My parents had possums in their roof and it took Dad and I over 6 months to get rid of them and it was one hell of a battle.
Being nocturnal they are dormant during the day and awake at night to go out and feed and what ever else they they feel like doing I guess. They would make quite a racket when they woke and left the house and it was waking Dad up every night. I think due to lack of sleep and delirium he declared war on the Possums.
He first tried all the anti possum sprays known to man including some random wood chips purchased off the internet that you soaked in a bucket and used the water to spray as a deterrent. They all smelt pretty bad but none had any effect on the possums as he had pumped gallons of these liquids into to the roof with a weed sprayer and they still remained. He even directly sprayed some Poss-Off on one that was perched on a down pipe and it did not even bat an eyelid.
Next he tried light. After reading about their nocturnal habits it was suggested that flooding the roof with light would drive them out so he set up numerous spot lights in and on the roof. Again the Possums were not deterred at all and Dad nearly burnt the house down because on of the halogen flood lights had a melt down and did not trip the circuit breakers.
After the failure of driving them out he decided to try and keep them out and enlisted my help in trying to seal up the house. After doing a little Internet research we discovered that they marked their main entrance with urine when coming and going so we were able to locate it so that we could try and lock them out. After watching one scale a brick wall and disappear through a very small gap between the bricks and eave lining we knew we had a huge task ahead.
We spent weeks sealing up every possible place that they could get into the roof through the eaves. Where we could we used timber but the best thing we found was chicken wire as you could crunch it to any shape to suit the need. We also used solid wire mesh sheets to seal some areas as it could be screwed into position. We sealed up everything bar their entrance where we made a simple gate which Dad closed after they departed in the night.
Again we failed as they were still in the roof the next night. But how? It took a few weeks to work it out but one night when Mum was awoken by noises on the roof she went out on the balcony and watched a possum disappear down the ventilation pipe for the kitchen exhaust fan.
So we sealed the all the exhaust pipes and the chimneys and again left the main entrance as the only way out and Dad stayed up to see them off. Out they went and he sealed the gate and this time success. We had sealed them out and they could not get back in. This did not stop them from coming back though and I believe they kept trying to get back in for quite some time but eventually they move on.
VICTORY!
I have been told that you can get traps from local councils or hire people that trap them for you but once released they will find their way back to their nest eventually.
From our epic saga (sorry for the length but that was the short version) I learnt a few things. These were WA possums but I would assume that this should apply to any suburban possum.
1) light, sprays and sound (I forgot to mention Dad did try an ultrasonic doodad) do not bother them
2) They can fit through holes the size of tennis balls so block everything.
3) Find the main entrance (should be marked with urine and smell bad)
4) Stay up late and watch said entrance until you see them depart and block it.
5) Job done
