic group of Australian Old Endemic murid rodents in the Tribe Hydromyini four of which, Notomys alexis, N. mitchellii, N. fuscus and N cervinus , occur in arid or semiarid environments. Here, we compare the size and morphology of their testes, spermatozoa, accessory sex glands and external genitalia across the species, and from these data, we draw conclusions as to their likely breeding systems. We show that both wild caught and laboratory bred adult N. alexis, N. fuscus and N. mitchellii individuals have extremely small testes, but their spermatozoa vary in morphology across the species. The ventral prostate is the only large accessory sex gland present, and their glans penis has very large spines. By contrast N. cervinus individuals have significantly larger testes with their spermatozoa being less variable but generally more complex in morphology, their seminal vesicles and coagulating glands are much larger, whereas the glans penis has only small spines. Since these reproductive traits in N. cervinus are more similar to those of most other hydromyine rodents in the genus Pseudomys, they are likely to reflect the retention of the ancestral condition within the Notomys lineage whereas the divergent reproductive traits of the other species of tiny testes, variable sperm, small seminal vesicles and coagulating glands and large penile spines are probably more recently derived traits. It is suggested that N. cervinus with its relatively larger testes mass and greater abundance of sperm of more consistent morphology has retained a mating system that may potentially involve some intermale sperm competition whereas, by contrast, the reproductive anatomy of the other three Notomys species suggests that these species exhibit monogamy.

Abstract Context. Translocations have been widely used to re-establish populations of threatened Australian mammalian species. However, they are limited by the availability of sites where key threats can be effectively minimised or eliminated. Outside of ‘safe havens’, threats such as exotic predators, introduced herbivores and habitat degradation are often unable to be completely eliminated. Understanding how different threats affect Australian mammal populations can assist in prioritising threat-management actions outside of safe havens. Aims. We sought to determine whether translocations of the greater bilby to two sites in the temperate zone of South Australia could be successful when human-induced threats, such as prior habitat clearance, historic grazing, the presence of feral cats and European rabbits, could not be completely eliminated. Methods. Greater bilbies were regularly cage trapped at two translocation sites and a capture–mark–recapture study was used to determine survival, recruitment and population growth at both sites. Key results. Our study showed that bilbies were successfully translocated to an offshore island with a previous history of grazing and habitat clearance, but which was free of exotic predators. At a second site, a mainland exclosure with feral cats and European rabbits present, the bilby population declined over time. Adult bilbies had similar survival rates in both populations; however, the mainland bilby population had low recruitment rates and low numbers of subadults despite high adult female fecundity. Conclusions. The results indicated that past grazing and habitat clearance did not prevent the bilby population on the offshore island establishing and reaching a high population density. In the mainland exclosure, the low recruitment is probably due to feral cats predating on subadult bilbies following pouch emergence. Implications. The results demonstrated that the bilby, an ecologically flexible Australian marsupial, can be successfully translocated to sites with a history of habitat degradation if exotic predators are absent. At the mainland exclosure site, threat mitigation for bilbies should focus on control or eradication of the feral cats. The control of European rabbits without control of feral cats could lead to prey-switching by feral cats, further increasing predation pressure on the small bilby population.

The spinifex hopping mouse (Notomys alexis)is an Australian arid zone rodent that undergoes boom and bust population cycles in its natural environment. Most populations studied to date have been sympatric with exotic predators and introduced herbivores, likely affecting their population dynamics. Therefore, it is unclear whether high-density populations of hopping mice are regulated by purely extrinsic factors or whether intrinsic factors are also at play. We hypothesized that reproductive suppression of femaleN. alexismay occur in high-density populations as has been observed in some other rodent species. Reproductive condition of adult femaleN. alexiswas compared between a high-density population within the Arid Recovery reserve, where exotic predators and introduced herbivores are excluded, and a low-density population on adjacent pastoral properties (no exclusions). Trap success was 10 times higher inside the reserve than at pastoral sites, and no adult females were observed breeding in the reserve population, despite 26 % of females at pastoral sites recorded breeding. Our results indicate that adult femaleN. alexisin the high-density reserve population were reproductively suppressed, but the similar sex ratios in both populations and the high female body mass and body condition in the reserve indicated that this was not due to demographic differences between the two populations or food scarcity. Our study indicates that the 'busts' observed in arid zone rodent populations may be amplified due to the presence of exotic predators and/or grazing by introduced herbivores. We contend that prior to the introduction of exotic predators and introduced herbivores in Australia, the arid zone rodentN. alexiswould likely have been more abundant and intrinsic population regulation through female reproductive suppression may have played a larger role in population regulation.

