ABSTRACT
Commensalism occurs when one population (the commensal) benefits from an interaction and the other population (the host) is unharmed. Bromeliads and orchids grow as epiphytes on trees without doing any harm. The house mouse (Mus musculus domesticus) has lived commensally with humans since the first permanent settlements were established in the Fertile Crescent (Boursot et al. 1993). The house mouse benefits from the food and shelter inadvertently provided by humans, while the humans suffer no adverse effects. Four other examples are as follows.
