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Won Wron Koala Surveys Update October 2024

Since early July, SKAT has been surveying the northern half of Won Wron State Forest for Strzelecki koala scats. Around 700 trees have been surveyed, with 86 survey sites completed. SKAT has determined that the forests of Won Wron have a strike rate of roughly half that of nearby Mullungdung. The northern half of Won Wron is approximately 3000ha in size and is State Forest managed as Special Protection Zones.

1.1% of trees recorded scats in 'unbiased' survey sites at Won Wron in comparison to almost 2.5% at nearby Mullungdung. Only one koala was seen during the survey days. SKAT will aim to complete surveys in the southern half of Won Wron in 2025 during the winter months, when there is less risk from snakes. It is likely that koala numbers will decline in the drier southern sections of Won Wron. FoE estimates a koala population in northern Won Wron of perhaps 100 animals or one every 30 hectares, with higher numbers in key riparian areas dominated by Mountain Grey Gums.

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An unexpected stand of Mountain Grey Gum occurs at Grass Tree Swamp in the centre of the northern half of Won Wron State Forest.

In the unbiased surveys at Won Wron, based on the grid system, Apple Top Box and Manna Gum had the highest percentage of scats 5.9% and 3.3% respectively, but the numbers of these trees were limited. Mountain Grey Gum, Yertchuk and Yellow Stringybark had percentages of just over 1%, meaning that if you went to 100 of these trees you'd find one scat under each of the tree types. At Mullungdung however, Mountain Grey Gum have a scat percentage of 7.4% and Swamp Gum 7.6%. Much of the northern areas of Won Wron are dominated by Yertchuk forest.

The likelihood of finding a scat increases significantly when you enter riparian zones at both Won Wron and Mullungdung. In fact 88% of all scats, in biased and unbiased surveys at Won Wron, were found within 20-30 metres of riparian areas. These riparian areas are clearly the key to the long term survival of koalas at Won Wron and Mullungdung.

Where the scats have been found at Won Wron. Three hotspots have been found, all in riparian areas. The different pin shadings relate to old and fresh scats.

In the biased surveys where individual trees were surveyed, outside of the grid, Mountain Grey Gum, Apple Top Box and Manna Gum were mainly investigated. 54 scats or 63.5% of the total individual scats found were under Mountain Grey Gum. This was a similar pattern that was found at Mullungdung with Mountain Grey Gum growing in riparian areas clearly the preferred koala tree at Won Wron. A clear difference between the two forests was the almost complete absence of Swamp Gum at Won Wron.

Koala presence 'hotspots' from the Strzelecki koala map in Mullungdung State Forest and Won Wron State Forest. A riparian zone on the eastern side of Won Wron comes in at about 6th most significant in both forests. Mountain Grey Gum are the key Preferred Koala Feed Tree in both forests.

Riparian zone including old growth at Won Wron State Forest


Perhaps one key difference between the higher numbers of koalas at Mullungdung, than Won Wron is the different soil types. The higher koala numbers at Mullungdung are dominated by the Sd soil types (Stockdale Tertiary sediments). Won Wron on the left of screen is dominated by Gormandale dunefield sediments. The Sd soil type most likely contains more nutrients, providing koalas with more tasty and nutrient leaf 'morsels'. This probably also explains the drop off in popularity of Mountain Grey Gums across relatively larger non-riparian areas at Won Wron.

Large areas of northern Won Wron are dominated by Yertchuk, banksia and Grass Tree forests. These areas are usually devoid of koalas.

 

Mainly horizontal koala claw marks on a Mountain Grey Gum at Won Wron. One question that came to mind during the surveys is, in the absence of scats, should claws marks on trees also be added to spreadsheets as signs of koala presence?

In terms of global heating, riparian areas will become increasingly important, as they will offer refuge to animals. They are however vulnerable to fire and as the planet rises the risks of fires increases significantly. There will also be a change of ecotones in these important areas where they will probably change to drier forests. There is clear evidence of this effect at Won Wron with plenty of gullies and riparian areas dominated by non koala preferred feed trees. In some riparian areas, PKFT's were located sometimes hundreds of metres apart. Global warming will also create a restriction of prime habitat in cooler upper elevations of the Strzelecki Ranges. These areas of potential refuge were privatised by the Victorian State Government in the 1990's and are now dominated by pine plantations. Not the best koala habitat! It was also clear that recent storms took out a number of trees at Won Wron and this tree loss on the viability of a long term koala population should not be underestimated.

Our project at Won Wron will be completed in Spring 2025. We are desperate to get the areas surveyed to complete the picture of what is occurring at both Mullungdung and Won Wron State Forests. Earlier in the year FoE called for a new 18,000 reserve at Mullungdung to protect perhaps the most Strzelecki koalas at any known location. It is clear that this reserve should also include a large portion of Won Wron State Forest as well.

SKAT relies entirely on donations and every dollar raised goes a long way. Donate here if you want to contribute.

Contact [email protected] for more details.

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