Antechinus Minimus Research Articles

Small mammal succession following low severity planned burns with different fire intervals

Understanding how mammal species respond to planned burns can assist managers of protected areas to better implement fire regimes for mammal conservation. I investigated the response of three small mammal species (Rattus lutreola, Mastcomys fuscus and Antechinus minimus) to low severity, consecutive planned burns with different fire intervals (6–9 and 22 years) over 17 years, using live-trapping in montane moorland. Following the burns, vegetation density decreased by 71–83% and the small mammal species were largely absent for at least 2 years. Vegetation recovery to pre-burn levels was slower (7–10+ years versus 4–5 years) following burns with short fire intervals (6–9 years) than long fire intervals (22 years), and this was associated with a slower and reduced recovery for A. minimus but not for R. lutreola and M. fuscus. This study suggests that these species are resilient to small scale, low severity planned burns in montane moorlands on moderate productivity soils provided fire intervals are not too short (<10 years). Further studies are required to augment these findings and to investigate small mammal responses in moorlands on less productive soils than those studied here, where recovery times are expected to occur over longer timeframes.

Notes on the "Swamp Antechinus"

Notes on the "Swamp Antechinus"

Decline of the dasyurid marsupial Antechinus minimus maritimus in south-east Australia: implications for recovery and management under a drying climate

Our understanding of recent extinctions and declines of Australian mammals is poor, particularly where there is a paucity of data to quantify change. The swamp antechinus (A. m. maritimus) has a fragmented, coastal distribution in south-east Australia. Although long-term studies (1975–2007) of this vulnerable species were conducted in the eastern Otways, its current status was unclear. We assessed the success of live trapping and camera trapping (2013–17) at 42 sites, 19 where the species was trapped previously. Between 2013 and 2015 A. m. maritimus was recorded at only 6 sites (n = 8), but at none in 2016–17. Assessment of long-term changes found that high-density populations occurred after above-average rainfall, and both low- and high-density populations collapsed after wildfire, after low rainfall, and in fragmented habitat. The species may now be restricted to very small populations in refuges such as coastal dunes, and predicted low rainfall and increased burning frequency pose major threats to the species’ survival. Recovery is unlikely without targeted management, including predator control and protection from inappropriate fire regimes and habitat fragmentation. If similar declines have been experienced across the species’ range, prevention of extinction of the species will require similar management strategies.

Taxonomy and redescription of the swamp Antechinus, Antechinus minimus (E. Geoffroy) (Marsupialia: Dasyuridae)

We provide a taxonomic redescription of the dasyurid marsupial Swamp Antechinus, Antechinus minimus (Geoffroy, 1803). In the past, A. minimus has been classified as two subspecies: the nominate A. minimus minimus (Geoffroy, 1803), which is found throughout much of Tasmania (including southern Bass Strait islands) and A. minimus maritimus (Finlayson, 1958), which is found on mainland Australia (as well as some near-coastal islands) and is patchily distributed in mostly coastal areas between South Gippsland (Victoria) and Robe (South Australia). Based on an assessment of morphology and DNA, we conclude that A. minimus is both distinctly different from all extant congeners and that the two existing subspecies of Swamp Antechinus are appropriately taxonomically characterised. In our genetic phylogenies, the Swamp Antechinus was monophyletic with respect to all 14 known extant congeners; moreover, A. minimus was well-positioned in a large clade, together with all four species in the Dusky Antechinus complex, to the exclusion of all other antechinus. Within A. minimus, between subspecies there were subtle morphological differences (A. m. maritimus skulls tend to be broader, with larger molar teeth, than A. m. minimus, but these differences were not significant); there was distinct, but only moderately deep genetic differences (3.9–4.5% at mtDNA) between A. minimus subspecies. Comparatively, across Bass Strait, the two subspecies of A. minimus are morphologically and genetically markedly less divergent than recently recognised species pairs within the Dusky Antechinus complex, found in Victoria (A. mimetes) and Tasmania (A. swainsonii) (9.4–11.6% divergent at mtDNA)

Taxonomy and redescription of the Atherton Antechinus, Antechinus godmani (Thomas) (Marsupialia: Dasyuridae).

