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Home , Aberfeldy River, Avoca River, Barwon River (Victoria), Broken River (Victoria), Buchan River, Campaspe River

The Victorian Naturalist

Volume 135 (3) June 2018

Published by The Field Naturalists Club of since 1884 Research Report

(Malacostraca: Decapoda) of the Pilliga Scrub in northern Roger E, Laffan SW and Ramp R (2007) Habitat selection inland . The Victorian Naturalist 128, by the Common Wombat (Vombatus ursinus) in a dis- 96–105. turbed environment: implications for the conservation of a Murphy MJ (2014) Roost caves of the Eastern Horseshoe ‘common’ . Biological Conservation 137, 437–449. Bat Rhinolophus megaphyllus Gray, 1834 (Chiroptera: Rhi- Roger E, Laffan SW and Ramp R (2011) Road impacts a nolophidae) in the Pilliga forest in northern inland New tipping point for wildlife populations in threatened land- South Wales, . Australian Zoologist 37, 117–126. scapes. Population Ecology 53, 215–227. Murphy MJ (2016) Survey of the reptiles and amphibians of Skerratt LF, Skerratt JHL, Banks S, Martin R and Handasyde Yarrigan National Park in the Pilliga forest of northern in- K (2004) Aspects of the ecology of common wombats land New South Wales. Australian Zoologist 38, 147–160. (Vombatus ursinus) at high density on pastoral land in Vic- Murphy MJ and Shea M (2013) Survey of the terrestrial and toria. Australian Journal of Zoology 52, 303–330. freshwater molluscan fauna of the Pilliga forest area in Triggs B (2009) Wombats (2nd edn) (CSIRO Publishing: northern inland New South Wales, Australia. Molluscan Collingwood) Research 33, 237–253. Turbill C and Ellis M (2006) Distribution and abundance of O’Connor L (2017) Are we in wombat territory? Coonamble the south-eastern form of the greater long-eared bat Nyct- Times, Wednesday 30 August 2017, p. 6. ophilus timoriensis. Australian Mammalogy 28, 1–6. Paull DC and Date EM (1999) Patterns of decline in the na- tive fauna of the north-west slopes of New South Wales. Australian Zoologist 31, 210–224. Ramp D, Caldwell J, Edwards, KA, Warton D and Croft DB (2005). Modelling of wildlife fatality hotspots along the Received 18 January 2018; accepted 6 March 2018 Snowy Mountain Highway in New South Wales, Australia. Biological Conservation 126, 474–490.

Distribution of the Australian Water-rat chrysogaster in Victoria: findings from community-based sightings and live-trapping surveys

Geoff Williams1 and Melody Serena1,2

1Australian Conservancy, PO Box 22, Wiseleigh, Victoria 3885 2Corresponding author Email: [email protected] Abstract The distribution of Australian Water-rats in Victoria was examined by analysing 1022 records obtained from 2000–2017 and data collected incidentally in Platypus live-trapping studies. Water-rats were sighted in all Victorian river basins apart from the Corangamite basin (which is dominated by saline ) and the very dry and Millicent basins in far western Victoria. Sightings occurred in a wide variety of habitats, including rivers (26% of records), creeks (25%), coastal habitats and (19%), natural and man-made lakes and reservoirs (18.5%), and morasses (7%), irrigation channels (4%) and sites lacking substan- tial surface water in the immediate vicinity (0.5%). The mean (or average) frequency of Water-rat captures in the western half of Victoria was significantly greater than the corresponding combined values for and eastern Victoria. Mean Water-rat capture frequency in and near Melbourne was also significantly greater than that in south-eastern Victoria. (The Victorian Naturalist 135 (3), 2018, 71–83) Keywords: amphibious mammal, Australian native , , habitat use, mortality factors Introduction The Australian Water-rat or Rakali Hydromys (notably the floating water fernAzolla filicu- chrysogaster is the largest and arguably most loides) also can contribute to the diet (Wool- specialised Australian rodent in terms of its lard et al. 1978). In addition, Water-rats have tooth structure and other physical features been documented to feed opportunistically (Watts and Aslin 1981). Weighing as much as on terrestrial prey, such as House mice Mus 1275 grams (McNally 1960), Water-rats feed musculus during a mouse plague; cannibal- mainly in the water on , insects, crusta- ism also can occur (Woollard et al. 1978). ceans, waterbirds, molluscs and (to a lesser ex- The Water-rat’s ability to swim efficiently and tent) and turtles; selected aquatic plants capture aquatic prey is facilitated by having

