Insects on the move
Wildfires, stowaways and impressive migrators - insect expert Eleanor Drinkwater speaks to Katie Haylor about insect movement. First of all, they hear a clip from our Animals on the Move show from Murdoch University biosecurity expert Simon McKirdy, who surveyed a cruise ship floating near an Australian island with a unique ecosystem. He was looking for stowaway insects that could pose a threat to the biodiversity of the area. And one critter proved extremely difficult to remove from the boat...
Simon - An insect called tribolium destructor, a tiny little beetle - we're only talking a beetle of about five millimetres in length - but despite all the effort we put into hunting for this beetle, and baiting and trapping and chemical treatments, even at the end of the 19 months when that vessel sailed away, we had not managed to kill the population. We were still finding larvae on the last few days before it left.
Katie - Eleanor, the insects on this boat were moving not under their own steam, as it were, because this was a cruise liner coming from the Baltic to Australia; but how do insects fare in terms of moving great distances under their own steam?
Eleanor - This is such a great question. There are a few different long distance insects that we know about. For example, there's the very famous, very flashy monarch butterfly. They do travel pretty long distances; however, their distances are completely shot out of the water by a creature that very few people have heard of. There is an incredible dragonfly which is known as the globe skimmer or the wandering glider. This is a very small creature, so it's only about two inches long and about three inches across the wingspan. And unusually for dragonflies, it has these incredible long distance migrations. They have developed enlarged hind wings that allows them to glide for incredible distances. In fact they do this migration from East Africa to India, and then back again.
Katie - Wow!
Eleanor - Yes, exactly! Which is the distance of around about 18,000 kilometres, which is just mind-blowing. This is multi-generational; so you get different individuals who do different legs of the journey. But even the individuals themselves go extraordinary distances. For example, there is one stretch in which they have to cross the Indian Ocean, which is a distance of 3,500 kilometres, that individual insects that are no longer than two inches manage to do. Which is just extraordinary!
Katie - Eleanor it puts my lunchtime walk around the block to shame a little bit. But we were talking about Australia earlier, and this year we've seen some enormous wildfires across numerous parts of the world. And I was just wondering how in general animal movement can relate to extreme conditions like fires.
Eleanor - The obvious thing is - a lot of animals, insects, are great to hiding from fires; so during the hot season they'll hide themselves in cracks and crevices. But what I find even more interesting is you get some insects who travel long distances towards the fires. In fact, some species like the black fire beetle: it needs fire in order to reproduce. So they use their sense of smell in order to detect fires, which long distances away, in order to be able to lay their eggs in recently burned wood. And their larvae can only develop if they have been grown in a piece of wood has been recently burned. And the fascinating thing is many of these animals are actually becoming quite rare because of the better fire management that we have these days.
Katie - That sounds like quite a tricky one from a biodiversity/conservation point of view, because there's massive amounts of animals that have perished in these wildfires; but on the other hand, you've got animals who actually require fire. Is that quite a difficult balancing act?
Eleanor - Yes, it is. It's really interesting because you get... it's not just these individuals who do very, very well, or need it to breed; but if you think about an area which has been burnt, suddenly there's no competition and there's very high nutrients in the soil, and also slightly raised temperatures. So there are certain species that do really well in these conditions, to the detriment of other individuals. So recently burnt areas are quite interesting from that point of view. But you're totally right that it does come at a big cost of a lot of other species. So it's a very difficult balancing act.