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Habitat preference of the Australian water rat (Hydromys chrysogaster) in a coastal wetland and stream, Two Peoples Bay, south-western Australia


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This study provides a preliminary investigation of the home range and habitat selection of the Australian water rat (Hydromys chrysogaster) in Two Peoples Bay Nature Reserve near Albany, Western Australia. Six individuals were captured (trap success 1.9%) from 810 trap-nights. This low number suggests that the water rat population in Two Peoples Bay Nature Reserve is much smaller than anecdotal evidence would suggest. Home-range size (neighbour-linkage method) averaged 18.9 ha (+/- 11.6). Individuals preferentially utilised wetland habitats characterised by dense, low-lying vegetation (0-30 cm from ground), low-density canopy cover and shallow, narrow water bodies.
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Habitat preference of the Australian water rat (Hydromys
chrysogaster) in a coastal wetland and stream, Two Peoples Bay,
south-western Australia
Peter C. Speldewinde
, Paul Close
, Melissa Weybury
and Sarah Comer
Centre of Excellence in Natural Resource Management, The University of Western Australia,
Albany, WA 6330, Australia.
The University of Western Australia, Perth, WA 6009, Australia.
Department of Environment and Conservation, Albany, WA 633, Australia.
Corresponding author. Email:
Abstract. This study provides a preliminary investigation of the home range and habitat selection of the Australian water
rat (Hydromys chrysogaster) in Two Peoples Bay Nature Reserve near Albany, Western Australia. Six individuals were
captured (trap success 1.9%) from 810 trap-nights. This low number suggests that the water rat population in Two Peoples
Bay Nature Reserve is much smaller than anecdotal evidence would suggest. Home-range size (neighbour-linkage method)
averaged 18.9 ha (11.6). Individuals preferentially utilised wetland habitats characterised by dense, low-lying vegetation
(030 cm from ground), low-density canopy cover and shallow, narrow water bodies.
Additional keywords: water rat, radio tracking, habitat use, home range.
Received 6 January 2012, accepted 30 April 2013, published online 14 June 2013
An estimated 27 small native mammals have become extinct
in Australia since European settlement, 15 of which had
Western Australian populations (DEWHA 2009). Increasing
rates of extinction require conservation strategies to protect
the remaining species and their habitats. Options for conservation
strategies such as habitat protection (Margules and Pressey
2000), rehabilitation of degraded habitats (Lindenmayer et al.
2002) or translocation of extant populations (Dodd and Seigel
1991) will benet from knowledge of an animals home range and
habitat preferences (Margules and Pressey 2000).
First described in 1804, the Australian water rat (Hydromys
chrysogaster) (or rakaliby its Aboriginal name) (Atkinson et al.
2008) inhabits waterways throughout Australia (Vernes 1998)
(including Tasmania) and some coastal islands (Scott and Grant
1997). Although, nation-wide, the H. chrysogaster population
is considered stable (although most studies have been carried
out in eastern Australia), individual populations face signicant
threats. Populations in Western Australia, particularly in the
wheatbelt region, have undergone signicant declines (Atkinson
et al. 2008) that have been attributed to salinisation and an
associated decline in preferred prey species (Scott and Grant
1997), waterway pollution and degradation (Lee 1995), and
reclamation of wetlands for urban development (Lee et al.
Despite its widespread distribution and local abundance
much of the available knowledge relates to populations from
south-eastern Australia, with knowledge of populations in
Western Australia contrastingly limited (Atkinson et al. 2008;
Chapman and Chuwen 2010; Smart et al. 2011). Limited
information on the specieshome range and habitat requirements
suggests that only localised movements, concentrated around
nesting sites and foraging areas, are undertaken (Harris 1978).
Preferred habitats tend to be complex (Harris 1978), with a
diversity of structural habitats, including sunken logs, roots
and vegetation (Harris 1978; Smart et al. 2011). Stable stream
banks with dense riparian vegetation (Smart et al. 2011) provide
protection from introduced predators such as foxes and cats,
as well as native raptors (Scott and Grant 1997).
Relationships between structural habitat and home-range
size, however, remain unclear and constrain the development
of management strategies that aim to protect suitable habitats
within appropriately sized reserves. In south-western Australia,
basic information on habitat use and home-range size is also
currently lacking and, given the isolation of populations within
south-western Australia and the unique coastal habitats in which
they occur, this knowledge is critical to their management.