Vol 135 (3) 2018 71 Research Report

documented to travel 3.1 km along a stream channel in just 5.5 hours (Gardner and Serena 1995), and at least 3.0 km (though possibly 4.5 km) overnight across dry land to reach a man- made dam (Vernes 1998). In contrast to most Australian , Water-rats are commonly visible during the day (Watts and Aslin 1981) and are relatively large with distinctively white-tipped tails. This means that opportunistic sightings of the species can be used as a cost-effective technique to help map where Water-rats occur. The main aim of this study was to summarise where Water-rat sightings were recorded in Fig. 1. A Water-rat or Rakali consuming food at in the period from 2000–2017. This in- Wendouree. Photo Carolyn Hall. formation was then used to address the follow- ing questions: (1) Does the frequency of Water- an elongated, streamlined body with small rat sightings vary regionally across Victoria? external ears that can be flattened tightly against (2) How does regional variation in Water-rat the skull, broad hindfeet with partial webbing sightings compare with regional variation in between the toes, water-repellent fur, a thick Water-rat live-trapping captures? In addition, and well-furred tail, and a blunt, otter-like the types of habitat where Water-rats were ob- muzzle furnished with dense whiskers (Watts served and factors contributing to Water-rat and Aslin 1981) (Fig. 1). mortalities are described. Menkhorst (1995) reported that Water-rats are widespread in Victoria, occupying saline Methods environments (such as beaches in Records of sightings Bay) as well as rivers, creeks, irrigation chan- We recorded pertinent details (locality, date nels and natural and man-made lakes. Though and, in the case of carcasses, the cause of death the Water-rat is unable to thermoregulate effi- if this was evident) of 804 first-hand reports of ciently at water temperatures below 20o C (Fan- Water-rat sightings occurring in Victoria from ning and Dawson 1980), the species occurs 2000–2017 (including 247 sightings reported up to an altitude of at least 1500 m in Mount from 2000–2009 and 557 sightings reported Buffalo National Park. Menkhorst (1995) also from 2010–2017). The standard criteria forac - noted that Water-rats often occur at sites where cepting a sighting record normally consisted dense vegetative cover occurs at the water’s either of photographic evidence or confirma- edge in the form of thick grass, riparian scrub tion that the in question had a white- or reed beds. Similarly, results of live-trapping tipped tail and otherwise conformed to the and radio-tracking studies carried out in south- expected size, appearance and behaviour of a western Western Australia indicate that Water- Water-rat. In practice, less than 2% of all sub- rats are most likely to utilise habitats character- mitted sighting records (N = 12) were excluded ised by low-growing dense vegetation on water on the grounds that they were of question- banks (Speldewinde et al. 2013) or by stable able validity or involved a different species be- banks and substantial vegetation growing in ing seen (mainly either a smaller rat lacking a and near water (Smart et al. 2011). Studies in white-tipped tail or Common Ringtail Possum both Western Australia and have Pseudocheirus peregrinus). To augment sample concluded that Water-rats prefer to forage in size, 118 Water-rat records obtained in Victoria relatively shallow water bodies, less than about from 2000 to 2017 and held independently by 2 m deep (Harris 1978; Speldewinde et al. the Atlas of Living Australia (ALA) were also 2013). The species is appropriately character- included in the study (ALA website). We also ised as active and mobile: Water-rats have been confirmed that the ALA database contained all 72 The Victorian Naturalist Research Report

Fig. 2. Victorian river basins as defined for the purposes of this study. The marks the north- ern border of Victoria from Basin E to Basin F inclusive. Basins = Campaspe (A), Loddon (B), Avoca (C), -Avon (D), Mallee (E), Mitta Mitta (F), (G), Ovens (H), Broken (I), Goulburn (J), (K), Yarra (L), Maribyrnong (M), Werribee, including (N), Moorabool (O), Barwon (P), Lake Co- rangamite (Q), Otway (R), Hopkins (S), Portland Coast (T), Glenelg (U), Millicent (V), Far East Gipps- land (W), Snowy (X), Tambo (Y), Mitchell (Z), Thomson (AA), Latrobe (BB), and South (CC). 1= Melbourne, 2 = , 3 = Port Phillip Bay. relevant records held by the Victorian Biodiver- Little Murray River) were grouped according sity Atlas as of 30 June 2017. to whether they occurred in or west of Echuca With three exceptions, the names and bound- (‘Murray West’) or east of Echuca (‘Murray aries of river basins used in the current analy- East’). Sightings recorded in the Gippsland sis are as defined by Department of Water Re- Lakes or other saline coastal localities (includ- sources Victoria (1989). The exceptions are: (1) ing Port Phillip Bay and ) were the Murray River and its minor stream tribu- deemed to be ‘Coastal’. The 29 river basins, two taries upstream of Lake were excluded Murray River segments and coastal sites were from the basin (and instead then allocated to six geographic regions: were deemed to comprise part of ‘Murray East’, • North-west: Murray West, Campaspe, see below); (2) south-flowing river catchments Loddon, Avoca, Wimmera-Avon, Mallee from the Bemm to the Genoa Rivers were col- • North-east: Murray East, Mitta Mitta, Kiewa, lectively referred to as the ‘Far ’ Ovens, Broken, Goulburn basin; (3) the Little River was included within • Melbourne: Bunyip, Yarra, Maribyrnong, the Werribee (rather than Moorabool) River Werribee basin (Fig. 2). Water-rat sightings recorded • South-west: Moorabool, Barwon, Lake along the Victorian portion of the Murray Corangamite, Otway Coast, Hopkins, River or in its anabranches and minor tributar- Portland Coast, Glenelg, Millicent ies (including the Gunbower Creek system and Vol 135 (3) 2018 73 Research Report

• South-east: Far East Gippsland, Snowy, at 0.05) after applying the arcsine-transforma- Tambo, Mitchell, Thomson, Latrobe, South tion to the frequency data to correct for pos- Gippsland sible non-normality due to their proportional • Coastal: , all other coastal nature (Zar 1984). sites (including Port Phillip Bay and Western Port) Results Regional distribution of sightings Live-trapping records Water-rats were reportedly seen in the period Data relating to the incidental captures of Hy- from 2000–2017 in all Victorian river basins dromys in fyke nets deployed by Australian apart from the basin (which Platypus Conservancy (APC) staff for Platypus is dominated by more or less saline lakes and Ornithorhynchus anatinus survey or monitor- their small inflowing streams: Department of ing purposes were summarised for the period Water Resources Victoria 1989) and the very from January 2000 through to June 2017. At dry Mallee and Millicent basins in far western each site, a pair of nets (one facing upstream Victoria. The absence of sightings in the Lake and one facing downstream) were set in the af- Corangamite, Mallee and Millicent basins may ternoon following methods outlined in Serena also have been influenced by the relatively low and Williams (2012) and monitored at intervals numbers of persons living in each of these ar- of 2–4 hours through the entire following night. eas. Based on the combined APC and ALA da- A Water-rat was deemed to have been captured tabases, the highest number of regional sight- if an animal was encountered in a net or if one ings was reported by those living in the densely or more holes were recorded of the type charac- populated Melbourne area (22% of all records), teristically appearing when a Water-rat chews followed by north-western Victoria (20%), its way through netting to escape. In practice, coastal habitats including the Gippsland Lakes it was rare for only a single hole to appear, pre- (17%), north-eastern and south-western Victo- sumably because a Water-rat typically tries to ria (16% each) and lastly south-eastern Victoria snip through netting at several points before (9%) (Fig. 3). settling down to create a gap large enough to accommodate its entire body. Capture fre- Distribution of sightings in north-western quency for a given water body was calculated Victoria as the number of live-trapping sites where a The largest proportion of sighting records for Water-rat and/or holes were recorded divided north-western Victoria originated in the Lod- by the number of site-nights of live-trapping basin (41%), followed by the Mur- effort (one site-night = two fyke nets set to ray River (23%) and basin sample a site overnight). Estimates of capture (16%). In the Loddon basin, Water-rats were frequency based on holes were potentially sub- reportedly seen upstream of Cairn Curran, ject to underestimation insofar as two or more Laanecoorie and Tullaroop Reservoirs in the individuals may have created holes at a given proper and Jim Crow, Creswick, site. However, given that there is no reason to Tullaroop/Deep and Bet Bet Creeks. Sightings believe that the amount of bias differed consist- also were recorded at Laanecoorie Reservoir ently between regions, this index presumably and particularly at Lake Daylesford, which was provides a reasonably valid basis for comparing the source of 12% of Water-rat records for this capture frequencies between areas. basin. Downstream of Laanecoorie Reservoir, Mean (or average) capture frequency is multiple sightings were reported in the Loddon reported plus or minus SEM (standard error of River at Bridgewater, along Serpentine Creek, the mean). The hypotheses that mean Water-rat in the Dingee irrigation district, and along capture frequency in western Victoria differs Creek; 13% of records in the Loddon from that in the rest of the state and mean capture basin occurred at Lake Weeroona in Bendigo frequency in south-eastern Victoria differs re- township. spectively from those in north-eastern Victoria In and near the Murray River, Water-rat sight- and the Melbourne area were tested statistically ings reportedly occurred from Echuca to as far using two-sample t-tests (with significance set downstream as Mildura. The species appeared 74 The Victorian Naturalist Research Report