Field studies often use external examination of the vagina or the swelling of the scrotum to make deductions about the reproductive condition of rodents. In this study we sought to determine what information on reproductive condition could be gained from external examination of the reproductive anatomy of spinifex hopping mice (Notomys alexis) using individuals from a captive colony. Female N. alexis with perforate vaginae had a significantly larger mean uterine mass and larger mean maximum ovarian follicle diameter than non-perforate females. Corpora lutea were recorded in two perforate animals but were not present in females with a 'pinhole'-size perforate or non-perforate vagina. In male hopping mice scrotal bulge size was unrelated to testes mass, ventral prostate mass or presence/absence of sperm in the cauda epididymides. Males with dark scrotal pigmentation had a significantly smaller mean testes mass than males with light or no pigmentation. However, there was no relationship between scrotal pigmentation and ventral prostate mass or sperm presence in the cauda epididymides. Our study suggests that vaginal perforation is an acceptable indicator of sexual maturity in female hopping mice, but scrotal bulge size and scrotal pigmentation should not be used to predict reproductive condition of males.

The populations of South Australian duck and wader species have recently decreased considerably, but their abundance at Bolivar Wastewater Treatment Plant in metropolitan Adelaide is poorly known. To help assess the importance of this site for ducks and waders, we made 25 trips to Bolivar between December 2018 and July 2020, during most of which time south-eastern Australia was experiencing a long dry period. On each trip, we observed between 11 and 26 species of ducks and waders, with a mean total of 9804 (range 2437–15,653) individuals per trip. At times, we observed several thousand Pink-eared Ducks Malacorhynchus membranaceus, Grey Teal Anas gracilis, and Australian Shelducks Tadorna tadornoides, with occasionally up to 1200 Blue-billed Ducks Oxyura australis and 2000 Hardheads Aythya australis. Several wader species that largely breed in Australia’s semi-arid and arid zones were also observed, including occasionally >1000 Red-necked Avocets Recurvirostra novaehollandiae. Five species of waders that breed in the Northern Hemisphere were also recorded fairly regularly in the summer of both 2018–2019 and 2019–2020, including up to ~2000 Sharp-tailed Sandpipers Calidris acuminata, 2000 Red-necked Stints C. ruficollis and 150 Curlew Sandpipers C. ferruginea. These observations indicate that this wastewater treatment plant is a critically important refuge site for several species of ducks and waders. Every effort should thus be made to maintain this site for the conservation of these species in the future.

In New Guinea there are around 100 species of native rodents in the family Muridae that are members of two tribes, the Hydromyini and Rattini, and five divisions—the Hydromys, Uromys, Mallomys, Pogonomys, and Rattus divisions. Here we review their basic reproductive biology so far as it can be determined from the material available. We find that females of most species in the Hydromys and Uromys divisions have 4 nipples, most species in the Pogonomys division have 6, whereas in the Mallomys division nipple number across species ranges from 2 to 6, and in the Rattus division from 4 up to 12. The number of fetuses observed in pregnant individuals in species of all of the hydromyine divisions was generally between 1 and 3 but in three species in the Rattus division up to 6, or even occasionally more, occurs. In males, the relative testes mass (RTM) of most species in the Hydromys, Uromys, Mallomys, and Rattus divisions was usually between 1 and 3% of body mass, whereas in the Pogonomys division it varied markedly from only around 0.4% in Hyomys goliath up to 5% in two species of Pogonomys. The spermatozoa of species in the Hydromys and Uromys divisions, like in the Australian species of these divisions, contained a head with an apical hook together and two ventral processes, whereas in the Pogonomys and Mallomys divisions marked interspecific differences occurred with some having a sperm head with an apical hook and ventral processes but in others there were no ventral processes but a long apical hook. Sperm tail length of most species was generally between 90 and 130 µm but Chiruromys and Xenuromys had sperm tail lengths of 150–153 µm. Male accessory sex glands were generally similar across the species except for that of the preputial glands which appeared to be absent in species of Pogonomys and Chiruromys but very large in Hyomys. The findings of large relative testes mass in Pogonomys and long sperm tails in Chiruromys and Xenuromys suggest selection for high levels of intermale sperm competition and hence multimale breeding systems in these species, whereas the variation in preputial gland size suggest interspecific differences in social organization.