We provide a taxonomic redescription of the dasyurid marsupial Atherton Antechinus, Antechinus godmani (Thomas). A. godmani is only rarely encountered and limited to wet tropical rainforests of north-east Queensland, Australia, between the towns of Cardwell and Cairns (a distribution spanning 135 kilometres from north to south). The distinctive species occurs at altitudes of over 600 meters asl, in all major rainforest types, and can be found with both the northern subspecies of the Yellow-footed Antechinus, A. flavipes rubeculus Van Dyck and the Rusty Antechinus, A. adustus (Thomas). A. godmani is clearly separated from all congeners on the basis of both morphometrics and genetics. A. godmani can be distinguished from all extant congeners based on external morphology by a combination of large size, naked-looking tail and reddish fur on the face and head. A. godmani skulls are characteristically large, with a suite of long features: basicranium, palate, upper premolar tooth row, inter-palatal vacuity distance and dentary. Phylogenies generated from mt- and nDNA data position Antechinus godmani as monophyletic with respect to other members of the genus; A. godmani is strongly supported as the sister-group to a clade containing all other antechinus, but excluding the south-east Australian Dusky Antechinus, A. swainsonii (Waterhouse) and Swamp Antechinus, A. minimus (Geoffroy). Antechinus godmani are genetically very divergent compared to all congeners (mtDNA: range 12.9-16.3%).

Multiple paternity in the swamp antechinus (Antechinus minimus)

Multiple paternity within litters or broods occurs across a variety of taxa. In the present study, paternity patterns in the swamp antechinus (Antechinus minimus), a small carnivorous marsupial, were investigated using genetic analyses. Microsatellite data confirmed that, of 10 litters sampled from two habitats, a minimum of eight litters were sired by more than one male. Mating with multiple males may enable female swamp antechinuses to increase offspring viability and to ensure fertilisation.

Inflated population density of island antechinus: a case of allochthonous marine inputs leading to increased food availability?

Resource availability and other processes that affect maintenance, growth and decline of animal populations are central to ecology and conservation. This study quantified features indicative of population fitness and the availability of food resources for island and mainland populations of an insectivorous marsupial, the swamp antechinus (Antechinus minimus). The aim of the study was to test the hypothesis that colonial seabirds increase productivity of island habitats, ultimately providing greater food resources. The study found that antechinus biomass density was 4–13 times greater on the island site compared with the mainland site and was associated with higher recapture rates, suggesting that more individuals were surviving on the island during spring and summer months. An index of antechinus food availability (abundance and biomass of invertebrates) was also higher on the island site. Island antechinus also accessed marine food subsidies, in the form of seabird carrion, during the energetically demanding post-weaning growth period in spring and summer. Furthermore, based on soil nutrient and stable isotope analyses, there was strong evidence of nutrient enrichment from marine sources in the island ecosystem, commonly linked to increased productivity. Therefore, greater antechinus biomass and abundance on offshore islands are likely to be, in part, due to greater survival caused by higher availability of food resources.

Energy Expenditure, Water Flux, and Activity Budgets of Female Swamp Antechinuses in Contrasting Habitats

Island mammals often differ behaviorally, demographically, and morphologically from their mainland conspecifics. A comparison of the water flux (WF, ml/day), daily energy expenditure (DEE, kJ/day), activity budgets, body mass, and diets of female swamp antechinuses (Antechinus minimus maritimus) from island and mainland habitats was undertaken to determine whether features associated with the island habitat influenced their physiological ecology. WF differed significantly between the 2 populations, with mainland animals having a WF 36% greater than island animals. However, there was no significant difference in DEE between individuals in different habitats (island versus mainland), although they exhibited markedly divergent behavioral patterns. Differences in diet and availability of free water for drinking may have caused the divergence in the WF values between mainland and island individuals. Although energy requirements play a key role in the spatial ecology of small mammals, other factors such as social interactions could cause observed differences in spatial organization between female A. minimus on the island and mainland.

Spatial and Temporal Organization in the Swamp Antechinus: Comparison between Island and Mainland Populations

Comparative analyses of the biology of insular and mainland populations of mammals have demonstrated a number of behavioral differences. Individuals from island populations generally have reduced home-range sizes, increased territory overlaps, and reduced aggressiveness with neighbors in comparison to mainland counterparts. We tested the hypothesis that island and mainland populations of the swamp antechinus (Antechinus minimus maritimus), an insectivorous marsupial, will differ in their use of space. We predicted that the home ranges of individuals on an offshore island are smaller and their territory overlaps greater compared to those of antechinus at an adjacent mainland site in southeastern Australia. We used radiotelemetry to measure home-range areas and overlaps, as well as the temporal activity patterns of 40 individuals in the nonbreeding and breeding seasons at island and mainland sites. These dasyurid marsupials were social animals and nested together at both sites, and a high degree of spatial overlap was recorded in both populations. Island individuals occupied significantly smaller home ranges and were mainly nocturnal, whereas mainland individuals were diurnal and had large home ranges. The small home ranges of island individuals may have been in response to increased food resources, resulting from large allochthonous inputs from seabirds. The nocturnality of island animals was likely a predator-avoidance mechanism to evade diurnal raptors in the open tussock grassland.