Archdale, Coonooer Bridge, Charlton, and below ). In the Wimmera basin, Water-rats were recorded at locations along the from Elmhurst downstream to . In addition, sightings were re- ported at Mount William Creek (two records), Concongella Creek (one record) and at Lake Lonsdale (three records) and Lake Fyans (two records). No Water-rat sightings were reported for the Avon-Richardson River system. Distribution of sightings in north-eastern Victoria The largest proportion of Water-rat sighting Fig. 3. Number of water-rat sightings recorded in records for north-eastern Victoria originated north-western Victoria (NW), north-eastern Victo- ria (NE), the greater Melbourne Area (Melb.), south- in the basin (45%), followed western Victoria (SW), south-eastern Victoria (SE) by the Murray River (23%) and and coastal Victoria from 2000–2017. Black bars = basin (17%). The frequency of sightings in the sightings from 2010–2017 (Australian Platypus Con- Goulburn system generally increased in the servancy (APC) database); light grey bars = sightings from 2000–2009 (APC database); dark grey bars = downstream direction, with 13% of records in sightings from 2000-2017 (Atlas of Living Australia this basin obtained upstream of Lake Eildon database). See Methods and Fig. 2 for the names and (in the Goulburn, Howqua, Jamieson, Big and locations of river basins located in these regions. Taponga Rivers and Mansfield’s Ford Creek), 38% obtained from Nagambie to Lake Eildon to be particularly widespread and abundant (in the Goulburn, Rubicon, Acheron and Yea in the Gunbower Creek system, with eight re- Rivers and Kilmore and King Parrot Creeks) ports received for Gunbower Creek and over and 48% occurring downstream of Nagambie. 30 reports received for associated lagoons and A large percentage of the Water-rat sightings irrigation channels. However, a number of in the last group comprised sightings for either Gunbower residents also mentioned that the Victoria Lake Park in (18% of all frequency of Water-rat sightings has dropped sightings for the Goulburn basin) or channels noticeably in recent years after local irrigation in the Shepparton-Tatura irrigation district channels were lined with thick plastic sheeting (15% of sightings). In addition, sightings re- in a bid to reduce seepage. Water-rats also were portedly occurred downstream of Nagambie in seen in several lakes on the Murray floodplain, the Goulburn River, Lake Bartlett (in Tatura), including and Kangaroo Lake, with Craig Muir Lake (in ) and Pranjip, multiple sightings made at Lake Charm and Faithfull and Honeysuckle Creeks. A number Little Lake Boort. of persons living near Shepparton or Tatura In the Campaspe River basin, Water-rats were reported that the practice of lining irrigation reportedly seen along the Campaspe River (at channels with plastic had resulted in a marked sites distributed from Woodend downstream to local reduction in Water-rat sightings. Echuca) and the (from Malms- Along the Murray River, 26% of Water-rat bury downstream to a site near Redesdale) records were for locations distributed from and in . One report described to as far upstream as the Murray the species as being particularly common in Gorge in Kosciuszko National Park, 68% for the Campaspe River near Elmore, with at least sites located from below Hume Dam to Lake 20 sightings made annually by the informant Mulwala, and 8% for sites located between while fishing. Although only five persons re- and Echuca. Water-rats were ported seeing Water-rats in the recorded upstream of Hume Dam along the basin, these sightings were widely distributed Murray River and in Thowgla, Corryong, Nari- along the Avoca River (at Avoca township, el and Koetong Creeks. Downstream of Hume

