Sometimes, they’re just hungry and strip bark to eat it. They may also gnaw on bark to “file” their teeth. Squirrels are “rodents,” a word that comes from the Latin rodere, meaning “to gnaw.”

If it has hair, stay away for an hour, while keeping watch. If the mother is going to retrieve her baby, she’ll do so as soon as she’s aware. If it’s hairless, the situation is more critical, but even then, keep watch for several minutes. Look to see whether it’s possible to return it to its nest, although most nests are out of reach. Keep the baby warm and get it to a licensed wildlife rehabilitator immediately.

It's not neccessarily bad to feed squirrel; however, by doing this you can encourage a large population to hang round your home. This can lead to increased chances for them to get into your home an cause damages.  

No squirrel species is aggressive by nature. However, they are wild animals and if they feel threatened by you or another animal, they may bite as a defense mechanism

Six squirrel diseases that people can get: 

• Salmonellosis: Salmonella bacteria found in droppings. Symptoms typically appear 12 to 72 hours after exposure and can include diarrhea, abdominal cramps, fever, nausea, vomiting, and headache. In some cases, complications such as dehydration, sepsis, and meningitis may occur. 

• Lyme disease: Spread by the ticks squirrels carry, symptoms include nerve pain, stiffness, and inflammation of the brain or spinal cord. 

• Ringworm: A highly contagious fungal infection that is usually spread through direct contact with an infected person or animal or indirect contact. An infected squirrel in your attic can contaminate a variety of objects and surfaces like floors, towels, furniture, and clothing.

• Tularemia: Infectious disease that attacks the skin, eyes lymph nodes, and lungs. Common symptoms include fever, chills, headache, ulcers, fatigue, swollen lymph nodes, and muscle aches.

• Leptospirosis:  Bacterial infection that causes fever, headache, vomiting, jaundice, and rash. 

• Rabies: Though rare, sometimes squirrels pass the rabies virus onto humans via biting or scratching. 

Many of these diseases are fatal when left untreated, so individuals should monitor for symptoms, and seek medical attention after coming in contact with squirrel urine or feces. Breathing in particles of the animal's excrement is the most common method of disease transmission.