Assertion: zebra | /r/AtLocation | group
Facets:
Source sentences:
text: They prefer to be in groups when they are grazing or when they are sleeping so they can have a warning in case a predator approaches them.
text: When zebras stand together, it is harder for predators to determine how many zebras are in the group.
text: Zebras sleep standing up, and only when they have been in groups which could warn these of risk.