Natal dispersal and social organization of the swamp antechinus (Antechinus minimus) in a high-density island population

Radiotelemetry, mark–recapture trapping, and microsatellite analysis of genetic variation among three subpopulations were used to investigate the natal dispersal patterns, genetic structure, and social organization within a high-density island population of an insectivorous marsupial, the swamp antechinus ( Antechinus minimus (É. Geoffroy Saint-Hilaire, 1803)). Both demographic and genetic data indicated a high degree of philopatry for both sexes. Associated with high philopatry is low gene flow, often leading to high population genetic structuring. However, there was only weak evidence to support this; allele frequencies and genotype composition of one population tended to be different from the other two. Interestingly, timing of breeding of this subpopulation was delayed compared with the other two subpopulations. The philopatry of both sexes and the apparent lack of kin avoidance behaviour could lead to inbreeding. However, no apparent inbreeding effects were observed and offspring survival was high compared with mainland populations. The fact that male home-range size increased during the breeding season, overlapping with several females, and single females were found nesting with different males at the time of mating (and vice versa) indicates a promiscuous mating system. Potentially, this may reduce inbreeding to some extent. Alternatively, inbreeding may not be purposefully avoided, potentially leading to purging of detrimental alleles, thereby reducing their damaging effects on inbreeding.

Comparison of life‐history characteristics of island and mainland populations of the swamp antechinus

AbstractThe reproductive ecology of the swamp antechinus Antechinus minimus, a small dasyurid (Dasyuridae) marsupial with obligate male semelparity, was investigated in populations inhabiting the mainland coast and on a nearby offshore island in south‐eastern Australia. The size and sex ratios of litters, individual body mass and size, timing of births and female longevity were determined from live‐trapped animals. The island population had significantly smaller litter sizes and greater adult body mass in comparison with the mainland population. This is consistent with features of the ‘island syndrome’, which predicts directional selection for these traits in high‐density populations with reduced extrinsic mortality. However, inter‐annual variability in litter sizes in the island population suggests that litter size is more responsive to fluctuating local conditions, such as population density, which is likely to affect food availability, rather than directional genetic changes. In contrast with other antechinus species, biased sex ratios were not evident. In addition, large variations of the timing of births were estimated at both sites and these appear to be related to seasonal conditions such as autumn rainfall and female body mass before mating.

Dispersal and the influence of rainfall on a population of the carnivorous marsupial swamp antechinus (Antechinus minimus maritimus)

Although there is evidence that recent climatic changes have had significant impacts on a wide range of species in the Northern Hemisphere, the influence of climate change, particularly drought, on Australian native small mammal species is poorly understood. In this study we investigated dispersal patterns and the influence of rainfall on the swamp antechinus (Antechinus minimus maritimus). Peak abundance occurred after the highest total annual rainfall for two decades, in 2001. A year later the population had declined to 10% of the peak. Birth dates appeared to occur three weeks earlier following a year of high rainfall. The dispersal of nine litters of pouch young (n = 62) was assessed following two breeding seasons. Young males remained on the natal site until December–January and dispersed before the breeding season. New males entered the population between January and June. More than 50% of females were residents and remained on the site to breed; the remaining females were trapped only once. After the male die-off the movements of pregnant females increased and they appeared to expand their home ranges. A. minimus exhibits philopatry of females and dispersal of males, as observed in other Antechinus species but dispersal occurs 2–3 months after weaning. This contrasts with juveniles of other Antechinus species that disperse abruptly after weaning. This study provides evidence that precipitation does have a major effect on the abundance of dasyurid species, making them vulnerable to drought and local or regional extinctions, particularly in areas of fragmented habitat and drying climates.

