Self mutilation is whenever a glider purposfully harms itself. Many things could be causing discomfort to the glider including, but not limited to:

• Poor diet
• Infection - most commonly a urinary tract infection
• Inbreeding ¹
• Depression
• A cut, bite or wound of any kind
• Parasites
• Intestinal blockage

A self mutilating glider can kill themselves within hours if not stopped. The only way to stop a self mutilator is to put them in an Elizabethan [[Collar]] If your glider is self mutilating a vet check is necessary. Your vet should give your glider a urinalysis to eliminate a urinary tract infection or bladder infection, a fecal smear to eliminate parasites, and your diet should be reviewed. The glider should also be examined for a wound in that area and an X-ray is needed to eliminate possible internal infection or intestinal blockage. If you have a lone glider that is self mutilating find them a friend but still go to the vet.

Please see:
You should know - Self Mutilation and other symptoms

Notes

   ¹ ^ Inbreeding can cause internal organs to vary in size, neurological damage, and other illnesses