What to do about a squirrel under the porch?
Squirrels have learnt to adapt to different kinds of environments. Their main requirement for a squirrel to nest is security, food and water. They can easily make themselves very comfortable under your porch. When you become aware of the presence of a squirrel under your porch you must act fast. Once a squirrel settles down you will soon have a colony of squirrels. Early spring is the best time to get rid of them. Delay will cause the mother to have babies and you may have to wait till late fall for the young ones to be independent.

Removing squirrels from under your porch
Poisoning or shooting squirrels is cruel and to be avoided at all costs. Do not attempt to directly confront or trap them. They have sharp teeth and nails and become aggressive when attacked. They are also very fast and sure to escape after biting you. Squirrels are sensitive creatures and easily irritated by sound, smell and light. By using a combination of these factors they can be driven out without killing them.
1. The first step is to ensure that all entrances to your house are closed. A squirrel should not be able to run inside to escape from the porch.
2. Squirrels return to their dens at night. Wait for them to return. Place bright lights in the porch near them. Battery operated lights are better since squirrels can chew any wire lying around.
3. Keep a battery operated radio tuned to a talk radio station. Squirrels are disturbed by human voices. Other loud sounds can also be used to repel them (of course, without disturbing your neighbors).
4. Squirrels detest strong smelling substances. Use rags soaked in ammonia. Place them under the porch. These can be placed in plastic bags which have holes punched. The smell of ammonia comes out without the rag drying up soon. The squirrels also do not run the risk of eating the rags and being poisoned.

The above steps can be repeated till the squirrels have left. Once you are sure that the squirrels have left, seal the openings under the porch. This is important to ensure that they not return. Install steel mesh on any opening under the porch. The area under the porch can be screened using 1/8" hardware cloth. This is buried 2" in all round the porch. Having mesh and lattice screen down under the porch will also prevent other animals from digging and entering. Regularly inspect the porch and check that it is secure.

Prevention
Preventing the entry of unwanted visitors is essential. Animals enter only if they find readily available food and water. Leaking pipes and water puddles must be promptly dealt with. Avoid feeding pets outside or leaving food unattended. Squirrels nest in leaf piles, unattended piles of wood and newspapers. Keeping the area clean and having garbage cans with secure lids are important. Trees near the porch with hanging branches must be regularly trimmed.