On Friday evening we met in the coolness of Blanche Cave for a welcome and introduction to the district by the Mayor followed by an intriguing illustrated talk about “The Disputed Country” along the SA border by the farmer/adventurer/map-maker John Deckett,author of a book of the same name and owner of Wesmaps of Nhill.
On Saturday morning nine of us donned knee pads, orange overalls and helmets and descended into the Stick-Tomato Cave to have a go at adventure caving. We crawled and wriggled and climbed and slid through this cave under the expert supervision of Amy, our guide. While the temperature is constant and cool in the caves I admit to a few periods of feeling quite hot and sweaty as we underwent some of the “introductory” exercises. We certainly had a better appreciation of the exploration involved when adventurers negotiated obscure openings that led to more and more caves being discovered.
On Saturday afternoon, after a brief explanation of the progressive discovery of new caves and the extent of the whole cave system to date, and the significance of the quite recently discovered fossil sites, we were very happy to escape the searing sun and descend into the World Heritage listed Fossil Cave. The vertebrate fossil material found in the cave provides a continuous record dating back perhaps 500,000 years. The animals have accidentally fallen down shafts or openings and been unable to get out.
After dinner we watched, through the use of infra-red cameras, Southern Bent-wing down in the caves in preparation for their feeding flights outside. And, when it was time, we walked down to a cave opening and watched as the bats emerged. A specially prepared Bat Trap yielded a couple of small bats that provided us with a close-up live view of these fascinating little creatures.
On Sunday we headed out to learn about the threatened south eastern Red-Tailed Black Cockatoos that feed on the Bulokes in the area. We visited the Mullinger Swamp Conservation Area. A popular swimming and picnic area where people once used the large burnt out trunk of a River Red Gum (11.6 m around) as a change room and where a separate hole was used to swim sheep to clean their fleeces before shearing. The swamp dried up in 1967.
We visited the 144sq homestead and once 13-stand shearing shed at “Benyeo” station. Both were built of ironstone by the Chinese on their way from Robe to the Goldfields in Victoria in the mid 1800s. The 45,000 acre property is now reduced to 6000 acres. We visited a sinkhole on the property where an area up to 100 acres would regularly flood to a depth of one to two metres but where, every five years or so, the water would suddenly disappear down this hole with a great roar and swirl, like going down a plug hole. The farmer said the sides were straight and water could be seen flowing 60ft below. 1965 was the last time this happened.
We drove through the Tallagera Scrub to look at the different effects on revegetation of a controlled “cool” burn and a “hot” burn that got out of control destroying the upper canopy that Red-tailed Black Cockatoos (RTBC) depend on and that can take up to 10 years to repair. On the edge of the scrub we looked at RTBC nesting boxes (large natural hollow branches) attached to unused electricity poles and large dead trees. They are very shy nesters and one sign of occupancy is the chewed rim of the nesting box where the debris falls into the box as nesting material.
Our last stop for the day was at a farm where some of the best Buloke feed trees in the district occur. The young farmer had placed a portion of his land under a Trust for Nature covenant and the remaining Buloke area will be rotationally grazed one week at a time about four times a year.
Martine who studied Bulokes as a food source for RTBC told us that her research has shown that food availability is the primary limitation on RTBC’s numbers. The RTBC is dependant on Bulokes for feeding for approximately two months of the year in late summer/ early autumn and then they move to areas of Brown Stringybark where they will feed for the other 10 months. They prefer the bigger individual Buloke trees to the suckers because they have the best fruit and also provide the most support for these large birds as they land to feed. They hold the cones in one claw, bite off the top of the cone and eat the seeds in whorls and normally spend 65% of their day feeding and up to 80% in dry periods.
Bulokes are slow growing and do not grow well from seed or by direct seeding. They are particularly threatened because they grow in good soil that is suitable for cropping, they are easily knocked down and a more recent threat is the trend towards centre pivot irrigation and the consequent removal of large isolated trees (that produce the most fruit). Protecting and planting trees is important. Endeavours are being made to maintain the endangered population and increase numbers to a sustainable level of 750 breeding pairs. RTBC take three years to mature and mate for life or until their partner dies.
Despite recent sightings, it seemed we had probably missed the RTBCs by about a week. However we did see two pairs of Bush Stone Curlews which was very exciting!
On Sunday evening in Blanche Cave we learned about “Water in the Southeast of SA”. Underground water is the main water source with bores reaching into the unconfined aquifers and more recently into the confined (deeper) aquifers. Farmers are being encouraged to be more careful with water and irrigation water is now being metered. Some of the areas of concern include evaporation from central pivots used during the day, increased salinity, the effect of plantation forests on recharge, severe pollution from dairy farming and a lowering of the water table.
Thanks to the efforts of the Lucindale/ Naracoorte members we had a very interesting (although hot) time and look forward to the next SEANA gathering at Healesville this Spring. Why don’t you come along?
Geraldine and Geoff Harris. Reprintinted from the Castlemaine Naturalist