Missing the thylacine
I was just reminded by a recent paper of a video clip from Hobart Zoo of a thylacine, sometimes called a Tasmanian tiger or Tasmanian wolf. I have always found it very moving. It’s believed to show the last of the species – it’s not actually known if it was male or female, but the nickname Benjamin seems to have stuck. I find myself wishing that I could see one, study one, that it was still here.
The thylacine was a marsupial so it had a pouch just like kangaroos do. Morphologically it was reminiscent of a wolf and had a similar lifestyle as an apex predator, mostly eating kangaroos, wallabies and wombats as well as other small birds and mammals. Before European settlement of Tasmania in 1803 they were broadly distributed, but the settlers blamed them for attacks on sheep. There seems to be pretty limited evidence that they really did cause much trouble for sheep farmers, but nonetheless the Tasmanian government of the time created a bounty payment system for dead thylacines. They paid out for 2184 carcasses although the actual number killed was probably much higher. By the beginning of the 20th century they were pretty much extinct in the wild and by 1936 the last zoo individual was gone too – the end of a species, but also the end of a whole biological family of which the thylacine was the last member.
The loss of the thylacine has been the subject of considerable study because of what it can teach us about extinction today. Some scientists have argued using mathematical models of the population that the decline in thylacine numbers was too rapid to be entirely explained by human hunting. They suggest a disease similar to canine distemper may have played a major role. However this new paper published in Journal of Animal Ecology overturns this idea – it seems that the evidence for a severe disease is very anecdotal and a more complex and realistic model suggests that a combination of other factors resulting from European settlement helped to drive the thylacine over the edge. These include land use changes as wild areas were converted to agricultural land, the introduction of dogs which may have competed with thylacines or even directly preyed upon them, and a reduction in the thylacine’s natural prey populations.
I don’t really blame the Tasmanian settlers for their persecution of the thylacine – they were seen as a threat to livelihoods and it was a different time with a different mentality in regard to the natural world. However I do hope that awareness of our past will help us to make more informed decisions, to protect what we have. Benjamin remains as a warning of how dangerous we can be.
Prowse TAA, Johnson CN, Lacy RC, Bradshaw CJA, Pollak JP, Watts MJ, Brook BW: No need for disease: Testing extinction hypotheses for the thylacine using multi-species metamodels. Journal of Animal Ecology 2013, 82(2):355-364.