25 Sept 2019
KEEPING TURTLES COOL
Bachelor of Science (Honours Class 1), University of Queensland and Lead
Working together with the University of Queensland, the Queensland Government and supported by furniture company Koala, we’re investigating simple but effective ways to cool sand temperatures and re-establish more natural gender numbers of offspring - ultimately saving the species. Melissa Staines, Project Lead of the Turtle Cooling project reflects on the second half of the trials...
My bags were packed for another adventure to Far North Queensland. To get to Milman Island is an adventure in itself, a 2-hour flight to Cairns, then an hour flight to Thursday Island (Torres Strait) where we stay overnight and buy more supplies. The current team on the island had been there for the past three weeks, withstanding the monsoonal rain which went on to flood Townsville.
When I arrived, I was shocked by how different the island looked compared to when I had left. Beach rock had been exposed by the huge waves that arrived with 40-knot northerly winds. In particular, the experiment site was just two metres from a towering erosion bank caused by the huge swell. The previous team had built an amazing retaining wall out of huge lumps of coral to protect the bank from the incoming tides. There were rocks exposed that the researchers had never seen before in almost 30 years of monitoring nesting turtles on the island. It was intense to think about how bad the rest of the island had been hit by waves, how many turtles were able to successfully nest each night and how many nests we might have lost.
The tides for the first week were terrible for monitoring. For a whole week, we had very little difference between high and low tide, which meant that the turtles can trickle up all night to nest. On one of the gloomier days, we had found a dead adult male hawksbill turtle. The turtle had been strangled by this huge bundle of plastic tubing. It was incredibly sad; the animal would have died a horrific death by strangulation and drowning. We also found a lesser frigate bird that had died underneath a tree. When I did an autopsy, I found a bundle of string which was from either a fishing line or a net. Coming across animals that had died directly from plastic pollution made me extremely concerned. I even came across some hawksbill hatchlings that had become entangled in a ghost net that was lying in the dunes. We freed them and made sure the net was removed so that no other wildlife would become trapped. Milman is so far away from civilisation, and it’s scary to see with your own eyes the impact it has on these defenceless animals. I want to use this opportunity now to urge you as a reader to make changes, and seek reusable alternatives.
Hawksbill hatchling caught in a fishing net
Leading up to the day of the king tide, the ocean was extremely calm, barely a breath of wind. The ocean was like a huge swimming pool and at sunset you could watch the blacktip reef sharks cruising around the reef with just their dorsal fin poking out of the water. That’s easily one of the greatest things about Milman, it has the best sunsets you could ever imagine. On the best of days, we would have a clutch of hatchlings emerge just as the sun was setting, and it made for the best photo opportunities. One particular afternoon, the sunset was dark pink and orange and we even saw a pod of Indo-Pacific humpback dolphins cruise by the island. On the day of the king tide (19 Feb), the ocean was still glassy, and was breaking metres away from the experiment. The weather was beautiful, but we were slowly running out of drinking water. That day we finally had rain! We were so excited running around with buckets to collect the fresh rainwater, it was the best feeling. Since the erosion around the island was widespread, much of our nights on the island involved rescuing emerged hatchlings from the crevices between rocks. At least half Milman Island was beach rock, meaning it was difficult for nesting females to climb the rocks and even more dangerous for hatchlings getting to the sea.
On 21 February, we had 15-knot winds and a 3.6-metre high tide… doomsday. The entire experiment had waves wash over them and seawater pooled over the nests and sunk down into the sand. For three hours, we protected the nests and shelter from the waves, but it wasn’t enough, and the forces of nature were too strong. Luckily no nests were washed away, but they were completely saturated with seawater and if we left them there the salinity would have dehydrated the eggs and killed the embryos. Additionally, the tides were similar the next day but with 20-knot winds, so there was a very good chance that the nests would be inundated again the following day. So, our amazing team relocated all 51 clutches within 28 hours to a new site that was far away from the tide line. This was an incredible effort by all, our fingertips were bleeding from digging in the coral sand, we had blisters from shovelling new holes and completely exhausted from digging 60 cm-deep holes… but we did it. We were even able to build a new shelter above the shaded nests by reusing the artificial shade cloth and some metal stakes. Although I was devastated that a large part of the treatment was not viable (hatchling data), I was lucky in that the sex-determination period had already finished for all of the clutches in the experiment, so the original treatments could still tell us if they could produce males.
A green turtle hatchling and a spectacular Milman Island sunset
On 27 February, Team 3 was packed and ready to leave and Team 4 were on their way down the coast. I’ll be honest, I was pretty jealous knowing that they were going back to civilisation, with sand-free beds, hot showers and an actual toilet. But I still had 3.5 weeks for my experiment to finish and to collect all the data.
One of the most rewarding parts about the research expedition was working so intimately with the sea turtles. I would spend hours each night checking the nests for tiny noses near the surface and proceeding to take measurements of their carapace size, body mass, crawl and swim speed as well as self-righting ability. The differences between our shaded and unshaded treatments were apparent, the hatchlings in the shaded nests were always larger and livelier than those from the unshaded nests. But even the hatchlings themselves would have individuality from the moment they emerged. Most nights I wouldn’t get to my sandy old bed until 2 or 3 am, and on the still nights with no wind, swarms of sand flies would herd around your face so you couldn’t even wear a head torch on your head. It was all worth it though, seeing those tiny flippers propel the hatchlings to the ocean meant that was another clutch making the journey to adulthood. My favourite part was sitting next to a clutch that was about to emerge and listening to the sand rustling below the surface. The sound of them digging was so peaceful, and often if one clutch was digging another clutch in a nest nearby would be triggered by the vibrations and start digging… i.e. peak hour for hatchlings on Milman Island.
Towards the end of our trip, we had the best sunrise and sunsets of the entire three months that we had been there. The ironic thing was that a cyclone was forming over Papua New Guinea and heading east to the Coral Sea only a couple hundred km away. I still had three nests left to emerge on the day that we had to be evacuated off Milman Island due to Cyclone Trevor crossing the coast 100 km south. The wind speed was too strong and dangerous for us to stay on the island, and when we returned to pack up, much of the northern end had been hit severely by three to four-metre waves. The damage had extended to a few metres from camp, meaning that most of the dunes were entirely gone and many of the natural nests with it. There were erosion banks that were greater than two metres high! It really put into perspective the strength and force of nature, as the cyclone had not even passed over Milman directly. When we hear about climate change, most of the associated issues arise from warmer temperatures but it will also increase sea levels and increase the intensity of weather systems, like cyclones. So even though there is more rain (great for producing male hatchlings) we could also lose nesting beaches due to sea level rise and erosion from cyclones. The importance of this research has never been so important, and I left Far North Queensland heading back home with that message strongly in my mind. We have to make a change, we have to protect these threatened species.
Melissa Staines (left) on Milman Island