In ethology, an aggregation is any form of gathering of organisms and the process of coming together. In some forms groups of unrelated species might form, in which interaction between members of the aggregation might be minimal; for example herds of grazing zebra and antelopes might combine, both the better to observe the approach of predators, and to improve the odds of escape in the event of attack by predators. Sometimes there might be some interaction, such as mixed flocks of birds that observe each other's foraging behaviour in searching for food. Sometimes there might be quite orderly common action, such as the queuing up for a resource; for example different species of fishes may aggregate around a cleaning station where cleaner wrasse and cleaner shrimp are active, more or less ta