Factors influencing population dynamics in island and mainland populations of the swamp antechinus (Antechinus minimus)

Simultaneously analysing demographic processes of small mammals living in different ecological contexts may help to understand mechanisms that influence the growth and decline of these populations. The size and demography of swamp antechinus (Antechinus minimus) populations located in a coastal mainland habitat and on a small offshore island in south-eastern Australia were investigated. Large demographic differences occurred between the two ecosystems, with the island population density often 100 times greater than that on the mainland. The swamp antechinus in the mainland habitat was influenced by extrinsic climatic forces, with juvenile recruitment, individual body mass and overall population size being affected by rainfall, a factor likely to influence food availability for the species. However, the island population did not appear to be affected by drought to the same degree where allochthonous marine nutrient inputs may have offset any drought-induced reduction in primary production. Significantly greater juvenile recruitment in the island habitats combined with restricted emigration and potentially reduced predation and interspecific competition are likely to be responsible for the high population densities on the island. Although island populations appear robust, future conservation efforts should focus on mainland populations given the genetic deficiencies in the island populations.

Aspects of the ecology of swamp antechinus (Antechinus minimus maritimus) on a Bass Strait island

The swamp antechinus (Antechinus minimus maritimus) is a small insectivorous marsupial inhabiting closed heath and tussock grassland in south-eastern Australia. The species is considered ‘Near Threatened’ on the Australian mainland. Populations persist on coastal islands off Wilsons Promontory, but their current status is unknown. This study investigated the density, diet and reproduction of the swamp antechinus on Kanowna Island. Data were collected by live trapping in different vegetation types during four trips between August 2003 and January 2004. Higher animal densities (47–129 ha–1) were found for Kanowna Island than for previously studied mainland populations (1–18 ha–1). Examination of scats showed that this species eats a wide variety of prey types, with moth larvae a major dietary component, particularly during the breeding season. Births were estimated to have occurred between 28 June and 8 August, which is a longer period than reported for other populations of this species. Factors including reduced predation, restricted dispersal and increased food availability may be responsible for supporting this dense population.

Dietary strategy of the swamp antechinus (Antechinus minimus maritimus) (Marsupialia:Dasyuridae) in coastal and inland heathland habitats

In the coastal heathlands of southern Victoria, populations of a rare dasyurid, the swamp antechinus (Antechinus minimus maritimus), are restricted to small and disjunct patches of suitable habitat. Although characteristics of their preferred habitat in terms of vegetation structure and composition have been described, little is known of their diet preferences. Diet and food availability of the species was examined at two coastal and two inland sites, during winter and spring by way of faecal analyses and pitfall trapping. Only minor differences in diet were observed between the coastal and inland habitats and this was consistent across season. There was, however, variation in food availability between the two habitat types, with generally higher frequencies of invertebrates occurring within the inland than in the coastal habitat during spring. Even so, when diet was directly compared with food availability, the differences observed within individual categories within each season were similar in magnitude and direction for both habitats, suggesting that inland and coastal populations of the swamp antechinus have similar dietary strategies. Insect larvae, Diplopoda and Coleoptera appeared to be favoured dietary items being almost consistently over-represented in the diet compared to their availability, whereas Collembola, Amphipoda, Dermaptera and Formicidae were avoided as they were never consumed in proportion to their availability. Although dietary preferences were evident, there was no clear selection of any one particular prey item, and so the swamp antechinus was considered a dietary generalist. Also, as the species sampled from most of the range of prey items available to them, it fits the qualitative criterion of opportunism. The generalist strategy of the swamp antechinus is likely to be advantageous in an environment subject to disturbance.

Modelling habitat suitability of the swamp antechinus ( Antechinus minimus maritimus) in the coastal heathlands of southern Victoria, Australia

In recent years, predictive habitat distribution models, derived by combining multivariate statistical analyses with Geographic Information System (GIS) technology, have been recognised for their utility in conservation planning. The size and spatial arrangement of suitable habitat can influence the long-term persistence of some faunal species. In southwestern Victoria, Australia, populations of the rare swamp antechinus ( Antechinus minimus maritimus) are threatened by further fragmentation of suitable habitat. In the current study, a spatially explicit habitat suitability model was developed for A. minimus that incorporated a measure of vegetation structure. Models were generated using logistic regression with species presence or absence as the dependent variable and landscape variables, extracted from both GIS data layers and multi-spectral digital imagery, as the predictors. The most parsimonious model, based on the Akaike Information Criterion, was spatially extrapolated in the GIS. Probability of species presence was used as an index of habitat suitability. A negative association between A. minimus presence and both elevation and habitat complexity was evidenced, suggesting a preference for relatively low altitudes and a vegetation structure of low vertical complexity. The predictive performance of the selected model was shown to be high (91%), indicating a good fit of the model to the data. The proportion of the study area predicted as suitable habitat for A. minimus ( Probability of occurrence ⩾0.5) was 11.7%. Habitat suitability maps not only provide baseline information about the spatial arrangement of potentially suitable habitat for a species, but they also help to refine the search for other populations, making them an important conservation tool.

