Friday, September 13, 2019

Wombat “hunting” across Australia and a wild ride

Picking up wombat poo--better than sitting behind a computer all day

         In 2007, I set out on a trip with Seth Newsome, husband Chris, and son Evan to study the geo-ecology of the Southern Hairy Nosed Wombat (Lasiorhinus latifrons). In a recent paper (Miller et al., 2005), we had compared the carbon isotope values of fossil emu and Genyornis eggshell with those of the wombat, an herbivorous grazer. The Southern Hairy Nosed Wombat is still extant in South Australia, so it seemed logical to study this modern organism in order to interpret a sizable collection of fossil specimens. I contacted Rod Wells at the University of Adelaide, who is the world expert on the Southern Hairy Nosed Wombat, and set up a field trip to his wombat preserve.

         Wombats live in burrows they excavate into the red, hard-pan soil. They aren’t strictly colonial, but you often find their burrows within 100 meters of one another. I’d read that wombats were slow - traveling at a top speed of 100 meters per hour  - and they foraged during the early morning and late afternoon. I also learned that if a predator (e.g., dingo) tried to enter their burrow, the wombat wedged its substantial rump in the burrow essentially blocking access.
Evan Swarth inside of wombat burrow, South Australia

         One evening, we went “wombat hunting” to observe them foraging on a local ranching station. Several wombats were grazing far from their visible burrows like gazelles grazing on the Serengeti Plain in Africa. Seth and my son Evan wanted to see how close they could get to them, so they started slowly walking then sprinting towards them. Within seconds, the wombats raised their heads, saw the impending danger, and ran towards their burrows. Quickly the pace increased until the wombats were running at full tilt, easily outrunning the humans. As they neared their burrows, the wombats took a dive and disappeared neatly underground. Definitely faster than 100m/hour!
Southern Hairy Nosed Wombat out for a stroll

         We were able to collect many wombat skulls, teeth, and bones because of their interesting, fastidious, and unique behavior. When a wombat is nearing death, it goes into its burrow to die. Later its younger relatives push the deceased animal just outside of the burrow leaving the skeleton conveniently available for sampling. We collected hair, teeth, skeletons, feces, and dietary plants from their range south of Adelaide all the way across the Nullabar Plain.

            Wombats have continuously growing teeth, so the teeth can be sub-sampled and analyzed to determine the variation in diet and drinking water across several seasons. We were interested in using carbon and oxygen isotope values in their teeth to examine seasonality in this region of Australia. Fossil wombat teeth collected in the Murray-Darling basin showed distinct seasonal trends providing us with a record of how influential the Intertropical Convergence Zone (ITCZ) has been in fueling the summer monsoon in this region over time.

Marilyn, Evan, and Seth Nullabar Plain 2007
            Unfortunately, we were unable to accurately date our fossil wombat teeth using radiocarbon methods, because apatite is contaminated during processing with modern carbon. When teeth are compared with eggshell material from the same location, we could use carbon isotopes as a record of whether grasses were C3 or C4, a parameter than remains important in interpreting the isotopic composition of eggshells and inferring the strength of the summer monsoon, and by extension ecosystem structure. Analyses of wombat teeth from specimens older than the megafaunal extinction >45,000 years ago had 60% C4 plants in their diet.  After the major extinction event, carbon isotope results from teeth showed only a 20% contribution from C4 plants, similar to the shifts we measured in the carbon isotopes of emu eggshells.

            At the end of our “wombat” expedition in 2007, we headed our 4WD vehicle towards Alice Springs from the Nullabar Plain. Seth and Chris were the drivers. Evan and I were passengers. There wasn’t a major road connecting the very southern part of the continent with central Australia. We’d need to detour about 400 km out of the way if we drove on paved highways. This was my 7th trip to the Outback, and all of us were accustomed to traveling on dirt tracks. A look at our atlas map showed a nice short cut called Googs Track, which seemed like an easy 2-3 hour short hop saving us a lot of time. We always traveled with plenty of water, extra fuel, spare tires, and food.
Googs Track memorial for Dinger

            We started heading north on the track around 10 am, thinking we’d be on the main road, Stuart Highway, going to Alice by about 2 pm, if we took our time and stopped for lunch. The track began easily. Chris started as the driver with me in the front passenger seat, Evan and Seth in the back. Our first high dunes brought shouts of yippee! I insisted that Chris toot the horn in case a vehicle was coming from the other direction. Fortunately, we hadn’t seen any vehicles coming south. After the 50th serious dune crossing, we stopped for a rest. It had taken us a couple of hours to go about 50 km of the 200 km track.

            The wilderness views were stunning. We climbed dune after dune each one a challenge to climb with a wild winding ride on the downsides. We were happy to be privileged to see such a beautiful landscape. After another hour we reached a small memorial to Goog and his son Dinger, who plowed the track with their bulldozers and tractors. It was just 1:30 pm when we pulled off the main track to see one of the salt lakes a few km off the track. Seth was now driving with Evan sitting shotgun next to him. We were going fast—then rounded a curve and saw another vehicle coming straight for us—also traveling fast. Seth slammed on the brakes, the vehicle fishtailed in the sand, and we stopped mere inches from the other vehicle.
Salt lake off of Googs Track, 2007
 Everyone jumped out of the vehicles. I was shaking. The guys in the other vehicle were what I’d call “hoons”, Australian rednecks. They thought this was funny. I did not. If we’d collided with them, we’d be stuck with no support likely for days.  Chris took over driving. Evan was banished to the back seat. If we had been lax about seat belts on dirt roads before, I was now strict that they were on for all at all times.     
            Chris wrote in his field notes:

“ The dunes became more frequent and they were high. Soon we were flying up one side of the dune to the crest at which point we lurched suddenly over the top and plummeted down the other side. On some descents our stomachs dropped out as we flew over the crest. The driver had the least uncomfortable seat because he could hang onto the steering wheel when the car began jostling and rocking. Our roller coaster ride over the dunes was a lot like being in a small boat going over big swells in the open ocean.”

            Three hours later at 4 pm, on our 250th huge sand dune, we were exhausted. Chris and Seth traded off, and fortunately we had not met any more vehicles head on.  We reached the end of Googs track in the village of Malbooma around 5:30 pm as the light was fading, shaking our heads on how this could have been thought of as a “short cut” in any sense of the word.
We made it to the end--safely!

            This journey was before cell phones gave you instant information on road conditions. We learned later that people took 2-3 days to traverse the 350 dunes on Googs track. Luckily for us, traffic usually always goes south to north, which saved us from further possibility of a head on collision. I’d take that road again any day, but this time, I’d want to enjoy its beauty and solitude for 2-3 days.
Watch out for wombats--you never know where you'll see one!

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