Many kinds of wildlife have responded to protection and restoration of Merri Creek. However some kinds of wildlife love revegetation to death! A trial by Merri Creek Management Committee (MCMC) has sought to improve establishment of plants where wildlife is determined to have it for lunch.
In industrial and rural sites, MCMC crews often notice that our planted shrubs and trees have been severely browsed by Swamp Wallabies. In extreme cases, repeated browsing dislodges or exhausts new plants, delays habitat creation, and causes increased maintenance costs. The typical tree-guards that MCMC install only protect plants for a few months. Wallabies may prune the tops of guarded plants for years, creating tiny triangular topiaries within the guards. Taller fencing or tree-guards are expensive and may be impossible to install on Merri Creek escarpments with shallow rock and steep slopes.
A spray-on browsing deterrent offers a possible solution. Sen-Tree™ Browsing Deterrent is a mixture of whole egg solids, acrylic polymer adhesive and water that is sprayed onto foliage of the trees. Then, before the mixture dries, silicon carbide grit is sprinkled onto the foliage to produce a double deterrent effect of unfamiliar smell and gritty texture. Eventually a plant matures to become less attractive to browsing or attains a size that can sustain browsing.
The effectiveness of Sen-tree™ has been assessed elsewhere, however wallabies are unpredictable so its performance needs to be checked on the Merri for our particular style of planting.
The intensity of browsing was recorded for over a hundred mixed trees and shrubs that were regularly sprayed with Sen-Tree™ browse deterrent, applied at recommended intervals, along the Merri Creek at Cooper Street Grassland, Campbellfield, (Bababi Marning) between May 2011 and February 2013.
Overall, Sen-tree™ appeared to improve early establishment of shrubs and trees, however some species were apparently so tasty that wallabies quickly ate any new regrowth beyond the treated foliage, preventing shrub expansion. The trial suggests that, for some species, browse deterrent will be effective, and for others, fencing or tall guards will be essential. Hedge Wattle, Acacia paradoxa, proved so irresistible to wallabies that it could explain why this species is absent from local escarpment remnants where wallabies are plentiful. This made us reconsider the suitability of Hedge Wattle for plantings on escarpments. We also learnt important lessons about running a research trial and will be keen to apply them to future trials.
Watch out wallabies, the free lunch is over!
This project was partially funded through Parks Victoria and the Australian Government’s Caring for our Country.