According to the American Society for the Prevention of Cruelty to Animals (ASPCA), teddy bear hamsters are known for biting. The ASPCA also states that they tend to bite if bothered during the day when they are sleeping. According to About.com, they can also bite because of improper handling.
The teddy bear hamster is the common name for the Syrian hamster. In the wild, this breed is usually found living alone. In captivity, teddy bear hamsters should strictly be housed alone. If kept in pairs or groups, the teddy bear hamsters will fight and could injure each other. However, they are generally good-natured and easy to tame and handle by their owners.