To address these knowledge gaps, this study investigated
the home range and habitat requirements of H. chrysogaster
within a small coastal reserve on the south coast of Western
Journal compilation Australian Mammal Society 2013
Australian Mammalogy, 2013, 35, 188194
Australia. We hypothesised that: (1) individual home ranges
will be centred on particular aquatic habitats (river, lakes
and wetlands) and associated riparian vegetation, and (2)
individuals will preferentially use habitats with high vegetation
density close to the ground that provides effective cover from
predators. The implications of our results for the development
and implementation of appropriate management strategies for
Western Australian populations are briey discussed.
Study site
The study was conducted along the Gardner Creek and Gardner
Lake, located in the Two Peoples Bay Nature Reserve (TPBNR),
~40 km east of Albany, Western Australia (Fig. 1). The Gardner
Creek complex drains a small coastal catchment comprising a
relatively extensive water body (Gardner Lake) that drains into a
0 0.5 1 2 3 4
Fig. 1. Map of Two Peoples Bay Nature Reserve, Western Australia, showing approximate location of trap
lines (indicated by asterisks). Shaded area indicates Gardner Lake, whilst the crosshatch areas indicate the two
swamplands associated with the study area.
Water rats in south-western Australia Australian Mammalogy 189
short (2 km) and narrow (~10 m) creek that occasionally ows
out to the sea. The catchment contains numerous small
perennial and ephemeral wetland areas adjacent to both the creek
and lake. TPBNR supports intact and relatively undisturbed
natural habitats that provide regionally important refuge for
the critically endangered Gilberts potoroo (Potorous gilbertii)
and the endangered noisy scrub bird (Atrichornis clamosus).
The principal vegetation types found in riparian areas of the
reserve include Taxandria juniperina Low Forest and Thicket,
Melaleuca Low Forest and Banksia littoralis Low Woodland
in the interdunal swales. Taxandria juniperina communities are
characterised by a variable mid-stratum of species including
Callistachys lanceolata, and all have lower strata of sedges
and shrubs such as Lepidosperma gladiatum and Myoporum
caprarioides. The riparian Melaleuca communities are
dominated by M. rhaphiophylla,M. preissiana with Agonis
exuosa and M. cuticularis closer to the margins of Gardner
Creek, and have a dense understorey of sedges.
Shefeld traps (300 300 700 mm with treadle), baited with
pilchards, were set within the riparian vegetation of Gardner
Creek, Gardner Lake and associated wetlands (Fig. 1). Traps were
placed within 2 m of the watersedge, facing the water and
covered on one end with a hessian bag. Traps were checked daily,
within 2 h of dawn, for the presence of animals. Trapping was
conducted between April and October for a total of 810 trap-
nights. All captured animals were weighed using a spring balance,
sexed and measured for long pes (mm) and head length (mm).
Animals were ear-tagged for identication purposes and released
at the point of capture.
Only individual H. chrysogaster large enough to carry collars
were retained for the tracking study. For all collared animals, the
weight of the collar was less than 5% of the total body weight (i.e.
animal weight >240 g) (Neubaum et al. 2005). Each animal was
sedated using Isouorane (Lichtenberger and Ko 2007) and tted
with a two-stage transmitter radio-collar (Sirtrack ).
Anaesthetised animals were allowed to recover before being
released at the point of capture at dusk.
Radio-collared individuals were given several days to adjust to
the presence of the collar before commencement of the tracking
study. Tracking commenced in early May and continued until
mid-July 2010. Animals were located hourly over a period of
68 h, approximately three times per week. To ensure that a full
24-h period of activity was observed, each tracking session
occurred over different times of the day and night. The location of
each animal was estimated from three separate compass bearings
to allow for triangulation. On several occasions the individual was
tracked to its burrow.
Habitat data
Habitat data were collected at 1-m intervals along 10-m transects
(n= 114). Each transect was spaced at ~50 m intervals and
positioned perpendicular to the watersedge. From the mouth of
Gardner Creek to Gardner Lake, transects extended 10 m on both
sides of the creek. Along the lake, transects included only the
south-eastern shore (Fig. 1). Transects were also positioned
within the two wetland areas, at ~50-m intervals following a
grid pattern that allowed for comparable quantication of
structural habitat with the remaining river and lake habitats. At
each 1-m offset, vegetation density (number of vegetation
touches) was recorded at 30-cm intervals along a vertical 2-m
staff. In addition, dominant plant species were recorded
between each 1-m offset. Canopy cover (%) was estimated
using a gridded cylinder at 0, 5 and 10 m along each transect.