Effects of fragmented habitat and fire on the distribution and ecology of the swamp antechinus (Antechinus minimus maritimus) in the eastern Otways, Victoria

This study investigated the distribution, habitat and population dynamics of the swamp antechinus (Antechinus minimus maritimus) in the eastern Otway Ranges. The species has a restricted, disjunct distribution and has been recorded at 25 sites between 1969 and 1999. All sites were located within 7 km of the coast, occurred at altitudes up to 80 m above sea level and within 10 m of a gully. Analysis of landscape site variables identified sun index as being significant in determination of the probability of occurrence of A. minimus. The presence of A. minimus is negatively associated with sun index, occuring at sites that have a southerly aspect and gentle slope. A. minimus was located in a range of structural vegetation including Open Forest, Low Woodland, Shrubland and Hummock Grassland and a number of floristic groups, some characterised by high frequencies of sclerophyll shrubs, others by high frequencies of Pteridium esculentum, hummock grasses and herbaceous species. A. minimus occurs in fragmented, small populations with maximum population densities of 1.1–18 ha–1. Populations at inland sites became extinct after the 1983 wildfire which burnt 41 000 ha. These sites have not been recolonised since, while on the coast the species did not re-establish until 1993–97. One population that is restricted to a narrow coastal strip of habitat is characterised by high levels of transient animals. The species is subject to extinction in the region due to habitat fragmentation, coastal developments and fire. Management actions to secure the present populations and ensure long-term survival of the species in the area are required and include implementation of appropriate fire regimes, prevention of habitat fragmentation, revegetation of habitat, and establishment of corridor habitat.

Reproduction in the Female Dasyurid Antechinus-Minimus-Maritimus (Marsupialia, Dasyuridae)

Reproduction in female Antechinus minimus maritimus was investigated in the field and laboratory. Field data were obtained from a mark-recapture study. A laboratory colony was maintained to investigate the oestrous pattern, length of gestation and development of pouch young. Breeding occurred in winter with births in July or August. Gestation (mean � SD) was 30.6 � l.5 days for animals mated in the laboratory. Epithelial cells were present in the urine for 34.8 � 8.3 days, a lengthy period compared to A. stuartii (19.3 � 4.4 days). Ovaries from females before the breeding season contained small developing follicles. During the breeding season Graafian follicles (4-8 per ovary) or corpora lutea (4-13 per ovary) were found. Reproduction in A. m. maritimus females is similar to that described previously in other Antechinus.

Reproduction in the Male Dasyurid Antechinus minimus maritimus (Marsupialia: Dasyuridae)

Reproduction in male Antechinus minimus maritimus was investigated in the field and laboratory by morphological, histological and endocrinological techniques. All males died in late July or early August immediately after mating. Testicular weight was maximal in May and then declined abruptly in June. Spermatogenesis lasted from February to May. The germinal epithelia of some tubules at the time of testicular regression consisted of only Sertoli cells, while in others some spermatogonia were also present. Prostate and Cowper's glands were maximally enlarged in June and July, which coincided with the maximal concentration (5 ng ml-�) of androgens in the blood. During the rest of the year concentrhtions were less than l ng ml-�. It is concluded that reproduction in male A. m. maritimus is essentially the same as in other Antechinus which exhibit male 'die-off'. The low concentrations of plasma androgens during spermatogenesis in Antechinus indicate that if these steroids are important for spermatogenesis, only relatively small amounts are required.

The Subspecific Biochemical Taxonomy of Antechinus minimus, A. swainsonii and Sminthopsis leucopus (Marsupialia: Dasyuridae)

Electrophoretic variation in mainland and Tasmanian populations of Antechinus minimus, A. swainsonii and Sminthopsis leucopus was examined. The degree of genetic divergence observed among the trans-Bassian populations of each species corroborates the currently accepted subspecific rankings of A. minimus minimus and A. m. maritimus, A. swainsonii swainsonii and A. s. mimetes, and S. leucopus leucopus and S.l. ferruginifrons. The Flinders Island population of A. minimus was tentatively referred to the mainland subspecies, A. m. maritimus, on the basis of genetic similarity. Generally, levels of genetic divergence were found to be low when compared to those of similar taxonomic ranks in other animals.