In a classic case of not knowing what you've got till its gone, Australians have been warned the demise of the moth they love to hate could have terrible consequences. Bogong moths are large hairy creatures that terrify some people and annoy others. They are also food for many beloved small mammals like the mountain pygmy possum, and the collapse in their numbers could push many of these animals over the edge.
Last year, scientists discovered the moth uses magnetic fields to migrate, rather than relying on the sky alone. This made them the first insects known to use the Earth's magnetic field in a manner similar to migratory birds.
The migration is conducted so the moths can spend the summer in high altitude caves. However, Dr Ken Green of the New South Wales National Parks and Wildlife Service told the Guardian after 40 years of counting the moths in these caves things have gone terribly wrong. “Last summer numbers were atrocious. It was not just really bad, it was the worst I had ever seen. Now this year it’s got even worse.” The statement was supported CSIRO's Dr Peter Caley, who shared data on Twitter.
One cave that normally provides shelter for millions of moths through the summer months had just three this year when Green checked it. Others were little better.
Residents of locations on the migratory path have noticed the absence as well:
The reports are yet another example of the “catastrophic collapse” of insects that has seen the loss of 2.5 percent a year for three decades. The causes of this collapse vary depending on the species and location. In some places, over-use of insecticides is thought to be to blame, and elsewhere the cause is unknown. However, Green blames climate change for the loss of moth numbers.
The moths' breeding grounds are experiencing a major drought. However, this is probably not the whole story. Droughts of similar intensity have struck the same area in the past, and while they caused a reduction in moth numbers, the effect appears to have been far less drastic. The moths' susceptibility to hot weather – the reason they make the migration to high altitude caves – may also be a factor. A small temperature rise has been enough to devastate insect populations in Puerto Rico's rainforests, indicating many species are operating at the edge of their capacity.
The moths' demise may attract some relief in towns on their flight path, including the national capital. However, the impact is likely to be felt on animals of which we are much fonder.
Marsupials, which the moths represent a substantial food source, include the almost unbearably cute, and critically endangered, mountain pygmy possum, various bats and several species of antechinus, the mouse-like marsupial famous for literally shagging themselves to death.
Researchers told the Guardian they found dead mountain pygmy possum litters.
It would appear, that in the changes we are making to the planet, humans may be doing something similar to the antechinus, but in a much less enjoyable way.