Width and depth of the main source of standing water was
noted. In wetland areas, the depth of standing water at each
transect offset was also recorded. Major sediment type was
recorded using a modied Wentworth scale (sand: 0.51 mm;
gravel: 28 mm; and mud: 3.962.5 mm in diameter) (Wentworth
Home-range estimation
Each animal location was calculated by plotting triangulated
bearings and using the Maximum Likelihood Estimator function
of LocateIII(Pacer Computing). The home range of each
animal was calculated using both the minimum convex polygon
(MCP) and the Kernel Density (xed) method using Ranges VI
(Kenward and Hodder 1996). For comparison, estimates were
made using the neighbour-linkage analysis of RANGES
IV. Instead of calculating ellipses and contours based on densities,
this analysis aimed to minimise the summed distances between
points. The neighbour-linkage analysis removes the large buffer
zonesaround animal location points (Kenward et al. 2001).
Home ranges were also manually estimated on the basis of
observations that movements of the individuals were largely
restricted to the waterways and associated riparian vegetation.
The calculation assumed that the animals located along Gardner
Creek and Gardner Lake would be conned to the riparian
vegetation (which generally extends ~10 m from the waters
edge) and that the entire area of each wetland in which animals
were located provided suitable habitat. The manual estimation of
home range therefore consisted of the length of river used
multiplied by 20 m plus the length of the lake shore multiplied by
10 m plus the area of any small wetland used.
Habitat preference
Four main habitat types were identied based on observations
made during trapping sessions: Riverine (R), Lacustrine (L) (i.e.
lake), Palustrine (P) (i.e. swamp) and Coastal Palustrine (CP).
Principal Component Analysis (PCA) and subsequent Analysis
of Similarity (ANOSIM) were conducted using PRIMER (ver.
5.0) (Clarke and Warwick 1994) to ensure that sufcient
differences existed between these sites and to conrm their a
priori classication. The R-statistic was used to indicate
signicant differences between habitats. All data were log(x+1)
transformed and normalised before analysis. The PCA was also
used to determine which habitat variables differentiated the
habitat types.
The habitat used by each water rat was determined by
summing the number of location xes within each habitat type.
The availability of each habitat type was determined through the
190 Australian Mammalogy P. C. Speldewinde et al.
transect data where each transect was classied as a particular
habitat type (total n= 114). A Chi-square analysis was conducted
using the frequency data for habitat used versus available for each
Six individuals were captured (trap success of 1.9%), including
two females (mean weight = 317.5 42.5 (s.e.) g) and four males
(mean weight = 663.7 66.0 g). An insufcient number of xes
were available for analysis for the individual identied as Male 1
and the two females. The combined trapping and radio-tracking
data from the three remaining males yielded 135 locations.
Male 2 and Male 3 were both recollared during the course of the
study due to faulty and dropped collars.
Average home-range size varied among estimation methods
(Table 1). The MCP and 50% Kernel methods estimated the
largest home ranges (45.6 12.5 ha and 42.8 13.7 ha,
respectively). The 95% and 80% kernel estimations were
32.0 19.7 ha and 27.3 8.6 ha, respectively. The neighbour-
linkage analysis and manual calculation method provided much
smaller estimates of home range (18.9 11.6 ha and 7.4 1.4 ha,
respectively) (Table 1; Fig. 2).
Habitat selection
ANOSIM indicated that all the a priori habitat types (Inland
Swamp, Coastal Swamp, River, Lake) were signicantly
different (P0.03) from one another on the basis of structural
habitat attributes (Fig. 3; Table 2). The rst two principal
components together explained 59.1% of the variation in the
original data matrix. The two palustrine habitats were
characterised by low-lying dense vegetation, sparse canopy cover
and narrow, shallow bodies of standing water. The riverine and
lacustrine habitats were characterised by higher levels of canopy
cover, higher average vegetation density above 30 cm and deeper,
wider bodies of standing water (Fig. 3; Table 3).
Ground cover in preferred habitats was dominated by mainly
sedge and grass species such as Lepidosperma gladiatum,
Meeboldinea scariosa,Juncus kraussii and Gahnia aristata.
Additionally, some taller species such as Taxandria juniperina
and juvenile paperbarks (Melaleuca ericifolia) were also
The frequency of habitats used by two water rats differed
from that expected on the basis of availability (Male 3: c
= 35.8,
d.f. = 3, P<0.01; Male 4: c
= 689.0, d.f. = 3, P<0.01)whilst one
did not differ (Male 2: c
= 6.1, d.f. = 3, P= 0.11), possibly due to
low sample size. Males 2 and 3 used the coastal palustrine
habitat more frequently than expected on the basis of its
availability (Fig. 4), and neither used the lake or inland swamp
habitat. Male 4 preferentially used river habitat and was not
recorded in the coastal palustrine habitat (Fig. 4).