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Dam, the species was seen in Lake Mulwala and ings for the basin), (15%), a number of lagoons, backwaters or anabranch- (15%), (9%), es of the Murray River (Brown’s Lagoon, Horse- (4%), shoe Lagoon, Wonga Wetlands and (mainly near Lilydale Lake, 4%), Mullum Mul- Creek at -Wodonga, Torgannah Lagoon lum Creek (4%), Diamond Creek (4%), Darebin near Koonoomoo, Lake Moodemere near Wah- Creek (2%), (2%) and Albert Park gunyah). Water-rats were also seen in Wodonga Lake (2%). Other notable records included one in Sumsion Gardens Lake and several small sighting made in the Fitzroy Gardens and one creeks (Fell Timber Creek, Huon Creek, House at Richmond train station, where a Water-rat Creek), and in Barmah National Park. was observed scavenging for food dropped by Elsewhere in north-eastern Victoria, Water- commuters. rats were recorded along the Ovens River at In the basin, 31% of sight- sites distributed from Harrietville to , ings occurred along the Werribee River at sites and also at ( Na- distributed from Ballan to just upstream of tional Park), in the upstream of Port Phillip Bay. In addition, Water-rats were Lake William Hovell (on the Wabonga Plateau) recorded along Skeleton Creek at Point Cook, and in Hurdle Creek (at Carboor Upper and Hoppers Crossing and Tarneit (20% of all sight- near the King River ), Tea Garden ings for the basin), at man-made lakes associ- Creek (near Milawa), Sheep Station and Sil- ated with housing developments at Point Cook ver Creeks (near ) and One Mile (20%), in ponds at the Werribee Sewage Treat- Creek (near ). In the ment Plant (13%), along (7%) basin, Water-rats were most often recorded at and along the Little River (4%). Single sightings (in the Broken River, Holland Creek were also recorded at in Altona and ), but also in Broken Creek (at and along Djerriwarrh Creek. In the Mariby- sites located from Goorambat downstream to rnong River basin, Water-rat sightings were Nathalia), Nine Mile Creek and . reported at sites distributed along the Mariby- In the basin, the species was seen rnong River from Keilor East downstream to at Pretty Valley dam (near Falls Creek) and Yarraville, along Jacksons Creek in Organ Pipes Sandy Creek Upper Reservoir, in Kinchington National Park and Emu Bottom Wetlands, and Creek, and in the Kiewa River near Tawonga in at Wybejong Park. and at sites along its east and west branches. In In Melbourne’s south-eastern outskirts, Wa- the Mitta Mitta River basin, Water-rats report- ter-rat sightings were recorded in Cardinia edly occurred upstream of Lake Dartmouth in Creek, Monbulk Creek at Belgrave, the Elwood the Big, Gibbo and Dart Rivers and Livingstone Canal and on the (at Creek. The species was also seen in the Mitta Kananook Creek, Paterson River, Devilbend Mitta River near Lake Hume. Creek and Bald Hill Creek). Water-rats also appear to be well-established at many coastal Distribution of sightings in the greater locations around Port Phillip Bay (see below). Melbourne region Across the greater Melbourne area, the largest Distribution of sightings in south-western proportion of Water-rat sightings occurred in Victoria the basin (67%), followed by the The greatest proportion of Water-rat sighting Werribee River basin (22%). In the Yarra catch- records for south-western Victoria originated ment, the frequency of sightings generally in- in the basin (40%), followed by creased in the downstream direction, with 7% the (30%) and the Otway Coast of records obtained along the river and streams and basins (each 12%). In the located upstream of Yarra Glen, 45% occurring Barwon system, 68% of all reported sightings between Yarra Glen and Dights Falls, and 48% were made at in . Wa- occurring downstream of Dights Falls. Three or ter-rats were also seen along the Barwon River more sightings were reported for eleven named from to as far downstream as Reedy water bodies: the Yarra River (22% of all sight- Lake Game Reserve (24% of all sightings), with

76 The Victorian Naturalist Research Report single reports of sightings received for Waurn Distribution of sightings in south-eastern Ponds Creek, West Barwon Reservoir, Goslings Victoria Creek, Warrambine Creek and Winter Creek. In south-eastern Victoria, the largest propor- Immediately to the north-east of the Barwon tion of Water-rat sightings was associated with catchment, Water-rats were recorded in the the basin (28%), followed by at Fyansford, in the west the Mitchell River basin (23%) and Latrobe branch of the Moorabool River upstream of Lal River basin (18%). In the Thomson River sys- Lal Reservoir, and in Hovell Creek near Lara. tem, sightings were recorded in the Thomson, In the Glenelg River basin, Water-rat sight- Macalister and Avon Rivers as well as the Ab- ings were distributed along the Glenelg River erfeldy and Perry Rivers, Valencia Creek, ir- from Cherrypool (i.e. upstream of Rocklands rigation channels near Nambrok and Lake Reservoir) to as far downstream as Lower Gle- Guthridge in Sale. In the Mitchell River system, nelg National Park. However, nearly two-thirds Water-rats were observed in the Mitchell River’s of all sightings originated in the lower reaches near Bairnsdale and Eagle Point, system near Hamilton, notably at Lake Hamil- in MacLeod Morass and in Clifton Creek at Wy ton (the source of 30% of sightings for the ba- Yung, and also in the upper Mitchell catchment sin) and the Hamilton Botanic Gardens Lake at sites along the Dargo and Crooked Rivers. In (11% of sightings). Elsewhere in south-western the system, sightings were made Victoria, sightings were recorded in the Hop- in the Latrobe River near Sale and in Lake Nar- kins River basin along the Hopkins River from racan. Upstream of , Water-rats Ellerslie downstream to Allansford and also at were recorded in the , Sandy Creek sites on Brucknell Creek, , (near Willow Grove), Narracan Creek and Bear Burrumbeet Creek, Bo Peep Creek, Creek; in the subcatchment, and the at and sightings occurred at Billys Creek, Waterhole Grassmere. The species was also seen in the Ot- Creek, Kernot Lake in Morwell township, the way Coast basin at Limestone Creek (a tribu- Hazelwood cooling pondage near Churchill tary of the ), along the Gellibrand and the Morwell River Wetlands. River and several of its tributaries (Love Creek, Elsewhere in south-eastern Victoria, fewer Cole Creek, Chapple Creek, Skinner Creek, than 10 sightings were obtained respectively for Latrobe Creek), and along the Barham, Wye, the , , South Gippsland St George and Erskine Rivers. In the Portland and Far East Gippsland basins. In the Tambo Coast basin, Water-rats reportedly occurred catchment, Water-rats were recorded in the along the at Hawkesdale West, at lower reaches of both the Tambo River (in and the confluence of the Shaw and Eumeralla Riv- downstream of Swan Reach) and the Nichol- ers in Lake Yambuk, and at Fawthrop Lagoon son River (in and downstream of Sarsfield). In in Portland township. the Snowy River basin, sightings were reported No reliable Water-rat sightings were received in the system’s lowest reaches at Marlo and also from the Lake Corangamite basin in the cur- farther upstream in the and in rent study period extending from 2000–2017. the Little River gorge. In the South Gippsland However, one person reported that the species basin, Water-rats were observed along the was seen reasonably frequently at Barongarook , Ayr Creek (near Inverloch), an Creek in Colac in the 1970s. The most recent unnamed creek on Wilsons Promontory, Fish Water-rat records held by the Atlas of Living Creek, the (at Tarwin Lower and Australia for this basin include two sightings Mirboo North) and Monkey Creek in the Merri- made at Floating Islands Reserve in the 1990s, man Creek system. Lastly, in the Far East Gipp- a Water-rat carcass found on the shores of Lake sland basin, sightings were recorded along the Milangil in 1994 and one sighting of a live ani- Goolengook, Cann, Thurra and Genoa Rivers. mal made at Lake Corangamite in 1996.