Many koalas (Phascolarctos cinereus) in the Mount Lofty Ranges, South Australia, are affected by oxalate nephrosis, in which renal calcium oxalate deposition occurs. In other species, suboptimal water intake increases the risk of urinary calcium oxalate crystal formation. Koalas principally rely on eucalypt leaf moisture content to maintain hydration but the Mount Lofty Ranges region has hot, dry summers. This study investigates the association between temperature, rainfall and eucalypt leaf moisture and the occurrence of oxalate nephrosis in this population of koalas. Koalas from the Mount Lofty Ranges population that had died or were euthanased between 2008 and 2016 were necropsied and oxalate nephrosis was determined by histopathology (n=50). Leaf moisture content of Mount Lofty eucalypts was determined seasonally. It was found that increased numbers of koalas with oxalate nephrosis died in the months following high mean maximal temperature and in the months following low rainfall. Eucalypt leaf moisture content was not significantly associated with koala deaths. These findings suggest that hot and dry summer/autumn periods contribute to an increased incidence of koala deaths due to oxalate nephrosis. This is probably due to the effects of evaporative water loss and/or lack of access to supplementary drinking water at this time.

Context Many of Australia’s threatened mammals were once widespread across the continent and present in both arid, semiarid and temperate habitats. However, data on breeding biology can be lacking for some climatic regions due to local extinctions of populations. The breeding biology of the greater bilby (Macrotis lagotis) has previously only been studied in captive colonies or free-ranging arid zone populations. Between 1997 and 2005, captive-bred bilbies were released at two sites in temperate South Australia. These populations provided an opportunity to determine whether bilbies adopt a seasonal reproductive strategy in the temperate zone, where this species has not been present since the early 1900s. Aims To determine the season of births, litter size and female reproductive potential in two free-ranging populations of the bilby in the temperate zone of South Australia. Methods Bilbies were regularly cage-trapped at Venus Bay Conservation Park and Thistle Island between August 2007 and April 2010 to obtain data on reproductive activity in both populations. Key results Births of pouch young in both populations occurred in winter (June–August), spring and early summer, but not between February and mid-May. Males had a significantly smaller mean testes size relative to head length in late summer, when breeding activity ceased. Average litter size at pouch emergence was between 1.00 and 1.47 pouch young, with females producing up to three litters per annum. The mean head length of females that successfully raised twins was significantly larger than that of females who raised a single pouch young. Conclusions The seasonal breeding pattern observed in the present study differs from that of year-round reproductive activity in captivity and the arid zone. The present study suggests that female body size influences fecundity, and that releasing large females at the start of the breeding season in temperate areas may maximise the initial rate of increase of a translocated bilby population. Implications The present study suggests previously widespread species such as the bilby can adapt their reproductive strategy to suit local conditions. Cessation of breeding in autumn, as observed in this study, has also been observed in other bandicoot species in southern Australia.

The population of water-rats (Hydromys chrysogaster) on the River Torrens in Adelaide was monitored over a three-year period. Initially, the population density was high but it became greatly reduced after the water level was lowered and did not recover again until over a year after the high water level had been restored. Males tended to have a larger home range than did females although they did not appear to exclude other individuals from their territory. Breeding generally took place in spring and summer although a few young appeared to be produced in most months of the year. This high population of water rats may, to some extent, be due to the abundance of the exotic fish species that occur in the River Torrens.