This study represents one of only a few on the home range and
habitat use by H. chrysogaster in Western Australia. While a
limited number of studies have been conducted on eastern
Australian populations (Atkinson et al. 2008), differences in
environmental conditions, including habitat, limit the extent
that these ndings can be generalised to Western Australian
Table 1. Home-range estimates (ha) for male H. chrysogaster at Two
Peoples Bay Nature Reserve, Western Australia
MCP95 represents the minimum convex polygon estimate at the 95% isopleth.
K95 represents the kernel density estimate at the 95% isopleth
Animal No. of
linkage (ha)
K95 (ha) MCP95 (ha)
Male 2 12 6.2 71.0 25.5
Male 3 48 8.4 17.4 42.8
Male 4 75 42.1 7.5 68.5
Mean ± s.e. 18.9 ± 11.6 32.0 ± 19.5 45.6 ± 12.5
0 250 500 1000 1500 2000 Meters
Fig. 2. Map of Gardner River (Two Peoples Bay Nature Reserve) showing approximate
area used by Male 3 (stipes) and Males 2 and 4 (crosshatch) (note use by Males 2 and
4 similar).
Water rats in south-western Australia Australian Mammalogy 191
populations. This has implications for management and
conservation of the species in south-western Australia, where
there has been substantial reduction in suitable habitat as a result
of both urban expansion and clearing of land for agriculture.
Knowledge of both habitat preferences and home range
represent key knowledge gaps for the implementation of effective
management and conservations efforts.
In riverine habitats, H. chrysogaster remains close to the water
and within the riparian vegetation (Fig. 2) (see also Harris 1978;
Serena and Gardner 1995). In the case of Gardner Creek, the
riparian zone extended ~10 m to either side of the creek. Estimates
of home-range size, based on neighbour-linkage analysis
(18.9 11.6 ha), are relatively large compared with previous
studies that describe home ranges of 1.211.5 ha (Harris 1978;
Serena and Gardner 1995). The manual calculation provided an
estimate much closer to those described in previous studies, as the
area calculated included only known suitable habitat. Most
studies have avoided these complications by reporting the lengths
of river, or river area (e.g. ha) utilised by individuals (Serena and
Gardner 1995). However, these calculations, like those of the
MCP method, can be strongly inuenced by outlying xes. MCP
and Kernel estimates of home-range size assume that the area
between individual locations is utilised by the animal. These
methods can overestimate home-range size when bends in the
river place estimates of home range boundaries well beyond the
terrestrial extent of the riparian vegetation. Our study included
only three individuals tracked over ~10 weeks so further studies
are required to provide a better understanding of home-range size
and use.
Our nding that H. chrysogaster prefers low-lying, dense
vegetation with little canopy cover supports previous
observations that the species is found only in wetlands with high
vegetation density (>50%) (Smart 2009). Similar observations
have been made for aquatic marsupials, such as the platypus
(Scott and Grant 1997). Selection of, and/or preference for, dense
vegetation close to the ground appears to be widespread among
small mammal populations (Stewart 1979; Lunney and Ashbey
1987; Ford et al. 2003), including H. chrysogaster (Scott and
Grant 1997), as these habitats provide shade, shelter, protection
and resources for prey species such as insects and frogs. Whilst the
water rat is mostly documented sheltering in burrows dug into
river banks (Serena and Gardner 1995), it is also known to use
reeds as nests, highlighting the potential importance of ground
–5 0 5 10
Fig. 3. PCA ordination of Principal Components 1 and 2 on habitat data
collected at Two Peoples Bay Nature Reserve, Western Australia.
River Lacustrine Palustrine Coastal
Habitat type
Percentage available/used
% available % used male 2
% used male 3 % used male 4
Fig. 4. Habitat use of Males 2, 3 and 4 at Two Peoples Bay Nature Reserve,
Western Australia, showing the percentage of habitat available to male
H. chrysogaster and the percentage of radio-telemetry location xes within
each habitat type.