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Distribution of sightings in coastal Victoria reportedly occurred in river estuaries, and just In Victorian coastal habitats, the largest pro- 0.5% at sites lacking substantial surface water in portion of Water-rat sightings originated in the the immediate vicinity. Gippsland Lakes (59%), followed by sites in Port Cause of death was identified in 40 Phillip Bay (37%). In addition, five coastal re- Water-rat mortalities described in reports dat- cords originated in eastern Victoria (including ing from 2001–2017. Of these, the factor most three sightings made near Mallacoota, one near often resulting in death was use of enclosed Cape Conran and one in Western Port) and one yabby traps or craypots in which Water-rats record originated near Portland in western Vic- drowned (17 records, 42.5% of incidents). An toria. None of these records appeared to involve additional 17.5% of mortalities were due to Wa- an ocean beach that is routinely associated with ter-rats drowning in other types of traps or nets large waves. Instead, habitats were described set to capture fish or , including one as being relatively sheltered, e.g. a flooded area incident in which a dead Water-rat was recov- behind beach dunes at Mallacoota or the San ered from a licensed eel-net. Predation was im- Remo back beach in Western Port. plicated in 15% of mortality records, including More than 90% of records for the Gippsland three observed attacks by pet cats and one by Lakes originated in Lakes King and Victoria, a pet dog, with Foxes Vulpes vulpes deemed to which broadly merge with each other and re- be responsible for two other deaths. Finally, five ceive inflows from the Tambo, Nicholson and deaths (12.5%) occurred when Water-rats were Mitchell Rivers. Other Water-rat sightings for hit by motor vehicles, one animal died after be- the Gippsland Lakes were distributed fairly ing shot with a small calibre rifle, one died af- evenly between Lake Wellington at the system’s ter consuming poisoned rodent bait, one died extreme western end (5%) and Lake Tyers at its after becoming trapped inside a disconnected extreme eastern end (3%). water tank, one apparently suffocated when a Although Water-rats were seen around the large pile of weeds in which it was sheltering entire perimeter of Port Phillip Bay, more than was burnt, and one was found tangled in fenc- half of all records for this water body (52%) ing wire (and presumed to have drowned) after originated around the northern end of the bay, major flooding. Although no cases were report- at sites contiguous with the Yarra, Maribyrnong ed in which a mortality was specifically attrib- and Werribee River basins. In addition, 22% of uted to drought, several persons reported that Water-rat sightings originated at the bay’s east- Water-rat sightings ceased when surface water ern end (at sites contiguous with the Bunyip vanished locally in extremely dry periods. In River basin along the edge of the Mornington the best documented case, Water-rats were seen Peninsula) and 26% of sightings originated at at Lake Wendouree in Ballarat as water depth its western end (at sites contiguous with the dropped progressively due to drought from Moorabool and Barwon River basins, especially 2004 to 2006, but disappeared when the lake in Corio Bay near ). dried out entirely in early 2007. The first sight- ing recorded after the lake refilled in 2010 -oc Habitat use and factors contributing to curred in late 2013; up to four Water-rats were mortality observed in the lake at the same time by June Water-rats were recorded in eight broadly de- 2015, with up to six seen concurrently fined habitat types. The animals were most by November 2016. commonly seen in or next to rivers (26% of all records) or creeks (25%), followed by natural Results of live-trapping studies and man-made lakes and reservoirs (18.5%) Water-rat capture frequencies varied by rough- and coastal habitats (17%). Though fewer per- ly an order of magnitude across water bodies sons reported sightings from wetlands and mo- sampled in both regional Victoria (Table 1) rasses (7%) or irrigation channels (4%), popu- and the greater Melbourne area (Table 2). Even lation density was often described as being high within a given river basin, a two- to five-fold in both habitat types with numerous sight- difference was recorded in capture frequencies ings made over time. Finally, 2% of sightings among different named waterways. The highest

78 The Victorian Naturalist Research Report

9 site-nights) > 9 site-nights) 0.6 0.25 0.3 0.5 0.6 0.6 0.2 0.1 0.4 0.6 0.4 0.9 0.04 0.1 0.2 0.1 0.1 apture apture requency f C

f

9 9 9 12 58 15 97 39 19 47 49 64 14 23 10 10 10 N o ite-nights s

5 7 8 5 8 5 5 5 5 f sites 13 25 10 16 15 20 25 11 ampled s N o

ears) rapping period rapping T (y 2001, 2010 2002 2000-02, 2004-06 2000-01 2000-05 2012-17 2003 2000-02 2003-06 2001-03 2002 2003-04 2009-10, 2012-13, 2017 2008 2008 2008 2008

capture frequency in Platypus survey nets set outside the greater Melbourne area (along water bodies sampled for for bodies sampled water (along area Melbourne survey the greater set nets frequencyoutside in Platypus capture ite Ck immera R, Nowhere Ck R,immera Nowhere ater body ater ackenzie R ackenzie Ck R, Pheasant entworth ount Cole Ck ount oorabool R Ck Emu ount oliban R oliban berfeldy R, Donnelly Ck R,berfeldy Donnelly urdies R urdies oosey Ck alencia Ck arwon R R,arkly uchan R uchan oddon R oddon ivingstone Ck ivingstone aponga R, aponga kenes Ck kenes W C L M M W L B T Wh M B C M B W B S V A

