<P> The term "species group" can be used to describe the manner in which individual organisms group together . In this non-taxonomic context one can refer to "same - species groups" and "mixed - species groups ." While same - species groups are the norm, examples of mixed - species groups abound . For example, zebra (Equus burchelli) and wildebeest (Connochaetes taurinus) can remain in association during periods of long distance migration across the Serengeti as a strategy for thwarting predators . Cercopithecus mitis and Cercopithecus ascanius, species of monkey in the Kakamega Forest of Kenya, can stay in close proximity and travel along exactly the same routes through the forest for periods of up to 12 hours . These mixed - species groups cannot be explained by the coincidence of sharing the same habitat . Rather, they are created by the active behavioural choice of at least one of the species in question . </P> <P> Humans also engage in mutualisms with other species, including their gut flora without which they would not be able to digest food efficiently . Infestations of head lice might have been beneficial for humans by fostering an immune response that helps to reduce the threat of body louse borne lethal diseases . </P> <P> Some relationships between humans and domesticated animals and plants are to different degrees mutualistic . For example, agricultural varieties of maize provide food for humans and are unable to reproduce without human intervention because the leafy sheath does not fall open, and the seedhead (the "corn on the cob") does not shatter to scatter the seeds naturally . </P> <P> In traditional agriculture, some plants have mutualist as companion plants, providing each other with shelter, soil fertility and / or natural pest control . For example, beans may grow up cornstalks as a trellis, while fixing nitrogen in the soil for the corn, a phenomenon that is used in Three Sisters farming . </P>

What is an example of a species that humans interact with mutually