Extreme stereotypies are stereotypies that might require direct contact between two animals and can lead to physical harm.

Feather Pecking – usually chicken (Jensen & al., 2005): 

Feather pecking is when birds, usually captive chickens,  bite the  feathers of other chickens and pull it out.

Risks: Increased aggression and infections.

Cannibalism:

 An animal consuming  another’s animal body part or its own body part  by performing a repetitive chewing behavior (Mason & Rushen, 2008).

Risks: Infection, aggression, increase level of stress and cortisol, distress and fear.