Traditionally, yes, they do. Rats will burrow under a muddy chicken shed, attracted by the food. They do not usually harm the birds or steal the eggs, but that doesn’t make them welcome guests.
How To Prevent Rats Occupying Chicken Runs
A modern, moveable coop such as the Eglu will deter rats. It’s not the damp wood-and-mud combination they’re looking for, and can be shifted around to prevent the rodents making permanent burrows underneath it. Wooden coops should be raised from the ground on legs, to prevent the rats burrowing underneath.
A modern coop like the Eglu helps keep the squatters at bay
Coop hygiene helps enormously too. Don’t leave food scattered around the chicken shed, and make sure all bags of chicken feed are kept in airtight containers that rats can’t enter.
If rats have moved in, you can deter them by putting cat poo or soiled kitty litter in and around their rat holes. Small jars of toilet cleaner, with a hole in the led to the let the odour out, will drive away the pests, without harming or bothering the hens (although make sure the bottles are in the rat holes or under the coop - not anywhere that a hen can access and cause the liquid to spill).
If rats are a real problem, an expert can advise on the best way forward with traps and, as a last resort, poison.