Table 2. ANOSIM test statistics and signicance levels demonstrating
differences between each of the habitat types used by H. chrysogaster at
Two Peoples Bay Nature Reserve, Western Australia
Groups RP
Global 0.389 0.01
River, Lake 0.343 0.01
River, Swamp 0.361 0.03
River, Coastal 0.363 0.01
Lake, Swamp 0.739 0.01
Lake, Coastal 0.876 0.01
Swamp, Coastal 0.386 0.01
Table 3. Eigenvectors displaying the main inuences in each principal
Coefcients shown in bold contribute most to determining the difference
between habitat types present at Two Peoples Bay Nature Reserve, Western
Variable PC1 (44.7%) PC2 (14.4%)
Height at maximum density 0.357 0.009
Mean density at 180 cm 0.353 0.063
Mean density at 150 cm 0.396 0.157
Mean density at 120 cm 0.423 0.137
Mean density at 90 cm 0.418 0.186
Mean density at 60 cm 0.365 0.124
Mean density at 30 cm 0.206 0.255
No. of plant species 0.1 0.166
Mean canopy cover 0.083 0.324
Width of standing water 0.117 0.621
Depth of standing water 0.176 0.565
192 Australian Mammalogy P. C. Speldewinde et al.
cover as alternative shelters for the species (B. Johnson, pers.
comm.). The selection of habitats with dense vegetation close
to the ground would provide protection against a variety of
predators, including foxes, cats and also raptorial birds (McNally
Permanent water is a critical component of water rat habitat
(Scott and Grant 1997; Valentine et al. 2009). A distinguishing
feature of the preferred habitats identied in this study, e.g. coastal
and inland swamps, was the presence of small (shallow and
narrow) bodies of standing water. This preference for palustrine
habitats has also been noted by Woollard et al. (1978).
Reclamation of swamp and wetland areas for development (Lee
et al. 2006), and increased groundwater extraction for urban
areas and agriculture are expected to represent signicant
threats to remaining populations due to reduction of permanent
shallow water bodies. The loss of riparian vegetation (through
clearing and salinisation) occurring throughout Western
Australia (Hancock et al. 1996) is also a signicant threat to
populations of H. chrysogaster. Habitat disturbance has been
implicated in the decline of a variety of other aquatic mammals
such as the otter (Barbosa et al. 2001) and the platypus (Grant and
Temple-Smith 2003). Considering the wide range of habitat
types in which H. chrysogaster has been observed (Atkinson
et al. 2008), an overall species preferencewould be difcult to
derive. Rather, when selecting vegetation types to support
H. chrysogaster, conservation priorities should focus less on
particular species and perhaps focus on the particular structural
characteristics that certain species exhibit (e.g. dense vegetation
along shallow water bodies). Although the results of this study
are preliminary they go some way to identifying critical habitats
for this species.
Thanks to Keith Morris and Brent Johnson from the Western Australian
Department of Environment and Conservation (Woodvale) for provision of
radio-tracking equipment and advice on project design. We are grateful to
several volunteer radio-trackers. This study was undertaken as an honours
project by MW under the supervision of the coauthors. Financial support for
MW was provided by the University of Western Australia Honours Research
program and we are grateful for the administrative support of the Centre of
Excellence in Natural Resource Management. All eldwork was conducted
under approval from the UWA Animal Ethics Ofce RA/3/100/888 and DEC
permits SF007023 and CE002513. We would like to thank the anonymous
reviewers who made comments on previous versions of this manuscript who
made suggestions to improve the paper.
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194 Australian Mammalogy P. C. Speldewinde et al.
... Hydromys chrysogaster)) was placed in each puzzle in the morning. Food options were chosen based on what is commonly used as bait for field work in the Wet Tropics region (Diete et al., 2016;Speldewinde et al., 2013). Puzzles were not set in wet or extreme weather to avoid them being damaged. ...
... For example, at least one individual water rat was observed interacting with tasks baited with a suitable food (e.g. sardines; Speldewinde et al., 2013) but did not solve it. Similarly, mosaic-tailed rats and giant white-tailed rats solved all of the puzzles, whereas another arboreal rodent species, the prehensile-tailed rat, did not. ...
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While many species of animals can solve food‐baited problems, most studies are conducted in captivity, which may not reflect the natural behavioural and cognitive abilities of wild animals. As few studies have explored problem solving of Australian animals generally, we investigated the problem solving abilities of native Australian species in natural rainforest in the Wet Tropics of Queensland. We baited multiple types of puzzles (matchbox task, cylinder task, and tile and lever tasks on a Trixie Dog Activity Board) with different food types (seeds, fruit, sardines) and placed the puzzles in front of trail cameras. We noted the species captured on camera, whether or not individuals interacted with the puzzles, the number of interactions with puzzles, and whether or not different animals solved them. We found that seven species from multiple taxa (mammals, birds, reptiles) could solve food‐baited problems in the wild, providing the first evidence of problem solving in these native species. As problem solving may help animals cope with anthropogenic threats, these results provide some insights into which Wet Tropics species may potentially be more vulnerable and which ones might be better at coping with changing conditions.
