In my recent walks along Merri Creek and Yarra Bend Park I have seen three Swamp Wallabies. Two were in the inaccessible western bank of Merri Creek in southern Reservoir, and one was in Yarra Bend upstream of the Studley Park Boathouse.
I find it very exciting to think that the two wallabies (definitely different individuals) I saw in close proximity in Reservoir are evidence that there is a breeding population there. I am sure there is in Yarra Bend, and has been for some time.
30 years ago, when I started on Merri Creek restoration, I imagined that getting large ground mammals back along the Creek was fanciful. Surely I thought, with cars and dogs and narrow links along the Creek at major road bridges there was no chance. There you are, I was clearly wrong, as there is a reproducing population of Eastern Grey Kangaroos at Ngarri-djarrang, a grassland reserve along Merri Creek's tributary Central Creek, and now I believe there is a breeding population of Swamp Wallabies. What is their future?
Swamp Wallabies are vulnerable to dog attacks, and I can remember the excitement around the sighting of a Swamp Wallaby in Brunswick sometime in 1993, and the sadness after its remains were found next to the Creek by one of MCMC's ecological management team. Only the tail was found, and we put the death down to dog attack.
In conversation with staff from Merri Creek Management Committee, there have been quite a few reports in the last few years of Swamp Wallabies in the East Brunswick/Northcote reach of Merri Creek, but it is not clear whether these are resident or just passing through.
What should we as a community do to encourage a re-founded population of Swamp Wallabies?
Refuges from dogs
Firstly Swamp Wallabies need refuges from dogs - both those accompanying people (particularly those off-leash) and the night-time roaming dogs which few people see. The section of the west bank of Merri Creek downstream of Lakeside Secondary College in Reservoir as far as Acheson Place Coburg North is a moderately good dog refuge although walking there recently a dog with a harness on visited me several times then dashed off again across the Creek. The 2.6km stretch of Creek bank is mostly adjacent to industrial areas uninterested in the Creek and access is difficult. Much of it is private land. The Merri Path runs along the west bank of the Creek, and unmaintained private land to the Creek bank cuts off access from the north and south. In this stretch there is plenty of prickly shelter (blackberry, boxthorn, hawthorn) which is useful shelter from roaming dogs too. However much of the section is subject to a heavy Desert Ash infestation which is turning the riparian zone into unsuitable habitat for Swamp Wallabies. The trees are themselves too tall to provide shelter and they are suppressing shrubby undergrowth, so causing a reduction in shelter.
Swamp Wallabies, unlike Grey Kangaroos, are browsers not grazers. They don't eat grass but chew leaves off shrubs. So their habitat needs to have lots of shrubs. The Ecological Vegetation Community called Riparian Shrubland, is ideal. This is the plant community which used to occur along the margins of Merri Creek, and is being re-established where possible by Merri Creek Management Committee, Melbourne Water, Friends of Merri Creek and local Councils, with mixed success. But the slopes leading away from the Creek in the stretch described above could also be planted up with shrubs to provide food for the wallabies. Caution needs to be taken in removing weeds though; I think the Wallabies are browsing on blackberry leaves.
Connectivity with other populations
For a small population of animals (or plants) to stay healthy, they need to interbreed with unrelated individuals. For Swamp Wallabies this means they need to be able, at least occasionally, to move up or down Merri Creek without getting eaten or hit by a car. The nearest accessible populations appear to be downstream at Yarra Bend Park (the Victorian Biodiversity Atlas records a few records from there), and upstream at Galada Tamboore and northwards (the VBA has quite a few records from there and the Creek to Cooper Street and Craigieburn Grassland Reserves). I have created a Google MyMaps Map of where I think there is potential for setting aside open space for wildlife refuges, particularly for Swamp Wallabies.
Going downstream from the Reservoir/Coburg North refuge, there are a number of smallish areas which are difficult for people to access, and which are therefore a bit protected from dogs. Maybe not suitable for resident populations of Swamp Wallabies, but suitable for moving through and maybe staying overday (Swamp Wallabies are mostly nocturnal). Many of them could be improved with Riparian Shrubland revegetation, and some would be better with some fencing to exclude dogs reinforced with no-dog regulation. The areas aren't used by dog-walkers currently. And mostly they are not practical walking routes anyway. MCMC has a policy that there should only be a shared pathway along one side of the Creek, and these sites are almost all on the other side.
Eastern Grey Kangaroos
It is hard to envisage these larger more open grassland-dependent animals moving down Merri Creek much further than they currently are. However it is important that the population in Reservoir is connected to populations further north so that they can escape if the population in Reservoir grows too high. Maintaining as much connectivity between Ngarri-djarrang and Merri Creek as possible is important, as is making ground mammal movement under the Mahoneys Road and Ring Road bridges. Once they reach Galada Tamboore, their movement is much less constrained.
Over the years I have been working on the Creek, a trickle of reports of echidnas along the Merri Creek have come in. I am skeptical that they would colonise Merri Creek however because they need good ant and or termite populations, and these are not present along Merri Creek, having been largely eliminated by grazing and urban development. I can't see much support building for re-introducing termites to Merri Creek (think of the damage they may cause to houses!). And ant reintroductions are well, complicated.
I don't really know whether Merri Creek would have been wombat territory. I have the impression that the Basalt Plains were not terribly wombat-friendly. The only records in the Victorian Biodiversity Atlas of Wombats are in the headwaters of Merri Creek near Wallan, in the foothills to the east of the catchment or in Deep Creek (all of which are predominantly not basalt). So again I think Wombats are unlikely to colonise Merri Creek. But who knows? I have been wrong before!