As promised, a story about leeches. Your intrepid scientist set off today to collect a few leeches in the name of science, or rather to get a good photo for this story.
I wandered for 30 minutes along the slopes of Wilsons Creek in Garrawarra Conservation Area, walking slowly, backtracking along the same routes in the wet undergrowth, a sure method of picking up leeches (if you go bushwalking with a group, make sure you are not last otherwise you will collect everything that has been disturbed). Well, they weren’t biting and I didn’t get any. Maybe I’m the wrong sort of human or something. I did see a fox. The nice leech photo used here is from the Australian Museum’s website.
Anyhow, I’m assured that a leech plague is going on and that people’s gardens are full of them, so I’m writing this to alleviate some concerns. Don’t be too bothered by them. Leeches don’t carry diseases that we know of, so compared with ticks and mosquitoes they are quite benign. And here in the Illawarra we don’t seem to have species with painful bites, like the Borneo tiger leech. So they are annoying more than anything else, especially when they get into sensitive bits. They are really only dangerous when they attach to an eyeball – in which case it’s best to wait until they drop off.
There are different approaches to dealing with them if you have to trek through rainforest. One way is to walk around in sandals and shorts and pick them off as seen. That works if there aren’t too many, but sometimes, e.g. in Borneo and the Daintree, they can quickly accumulate between each toe, and any that are missed up the legs get into some very sensitive areas. Another approach is to completely cover up with gaiters, trousers, raincoat. That produces a nice ring of leeches around the neck, sometimes other interesting places like inside the mouth or on the eye. Yes, in our wetter forests they are definitely a nuisance.
Leeches are related to earthworms. They both need moisture. Earthworms are important for creating soil. Leeches are important for … well, for leeches. Actually, what feeds on a leech? Frogs and birds do, especially pittas, rarely seen beautiful rainforest birds. So, having lots of leeches around is a sign of a healthy moist environment.
Three years ago the leeches seemed to have completely disappeared due to the prolonged heatwaves and drought. But they can’t fly so they didn’t really ‘go’. Leeches produce eggs in a thick-walled case, which resists drought, so that’s where they were.
Keep well.
Further reading:
https://australian.museum/learn/animals/worms/leeches/
theconversation.com/curious-kids-why-do-leeches-suck-our-blood-117316
www.smithsonianmag.com/science-nature/why-world-needs-bloodsucking-creatures-180973670/
