What is your geographic area ?
Can you see under the deck with a flashlight?
What type of live trap , and is it large enough to hold a 'possum?
Unless we have an idea of the identity of the critter it will be hard to determine how to capture it. Certain baits will be attractive to some species but not others. Ie Possums like apples but housecats do not.

they arent pests....

they are animals..

you need a trapper ... such as at the link ...

dont know where you are.. but good luck

ken

ps: moving trapped animals is illegal in many areas.. so even if you do trap it.. you will end up a felon.. and then have trouble sleeping in prison ... hire a professional ...

Here is a link that might be useful: link

You need to block access. If it's out of the nest at night, that's the time to rig the "block."

But first you need to ID what it is. And when you know that, you can determine when the animal has babies. Not nice -- or legal, if it's a protected animal -- to block the entry and allow the babies to starve. (Beyond that, dead animals often develop a stink that's hard, if not impossible, to eradicate.)

To ID the critter, sprinkle either cornstarch or flour at the entry/exit holes. In the morning take digital images of the tracks and post here, or send to a local wildlife expert for ID.

just to clarify jean ...

you need to get rid of it..

THEN block access ...

once the vermin find a spot ... its a pain ... i have a small shed ... 8 by 12 or so ... on top of a lose stone foundation ... thank you prior owner ...

over the years i have removed.. groundhog ... rabbit .... possum and the worst.. skunk ...

you have to take care of this before they breed down there ...

the problem is.. that i can not dig in the heavy gravel.. but apparently they can ...

for future prevention ..... what you need to do.. after removal .... is something like that at the link ...

good luck

ken

Here is a link that might be useful: link -- perhaps traper bob is a better name than skunk whisperer ... lol ..

Your Natural resources Department can give you the particulars on the legalities of live-trapping, or even permits to dispatch an animal. In my state, it's quite legal to relocated certain live-trapped pests (yes, animals can present a pest situation) to other property, IF you have that property owner's permission. It's also legal to trap and release them on your own property or humanely euthanise them depending on the animal. Some you will need permits to do, some you won't, some are protected, many are not. You need to identify what animal is under your deck and then find out the regulations concerning removing them first, or work through a pest removal service. Not every exterminator removes animal pests, btw. Our state issues licenses after training and an examination for those people who do this. There should be a listing of those who have these credentials in your area, either through the DNR or your county extension.