Mission: Find Bats and Clean Ancient Fossils

This past weekend Chris and I had a fun adventure into several of the caves in the nearby area. Steve Bourne took us around to the caves during the day to see if the Southern Bent-wings were using them as day roosts. My nightly emergence counts have shown that the night-to-night numbers fluctuate quite a bit. One night I may count 35,000 bats, the next night 30,000, and the next night 25,000, and then the numbers jump up again. Obviously the bats aren’t dying, so this suggests that the bats are moving around between the maternity colony at Bat Cave and other caves in the area. We had previously thought that once the bats congregate at Bat Cave for the summer breeding season, they stay there until they disperse for the winter. This might not be the case.

Steve took us to three caves, all within a 30 minute drive of the park. Our first stop was an old mining area. We scrambled down the loose gravel slope (the whole while I was thinking, “Please don’t have a repeat of my knee debacle.”) and then up the other side to look for a bed of 1-2 million year old oyster shells that had been uncovered. We couldn’t find the bed, but we did find one lonely oyster shell.

Heading down into the mine.

 The separation in deposits between the old limestone (solid bottom rock) and the Pleistocene Bridgewater Formation that occurred about 12,000-126,000 years ago (the looser rock at top).

 

A 1-2 million year old oyster shell.

We then continued on to our first cave, Joanna Bat Cave. After about 20 minutes of searching in the grassy woodland for the cave entrance, we finally found it and prepared to go in.

Preparing to enter Joanna Bat Cave.

Once inside, we looked up at the ceiling and along the walls for any roosting bats. We also looked for fresh guano. We found a total of four bats. There were a few piles of old guano from when the bats have used the cave during the winter, but there was no fresh guano.

Two of four Southern Bent-wing Bats roosting in Joanna Bat Cave.

Looking up at the bats roosting in the hole.

Our next stop was Robertson Cave, which was a much bigger cave with two main chambers: one close to the entrance hole that was fairly sunlit and another chamber that you had to crawl through a 2-3 meter hole to get into. We found 14 bats, all in the second chamber. People used to mine limestone out of the second chamber through a big hole in the ceiling. Steve and others installed a metal roof to cover the hole in hopes that the bats would begin using the cave as a maternity cave again. Some believe that the cave used to be a maternity cave, although Steve doubts it as there are no huge guano piles that should be present if it used to be a maternity cave. While the bats aren’t using it for that purpose now, they still use the cave as an important over-wintering site. However, once the fence separating the two chambers was installed to keep people out, the numbers of bats using the cave during the winter decreased from 6,000-7,000 to a few hundred. Apparently Southern Bent-wings are very sensitive to gates and obstructions over their cave entrances. 

 

Probably the neatest cave art/graffiti I’ve ever seen.

The third “cave” we visited was actually a side chamber, called Robertson’s Chamber, off the tourist path in Blanche Cave. Bats like to go there after they emerge from Bat Cave in the evening, perhaps to get some water from the wet stalactites hanging from the ceiling. Again, there were no bats there, but Steve informed us that that chamber was where all the sounds from James Cameron’s movie “Sanctum” were recorded. Apparently the movie people contacted Steve asking where there was a cave with good acoustics, and Steve suggested this chamber. So all the footsteps, carabiner clanking, etc. that you hear in that movie were filmed here at Naracoorte Caves National Park. Now I have to go watch the movie!

Our fourth and final cave visit was to Cave Park Cave, at which we had to fight our way through thick, extremely prickly blackberry bushes. Ouch!

 

Watching Cath blaze the way through the prickly blackberry bushes into Cave Park Cave.

We didn’t find any bats inside, but our foray into the prickliness of the blackberries was well rewarded once we came out. Near the cave entrance was a large patch of blackberries, ripe and ready to be picked, and eaten! We spent a few minutes collecting handfuls of the juicy fruit, although mine didn’t last very long. I must say they were hands down the BEST blackberries I’ve ever had. It was a fantastic way to end our fun caving expedition.

A sweet reward!

However, the day was not over yet! We went back to the “Fossil Lab” in the park to help Steve and Cath wash and dry the bags of dirt and fossils they had taken from the cave dig site a few days before. We helped them haul the bags up from the cave into Steve’s car (and despite the fact that the bags are relatively small, the dirt is very compact and quite heavy!), then from Steve’s car to the washing trough. We then dumped each bag into a sifter and washed the dirt out, leaving only the bones/fossils. 

 

The bags of dirt from the cave dig site are dumped into the sifters, which go in the trough full of water.

We then gently shake the sifters to get the dirt out.

After getting most of the dirt out, we take the sifters out of the trough and give the bones a final rinse with the hose, and then we let them dry in the sifters for a few minutes. Once the bones are dry enough, we transfer them into pans to finish drying in the sun. Because it’s been so hot out the bones don’t take long to dry.

One last rinse of the remaining fossils.

The fossils then partially dry in the sun in the sifters before we transfer them to pans to finish drying.

The final step (which Chris and I didn’t help with because the fossils weren’t dry enough by the time we left) is to sort the fossils and identify and catalogue everything. I’m not sure how much help I would have been with that task even if we had helped! So maybe it was a good idea that Chris and I just got to be free manual labor for the day. I got good exercise and got to see another field of science in action!

Sorted and identified fossils.

Parting words of wisdom.