. Estimated Hydromys. Estimated

trapping periods. Locations = Malmsbury area (Coliban R), Vaughan Springs area (Loddon R), Grampians National Park to Laharum (Mackenzie R), head- Laharum to (Mackenzie Park National (Loddon R), Grampians area Springs (Coliban R), Vaughan periods. area = Malmsbury Locations trapping (Boosey Ck), Lake Katamatite to Ck), Lake Rowan (Livingstone R), area (Wimmera Glenorchy to Cole Ck), Elmhurst R (Mount Wimmera to waters Ck), Emu (Mount area (Barwon R), Skipton Fyansford to R), Birregurra (Moorabool Batesford to Ck), Morrisons R, White (Taponga Park National Eildon Ck), (Valencia Forest State Creek Ck), R,Valencia (Barkly Skenes area Ck), Glencairn R, Pheasant (Wentworth Forest State R), Wentworth (Buchan area Buchan Ck). R, Donnelly (Aberfeldy Forest State Thomson from 2000–2017. See Methods for definition of a site-night and description of how capture frequency was calculated. Nets were set in every year of hyphenated hyphenated set in were of everyNets year was calculated. frequency capture how of description and of a site-night definition 2000–2017. See for from Methods Table 1 River basin NW Victoria Campaspe Loddon Wimmera Wimmera Wimmera NE Victoria Mitta Mitta Broken Goulburn SW Victoria Moorabool Barwon CoastOtway Hopkins SE Victoria Snowy Mitchell Thomson Thomson Thomson

Vol 135 (3) 2018 79 Research Report - - 0.45 0.2 0.11 0.2 0.12 0.3 0.4 0.28 0.2 0.44 0.34 0.1 0.2 0.5 0.9 0.3 0.3 apture apture C requency f 9 site-nights) from from > 9 site-nights)

f

9 33 13 43 22 84 95 33 15 37 14 52 12 113 235 126 118 N o ite-nights ite-nights s

8 9 9 6 6 9 7 9 f sites 10 14 24 10 13 14 12 10 12 ampled s N o

ears) 2001 2000 (y 2002–05 2000–01 2003–13 2001–04 2000–07 2000–02 2000–07 2000–04 2000–07 2000–07 2000–04 2001–06 2001, 2003 rapping period rapping 2000, 2002–03 T 2000, 2002, 2004–06

capture frequency in Platypus survey nets set in the greater Melbourne area (along water bodies sampled for for bodies sampled water (along area survey Melbourne set nets frequencyin the greater in Platypus capture amond Ck amond ater body ater aribyrnong R aribyrnong erribee R onbulk/Corhanwarrabul Cks onbulk/Corhanwarrabul ullum Mullum Ck Mullum ullum . Yallock Ck, Ck, Sassafras Emerald Ck . Yallock linda Cklinda eep Ck pper Dandenong Ck, Dobsons Ck Ck, Dobsons Dandenong pper ardinia Ck ardinia unning Ck, Arthurs Ck Ck, Arthurs unning unyip unyip R lenty R (E branch), Jacks Ck Jacks R (E branch), lenty R (gorge) lenty R (lower) lenty ittle Yarra R Yarra ittle arago R, Ck Labertouche arago W T B C U M L W O R Di M P P P M D W

. Estimated Hydromys. Estimated

Bunyip Table 2 River basin Bunyip Bunyip Bunyip Bunyip Yarra Yarra Yarra Yarra Yarra Yarra Yarra Yarra Yarra Maribyrnong Maribyrnong Werribee 2000–2017. See Methods for definition of a site-night and description of how capture frequency was calculated. Nets were set in every year of hyphenated trap hyphenated set in were of everyNets year was calculated. frequency capture how of description and of a site-night definition 2000–2017. See for Methods Dob Ck, Dandenong (Upper Basin The R), (Bunyip Iona to Weir R, Ck), Labertouche Bunyip Longwarry of (Tarago periods. North upstream = Locations ping Yallock Ck, Sassafras (Woori area Monbulk R), Yarra (Little Junction Yarra to Bridges Ck), Three Ck, Corhanwarrabul (Monbulk Scoresby Ck),to Belgrave sons Eltham to Ck), Hurstbridge Ck, Running (Arthurs Creek Arthurs to Park National Lilydale Lake to Ck), (Olinda Strathewen/Kinglake Evelyn Ck, Emerald Ck), Mt (lower Greensborough to Plenty Ck), Lower R, Reservoir Jacks (Plenty Toorourrong of Ck), upstream Mullum (Mullum Templestowe to Ck), Donvale (Diamond R). (Werribee area (Deep Ck), area Werribee Guim R), Darraweit (Maribyrnong Park Brimbank to North R), Keilor Plenty

