Squirrels are members of the rodent family. The most frequently dealt with nuisance squirrel is the Eastern Gray Squirrel. They measure around 16-18 inches from nose to tail and weigh approximately one pound. Gray squirrels are active year-round and arboreal, meaning that they live primarily in trees. They feed on a great variety of foods, such as nuts, seeds, fungi, fruits, and of course the seed in your birdfeeder. They store nuts and acorns in holes in the ground. Gray squirrels breed throughout the year, but there are two distinct peaks, in the winter and summer. After about six weeks, two to four young are born, and raised in a nest for about three months. They prefer cavities in trees (or homes), and when cavities aren’t available, they will build a nest out of leaves and twigs high in a tree.
Nuisance concerns:
Squirrels have easily adapted to humans. They frequently use buildings as nesting areas. Squirrels love to break into a house and stay in an attic or soffit. They often find a small opening and will chew a wider hole to gain access to the building. They bring nesting material into the home, and make quite a bit of noise scurrying around and caching nuts. They often fall down the chimney flue and make a lot of noise or enter the fireplace. Sometimes they fall down a wall from the attic and get stuck. They often chew their way into commercial buildings or apartments. They often enter the attic through the gable vent. Squirrels can cause a fire hazard in homes by bringing in nesting material, and by chewing on power lines. Squirrels can leave behind a lot of droppings and urine in the attic. The droppings not only smell bad, but they pose a biohazard, and the smell attracts new squirrels. I highly recommend attic decontamination services if you’ve had squirrels living in your attic.
  Wondering how to get rid of squirrels? There is no magic spray or device that you can use to make them go away. Some people try to sell predator urine, such as coyote or fox urine to get rid of squirrels, but that doesn’t work. They also try to sell ultrasonic sound emitters. These devices are worthless at eliminating squirrels. Some old wives’ tales recommend the use of mothballs or ammonia-soaked rags to make them leave, but I’ve been to countless homes where these techniques failed – biologists know that these attempts won’t work. The ONE AND ONLY WAY to take care of your problem is with trapping and removal of the animals. People ask me – how do you get rid of squirrels in your attic – If you have squirrels in your house, chimney, attic, on the roof or other areas, you need to catch and remove them. The same goes if you want to get rid of squirrels in the walls, ceiling, or garage. 

Many people as me how to catch squirrels, and as usual, the key is to set the correct types of traps (6x6x18 cage traps) in the right areas (usually on the roof or bolted to the squirrel entry holes) with the right bait (peanuts and peanut butter). 
Trapping is really the only way to get rid of squirrels in a garden.
But there’s far more to squirell control than just trapping. The identification of entry points, sealing shut entry holes and prevention, droppings and urine cleanup, and the removal of babies in nests all factor into complete squirrel solutions, especially when the animals are in the house. It’s often very difficult work to do properly. Most do-it-yourself jobs that I’ve ever seen do not solve the complete problem, and often create more problems