This was sunset on the wild shore of Arthur River, north-west Tasmania, a couple of weeks ago.
Fortunately, it looks as though there will not be a spectacular sunset, or a sunset of any kind, for the Tasmanian devil species. Hope is on the horizon.
Many people are working very hard to solve the mystery of Tasmanian devil facial tumour disease (DFTD). Why is this so?
There are several reasons:
- The devils are intrinsically interesting, even cute, and worthwhile saving for themselves alone. They are not the savage creatures often portrayed – they scream to establish a pecking order, and only bite if this doesn’t work (biting is how the cancer gets transmitted); they are generally timid. Can DTFD be stopped?
- They play an important part in the food web, being the largest predator in Tasmania now that the thylacine has gone (the spotted-tail quoll is slightly smaller). As their populations crash (80% in some areas, 95% in others) due to starvation as the tumours grow to a large size and stop them feeding, and breakdown of body functions, the balance adjusts. They are mostly scavengers and occasional predators on things like possums, so fewer devils mean more carcasses (often road kill) for the spotted-tailed quolls, more food for the meat-eating European wasps (an introduced pest), more for the wedge-tailed eagles, and more for the remaining devils, enabling them to be healthier and breed earlier (this is actually happening). More possums mean less grass, affecting other grass eaters. Owls and bird of prey eat baby devils (called ‘imps’), so fewer of them means changes in population for these others. How will the food web change when DTFD reaches Arthur River? (DTFD has moved steadily west from the east coast beginning in 1995 and has now reached Smithton, 50 km east of Arthur River on the west coast.)
- The facial cancer is interesting to cancer scientists. It is one of only four known transmissible cancers, the others being in dogs, North American soft-shelled clams and Syrian hamsters (and extremely rarely in humans). They are transmissible only within their ‘host’ species, so you won’t catch them. The immune system doesn’t recognise the cells as foreign, so is not activated to fight it. Two types have now been found. DFTD1 cells are all genetically identical. They originated from a single nerve cell pre-1995; DFTD2 was detected in 2014, and eight animals have been found to have it. The cancer is evolving genetically and, interestingly, at least 12 devils have had their tumour regress and they have survived. Biopsies have shown that the cancer is still present. Why does the immune system not recognise this cancer, and what do the cancer’s evolution and some survival imply?
The Save the Tasmanian Devil website has lots of up-to-date information on the lifestyle of the devil, the history of the disease and current progress in saving the devils. Rather than regurgitating all this, I will concentrate on telling about the studies of the University of Tasmania (UTAS) I and eight other volunteers helped with in March 2016, organised by the Curious Traveller.
Four scientists oversaw the project: Associate Professor Menna Jones (who has been working with devils for over two decades), Professor Chris Johnson (who is interested in the mechanisms of wildlife extinction), and PhD students Gini Andersen and Sebastian Comte. Gini’s been working on the Arthur River devils, who are presently disease-free, and Seb on the Freycinet Peninsula (east coast) ones, where the disease has been for some time.
The nine volunteers were divided into teams and sent out daily with each scientist on a rotational basis to help with that scientist’s task: bird survey, European wasp count, checking traps and recording who’s been caught, recovering camera traps, doing vegetation surveys and spotlighting. Team members rotated so we got to work with all scientists and each other (except for me and Seb, due to my great trip – literally – down a mountain; more on that later). Some afternoons involved other activities (a boat trip down the Arthur River; to Preminghana Indigenous Protected Area; a fossil hunt through the devastatingly burnt-out World Heritage Area; ancient petroglyphs; trying to watch wild devils eat) – more about these later. Talks by each scientist and spotlighting after dinner made for very full days, tiring but satisfying.
The raven survey
Every morning, the first job of one of the teams was a raven count. The number of forest ravens (Corvus tasmanicus, the only corvid in Tasmania and the biggest one in Australia, feeding on carrion) is likely to change when the devil population drops. We just drove along the road to the sites and counted ravens for a particular time along a particular section of road.
We consistently found a couple of pairs and a flock of about 14 juvenile males (probably) about 7:30 a.m. On the day we left, at about 10:30 a.m. we counted 35 along the same stretch of road, so time of day is important, but it is also important to have a count at a consistent time of day.
The first job was baiting the large-mammal (devils and spotted-tailed quolls), Mascot (possums, cats) and Elliot (rodent) traps that Gini had placed earlier.
Meat was put in each devil/quoll trap and a baitball (a honey/oats/peanut butter 3 cm diameter sphere) in each of the Mascot and Elliot traps. The animal enters the trap and either pulls at the meat (devil trap) or trips a plate (Mascot and Elliot) on its way to the food.The door then shuts, securing the animal inside. Crack-of-dawn departures ensured the animal was found and freed as soon as possible after its data were collected.
And Gavroche was the first quoll we caught. All quolls and devils caught so far have been chipped and named, so a swipe of a detector tells us who. His weight and width of tail and neck were recorded.
Juveniles who have not been caught before are chipped, weighed, and blood, poo, whisker and hair samples are taken. I helped Gini get Gavroche out of the trap for his ‘processing’.
Spotted-tailed quolls are more nervous than devils when caught, and sprint off quickly. Devils seem calmer. The green bags are used for quolls as they are made up of more opaque and stronger material than hessian bags – quolls cannot see through them so are calmer and cannot get a fix on a person to bite them.
The devil in the next photo was a juvenile, never encountered before. We named him ‘Macbeth’, as one of the researchers was calling their new devils after Shakespearean characters. We named another one ‘Juliet’. Another researcher was using Scottish island names, yet another Greek gods.
Quolls don’t get anywhere near as many ticks as devils do – from memory, Macbeth had eight on one ear and 12 on the other.
Devils walk on the balls of their feet.
Whisker sampling …
The teeth look pretty healthy on this young one. The very strong jaws allow devils to demolish a carcass in short order, bones and all.
He’s outa there! More in the next post.