80 The Victorian Naturalist Research Report frequency of Water-rat captures (one or more sightings occurred in saline coastal habitats, animals present at 90% of sites) was recorded mainly around the perimeter of protected bays along Mount Emu Creek in and near Skipton or in river estuaries. and along the between The findings also confirm that Water-rats can Keilor North and . The lowest adapt successfully to the human transformation capture frequencies (one or more animals pre- of natural landscapes. Numerous sightings orig- sent at < 10% of sites) were recorded mainly inated in man-made impoundments, including in waterways located in south-eastern Victo- major water storages (e.g. Lake Mulwala, Lake ria (Buchan River, Wentworth River, Valencia Eppalock, Laanecoorie Reservoir, Lake Lons- Creek, ) but also the Taponga dale, Lake Fyans) and smaller lakes (e.g. Victo- River in Lake Eildon National Park (north- ria Lake in Shepparton, Lake Weeroona in Ben- eastern Victoria) and the two streams flowing digo, Lake Wendouree in Ballarat, and Lakes into Toorourrong Reservoir in the Daylesford and Hamilton). In the greater Mel- catchment (north of Melbourne). bourne area, nearly half of all Water-rat sight- When analysed regionally, Water-rat capture ings in the Yarra basin were recorded in the frequency was highest in south-western Vic- highly urbanised habitats found downstream toria (mean ± SEM = 0.58 ± 0.12, n = 4), fol- of Dights Falls; one-third of sightings made in lowed by north-western Victoria (0.45 ± 0.07, the Werribee basin originated either in ponds n = 5), the Melbourne area (0.31 ± 0.05, n = at the Werribee Sewage Treatment Plant or 17), north-eastern Victoria (0.30 ± 0.15, n = artificial lakes developed in conjunction with 3) and south-eastern Victoria (0.11 ± 0.06, n = housing estates at Point Cook. Large numbers 5). The combined mean capture frequency for of sightings were also associated with irrigation the western half of Victoria significantly ex- channels in parts of northern Victoria (e.g. in ceeded the combined mean capture frequency the Gunbower area and the Dingee and Shep- for the eastern half of Victoria and Melbourne parton-Tatura irrigation districts). Similarly, (t = 3.208, P = 0.003). Within the latter group, McNally (1960) and Olsen (1980) reported that the mean capture frequency for south-eastern substantial Water-rat populations were estab- Victoria differed significantly from the mean lished in irrigation districts located respectively capture frequency for the Melbourne region in the Rochester–Echuca area in Victoria and (t = 2.930, P = 0.008). There was no significant near Griffith, New South Wales. difference between mean capture frequencies The Water-rat’s adaptability is presumably for north-eastern and south-eastern Victoria founded in part on its catholic diet and flexible (t = 1.722, P = 0.136), though this finding re- feeding habits. Animals are known to forage mains equivocal due to low sample size, par- both during the day and at night (Watts and ticularly in the case of north-eastern Victoria. Aslin 1981; Gardner and Serena 1995), and to A comparison of regional variation in Water- feed on aquatic species ranging in size from rat capture frequencies as summarised above insects and spiders to sizable fish and adult with regional variation in Water-rat sightings waterbirds (including ducks, grebes, Eurasian as portrayed in Fig. 3 supports the conclusion Coot Fulica atra, Western Purple Swamp Hen that sightings were under-reported in western Porphyrio porphyrio and Short-tailed Shearwa- Victoria compared to the rest of the state. ter Puffinus tenuirostris) (Woollard et al. 1978). Furthermore, introduced fish species such as Discussion Goldfish Carassius auratus, Redfin PerchPerca This study indicates that the Water-rat is ap- fluviatilis and Mosquito Fish Gambusia affinis propriately classified as a habitat generalist in are readily consumed and may actually be eaten aquatic ecosystems. Slightly more than half of in preference to indigenous fish (Woollard et al. all Water-rat sightings occurred along freshwa- 1978). Although most of their food is obtained ter rivers and streams, with around one quarter in the water, Water-rats are capable of foraging of sightings originating in more or less static on land and have even been observed search- water bodies, including ponds, lakes, lagoons, ing inside hollow trees in presumed pursuit wetlands and morasses. Most of the remaining