... The sex ratio reported in this study was equal; rakali, bush rats, and long-haired rats-which account for the majority of those records-often exhibit even sex ratios (Predavec & Dickman, 1994;Press, 1987;Smart et al., 2011;Speldewinde et al., 2013;Valentine et al., 2009), although populations of long-haired rats can skew towards either males or females (Carstairs, 1976;Predavec & Dickman, 1994). Furthermore, a survey of rakali by Bettink (2016) identified a male-skewed sex bias on Barrow Island, albeit from a relatively small sample (n = 11). ...
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Abstract While almost half of all mammal species are rodents, records of albinism in free‐ranging rodents are very rare. Australia has a large and diverse assemblage of native rodent species, but there are no records of free‐ranging albino rodents in the published literature. In this study, we aim to improve our understanding of the occurrence of albinism in Australian rodent species by collating contemporary and historic records of this condition and providing an estimate of its frequency. We found 23 records of albinism (i.e., a complete loss of pigmentation), representing eight species, in free‐ranging rodents native to Australia, with the frequency of albinism being generally
... In the wild, feral cats and dogs may also consume toads, although cats, at least, are thought to mostly consume mammals and birds (Kutt et al., 2012). Native rodents may consume toads, in particular, water rats (Hydromys chrysogaster) are voracious predators of toads (Ree, 2004;Speldewinde et al., 2013). Water rats can inhabit urban and peri-urban areas as well as natural habitats, although they are very common in rural areas. ...
Urbanization is a principal driver of global biodiversity loss. Although many studies have examined the impacts of urbanization on biodiversity, we are only beginning to study urbanization as an evolutionary force. Urban environments are hotspots for invasive species, but most previous studies have focused on phenotypic changes in native species responding to urbanization. Quantifying the phenotypic responses of invasive species to urbanization may help reveal mechanisms promoting invasion. There are, however, few studies investigating the phenotypic response of invasive species to urbanization. We compared morphological traits of invasive cane toads (Rhinella marina) between urban and rural areas in three cities in north-eastern Australia using generalized linear mixed models. We found that the parotoid glands, which are the major anti-predator defence of toads were smaller in urban than in rural populations. The tibiofibula length of males in urban populations was longer than those in rural populations, but females showed opposite trends, suggesting potential effects of urbanization on sexual dimorphism. These results demonstrate that urbanization drives morphological changes in invasive toads, suggesting they may adapt to urban environments rapidly.
... Rakali typically escape from fyke nets quite rapidly by chewing a hole through netting, and so are mainly targeted by setting baited wire mesh cage traps on the banks (e.g. Speldewinde et al. 2013). Welfare risks in fyke nets are mainly to ducklings or fish that are injured or killed by larger predatory species. ...
This chapter provides a general discussion of ethical considerations and procedures relating to the capture and handling of freshwater animals, including welfare considerations for the study species and non-target species.
... A dense riparian vegetation also provides suitable shelters and refuges to hide from predators. In addition, riparian vegetation may be a direct (i.e. for herbivores) or an indirect (i.e. by hosting terrestrial prey) source of food, which benefits several semi-aquatic mammals (Greenwood et al. 2002, Eubanks et al. 2011, Hysaj et al. 2013, Mate et al. 2013, Speldewinde et al. 2013. ...
To date, the large-scale distribution of the endangered Pyrenean desman, Galemys pyrenaicus , has been related to various abiotic factors (e.g. riverbed and riverbank characteristics, hydrology, topography, climate). However, none could fully explain the recent observed range contraction of the species, suggesting the influence of other drivers. In this study, the potential effect of some unexplored variables on the Pyrenean desman presence was investigated at the local scale (i.e. stream reaches) in the French Pyrenees. They described not only the riverbed, riverbanks, water chemistry, topography and pedology but also the presence of potential interacting species. Generalised linear models were implemented to select the best drivers of the Pyrenean desman presence. Our results stressed the relevance of considering human impacts at the riverbed scale, river narrowing and water chemistry to explain the local distribution of the Pyrenean desman. The presence of two potential competitors, the Eurasian water shrew Neomys fodiens and the dipper Cinclus cinclus , was also highly correlated to the species presence in stream reaches. This suggests that all three species may use the same resources within streams, which could be a potential source of competitive interactions. This study not only highlights the importance of maintaining the riverbed integrity for the Pyrenean desman but also stresses the need to assess the extent to which biotic interactions may affect its distribution in order to understand its current decline.
