By Jack Ashby, on 24 February 2011
From April 2010 I spent about five months undertaking several zoological field projects across Australia. I worked with government agencies, universities and NGOs on conservation and ecology studies ranging from Tasmanian devil facial tumour disease, the effect of fire, rain and introduced predators on desert ecology and how to poison cats. This series of blog posts is a delayed account of my time in the field.
Last week I described Tasmanian Devil Facial Tumour Disease (DFTD), and the population that was being studied by the University of Tasmania (UTas) which seems to be showing some positive immune response. I joined them early in the Tasmanian winter to trap devils in the population, monitor the spread of the cancer take blood samples and measurements. This is how we did it…
The population has been part of a UTas study going back several years, so the spread and behaviour of the contagious cancer is becoming quite well understood. The site was near Cradle Mt in the central highlands, but I was surprised to learn that the traps were placed on transects inside logging plantations. Tasmania has a difficult history with forestry, and it is one of the major political issues in the state. The largest trees in the southern hemisphere are found in Tassie, in temperate rainforests (itself a rare habitat) yet there is a massive logging industry selling wood pulp to Asia. Tasmania has an incredible endemic fauna which is significantly put at risk by this industry. Watching a single tree trunk so big that it takes five different articulated lorries to carry it is upsetting.
However, it seems that devils quite like forestry plantations, as they provide a mosaic habitat with piles of logs for them to den in, and loads of sapling trees which their prey feed on. So we had baited forty plastic tubes lined up down truck tracks through the plantations which we visited once a day, starting EARLY in the morning.
On the long drive from Hobart to Cradle I asked the project manager what our chances were of catching any devils. It turns out this was a stupid question. We trapped 72 devils 250 times. It was a genuine eye-watering privilege to hold an endangered animal in my hands, and continued to be 250 times in.
The traps work like this – one end of the tube is closed, the other end has a swinging door held open by a pin on top. To the pin is tied a piece of string, which runs outside the length of the pipe and in through a hole, on the other end (inside the closed end of the pipe) is a lump of lamb. The devils smell the bait, go in the tube, bite the lamb which pulls the pin out and the door slams shut.
A three man team checks the traps each day in a set order. Each trap is recorded as “Not sprung, bait present”, “Not sprung, bait gone” (which is when you try and work out how they did it, or because the snow has frozen the trap open), “Sprung, bait present” (these you normally find rolled out of position as the devils (or quolls) have tried something cunning but closed the trap, then they get annoyed that they can’t get to the bait). The other option is that there is a devil in your trap.
Person one: Prepares sampling and recording area nearby.
Person two: Puts hessian bag over end of trap, opens door, holds bag tight.
Person three: Tips contents of trap into bag.
Each devil that is trapped gets a microchip, and as the team comes out regularly most adults we trapped had already been chipped, so the first thing to do is scan them, and read their number (if they don’t have a chip – mostly babies – you give them one using a long syringe, just under the skin on the head).
Persons two and three then sample the devil: check for any tumours which are photographed, measured and biopsied using something similar to hole-punch, measure various sizes and weights, and take a blood sample before releasing them. Each individual is only sampled once per trip, no matter how often it is caught (some were caught nine days out of ten).
Surprisingly, despite their vicious reputation, once you’ve got the animal in a bag, they rarely struggle at all, and just stay floppy, even when inspecting their mouths for tumours. UTas research must adhere to strict ethics rules to ensure the well-being of animals involved. On two days we had vets with us, who could take arterial blood, but for the rest of the time we had to make a tiny pin-prick in the ear and scoop the blood up a drop at a time. Fortunately the vets were with us on the day we caught both of the mean individuals which bite – called Boludo and Cortazar, as they were able to anaesthetise them with gas in order to take samples.
Meanwhile person one resets the trap for the next day. The main job here is to clean the devil faeces out of the trap. A ten kilo devil make A LOT of faeces in one night. This is not a nice job.
Fortunately, the blood samples could last a day outside in the winter, and once we got back to our cabins we stuck them in the freezer. These are then sent back to the labs to analyse for any immunological responses.
After a couple of weeks of this, we returned to Hobart. My next field project was with the same team at UTas, but looking at how the rest of the Tasmanian fauna has responded to the massive and sudden disappearance of devils, the island’s major native predator.
UPDATE: PART SIX HERE