Mice, rats and other vermin

We've had unwelcome visitors since the end of December. At first we had the romantic idea that it might be a squirrel sized creature we get in these parts, a stone marten or la fouine, but a web cam showed that a rat was indeed enjoying the warmth that a real fire and lots of insulation can provide. As the loft has 350mm of insulation, the rodents can run around under this lot without being seen. Apple was the best bait.
However, the quandary was how the rats were getting in. I blocked a few holes in roof vents, but quickly realised that they were getting in through the enormous gap created by every single roof tile where it meets the gutters. So around 320 doors over a distance of 65m. The next problem to solve was how they were getting there.  As all our drain pipes connect together and run the 70m to the road, there was a chance they were like err a rat up a drain pipe?  I'd already fitted grills to a lot of the down pipes to stop leaves, so a few more went in. The only other route is along the pergola.  The rose has been growing and had reached to roof this year.  As we can't stop rodents scaling the plants, we were going to have to block the holes created by the roof tiles.

Foam was the first idea, but most foam breaks down under UV exposure, and there is little space to get purchase with the foam. The solution in the catalogue of tile supplier looks like a comb in 1m lengths. Being (presumably) made of gold and platinum, this was not a cheap option. Google turned up some copies which were ordered for around €60. As you have to remove the last row of tiles to install it, this was not the quickest of jobs, but 5 hours saw around 1/3 of the house done. The bulk of the time is spent on the corners as the hip tiles can't be removed without starting at the ridge. The next time consuming job is moving the working platform around.
There was no evidence of rodents until the corner adjacent to the rose and pergola. Being small, the mice had a nice path on the wall plate.  The rats strolled in over the covered terrasse.
Going further along the south side, I noticed a fair amount of mouse droppings. 5 hours toil saw the last of the house protected and the first few metres of the 2 gullies had grilles fitted with the remaining 10m (of 70m)
If possible slide the tiles towards the ridge avoiding the combs then into place; this stops the combs jamming the correct seating of the tile.  A wooden chock holding the tile above out of the way helps.

To date we've caught 3 rats which went, in their mobile 'home', to stay with their friends in the forest a few km away. Having caught all the rats we'd seen on the webcam, there was still noise from the loft.  This turned out to be mice. The interweb has may reports of rats being hunters of mice, so whether we had mice to begin with, which the rats followed, or the mice moved in just after the rats is anyone's guess.  3 mice were caught very easily, but the scratching continues, but nothing on the camera. At this point the main entry point is blocked, but the rodents could still run around the gutters to find another door. Rain is preventing further work.
Having moved the camera to the area of scratching, we have another mouse.  A lazy, or possibly well fed with a good stash. It runs over the trap which I've put adjacent to the scratching and it shows a little interest. 
update. This mouse, no 4 is now caught and released. No 5 is very camera shy. Today's cocktail for its delectation is Camembert (what else, it's French) cashew nut, cat biscuit and the firm favourite of apple.
15/3. A further update! The mouse was a rat, but it ignored the trap, baited with prune. I found that one blocked hole in the gable was re-opened, so blocked it with steel mesh.  That night there was a noise from the garage.  I opened the door the next day. The rat has not been heard or seen since. Hopefully that is now it.  All traps and camera removed.
21/3 Heard nibbling again, and a look outside showed 4 fingers missing off a comb. I shoved some metal mesh in that hole (the most inaccessible in the entire roof) and set the rat trap with apple just adjacent. Within a day we'd caught one, but no more nibbled combs.
Looked like a young female. Have re-set the trap and we'll see.
Below is a shot of one of the rats inspecting one of the home made traps. As an idea of scale the hole it's in is 76mm diameter. All the rats were about the same size - say a body of 200mm and a similar length tale.
The trap on the right was the only success and was a hole with a wire taper reducing the diameter in a cardboard box. The photographed rat decided the best way to get the bait (apple & cat biscuits) was to chew its way in. Twice. Got a steel trap after that.
The next trap to the left is a see-saw, but it's too small.  Didn't know how big these guys were...
The trap on the left was a electric remote release. Rats are very inquisitive, but not a single rat entered.

October 2022 and the rats are back.  Very enthusiastic this time. So noisy I thought it was probably a dormouse.  It turned that they were rats and the noise was the breaking open of snail shells.  We have a fair number of snails up against the house and the rats have been taking them to a warm place to eat. The little shits have found unblocked holes around the ridge where it meets the gutter. Blocking these holes and setting a trap got us a mouse and 4 rats. However, the last one, 3 months on, has worked out it can chew its way in and out. The combs are plastic and down the west face there are now more holes than comb. Even if I didn't block the new holes, it cut a new one. I found one supplier of aluminium combs in Belgium, but I reckon a rat could nip these off. 

Jan 2023. I eventually remembered brick reinforcement mesh. 

65mm width is readily tacked on, once the old combs are removed. A pleat is required to fill the hole. I also put some mesh behind the roof vents, but it's pretty unlikely a rat would expose itself climbing up a roof. 11 vents in all.

Just over 4 x 20m rolls did the job. 

July 2023. Well, what d'you know. Rats and mice will exposed themselves in a roof valley. Having collected 2 rats, 1 wood mouse and 6 mice (5 in one trap) this week, I'm now busily filling the gaps around the tiles in the valleys. They did mostly have plastic combs, and 1 large hole had been cut. The significant thing was how shiny parts of the valleys were, polished by the rodents coming and going. Finished the 5th roll and took 5.5m off an old roll I've had a long time.

23/7/23 Rats have been busy. Saw 2 inside last week, and they have ignored the trap. However, we've heard them. It the most inaccessible corner of the roof, they have managed to displace 5 bits of mesh. Mesh that is push in place as it cant be nailed due to the proximity to the ridge, and the tiles can't be removed. A bit more reinforcement today might fix them!