In May after seeing Swamp Wallabies along Merri Creek and at Yarra Bend Park I published an article speculating on ground mammal refuges and movements along Merri Creek. The article was kindly featured on the Friends of Merri Creek Facebook page, and got a lot of feedback, with many people reporting their own recent sightings of Swamp Wallabies.
To better understand the movements of Swamp Wallabies along Merri Creek I mapped these sightings as best I could (they are in red in the map on the right from Google MyMaps). I also included reports from the Victorian Biodiversity Atlas (there were only a few) in red also. I approached Wildlife Victoria, who kindly compiled and provided (with a data licence) details of reports to them of Swamp Wallabies in suburbs adjoining the lower Merri Creek over the last seven years. The Wildlife Victoria data points are purple.
I also searched through Merri Creek Management Committee's fauna sightings records; these are shown in green. The records are in 3 handwritten log books covering the period 1997 to the present.
Mapping these records cannot be used to undertake probablility-based analyses unfortunately, because the three data sources have their own limitations. The Merri Creek data was collected predominantly by MCMC field staff where they were working, which was predominantly along Merri Creek. But to add to the confusion, MCMC's work along Merri Creek is not uniform, and it is possible that some of the gaps in the mapped sightings reflect areas MCMC hasn't worked in much or at all.
Where community reported sightings to MCMC (which were recorded in the books too), they reported them to MCMC because they sightings were along Merri Creek. Who knows how many other community sightings there were away from Merri Creek that are not reflected in MCMC data.
Well actually the Wildlife Victoria data do show some of these sightings, but only where the person reporting the Swamp Wallaby felt the wallaby was in danger (or was already injured or dead).
And of course the Facebook reports in response to my first article were shaped by my article but also by the way it was publicised - by Friends of Merri Creek. So responses are biased towards Merri Creek again.
Apart from the frequency of human visitation affecting the rate of sightings, the density of the vegetation will affect the visitor's ability to observe Swamp Wallabies, and this varies markedly along the lower Merri Creek.
There is a slight chance that some sightings referred to as 'Wallabies' may have been Eastern Grey Kangaroos, which are present in Reservoir, and to the north, however this is unlikely in the MCMC or Wildlife Victoria records, and community reporters have been surprisingly clear about the distinction. I have used my judgement to exclude a few reports where there is reason to be suspicious.
Observations from the map
It is fairly clear from the map that there are two areas where sightings along Merri Creek are concentrated - in North Coburg/south-west Reservoir, and in Brunswick East/Thornbury/Northcote. These are each discussed below.
Equally interesting is the relative lack of sightings in some stretches of the Creek, notably:
- North-west Reservoir/north Fawkner, apart from a few sightings in the relatively inaccessible area on the east bank of the Creek in the vicinity of BT Connor Reserve. Apart from that, the reach is almost all parkland accessible to people, cyclists and dogs.
- The Coburg Lake vicinity. This area is characterised by lots of mown grass, few shrubs, and lots of human access.
- Downstream from St Georges Road. There are a scattering of sightings along Merri Creek in Clifton Hill/Yarra Bend Park, but not many. There is though a clump of Wildlife Victoria reports away from the Creek around High Street in Fitzroy North, suggesting that Swamp Wallabies may be having trouble navigating under the High Street Bridge.
- Edgars Creek (a major tributary of the Merri). There are surprisingly few sightings along Edgars Creek, given the proximity of sightings along the Merri.
In Reservoir in particular there are a lot of sightings from Wildlife Victoria away from Merri Creek, and Creeks in general.
North Coburg/Reservoir Refuge
Much of the east bank of Merri Creek in this apparent Swamp Wallaby refuge is quite inaccessible. It stretches from the Bakers Road Footbridge north as far as the Iplex Pipelines factory. The Merri Path follows the west bank of the Creek here, leaving a 2.5 km long rarely visited east bank.
I have walked the east bank in this reach but it is difficult and hazardous. One of the major hazards is the exceedingly spiny African Boxthorn bushes. But I think the Boxthorn is one of the strengths of this refuge, in that it deters humans and dogs from accessing the east bank.
There are 45 sightings recorded in this section of Merri Creek. While many of the sightings are on the west bank of the Creek, I believe the core refuge is the the weedy east bank, and the wallabies cross the Creek to feed at night. One of the weediest sections is at the sharp bend of the Creek south of Iplex Pipelines. This is where I have seen several wallabies this year. Yet the earliest recorded sightings I have for this refuge are from 2006 and 2007 near and south of the Drive-in, and sightings from near Iplex date only from 2014. Yet further north there was a sighting reported by a resident in the Bababi Djinanang grassland adjacent to Jukes Road in 1998.
Northcote Golf Course-Merri Park Refuge
Maybe I am being a bit optimistic calling this a refuge, but there are 25 sightings in this vicinity, stretching over a 2km length of Merri Creek, dating from 2007 to this year. It seems quite likely that the Northcote Golf Course - closed for dog walkers - is the core of this refuge, together with the very weedy west bank of the Creek adjacent to Goldsmith Grove.
