On moths and pygmy possums - a lesson in ecology

I rarely revert to my past these days, but the recent influx of Bogong moths into Sydney, and the stories being told me of friends' little boys counting how many they can catch and kill, has sent me back there. So, I decided to give you all an ecology lesson. Ecology was one of my favourite parts of biology at school, and the subject I later pursued at University. Ecology is the analysis of distribution and abundance, for those who may not be so sure about that - the exploration of why species live where they do, and what influences their population levels. That sounds simple enough, but ecosystems can be complicated things, and species are often interconnected in ways not readily apparent.

A lot of people I've been chatting to seem unaware that the Bogong moth is only on a migratory path through Sydney, so if you can bear it a little while they will soon be gone. They are on their way to the Southern Highlands for the summer. And waiting for them in the Southern Highlands, or Australian Alps, is a very small marsupial called the Mountain Pygmy Possum. It was thought to be extinct, and known only from fossil records, before it was rediscovered in 1966. There are now estimated to be less than 3000 individuals living in a habitat of only around 10 square kilometres in the Alps. The Mountain Pygmy Possum is one of the only marsupials in the world that hibernates for the winter, and when it emerges in Spring it's energy requirements are understandably high. The Bogong moth is a very important food source for the possum and part of its staple diet through the Summer. So that is one reason why we should let the moths go unharmed on their merry way to the Alps. The moths themselves are also showing alarming levels of arsenic contamination of late, possibly from agricultural chemicals in the soil of their larval pasturelands in the Darling Downs, where they start their migration, and these high arsenic levels have been found in the scats of the pygmy possum.

So, next time you feel tempted to swat or spray a completely harmless, though perhaps a little annoying moth, spare a thought for the moths themselves, for the hungry mountain pygmy possum waiting in the Alps and for the God who made such an amazing and interconnected world.