A leech survives by feeding off the blood of other larger beings. This type of behavior is known as what?

The behavior described in the question, where a leech feeds off the blood of larger beings, is classified as parasitism. In this relationship, the leech benefits by obtaining nourishment from its host, while the host typically suffers negative effects, such as blood loss or potential transmission of disease.

Parasitism is characterized by one organism living on or in another organism (the host) and deriving benefits at the host's expense. In this case, the leech relies exclusively on the host for sustenance, highlighting the nature of the parasitic relationship.

Commensalism involves one organism benefiting while the other is neither helped nor harmed, which does not apply here since the host is adversely affected. Predation refers to one organism preying on another for food, which implies killing the prey, unlike in parasitism where the host is usually not killed. Mutualism describes a mutually beneficial relationship between two organisms, which again does not fit the leech's behavior. Thus, the leech's feeding behavior is a clear example of parasitism.