Habitat in this reach of Merri Creek has improved drastically since I started work on the Creek:
- Merri Park was transformed from a fenced Melbourne Water Depot, with planting starting in 1988 after extensive earthworks;
- The Northcote Golf Club creek frontage has been extensively revegetated, providing much better cover and browsing for swamp wallabies;
- The weedy section adjacent to Goldsmith Grove has had several not very successful attempts at revegetation after the factories were built, but the vegetation that is there is better than the bare rubble slope that was there 25 years ago.
- On the Moreland side, north from Albion Street there is cover and browsing now available thanks to revegetation efforts, although if Swamp Wallabies ate fennel, they may have had suitable habitat beforehand. [I am trying to be funny here].
My own sightings, the sightings from Facebook, and from the VBA, closely follow Merri Creek, but they are clustered in sections of the Creek which are difficult to visit, and protected from dogs. There is usually dense shrubbery (often the introduced African Boxthorn), blackberries, steep banks, poor access, or management that excludes dogs (e.g. the Northcote Golf Course). It seems that maintaining areas where Swamp Wallabies are protected from dogs will be critical to their survival along Merri Creek.
I suppose on the other hand it could be argued that Swamp Wallabies have always been predated by dingoes, and dogs might be keeping the Wallaby population in check. But I think the large number of dogs and the limited habitat along Merri Creek for Wallabies, especially the limited safe harbour from dogs is a problem for the long term survival of the population.
The purple records from Wildlife Victoria provide interesting insight here. They represent records where a wallaby has got into enough trouble that someone has gone to the trouble to report the wallaby to Wildlife Victoria. For example the animal might have been injured, in danger from traffic (or to traffic), or 'lost' in the suburbs. This information hasn't been provided by Wildlife Victoria, but nonetheless from the map we can see wallabies getting into trouble at Mahoneys Road, Bell Street, Moreland Road and St Georges Road. One Facebooker reported that "I saw one recently trying to cross Moreland Road until it nearly bumped into me and turned back (upstream)". The passage under these bridges is barren and I am sure unwelcoming. Melbourne Water prefers the space under bridges to be as clear as possible of obstructions, as when the Creek is in flood, the bridges as they are cause floodwaters to back up and vegetation under the bridges would make this worse. Nor is there much shrubby cover to guide wallabies to go under the bridges. Working to improve these and other road crossings of Merri Creek is likely to help wallabies stay on the Creek rather than cross the road and get into trouble.
Other east-west movements
Surprisingly the data from Wildlife Victoria show a history of Swamp Wallaby movement between Darebin Creek and Merri Creek through Reservoir South and through Reservoir North. This through ordinary suburbs not at all well suited to Wallabies. At least I wouldn't have thought so. These movements are not multiple sightings of the one wallaby; often they are years apart. There is less movement west from Merri Creek except in Coburg and Coburg North, where Wallabies got into trouble when they reached Sydney Road.
I wonder what on earth stimulates Wallabies to venture into the suburbs away from the waterways. Two possibilities come to mind: perhaps for finding opportunities to breed, as that is often a driver for dispersal in the natural world, or possibly dogs I know will chase and harry Wallabies, and if there is no suitable refuge along the Creek, perhaps someone's back or front yard would be better? And then I imagine it could be the same dilemma all refugees face - to go back to danger, or to go forwards into danger.
Sections with no sightings
It stands out from the map that a few stretches of the Creek have no sightings; these include:
- downstream from the Bakers Road Footbridge, through Coburg Lake - developed parkland on both sides of the Creek - and as far south as Connolly Avenue where some wild difficult to access land adjacent to properties in Elizabeth Street starts;
- downstream from Joe's Farm to Moreland Road, again developed parkland on both sides of the Creek, and with plenty of dogs;
- the Clifton Hill area, where there is wild land on the east bank of Merri Creek, and some on the west.
Open parkland is doubly unsuitable for Swamp Wallabies. Wallabies don't eat grass, they browse on shrubs, so there is little for them to eat. And in terms of shelter and the ability to hide from people and dogs, the lack of dense shrubby areas in these parks make them unsuitable. But Clifton Hill doesn't follow this pattern. I wonder if Wallabies are just not successfully moving down the Creek to spend time in these areas. There have been sightings at Yarra Bend Park and Studley Park, but chatting to the Manager of the Studley Park Boat-house Cafe, he said that in his decade working there he was only aware of 2 sightings. So perhaps there isn't a permanent population at Yarra Bend Park acting as a source of Wallabies moving north along the Creek. And the Clifton Hill section is bracketed by dense patches of reports to Wildlife Victoria, suggesting that getting there might be difficult.
Lessons for Management
- It is important to retain refuges for Wallabies along the Creek if we want the Wallaby population to survive along Merri Creek. These should be areas with minimal dog access.
- Dense prickly shrubs which deter dogs are an important elements of Wallaby refuges.
- Wallabies browse on shrubs and leafy things like Blackberry rather than grass, so shrubby plants need to be encouraged.
- In the North Coburg/Reservoir refuge area plantings of shrubs are showing signs of wallaby grazing, and future plantings need to incorporate methods to protect shrubs from grazing until they are tall enough to survive.