... This is consistent with findings from other studies that reported that rakali prefer habitat with high vegetation density, in particular low-lying, dense vegetation, as this habitat provides shelter and protection from predators, as well as higher concentration of prey such as frogs and insects. 32,47,48 Consistent with Smart et al., 32 river sites with steep banks were found to be associated with increased rakali activity. The majority of the surveys were done during the breeding season (i.e. ...
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.
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Reviews information on relocations, repatriations, and translocations (RRT) projects involving amphibians and reptiles, examines the motives for advocating RRT strategies, and recommends biological and management criteria that should be considered prior to undertaking RRT projects. Most projects involving amphibians and reptiles have not demonstrated success as conservation techniques and should not be advocated as if they are acceptable management and mitigation practices. -from Authors
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This study investigated the distribution of the water-rat (Hydromys chrysogaster) in the greater Perth region, and proposes the potential of the species as a bioindicator of habitat quality. The degradation and loss of wetlands on the Swan Coastal Plain are associated with changes to habitat quality, including vegetation cover, stream cover, habitat diversity and bank stability. The occurrence of H. chrysogaster was analysed with respect to these factors at various water bodies around the greater Perth area. Sites positive for the presence of H. chrysogaster correlated with high value habitat quality characteristics, including high bank stability, habitat diversity, stream cover and foreshore vegetation. The presence of H. chrysogaster was not correlated to the occurrence and abundance of other local mammal species, except for a positive relationship with the introduced black rat (Rattus Rattus) in relation to abundance. Based on the habitat requirements of H. chrysogaster, the species has some potential as a bioindicator of wetland condition on the Swan Coastal Plain, Western Australia, although the viability of such a method is uncertain.
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A population of the white-footed dunnart Sminthopsis leucopus was studied from 1981 to 1983 in a forest that had been logged in 1979, burnt in 1980, and was drought-affected throughout the study. S. leucopus bred in this disturbed habitat but did not persist when the vegetation regrew and became dense. Pouch young were present in August, September and October 1981. There was no evidence of polyoestry in the field, although breeding potential may have been suppressed by a combination of the drought and habitat change. There were few brown antechinus Antechinus stuartii present at any time. The population of the bush rat Rattus fuscipes increased as its preferred habitat of dense vegetation grew. An irruption of the house mouse Mus rnusculus in autumn 1982 coincided with a brief respite from the drought. The differing responses of these species to the same set of environmental conditions illustrates that no one management option in such forests will be optimal for all species of small mammals. The conclusion drawn here for the conservation of S. leucopus in forests subject to woodchip logging and fire is to stagger the forestry operations to ensure that not all parts of the forest are covered with dense regrowth at any one time.
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The platypus (Ornithorhynchus anatinus) is an Australian icon. It is an integral part of the biodiversity of many eastern Australian freshwater ecosystems and is protected by legislation in all States in which it occurs. Its conservation is of considerable importance not only because of its unique features, status and niche but also because it is the only living representative of a significant lineage of platypus-like animals with a 60 million year fossil history. As a result of its specific habitat requirements it is affected by many of the widely recognised threatening processes operating in Australian limnological systems. In spite of these threatening processes, the species has continued to inhabit and reproduce in considerably degraded environments. The present overall distribution of the platypus appears to be little different from pre-European times. There are, however, now almost certainly no naturally occurring populations in South Australia, where it once occurred, and its distribution has apparently shrunk in the lower reaches of the Murray and Murrumbidgee River systems in Victoria and New South Wales. Despite being considered common throughout its current distribution its abundance is not readily measured and therefore its future conservation status is not easily predicted. Several studies have reported fragmentation of platypus distribution within individual river systems. This has been attributed to poor land management practices associated with stream bank erosion, loss of riparian vegetation and channel sedimentation. There is currently also evidence for adverse effects of river regulation and impoundments, introduced species, poor water quality, fisheries by-catch mortality and disease on platypus populations, but none of these has been well studied. Investigations of these aspects of the species' biology and interaction with human activities are research priorities, while management priorities include the development and implementation of strategies aimed at reducing the effects of these human activities on the platypus and its habitat.
Methods used to estimate home ranges from point locations are based either on densities of locations or on link distances between locations. The density-based methods estimate ellipses and contours. The other class minimizes sums of link distances, along edges of polygons or to range centers or between locations. We propose a new linkage method, using nearest-neighbor distances first to exclude outlying locations and then to define a multinuclear outlier-exclusive range core (OEC) by cluster analysis. The assumption behind exclusion of outliers, that movements inside and outside range cores involve different activities, was supported by data from radio-tagged Common Buzzards (Buteo buteo). We compared the new method with other techniques by using location data from each of 28 goshawks, 114 buzzards, 138 gray squirrels, and 14 red squirrels. Range structure statistics from OECs showed marked differences between species in numbers and extent of core nuclei. Range analysis displays illustrated relationships of range area with age categories, food supply, population density, and body mass within species. The OECs gave highly significant results in three of five within-species tests, perhaps because animal movements in these cases were affected by coarse-grained habitat boundaries. When movements were likely to have been influenced by diffuse social interactions and foraging for scattered prey, the most significant results were from density-based estimators, especially kernel contours that had been optimized by least-squares cross validation. We recommend use of both density and linkage estimators of home range until a basis for a priori choices has been established.
