Although they are not normally dangerous, koalas do occasionally fight back when cornered or threatened. Their sharp teeth and claws can cause significant injuries to humans or other animals.
Koalas subsist primarily on eucalyptus leaves, which are a low-energy food. As a result, koalas spend most of their time sleeping and do their best to avoid unnecessary high-energy activities. These traits make them fairly safe because aggressive behavior wastes energy. Koalas also only weigh 20 to 30 pounds, making them too small to pose a serious threat to most adult humans. However, koalas do have sharp scissor-like incisors and canines and strong jaws that can cause deep bite wounds. They also have long, sharp claws they use primarily for climbing, but can use defensively as well. While koalas are generally slow, they can move quickly for short periods when threatened.
There have been documented koala attacks on humans that have resulted in injuries that required medical attention. Koala bites and scratches may require stitches, antibiotics and a tetanus booster. Koalas are most likely to attack when they feel cornered. People walking dogs in koala habitats are at a higher risk of attack because koalas see the dogs as threats. Female koalas may also attack if a person accidentally wanders too close to her offspring. Experts suggest that people stay cautious and keep a good distance between themselves and wild koalas.