Vol 135 (3) 2018 81 Research Report of roosting bats (Woollard et al. 1978). Water- Along with having less to eat in such circum- rats also have been documented to feed on stances, Water-rats are presumably more likely fish netted by commercial fishermen and offal to be killed by a predator if they spend more generated by fish canneries or recreational time on dry land, particularly if vegetation anglers, to raid poultry runs, and to consume cover is sparse. In addition, female Water-rats human food waste and reasonably fresh carrion become reproductively senescent by the age of (Woollard et al. 1978; Smales 1984; this study). 3.5 years, even when surviving in captivity for Nets or traps set for crustaceans or fish were up to 6 years (Olsen 1982). Accordingly, pro- responsible for 56% of Victorian Platypus mor- tracted drought may plausibly result in popula- talities reported from the 1980s to 2009 where tions disappearing if reproduction fails widely the cause of death could be reliably assigned, in three consecutive dry years. with 13% of mortalities due to predation by As suggested by observations recorded at raptors, dogs or foxes (Serena and Williams Lake Wendouree, it may take a number of years 2010). Similarly, 60% of the Water-rat deaths for a previously sizable Water-rat population described in the current study were caused to recover after a severe drought concludes. In by animals drowning in enclosed places where the species has disappeared, the traps or fish nets (including a commercial length of the recovery period presumably will eel net), with 15% of deaths due to observed be dictated in part by the time required by mi- predation by pet cats and dogs or presumed grants to find and colonise the vacant habitat. predation by foxes. Water-rat deaths in Victo- This in turn will be influenced by the distribu- rian eel nets have been documented previously tion of reliable drought refuges that continue to by Department of Primary Industries (2008): support the species. Population recovery time four Hydromys reportedly drowned as bycatch will also be limited by the reproductive rate of in licensed eel nets set in Lake Wellington in the new migrants, although this can be quite rapid mid-2000s, representing an estimated mortali- in favourable circumstances: female Water-rats ty rate of one Water-rat per 42.5 net-days of eel- may first breed when less than six months old netting activity. In Western Australia, Trocini et and are capable of producing more than one lit- al. (2015) reported that 43% of the 30 Water-rat ter annually (Olsen 1982), with litters of 4–5 ju- deaths described in a community-based survey veniles often born in the wild (McNally 1960). were caused by animals drowning in enclosed Presuming that the frequency of Water-rats traps set for Hairy Marron Cherax tenuimanus, entering nets mirrors the species’ relative abun- with predators and motor vehicles respectively dance, Water-rats typically occur in higher accounting for 7% and 20% of mortalities. numbers in western than eastern Victoria, with The remaining Water-rat mortalities reported the sparsest populations most often found in in the current study were largely due to animals the state’s south-eastern quadrant. The occur- being hit by motor vehicles (12.5%) or flood- rence of low numbers of Hydromys in south- ing/misadventure (7.5%), but also included eastern Victoria has been reported also by one animal that was shot and one that died Smales (1984), who succeeded in capturing the after ingesting poisoned bait distributed near species in just two of seven rivers or creeks in a river. Improved public awareness of the fact the Latrobe, Thomson and Tambo River ba- that the Water-rat is a protected native species sins where wire mesh cage traps baited with would presumably help to reduce the number fish were deployed. One factor that potentially of animals that are killed deliberately, including may contribute to reduced Water-rat numbers those that provoke human ire by consuming in south-eastern Victoria as compared to the ornamental goldfish or using moored boats as rest of the state is predation by Long-finned handy but messy feeding sites. Eels Anguilla reinhardtii, which are restricted Although no formal studies have been con- to coastal catchments east of Wilsons Promon- ducted to date to monitor how Water-rats re- tory and can weigh up to nearly 17 kg (Cadwal- spond to drought, population size is predicted lader and Backhouse 1983). It is therefore con- to drop when aquatic habitats contract or dis- ceivable that they could prey successfully on appear, as supported anecdotally in this study. Water-rats, particularly small juveniles, though 82 The Victorian Naturalist Research Report corroborating data (e.g. in the form of Water- Department of Water Resources (1989) Water Victoria: A Re- source Handbook. (Victorian Government Printer: North rat remains recovered from eel stomachs) are Melbourne) currently not available. Fanning FD and Dawson TJ (1980) Body temperature varia- bility in the Australian water-rat, Hydromys chrysogaster, in The relatively large size and distinctive ap- air and in water. Australian Journal of Zoology 28, 229–238. pearance of the Water-rat, and the fact that it is Gardner JL and Serena M (1995) Observations on activity partly diurnal, means that there is considerable patterns, population and den characteristics of the water rat Hydromys chrysogaster (: Hydromyinae) along potential for describing its distribution (and Badger Creek, Victoria. Australian Mammalogy 18, 71–75. monitoring its population status) by collecting Harris WF (1978) An ecological study of the Australian water-rat (Hydromys chrysogaster Geoffroy) in southeast observational data. The occurrence of this spe- Queensland. (Unpublished MSc thesis, University of cies in a diverse range of fresh and saline water Queensland) McNally J (1960) The biology of the water rat Hydromys chry- bodies, including those found in urbanised set- sogaster Geoffroy (Muridae: Hydromyinae) in Victoria. tings, also means that it is well placed to help Australian Journal of Zoology 8, 170–180. command community support for protecting Menkhorst PW (1995) of Victoria. (Oxford Uni- versity Press: South Melbourne) and improving aquatic habitats, particularly in Olsen PD (1980) Seasonal and maturational pelage changes, modified landscapes. By the same token, there and injuries, in the eastern water rat, Hydromys chrys- ogaster, at Griffith, N.S.W.Australian Wildlife Research 7, is an onus on management agencies both to be 217–233. aware of the role of modified habitats in sup- Olsen PD (1982) Reproductive biology and development of the water rat, Hydromys chrysogaster, in captivity. Austral- porting Water-rats and to proceed with appro- ian Wildlife Research 9, 39–53. priate care when substantially altering those Serena M and Williams G (2010) Factors contributing to habitats. For example, anecdotal evidence ob- Platypus mortality in Victoria. The Victorian Naturalist 127, 178–183. tained in this study suggests that lining irri- Serena M and Williams GA (2012) Effect of sex and age on gation channels with plastic as a water-saving temporal variation in the frequency and direction of platy- pus (Ornithorhynchus anatinus) captures in fyke nets. Aus- measure can have devastating consequences for tralian Mammalogy 34, 75–82. associated Water-rat populations. Further re- Smales LR (1984) A survey of Hydromys chrysogaster, the Australian water rat in central Gippsland. The Victorian search on this issue is warranted, both to assess Naturalist 101, 115–118. the actual impact on Water-rat numbers and Smart C, Speldewinde P and Mills H (2011) Influence of develop strategies for addressing immediate or habitat characteristics on the distribution of the water-rat (Hydromys chrysogaster) in the greater Perth region, West- longer-term adverse outcomes. ern Australia. Journal of the Royal Society of Western Aus- tralia. 94, 533–539. Acknowledgements Speldewinde PC, Close P, Weybury M and Comer S (2013) This study was supported by The Wettenhall Envi- Habitat preference of the Australian water rat (Hydromys ronment Trust’s Small Grants program. We are par- chrysogaster) in a coastal and stream, Two Peoples ticularly grateful to the Trust’s Executive Director, Bay, south-western Australia. Australian Mammalogy 35, 188–94. Beth Mellick, for her advice. We also thank the many Trocini S, Barrett G, Howard K and Ramalho C (2015) Rakali other persons, too numerous to list individually, who Community Survey 2014–2015. Report by WWF-Australia contributed sighting records or helped to host and and Western Australia Department of Parks and Wildlife. promote the community talks and other activities (WWF-Australia: Perth) that were integral to the project’s success. Lastly, the Vernes K (1998) Observation of a long-range overland move- role of the Atlas of Living Australia in recording and ment event by an adult common water rat, Hydromys chry- sharing details of Water-rat sightings is gratefully ac- sogaster. Australian Mammalogy 20, 409–410. Watts CHS and Aslin HJ (1981) The Rodents of Australia. knowledged. Live-trapping activities were authorised (Angus & Robertson: Sydney) by Victorian Wildlife Research Permits 10000390, Woollard P, Vestjens WJM and Maclean L (1978) The ecology 10000929, 10001440, 10001899, 10003545, 10004761, of the eastern water rat Hydromys chrysogaster at Griffith, 10006077, 10006959 and 10008195 and Fisheries Per- NSW: food and feeding habits. Australian Wildlife Research mit RP 553. 5, 59–73. Zar JH (1984) Biostatistical analysis, 2nd Edition (Prentice References Hall: Englewood Cliffs) Atlas of Living Australia website at http://bie.ala.org.au/ species/Hydromys+chrysogaster. Accessed on 30 June 2017. Cadwallader PL and Backhouse GN (1983) A Guide to the Freshwater Fish of Victoria. (Victorian Government Printer: North Melbourne) Received 8 February 2018; accepted 16 April 2018 Department of Primary Industries (2008) Fisheries Status Report 2008. (Department of Primary Industries: Melbourne)

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