In the wild population of water rats studied, males were more numerous and larger than females. In a population of 589 water rats, 323 were males and 266 females. Whole weights ranged from 170 to 1275 g for males and 156 to 992 g for females. Males were age-grouped into adults (including subadults) and juveniles on the basis of combined testes weights. Sexual maturity is reached when a whole weight of between 400 and 600 g (14-21 oz) is attained. Females were age-grouped on the stage of maturity of the reproductive tract. Female rats can reproduce when a whole weight of 425 g (15 oz) is attained. Mating takes place in late winter and continues through spring. The breeding season extends from September to January, with the peak in early spring. Females are in anoestrus in late summer, autumn, and early winter. The number in each litter varies from one to seven: the usual number is four or five. Growth is rapid; young can reach adult size in less than one year. The structure of the population varies throughout the year. The proportion of adults (including subadults) is high in winter and spring and falls in summer and autumn when juveniles appear in numbers. The fecundity of water rat's is lower than normal for murid species, but fertility is high and a substantial population turnover occurs each year when conditions for breeding are favourable. It is considered therefore that the water rat has potentiality for management as an economic fur-bearing animal.
The smoky mouse, Pseudomys fumeus, is an endangered rodent for which ecological information is lacking across much of its range. This paper provides the first detailed study of the local diet and habitat preference of P. fumeus since 1980, conducted on the recently discovered Nullica population in New South Wales. Diet and trap-revealed movements were examined in conjunction with 18 characteristics of habitat to determine the factors influencing habitat choice. Multiple logistic regression of habitat variables and capture locations revealed a floristically determined preference for heath habitat characterised by Epacris impressa, Monotoca scoparia, Leptospermum trinervium, Xanthorrhoea spp. and a variety of legumes. Hypogeal fungi and seeds were the most common food items in the diet of P. fumeus. Fungi were most abundant in winter diet, while seeds and fruit became dominant in late spring and summer. The spring and summer preference for ridge-top heath habitats observed in this study is probably the result of this dietary preference. Resident females constituted 71% of the population in early spring. However, there was a severe decline in numbers of female mice during early spring, and resident males also disappeared from the population. Causes of the decline were unclear. Five of eleven males captured during this study were transient, while no transient females were caught. The sudden decline in the study population, combined with the patchy distribution of suitable habitat and high level of male transience, suggests that P. fumeus form a metapopulation in the Nullica region.
The effect of trap placement on trapping success was investigated with the small mammals Rattus fuscipes, Antechinus swainsonii and A. stuartii. Trapping success for A. stuartii was not affected by density of ground cover (measured qualitatively and by the penetration of light), type of ground cover, presence of logs or presence of runways (either small natural openings in the ground cover or wombat pathways). R. fuscipes and A. swainsonii were caught more frequently in areas of good cover, in fishbone water-fern Blechnum nudum and on runways. The two indices of cover gave similar results. A. swainsonii was often caught on wombat pathways but not often on small natural runways; preference for wombat pathways increased in winter. Logs were not preferred by any of the species. Some latitude may be desirable in trap placement within a predetermined trapping configuration, especially when small mammals are sparsely distributed.
A total of 408 stomach contents and 316 combined caecal and rectal contents collected from Griffith, N.S.W., during 1970-73 were analysed. Fish, in particular, and large aquatic insects were of primary importance in the diet in terms of constancy and biomass. Semi-aquatic spiders and fully aquatic damsel and dragonfly nymphs were of major seasonal importance. Birds, both waterbirds and small passerines, crustaceans and possibly mussels were important secondary items. Supplementary prey included frogs, turtles and bats. Mice were readily taken during a plague. Traces of plant material, present in many guts, formed a small part of the diet increasing somewhat in importance during the winter months. Although invertebrates formed a higher proportion of the diet in the spring and summer months, vertebrates formed the major component in the winter. Females ate a greater proportion of insects, males more fish, while young animals ate a similar range of items to adults but consistent with their size. Some evidence of intraspecific predation, confined to males, was found.