Worm exodus from compost bins - Why?

[GliderRider]

I have a couple of 220 litre plastic 'Compost Converter' bins which receive a mix of grass cuttings, kitchen vegetable matter and some earth. I also put in a bit of wet corrugated cardboard now and then for some wood fibre content.

A few times I've noticed large numbers of worms in and around the lids, plus other worms making their way up the sides of the bin as if they want to escape. What would it be about the conditions in the compost bin that makes them want to leave?

[otolith]

Heat. I have a thermometer in mine, and that always happens when the compost gets properly hot.

[Byker28i]

Or damp.

I put shredded paper in ours, along with every snail I can find in the garden, coffee grounds, vegetable peelings
I thought this might have been about the fresh compost ejected from the compost bin door every day. I'm scooping it up and putting it on the garden

[otolith]

All the cardboard that comes into the house goes into the office shredder, then gets stored in a bin outside. We run one compost bin for kitchen waste and another for garden waste. When I empty the kitchen compostable waste bins, I chuck a few handfuls of shredded cardboard on top, and when I mow the lawn or cut the hedge I mix it up with cardboard. The kitchen waste one never seems to get hot enough to bother the worms, probably because it's drip fed rather than getting a massive load of grass or hedge trimmings at once, but the other one does.

[Byker28i]

I generally don't put garden waste in, as it's usually me pulling weeds etc, so that goes into the green dustbin. I found the grass cuttings went too slimey? so that goes in green bin as well

So it's really there to take veg peelings, coffee grounds etc from the kitchen, minimising the amount we put out in the food big to a tiny amount.
We shred everything with our name and adddress on, so that goes in.

It's well established now, about 20 years old?, and seems to hover around 2/3rd full as we keep topping it up, it rots down... I empty about a third every year, we stop using it for about 3 months over winter when it's cold as it slows right down. It's stuffed with worms, snails and insect life

[otolith]

Avoiding the slimy grass cuttings effect is one of the main reasons for the cardboard! You can also use dry leaves or wood/bark chippings, but cardboard is abundant and convenient. And of course it means more compost produced. You just want something high carbon / low nitrogen and less moist to balance out the wet, high nitrogen grass. But it needs to be mixed in, not layered. The kitchen waste, I just chuck the cardboard on top, but with the grass cuttings and hedge trimmings I get the fork out and mix it all together.